TECHNICAL FIRLED [0001] The present invention relates to a porous molded body having an adsorption function suitable for various water treatments such as drinking water production, industrial water production, water purification treatment, wastewater treatment, seawater desalination and industrial water production. BACKGROUND ART [0002] A synthetic resin has a wide variety of uses, and its application field to a packing material, a magnetic recording material, a printing material, an electrically insulating material and an optical material has been expanded by taking advantage of the properties of the material, by improving the properties with the help of copolymerization, blending or additives, or further by combining it with various steps or processes. Among others, demands for a porous membrane are recently increasing, and the porous membrane is utilized in various areas, e.g., a water treatment field such as water purification treatment and wastewater treatment, a medical application such as blood purification, a food industry field, a battery separator, a charged membrane, and an electrolyte membrane for fuel cells. [0003] Above all, in the drinking water production field and industrial water production field, i.e., the water treatment field such as usage for water purification treatment, wastewater treatment and seawater desalination, a porous membrane is used as an alternative to conventional sand filtration, coagulating sedimentation and evaporation or for enhancing the quality of treated water. [0004] As the porous membrane for water treatment, a membrane appropriate to the size of a separation target substance contained in water to be treated is used. Usually, natural water contains many suspended components, and a microfiltration membrane or ultrafiltration membrane for removal of suspended components in water is therefore used in general. [0005] However, utilization of an additive, which is actively used in the field of molding of synthetic resins, particularly, addition of an inorganic particle, is little done in the field of porous membranes except for utilization of a pore-forming agent at the time of membrane production. It is thought that when a porous membrane contains a high concentration of inorganic particles, this gives rise to breaking. [0006] On the other hand, demands for a membrane capable of removing small size ions or low molecular organic compounds, as well as removing suspended components, are increasing. The ions or organic compounds are, for example, arsenic contained in ground water, phosphorus contained in wastewater, and boron contained in seawater, etc., but such ions cannot be removed by filtration/separation with a porous membrane. Among these, boron in seawater is actually removed by reverse osmosis through a semipermeable membrane, but it is not easy to decrease the boron concentration to a value equal to or less than a provisional value even by reverse osmosis. For example, when the semipermeable membrane is designed as a dense membrane, the water permeation performance is reduced, leading to a rise in the processing cost such as electric power cost, and when an alkali is used so as to increase the removal ratio, deterioration of the reverse osmosis membrane is accelerated. [0007] Studies are being made to remove ions derived from boron, etc. by an adsorbing agent containing an inorganic particle as a main component, and Patent Documents 1 and 2 describe a porous molded body containing a fibril formed of an organic polymer resin, and an inorganic ion adsorbent, in which the fibril has a void inside thereof, at least part of the void is opened to the surface of the fibril, and the inorganic ion adsorbent is supported on the outside surface of the fibril and on the surface of the internal void. [0008] In addition, Patent Document 3 describes a composite separation membrane containing a layer of a three-dimensional network structure formed from a thermoplastic resin, and a layer formed of a porous structure which is formed from a thermoplastic resin and contains an adsorbent. In Patent Document 3, the layer formed of a porous structure containing an adsorbent forms a spherical structure, and the adsorbent is held in a pore. BACKGROUND ART DOCUMENTS PATENT DOCUMENTS [0009] Patent Document 1: JP-A-2009-297707 Patent Document 2: JP-A-2007-14826 Patent Document 3: JP-A-2010-227757 SUMMARY OF THE INVENTION PROBLEMS THAT THE INVENTION IS TO SOLVE [0010] The molded body or composite separation membrane obtained by these conventional techniques tends to break and suffers from poor mechanical strength. In consideration of the problems of the above-described conventional techniques, the present inventors aim at providing a porous molded body possessing high strength, while adding an inorganic particle, by using a crystalline polymer with high chemical resistance. MEANS FOR SOLVING THE PROBLEM [0011] The present inventors have intensively studied to create a molded body to which inorganic particles having characteristics such as adsorption function are added in high concentration yet the molded body maintains sufficient strength for practical use. As a result, it was found that it can be achieved by providing a columnar texture containing inorganic particles and crystalline polymers, and thus the present invention is accomplished. Namely, the present invention relates to following [1]-[16]: [ 1] A porous molded body including: a plurality of columnar textures each containing a crystalline polymer and having an aspect ratio (long side/short side) of 2 or more, and an inorganic particle. [2] The porous molded body according to [1], in which long sides of the columnar textures are aligned in a direction from an arbitrary one end to another end. [3] The porous molded body according to [1] or [2], in which in the columnar texture, a molecular chain of the crystalline polymer is oriented in the longitudinal direction of the columnar texture and an orientation degree TT of the molecular chain calculated, based on the following formula (3), from a half-width H (°) obtained by wide-angle X-ray diffraction measurement is 0.4 or more and less than 1.0: Orientation degree 71 = (180°-H)/180° formula (3) (in which H is a half-width of an intensity distribution obtained by scanning a crystal peak in a circumferential direction in the wide-angle X-ray diffraction determination). [4] The porous molded body according to any one of [1] to [3], in which a thickness uniformity of the columnar texture is 0.45 or more. [5] The porous molded body according to any one of [1] to [4], in which a short-side length of the columnar texture is from 0.5 to 3 um. [6] The porous molded body according to any one of [1] to [5], in which the inorganic particle is included inside of the columnar texture. [7] The porous molded body according to any one of [1] to [6], in which the crystalline polymer is a fluorine-based resin. [8] The porous molded body according to any one of [1] to [7], in which the inorganic particle is any of an oxide, a hydroxide and a hydrous oxide of cerium or zirconium. [9] The porous molded body according to any one of [1] to [8], which is in a hollow- fiber membrane shape. [10] A method for producing a porous molded body, including: 1) a step of dissolving a crystalline polymer and an inorganic particle in a poor solvent for the crystalline polymer to obtain a membrane forming solution, 2) a step of solidifying the membrane forming solution by solid-liquid thermally induced phase separation in a cooling bath, and 3) a step of stretching the solidified product at a ratio of 2.0 to 5.0 times by raising a temperature thereof to 60 to 140°C. [11] A method for producing a porous molded body, including: 1) a step of mixing a crystalline polymer and an inorganic particle by melt-kneading, 2) a step of dissolving the mixture in a poor solvent for the crystalline polymer to obtain a membrane forming solution, 3) a step of solidifying the membrane forming solution by solid-liquid thermally induced phase separation in a cooling bath, and 4) a step of stretching the solidified product at a ratio of 1.5 to 5.0 times by raising a temperature thereof to 60 to 140°C. 5 [12] The method for producing a porous molded body according to [10] or [11], including a step of discharging the membrane forming solution in a pressurized state from a spinneret into the cooling bath. [13] A method for operating a hollow-fiber membrane module, in which a hollow-fiber membrane bundle formed of a plurality of hollow-fiber membranes is inserted into a cylindrical case having one or more lateral nozzles at least on a side surface and an end nozzle on both end faces, and at both end parts of the hollow-fiber membrane bundle, end face of the hollow-fiber membrane is fixed to the cylindrical case with an adhesive with the end face being open, to form an end bonded part, and the hollow-fiber membrane has an adsorption function of adsorbing a specific component in water to be treated, the method includes a filtration cycle 1 including a filtration step 1 in which water to be treated is treated at least by the hollow-fiber membrane and resulting membrane filtrate is taken out through one end nozzle, a filtration cycle 2 including a filtration step 2 in which at least membrane filtrate is taken out through another end nozzle, and a regeneration step of restoring the adsorption function, and the filtration cycle 1 and the filtration cycle 2 are performed at least one or more times between the regeneration steps. [14] The method for operating a hollow-fiber membrane module according to [13], in which the amount of membrane filtrate obtained from the filtration cycle 1 and the amount of membrane filtrate obtained from the filtration cycle 2 between the regeneration steps are the same. [15] The method for operating a hollow-fiber membrane module according to [13] or [14], in which the filtration cycle 1 and the filtration cycle 2 are switched alternately every time. [16] The method for operating a hollow-fiber membrane module according to any one of [13] to [15], in which the filtration cycle 1 includes a backwashing step 1 of supplying the membrane filtrate to the hollow-fiber membrane through a lower end nozzle in the filtration step 1 to perform backwashing after the filtration step 1 and the filtration cycle 2 includes a backwashing step 2 of supplying the membrane filtrate to the hollow-fiber membrane through a lower end nozzle to perform backwashing after the filtration step 2. ADVANTAGE OF THE INVENTION 6 [0012] According to the present invention, a porous molded body having added thereto a high concentration of inorganic particles, for example, a porous molded body having added thereto an inorganic particle to which specific ions or low molecular organic compounds are adsorbed, particularly, a porous molded body capable of simultaneously performing removal of suspended components by filtration/separation and removal of specific ions or low molecular organic compounds by adsorption, is provided. BRIEF DESCRIPTION OF DRAWINGS [0013] [FIG. 1] FIG. 1 is a schematic diagram illustrating a porous molded body containing a three-dimensional network structure and an inorganic particle. [FIG. 2] FIG. 2 is a schematic diagram illustrating a porous molded body containing a spherical structure and an inorganic particle. [FIG. 3] FIG. 3 is a schematic diagram illustrating a porous molded body containing an inorganic particle positioned outside a columnar texture. [FIG. 4] FIG. 4 is a schematic diagram illustrating a porous molded body containing an inorganic particle included inside a columnar texture. [FIG. 5] FIG. 5 is an enlarged image of the porous molded body containing an inorganic particle included inside a highly oriented columnar texture in Example 10. [FIG. 6] FIG. 6 is an enlarged image of the porous molded body containing a coarse inorganic particle outside of a spherical texture in Comparative Example 1. [FIG. 7] FIG. 7 is an enlarged image of the porous molded body containing a fine inorganic particle outside of a spherical texture in Comparative Example 5. [FIG. 8] FIG. 8 is an enlarged image of the master pellet of a crystalline polymer and an inorganic particle in Example 10. [FIG. 9] FIG. 9 is an enlarged image of the highly oriented columnar texture surface formed by stretching at a ratio of 2.3 times in Example 11. [FIG. 10] FIG. 10 is an enlarged image of the highly oriented columnar texture surface formed by stretching at a ratio of 1.5 in Example 10. [FIG. 11] FIG. 11 is an enlarged image of a spherical texture surface formed by non-stretching. [FIG. 12] FIG. 12 is a schematic configuration diagram of a hollow-fiber membrane module according to the present invention. 7 [FIG. 13] FIG. 13 is a flow diagram of a membrane filtration apparatus according to the present invention. MODE FOR CARRYING OUT THE INVENTION [0014] 1. Porous Molded Body The porous molded body according to the present invention includes a plurality of columnar textures each containing a crystalline polymer and having an aspect ratio (long side/short side) of 2 or more, and an inorganic particle. [0015] 1-1. Columnar Texture The porous molded body of the present invention contains a columnar texture. The columnar texture is a solid material having a shape long in one direction. The porous molded body has a plurality of columnar textures. [0016] FIG. 1 shows a schematic diagram of a three-dimensional network structure, FIG. 2 shows a schematic diagram of a spherical structure, and each of FIGs. 3 and 4 shows a schematic diagram of a columnar structure. [0017] The three-dimensional network structure 1 illustrated in FIG. 1 has a spherical portion 2 and a fibril 3. In the three-dimensional network structure 1, the spherical portion 2 is small, and fibrils 3 are intertwined with each other to form a three-dimensional network. In this case, the inorganic particle is held by being attached to and supported on the three-dimensional network structure, but the three-dimensional network structure has low pure-water permeation performance and it is easily broken at the interface between the inorganic particle 4 and the fibril 3, and thus its strength is low. In addition, due to large amount of a polymer attached to the inorganic particle, the exposed surface is small and thus in the case of adding an inorganic particle having an adsorption function, the adsorption rate is low. [0018] As illustrated in FIG. 2, the spherical structure 5 also has a spherical portion 2 and a fibril 3. However, in the spherical structure 5, due to large growth of the spherical part 2, the fibril 3 is short and thick, and the fibril 3 is therefore recognized as a narrowed part 6 between spherical parts 2. Hereinafter, the grown spherical part 2 is referred to as 8 "spherical texture". A void is formed by the narrowed portions 6, and a molded body having the spherical structure 5 has higher pure-water permeation performance than a molded body having the three-dimensional network structure 1. However, on the other hand, in the spherical structure 5, when a stress is generated in the molded body, the stress is concentrated between the inorganic particle 4 and the narrowed portion 6 as a result, deformation or breaking of the molded body is likely to occur. [0019] The columnar structure 7 illustrated in FIG. 3 is an aggregate of columnar textures 8. In the columnar texture 8, the fibril is grown to the same level as the spherical part and therefore, the narrowed portion 6 is undistinguishable, compared to the spherical structure 5. Since the columnar structure 7 has a columnar texture 8 with relatively high thickness uniformity, a stress can be dispersed and in turn, high strength is obtained. FIG. 4 also illustrates a columnar structure, but while the inorganic particle 4 is positioned outside the columnar texture 8 in FIG. 3, the inorganic particle 4 is included inside the columnar texture 8 in FIG. 4. When the inorganic particle is included inside, higher strength is obtained. In FIGs. 1 to 4, the inorganic particle is indicated by numerical reference "4". [0020] Specifically, in the columnar texture, the aspect ratio (i.e., ratio of long side/short side) is 2 or more. Thanks to the presence of a columnar texture having an aspect ratio of 2 or more, even when an inorganic particle is contained, high strength can be obtained. [0021] The aspect ratio is preferably 3.5 or more, more preferably 8 or more. In addition, the aspect ratio is preferably 20 or less, more preferably less than 15, still more preferably less than 12. Long sides of the columnar textures are preferably aligned in the same direction from arbitrary one end to arbitrary another end, more preferably aligned in parallel in the longitudinal direction of the porous molded body. When long sides are aligned in the same direction, the tensile strength in the long-side direction can be increased, and when long sides of the columnar textures are aligned in parallel in the longitudinal direction of the porous molded body, this configuration can be usefully utilized for tension particularly in an anisotropic shape such as fiber and hollow-fiber membrane. [0022] Here, the longitudinal direction of the porous molded body is an axial direction in which the raw liquid runs after being discharged from a spinneret at the time of molding of the porous molded body. When the porous molded body is a hollow-fiber membrane or a fiber, the longitudinal direction is a direction perpendicular to the hollow surface and in the case of a flat membrane or a sheet, it is a long-length direction at the time of being wound on a core. The transverse direction of the porous molded body is a direction perpendicular to the longitudinal direction, i.e., an in-plane direction of the hollow surface in the case of a hollow fiber or a fiber and is a short-length direction at the time of being wound on a core in the case of a flat membrane or a sheet. In the columnar texture, the "long side" indicates the length of a longest portion of the columnar texture, and the "short side" indicates the length when a line is drawn perpendicularly from the central part of the longest portion of the columnar texture. These lengths are determined by measuring the length of the columnar texture at arbitrary 20 points or more and calculating the average value thereof. [0023] The porous molded body of the present invention is formed by aggregation of a plurality of columnar textures each having the above-described aspect ratio, and the proportion of the columnar texture in the porous molded body is preferably 60% or more, more preferably 80% or more, still more preferably 90% or more. The structure other than columnar includes, for example, a spherical texture having an aspect ratio of less than 2. When the short side and long side of the spherical texture are in the range of 0.5 um or more and less than 3 um, reduction in the strength is prevented, and good pure-water permeation performance is maintained. However, if the proportion of such a spherical texture in the porous molded body is increased, the possibility of an inorganic particle being present in the vicinity of the narrowed portion between spherical textures increases, and a stress from the inorganic particle is disadvantageously applied to the narrowed part to readily cause fiber breakage. For this reason, the proportion of the columnar texture is preferably as large as possible. [0024] Here, the occupancy (%) of the columnar texture is determined by taking a photograph of a cross-section in the longitudinal direction of the porous molded body by means of SEM, etc. at a magnification enabling clear identification of a columnar texture and a spherical texture, preferably at a magnification of 1,000 to 5,000 times, then dividing the occupied area the columnar texture by the area of the entire photograph of the molded body, and multiplying the obtained value by 100. In order to increase the accuracy, it is preferable to determine the occupancy for arbitrary 20 or more cross-sections and calculate an average value thereof. Incidentally, the area of the entire photograph and the area occupied by a texture can be determined preferably by employing a method of replacing the area by the weight corresponding to each texture photographed. That is, after the photograph taken is printed on paper, the weight of paper corresponding to the entire photograph and the weight of paper corresponding to a texture portion cut out therefrom may be measured. In addition, before taking a photograph by SEM, etc., the above-described resin embedding/dyeing treatment and FIB cutting are preferably applied, because the observation accuracy increases. [0025] In the case of using the porous molded body of the present invention in a filter state, the pure-water permeation performance at 50 kPa and 25°C is preferably 0.5 m3/m2-hr or more, more preferably 1.0 m3/m2-hr or more, still more preferably 1.5 m3/m2-hr or more. When the pure-water permeation performance is 0.5 m3/m2-hr or more, the throughput is increased, and cost superiority can be achieved. On the other hand, in the case of molding the porous molded body in a hollow-fiber membrane shape or a fiber shape, the breaking strength is preferably 3 MPa or more, more preferably 7 MPa or more, still more preferably 10 MPa or more. Since a trade-off relationship is established between pure-water permeation performances and breaking strength due to, for example, the number of textures per membrane volume, a more preferable configuration is that the pure-water permeation performance at 50 kPa and 25°C is from 1.5 m3/m2-hr or more and the breaking strength is 3 MPa or more. In particular, from the viewpoint of forming a high-performance hollow-fiber membrane satisfying both high pure-water permeation performance and high strength, it is preferred that the pure-water permeation performance at 50 kPa and 25°C is from 0.5 to 5.0 m3/m2-hr and the breaking strength is from 7 to 60 MPa, and it is more preferred that the pure-water permeation performance at 50 kPa and 25°C is from 1.0 to 5.0 m3/m2-hr and the breaking strength is from 10 to 30 MPa. [0026] The columnar texture constituting the porous molded body of the present invention is a solid material containing a crystalline polymer. The columnar texture preferably contains a crystalline polymer as a main component, and the proportion of the crystalline polymer in the columnar structure is preferably 80 wt% or more, more preferably 90 wt% or more, still more preferably 95 wt% or more. When the proportion of the crystalline polymer is 80 wt% or more, the membrane strength increases. The crystalline polymer includes polyethylene, polypropylene, polyvinylidene, polyester, and a fluororesin-based polymer. The fluororesin-based polymer is preferably a resin containing a vinylidene fluoride homopolymer and/or a vinylidene fluoride copolymer, and the resin may contain a plurality of kinds of vinylidene fluoride copolymers. [0027] The vinylidene fluoride copolymer is a polymer having a vinylidene fluoride residue structure and is typically a copolymer of a vinylidene fluoride monomer with another fluorine-based monomer, etc. Such a copolymer includes, for example, a copolymer of vinylidene fluoride with one or more kinds of monomers selected from vinyl fluoride, tetrafluoroethylene, hexafluoropropylene and chlorotrifluoroethylene. [0028] In addition, a monomer other than the above-described fluorine-based monomer, for example, ethylene, may be copolymerized to an extent not impairing the effects of the present invention. The weight average molecular weight of the fluororesin-based polymer may be appropriately selected according to the pure-water permeation performance and strength required for the polymer separation membrane, but as the weight average molecular weight increases, the pure-water permeability decreases, and as the weight average molecular weight decreases, the strength decreases. For this reason, the weight average molecular weight is preferably from 50,000 to 1,000,000. In the case of a water treatment application where the polymer separation membrane is subject to chemical cleaning, the weight average molecular weight is preferably from 100,000 to 700,000, more preferably from 150,000 to 600,000. [0029] The porous molded body of the present invention includes a plurality of columnar textures and an inorganic particle, and the length of the short side of the columnar texture is preferably from 0.1 to 5 um, more preferably 0.5 um or more and less than 3 um, still more preferably 0.7 um or more and less than 2.5 um. When the length of the short side of the columnar texture is 0.1 um or more, the strength increases. In addition, when the length of the short side of the columnar texture is 5 um or less, the void between columnar textures becomes large and in turn, good pure-water permeation performance is obtained. [0030] The thickness uniformity (the later-described average value D) of the columnar texture in the porous molded body of the present invention is preferably 0.45 or more, more preferably 0.50 or more, still more preferably 0.65 or more. Although the thickness uniformity is 1.0 at most, the columnar texture may have a thickness uniformity of less than 1.0. Since the columnar texture has such thickness uniformity with little formation of a narrowed portion in the columnar texture, the breaking strength is increased. The smaller the variation among respective short sides of the columnar texture is, the less narrowed portion is formed in the columnar texture, and the thickness uniformity becomes higher. In the case of a spherical texture or a columnar texture with non-uniform thickness, a stress from an inorganic particle is applied to a narrowed part and causes breaking, but in the case of a columnar texture with uniform thickness, a stress can be dispersed by the columnar texture and therefore, the strength increases, which is useful. In addition, a porous molded body having a columnar texture with high thickness uniformity is advantageous also in that it can be stretched at a high ratio and be highly oriented. A highly oriented columnar texture obtained by stretching a columnar texture with high thickness uniformity also has high thickness uniformity. [0031] The thickness uniformity of the columnar texture is determined by comparing a first cross-section and a second cross-section each running in parallel to the long-side direction of the columnar texture. In the case where the long-side direction of the columnar texture coincides with the longitudinal direction of the porous molded body, measurement may be performed relative to the longitudinal direction of the porous molded body. This is specifically described below. At the beginning, a first cross-section and a second cross-section running in parallel to each other are selected. The distance between the first cross-section and the second cross-section is set to be 5 um. First, in each cross-section, a portion composed of a crystalline polymer and a void portion are distinguished, and the area of the crystalline polymer portion and the area of the void portion are measured. Next, the area of a portion where when the first cross-section is projected onto the second cross-section, the portion composed of a crystalline polymer in the first cross-section and the portion composed of a crystalline polymer in the second cross-section are overlapped, namely, the overlap area, is determined. With respect to arbitrary 20 pairs of first cross-section and second cross-section, thickness uniformities A and B are determined based on the following formulae (1) and (2), respectively: Thickness uniformity A = (overlap area)/(area of resin portion of second cross- section) formula (1) Thickness uniformity B = (overlap area)/(area of resin portion of first cross- section) formula (2) [0032] That is, 20 pairs of thickness uniformities A and B are obtained. A larger value means that the thickness of the columnar texture is more uniform. With respect to each pair, an average value C of thickness uniformities A and B is then calculated. That is, 20 average values C are obtained. With respect to these average values C, an average value D is further calculated. The average value D is the thickness uniformity of the columnar texture in the porous molded body. [0033] In measuring the thickness uniformity of the columnar texture, in order to clearly distinguish the crystalline polymer portion and the void portion, it is preferable to previously perform resin-embedding of the porous molded body in an epoxy resin, etc. and dyeing treatment of the epoxy resin, etc. with osmium, etc. By such resin embedding/dyeing treatments, the void portion is filled with an epoxy resin, etc., and at the time of cross-sectional processing with a focused ion beam described later, the portion composed of a crystalline polymer and the void portion (i.e., the epoxy resin portion) can be clearly distinguished, leading to high observation accuracy. [0034] Furthermore, in order to obtain a first cross-section and a second cross-section each running in parallel to the transverse direction of the above-described porous molded body, a scanning electron microscope (SEM) equipped with a focused ion beam (FIB) is preferably used. A face parallel to the transverse direction of the porous molded body is cut out using FIB, and FIB cutting work and SEM observation are performed. Subsequently, the same operation is repeatedly conducted 200 times at 50 nm intervals toward the long side of the columnar texture. By such continuous cross-sectional observation, information at a depth of 10 nm can be obtained. Arbitrary first and second cross-sections making the faces running in parallel to each other and being spaced 5 nm apart are selected therefrom, and the thickness uniformities can be determined using formulae (1) and (2). The observation magnification may be sufficient if it is a magnification enabling clear identification of a columnar texture and a spherical texture, and, for example, a magnification of 1,000 to 5,000 times may be used. [0035] 1-2. Orientation of Molecular Chain In the porous molded body of the present invention, the molecular chain of the crystalline polymer is preferably oriented in the long-side direction of the columnar texture. At this time, the long-side direction of the columnar texture preferably coincides with the longitudinal direction of the porous molded body. The method for achieving high orientation includes stretching at a high ratio, but it has been difficult to stretch a molded body to which an inorganic particle is added at a high stretch ratio. In the present invention, it has been found that when the columnar structure is the above-described columnar structure having high thickness uniformity, stretching at a high ratio is possible. The orientation degree TT of the molecular chain is preferably 0.4 or more and less than 1.0, more preferably 0.45 or more and less than 0.95, still more preferably 0.6 or more and less than 0.8. When the orientation degree in the long-side direction of the columnar structure is 0.4 or more, high modulus is achieved, and when the orientation degree is less than 1.0, the flexibility increases. Accordingly, within the range above, breaking of the columnar texture can be prevented. The orientation degree TT is calculated from a half-width H (°) obtained by wide-angle X-ray diffraction determination, based on the following formula (3): Orientation degree 71 = (180°-H)/180° formula (3) (in which H is a half-width of an intensity distribution obtained by scanning a crystal peak in a circumferential direction in the wide-angle X-ray diffraction determination). [0036] The orientation of the molecular chain in the long-side direction of the columnar texture and the method for measuring the orientation degree TT are specifically described below. In order to calculate the orientation degrees, the columnar texture is fixed to a sample stage by arranging its long-side direction to run vertically and irradiated with an X-ray beam perpendicularly to the long-side direction of the columnar texture. In the case where the molecular chain is unoriented, a ring-like diffraction peak is observed over the entire azimuth angle of 360°. On the other hand, in the case where the molecular chain is oriented in the long-side direction of the columnar texture, when irradiated with X-ray perpendicularly to the long-side direction, a diffraction peak is observed on an azimuth angle in the short-side direction (on the equatorial line) around 29=20°. The diffraction peak around 29=20° indicates a distance between polymer molecular chains. [0037] The value of 29 differs depending on the structure or blending of a polymer and may range from 15 to 30°. For example, when the crystalline polymer is a polyvinylidene fluoride homopolymer and has a crystal or p crystal, a diffraction peak derived from a (110) plane of a crystal or p crystal, i.e., a plane parallel to the molecular chain, is observed around 29=20.4°. [0038] The intensity distribution in the azimuth angle direction is obtained by fixing the value of 29 and furthermore, measuring the intensity in the range from 0° to 360° in the azimuth angle direction (circumferential direction), and the obtained result is the intensity distribution determined by scanning a crystal peak in the circumferential direction. Here, in the case where the ratio between the intensity at an azimuth angle of 180° and the intensity at an azimuth angle of 90° is 0.83 or less or is 1.20 or more, it is regarded that a peak is present, and using the intensity distribution in this azimuth angle direction, the width at a position of half the peak height (half-width H) is determined. [0039] The orientation degree TT is calculated by substituting the half-width H into formula (3). In the porous molded body of the present invention, the orientation degree TT in the long-side direction of the columnar texture is preferably 0.4 or more and less than 1.0, more preferably 0.5 or more and less than 1.0, still more preferably 0.6 or more and less than 1.0. When the orientation degree TT is 0.4 or more, fiber breakage is less likely to occur. This is considered achieved because a stress locally generated from an inorganic particle is absorbed by the columnar texture. [0040] In the intensity distribution obtained by scanning a crystal peak in the circumferential direction, when the ratio between the intensity at an azimuth angle of 180° and the intensity at an azimuth angle of 90° is more than 0.83 and less than 1.20, it is regarded that a peak is absent. That is, in this case, the crystalline polymer is determined to be unoriented. [0041] In the case where the porous molded body contains a crystal or p crystal of polyvinylidene fluoride, the half-width H is preferably a half-width obtained using an intensity distribution determined by circumferentially scanning the crystal peak (29=20.4°) derived from a (110) plane of the a crystal or p crystal above in wide-angle X-ray diffraction determination. [0042] 1-3. Inorganic Particle The porous molded body of the present invention includes a columnar texture and thereby has high strength despite containing an inorganic particle. The inorganic particle includes a metal oxide such as wet or dry silica, colloidal silica, alumina, zirconia, aluminum silicate, zinc oxide and copper oxide, a metal hydroxide, an inorganic metal particle, e.g., gold, silver, copper, iron, platinum, etc., and a particle of calcium carbonate, calcium phosphate, hydroxyapatite, barium sulfate, carbon black, activated carbon, etc. Addition of such an inorganic particle at a high concentration enables to utilize the properties possessed by an inorganic particle, and the properties thereof are, for example, an adsorption function. The inorganic particle having an adsorption function can be arbitrarily selected from activated carbon, various catalysts, metal elements, derivatives thereof, etc. according to the target to be adsorbed. [0043] Handling of a fine particulate inorganic particle is difficult, but the present invention is applicable also to such a fine particulate inorganic particle. The secondary particle diameter or the average of primary particle diameter and secondary particle diameter of the fine particulate inorganic particle is preferably from 0.05um to 80 um, more preferably 0.1 um or more and less than 10 um, still more preferably 0.5 um or more and less than 2 um. [0044] For example, in the case where the target to be adsorbed is boron and/or phosphorus, a metal oxide and a hydrate thereof are used as the fine particulate inorganic particle, and in view of adsorption capacity, a metal oxide, a metal hydroxide, and a hydrous metal oxide are preferred. The metal oxide, metal hydroxide and metal hydrous oxide include a rare earth oxide, a rare earth element hydroxide, and a hydrous rare earth element oxide. The rare earth element constituting those oxides includes Scandium Sc of atomic number No. 21 in the periodic table of elements, yttrium Y of No. 39, and lanthanoid elements of Nos. 57 to 71, i.e., lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, promethium Pm, samarium Sm, europium Eu, gadolinium Gd, terbium Tb, dysprosium Dy, holmium Ho, erbium Er, thulium Tm, ytterbium Yb and lutetium Lu, and among these, in view of boron removal performance, the preferable element is cerium, with tetravalent cerium being preferred. A mixture of these rare earth element oxide and/or hydroxide and/or hydrous oxide is also useful. [0045] As the percentage content of the inorganic particle in the porous molded body (wt% of the proportion of the inorganic particle in the porous molded body) is higher, the adsorption function increases. Accordingly, the percentage content is preferably 10 wt% or more, more preferably 20 wt% or more, still more preferably 30 wt% or more. On the other hand, if the percentage content is too high, the strength of the porous molded body is reduced, leading to deformation or breaking. Accordingly, the upper limit thereof is preferably 50 wt% or less, more preferably less than 40 wt%. [0046] The method for measuring the percentage content of the inorganic particle includes: (1) a method of dissolving the porous molded body in a good solvent for the crystalline polymer and filtering the solution, and (2) a method of taking out the inorganic particle by combining the method above with a method of heating at 800°C or more by an electric furnace, and calculating the weight thereof by comparison with the weight of the original porous molded body. [0047] 1-4. Columnar Texture and Inorganic Particle As described above, the porous molded body of the present invention contains a columnar texture and an inorganic particle. The inorganic particle may be included inside of the columnar texture or exposed to the outside but is preferably included inside, because the strength is enhanced. In the known membrane-forming method, the inorganic particle is expelled outside the texture in the process of producing a spherical texture or a columnar texture and is not included inside, but, as a result of intensive studies, the inorganic particle could be successfully included inside, and the method therefor is described later. The rate at which the inorganic particle included inside may be arbitrarily determined from the required properties, but the more inorganic particle is included inside, the higher the strength is. Accordingly, the rate is preferably 20% or more, more preferably 50% or more, still more preferably 90% or more. As to the method for causing the inorganic particle to be included inside, this can be achieved by producing a master pellet of a crystalline polymer and an inorganic particle as illustrated in FIG. 8 and then performing solid-liquid thermally induced phase separation. Details are described later. [0048] In the conventional molded body, an inorganic particle is present in a void between thin fibrils, but out of embodiments of the present invention, in the case of an embodiment where an inorganic particle is present between relatively thick columnar textures, even though the concentration of the inorganic particle in the molded body is the same, the adsorption rate increases, and since the inorganic particle is held between high-strength columnar textures, the strength and pure-water permeation performance are also increased. [0049] On the other hand, when the inorganic particle is included inside the columnar texture, higher strength is obtained and at the same time, in the case where the columnar texture itself is a porous body, the inorganic particle included inside the columnar texture can also take advantage of the properties thereof. When the columnar texture is in a form of porous body, the diameter of the pore thereof is preferably 0.0001 um or more, more preferably 0.001 um or more, still more preferably 0.005 um or more. When the diameter is not less than the range above, a fluid readily penetrates the columnar texture and useful properties of the inorganic particle, such as adsorption, can be utilized. On the other hand, the diameter of the pore is preferably 0.1 um or less, more preferably less than 0.05 um, still more preferably less than 0.02 um, and in this case, the strength of the molded body can be maintained. Each of FIGs. 9 to 11 shows an enlarged image of a columnar texture or a spherical texture. The diameter of the pore possessed by columnar and spherical textures could be successfully controlled, and the method therefor is described later. [0050] 1-5. Porosity In the porous molded body of the present invention, in order to satisfy both high pure-water permeation performance and high strength, the porosity is preferably from 35 to 80%, more preferably 45% or more and less than 70%, still more preferably 50% or more and less than 65%. If the porosity is less than 35%, the pure-water permeation performance is reduced, whereas if it exceeds 80%, the strength significantly decreases and at the same time, the target can hardly contact with the inorganic particle, failing in having a sufficient adsorption function. The porosity of the porous molded body is determined according to the following formula (4) by using the area of resin portion and the area of void portion in the above-described cross-section. In order to increase the accuracy, it is preferable to determine the porosity for arbitrary 20 or more, preferably 30 or more, cross-sections and use an average value thereof. Porosity (%) = {100x(area of void portion)}/{(area of resin portion) + (area of void portion)} formula (4) [0051] The porous molded body described above has sufficient pure-water permeation performance, strength and elongation for various water treatments such as drinking water production, industrial water production, water purification treatment, wastewater treatment, seawater desalination and industrial water production. [0052] 2. Shape The porous molded body of the present invention may have any shape, and examples of the shape include a membrane shape such as hollow-fiber membrane or flat membrane, and a fiber shape. The fibrous porous molded body may be formed into a knitted fabric or may be cut into fine pieces after forming in a fiber shape and processed into a column. [0053] In the following, the preferable shape is described by taking a hollow-fiber membrane as an example. The shape of the hollow-fiber membrane may be determined according to the pure-water permeation performance and adsorption function required as a membrane module without impairing the breaking strength of the membrane by taking into account the pressure loss in the length direction inside of the hollow-fiber membrane. [0054] 2-1. Outside Diameter The hollow-fiber membrane of the present invention preferably has an outside diameter of 1,800 um or less, more preferably 1,300 um or less, still more preferably less than 1,100 um. When the outside diameter of the hollow-fiber membrane is small, at the time of packing a maximum amount of the membrane into a module, the membrane area becomes large and in turn, the permeation amount of product water increases. [0055] On the other hand, the lower limit of the outside diameter may be set according to the strength required against bending and breaking of the hollow-fiber membrane but is preferably 750 um or more, more preferably 850 um or more, still more preferably 950 um or more. [0056] 2-2. Inside Diameter The inside diameter of the hollow-fiber membrane of the present invention may be set according to the outside diameter, and the upper limit thereof is preferably 1,000 um or less, less than 700 um, or less than 600 um, because collapse resistance increases. On the other hand, when the inside diameter is set large, the pressure loss is reduced and therefore, the amount of water passing through the inside, i.e., the permeate amount, increases. For this reason, the lower limit is preferably 180 um or more, more preferably 320 um or more, still more preferably 550 um or more. [0057] 3. Production Method of Porous Molded Body The method for producing the porous molded body of the present invention is described below by taking a hollow-fiber membrane composed of a crystalline polymer and an inorganic particle as an example. The production method of the hollow-fiber membrane preferably includes: 1) a step of applying a pressure to a membrane forming solution containing a crystalline polymer and an inorganic particle on a liquid feeding line before a spinneret, 2) a step of discharging the membrane forming solution pressurized in 1) above from the spinneret to form an unoriented hollow-fiber membrane with high thickness uniformity by thermally induced phase separation near the crystallization temperature of the membrane forming solution, and 3) a step of stretching the unoriented hollow-fiber membrane obtained in 2) above in the longitudinal direction of the membrane to obtain a highly oriented columnar texture. [0058] 3-1. Preparation of Membrane Forming Solution The production method of a hollow-fiber membrane in this embodiment includes a step of preparing a solution in which a crystalline polymer and an inorganic particle are mixed. A membrane forming solution is prepared by dissolving a crystalline polymer and an inorganic particle in a poor or good solvent for the crystalline polymer at a relatively high temperature of not less than the crystallization temperature. In addition, before the preparation of the membrane forming solution, a master pellet containing inorganic particles dispersed in a crystalline polymer is prepared in advance and the pellet is dissolved in a good or poor solvent and thus a polymer molded body in which an inorganic particle is incorporated into a columnar texture can be produced. This is considered because when a master pellet is prepared, a crystalline polymer is fused around an inorganic particle and spherical and columnar textures are formed while allowing the inorganic particle and the crystalline polymer in the periphery thereof to serve as a core. The master pellet is preferably prepared by a method of kneading the inorganic particle by a multi-screw kneader, etc. while heating the pellet at not less than the melting point of the crystalline polymer. Kneading by a multi-screw kneader also provides an effect of enabling those having a secondary particle diameter, such as cerium hydrous oxide, to be finely dispersed. FIG. 8 is an enlarged image of a master pellet in which a cerium hydrous oxide having an average particle diameter of 4.5 Um is kneaded into a vinylidene fluoride homopolymer, and it is seen that the cerium hydrous oxide is more finely dispersed than the average of secondary particle diameters at a time when the oxide is in a particulate state. [0059] When the concentration ratio of a crystalline polymer and an inorganic particle to a solvent in the membrane forming solution is high, a columnar texture and an inorganic particle are increased and at the same time, a hollow-fiber membrane having high strength is obtained. On the other hand, when the polymer concentration is high, the porosity of the hollow-fiber membrane becomes large, and the pure-water permeation performance is enhanced. Accordingly, the ratio of the sum of the weight of crystalline polymer and the weight of inorganic particle to the weight of membrane forming solution is preferably from 30 to 60 wt%, more preferably 35 wt% or more and less than 50 wt%, still more preferably 41 wt% or more and less than 48 wt%. [0060] In the present description, the poor solvent is a solvent in which the crystalline polymer cannot be dissolved to a concentration of 5 wt% or more at a low temperature of 60°C or less but can be dissolved to a concentration of 5 wt% or more in a high- temperature region between 60°C or more and not more than the melting point of the crystalline polymer. The good solvent is a solvent in which the crystalline polymer can be dissolved to a concentration of 5 wt% or more even in a low-temperature region of 60°C or less. The non-solvent is defined as a solvent in which the crystalline polymer is neither dissolved nor swollen at a temperature up to the melting point of the crystalline polymer or the boiling point of the solvent. [0061] The poor solvent for the crystalline polymer includes cyclohexanone, isophorone, y-butyrolactone, methyl isoamyl ketone, propylene carbonate, dimethyl sulfoxide, etc., and a mixed solvent thereof. The good solvent includes N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, methyl ethyl ketone, acetone, tetrahydrofuran, tetramethylurea, trimethyl phosphate, etc., and a mixed solvent thereof. The non-solvent includes water, hexane, pentane, benzene, toluene, methanol, ethanol, carbon tetrachloride, o-dichlorobenzene, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol, an aliphatic hydrocarbon such as low-molecular-weight polyethylene glycol, an aromatic hydrocarbon, an aliphatic polyhydric alcohol, an aromatic polyhydric alcohol, a chlorinated hydrocarbon, other chlorinated organic liquids, and a mixed solvent thereof. [0062] 3-2. Formation of Hollow-Fiber Membrane In the hollow fiber membrane forming step, a thermally induced phase separation method, in which phase separation is induced by temperature change, is utilized to obtain a (substantially) unoriented hollow-fiber membrane from a membrane forming solution containing a crystalline polymer and an inorganic particle. At this time, when the membrane forming solution before phase separation is retained and pressurized, a fibril grows during the subsequent solidification by cooling, and the columnar texture of the present invention having an aspect ratio of 2 or more is obtained. In this instance, it has been found that the addition of an inorganic particle enables to obtain a columnar texture with high thickness uniformity compared to a case of including only a crystalline polymer (fibrous texture in JP-A-2006-297383). This is considered because due to addition of a particle, the crystalline polymer in the periphery of the particle first produces a crystal nucleus and then the crystalline polymer is incorporated into a fibril in the periphery of the crystal nucleus to promote the growth of the fibril. This columnar structure with high thickness uniformity enables providing high orientation in the subsequent stretching step. Accordingly, more preferred method include obtaining the columnar structure with high thickness uniformity and performing stretching basically at a ratio of 2.0 times or more to form a columnar texture being highly oriented in the long-side direction (stretching direction). A membrane with higher strength can be obtained by this method, and the method is described in detail below. [0063] As for the phase separation method, a non-solvent induced phase separation method using a non-solvent for the polymer, and a thermally induced phase separation using temperature change are known. Furthermore, as for the thermally induced phase separation method, a solid-liquid separation method in which crystallization of a polymer occurs, a liquid-solid phase separation method in which crystallization of a solvent occurs, and a liquid-liquid phase separation method in which phases are separated in a liquid-liquid state, are known. [0064] Among these, in the solid-liquid phase separation method, it has been found that phase separation occurs due to production and growth of a crystal nucleus and therefore, not only a spherical texture including a polymer crystal is formed but also the inorganic particle transfers to the surface. Accordingly, when a solid-liquid phase separation method is employed, a porous molded body in which an inorganic particle is held between spherical or columnar textures is obtained, and a polymer concentration and a solvent, inducing the solid-liquid phase separation, are selected. In addition, when a solid-liquid phase separation using a raw material prepared by forming a crystalline polymer and an inorganic polymer into a master pellet is employed, a porous molded body in which an inorganic particle is included inside a texture of the crystalline polymer is obtained. Furthermore, the texture in this porous molded body include fine pores, so that the effect of the inorganic particle included inside (for example, adsorption function) can be utilized. [0065] In phase separation other than the solid-liquid separation, the above-described columnar texture oriented in the length direction of the hollow fiber membrane can be hardly developed. In addition to solid-liquid phase separation, a columnar structure with uniform thickness is obtained using the later-described technique, and this is further stretched at a ratio of 2.0 times or more, whereby a highly oriented columnar texture can be formed. 24 [0066] As a specific method, a hollow part-forming liquid is discharged through an inner tube of a double tube-type spinneret while discharging the above-described membrane forming solution from an outer tube of the double tube-type spinneret, and a polymer in the membrane forming solution discharged in this way is cooled and solidified in a cooling bath to obtain an unoriented hollow-fiber membrane. [0067] At this time, the membrane forming solution is, before being discharged through the spinneret, held at a specific temperature condition for a given time under pressure. The pressure is preferably 0.5 MPa or more, more preferably 1.0 MPa or more. The temperature T of the membrane forming solution preferably satisfies Tc+35°C