FIELD OF THE INVENTION
The present invention relates to development of chitosan zinc-oxide nanoadsorbent coated sand filter bed for dairy industry wastewater treatment. It particularly relates to the development of suitable method for synthesis of chitosan zinc-oxide nanoadsorbent coated sand filter bed for dairy industry wastewater treatment. It specifically relates to the development of effluent treatment plant having chitosan zinc-oxide nanoadsorbent coated sand filter bed in column for treatment of dairy industry wastewater. The present invention also relates to the suitable method for treatment of effluents from dairy industry by using chitosan zinc-oxide nanoadsorbent coated sand filter bed in fixed bed column.
BACKGROUND OF THE INVENTION
Water is a source of life and regarded as the most essential natural resources. Approximately 98% of water available on the earth is seawater but it is unusable because of high concentration of salt and remaining 2% is fresh water, but 1.60% of this is locked up in polar ice caps and glaciers and another 0.36% is found underground in aquifers and wells. Therefore, only about 0.036% of the planets total water supply is accessible in lakes and rivers. Existing freshwater resources are gradually becoming polluted and unavailable due to industrial activities. The increasing contamination of freshwater systems with thousands of industrial and natural chemical compounds is one of the key environmental problems facing worldwide. World Health Organization (WHO) estimates that, about 1.8 million people die from diarrheal diseases annually. Polluted water not only affects the life of present generation but it also affects the life of upcoming generations because of its residues that remains for long time.
Dairy industry is growing at a substantial rate and it generates enormous volumes of effluents through its different operations like pasteurization, bottling, whey generation, cleaning, sanitization, heating, cooling, washing of floor and utensils etc.
The dairy industry leads to water pollution at large scale, not only in terms of the volume of wastewater generated, but also in terms of its characteristics as well. Among all industrial sectors, dairy industry is major contributor of wastewater generation. It requires about 0.2-10 litres of water per litre of processed milk with an average generation of about 2.5 litre of wastewater per litre of the milk processed. Water management in dairy industry is well documented but wastewater production and disposal remains a problematic issue for dairy industry.
Wastewater from the dairy industry contain a high concentration of organic constituents such as proteins, carbohydrates, lipids, BOD, COD, suspended solids, oil and grease. All of these require specialized treatments to prevent environmental problems. To comply with new discharge

standards, the dairy industries have adopted an elaborate effluent treatment protocol that is affecting the overall economy of the industry and increase the cost of conventional treatment systems.
Noteworthy, a number of physical, chemical and biological treatment methods have been reported such as anaerobic, aerobic, advanced oxidation processes, ozonation, electro-oxidation, photochemical oxidation using UV/H2O2, electro-chemical techniques, coagulation or flocculation, ion exchange, membrane technology and biosorption have been used to treat the various industrial watewater. However, these treatment methods are limited because they are too expensive to find a wide application, ineffective in meeting stringent effluent standards and could result in huge amount of sludge. Among these methods, chemical coagulation is a widely used method for the treatment of industrial wastewater, due to its superior removal efficiency of toxic substances. In chemical coagulation processes, aluminum and iron salts are widely used as coagulants that destabilize the colloidal materials and cause the small particles to agglomerate into larger settable flocs, thus effectively reducing the content of organic matter. However, the chemical coagulation method has some disadvantages, such as large chemical addition, sludge generation, economic viability and secondary pollution may arise.
To comply with the discharge standards, the dairy industries in are practicing an elaborate effluent treatment protocol. The main objective of treating dairy industry wastewater is reduction of organic load. The dairy industry wastewater contains large quantities of milk constituents such as casein, lactose, fat inorganic salt, besides detergents and sanitizers used for washing. As per different research findings carried out at national and international levels, a typical untreated dairy wastewater is characterized by high organic loads such as total dissolved solids (TDS), total suspended solids (TSS), pH, electrical conductivity (EC), turbidity, biological oxygen demand (BOD), chemical oxygen demand (COD), oil, grease, phosphate, sulphate, nitrate, ammonical-nitrigen and chloride.
All of these require specialized treatments to prevent environmental problems. Dairy wastewater is characterized by wide fluctuations in flow rates, related to discontinuity in the production cycles of different products. The variable nature of dairy wastewater in terms of volume, flow rates, pH and suspended solids (SS) makes it difficult to choose an effective wastewater treatment regime. To comply with new discharge standards, the dairy industries have adopted an elaborate effluent treatment protocol. This is affecting the overall economy of the plant and increasing the costs of conventional treatment systems.
Based on numerous studies, nanoadsorbents have great potential as effective adsorbents in various processes of wastewater treatment. BOD and COD are the major contributors of the organic load in the wastewater of dairy industry. Chitosan is biopolymer used for adsorption of BOD and COD. Amino groups present in the chitosan serve as chelation sites for adsorption of BOD and COD. Thus, the binding of chitosan onto zinc oxide will probably yield another novel

chitosan zinc oxide (CZnO) nanoadsorbent for the efficient removal of COD and BOD from dairy industry wastewater.
Researchers have shifted their interests to the possibilities of recycling of industrial wastewater with adsorption techniques. Adsorption works on the principle of adhesion. The process of adsorption involves separation of a substance from one phase accompanied by its accumulation or concentration at the surface of another. The adsorbing phase is the ‘adsorbent’ and the material concentrated or adsorbed at the surface of the adsorbing phase is the ‘adsorbate’. Adsorption is commonly employed as a polishing step to remove organic and inorganic contaminants in wastewater. Efficiency of conventional adsorbents is usually limited by the surface area, active sites, lack of selectivity and the adsorption kinetics.
Many researchers have studied the adsorption characteristics of pollutants on the metal oxides coated with sand. Nanoadsorbent coated with sand is capable of adsorbing pollutants to much lower concentrations than precipitation.
A fixed bed column is a chemical adsorption method consisting of an hollow tube, pipe that is filled with a adsorbing material. The purpose of a fixed bed is typically to improve contact between two phases in a adsorption process. A fixed bed column study is important to predict the column breakthrough, which determines the operation life span of the filter bed and generation time. Furthermore, in order to obtain basic engineering data, it is essential to study the continuous flow system. Column operation system may give accurate scale-up information than adsorption capacity from batch system. Hence, there is a need to perform dynamic studies using fixed bed columns. The adsorption behavior of chitosan zinc oxide nanoadsorbent coated sand filter bed was selected for the reduction of simulator organic pollutants (BOD and COD). Thomas, Yoon and Nelson and Adams-Bohart model were most commonly used to analyze the behavior of adsorbent-adsorbate system.
Another method for wastewater treatment of dairy industry is through the membrane technology and the possibility of reuse. Novel studies revealed that, the membrane technology may help in solving problem of attaining a quality of wastewater that can be recycled back to the process. It was tested for various chemical industries and in some food processing industries also. But using this membrane technology the proteinous materials of the dairy effluent were found to be severe foulant for the existing membrane materials. With the advent of membrane technology, there is a significant improvement in effluent treatment but it is not cost effective.
Nanotechnology is one of the most rapidly emerging technology for the remediation of contaminated industrial wastewater. Advances in nanoscale science are providing immense opportunities to develop more cost effective and environmentally acceptable wastewater treatment processes. Nanomaterials are very well suited for water and wastewater treatment owing to their unique and varied properties such as large specific surface area, high reactivity, high degree of functionalization, size dependent properties, affinity for specific target

contaminants, which render them excellent adsorbents and catalysts. Nanoadsorbents and filters combine separation processes are other functions to improve life and efficiency, and can be reused for number of times, thus making them eco-friendly.
There are few reports which reported the chitosan zinc-oxide nanoadsorbent and its various applications and the important ones include Dehaghi et al., 2014 [Journal of Saudi Chemical Society (2014) 18, 348–355] which discloses removal of permethrin pesticide from waterby chitosan–zinc oxide nanoparticle composite as an adsorbent.
Yazdani et. al., 2018 [Polymers 2018, 10, 25] discloses chitosan–zinc (II) complexes as a bio-sorbent for the adsorptive abatement of phosphate: Mechanism of complexation and assessment of adsorption performance.
Sharma et. al., 2009 [Environmental Technology, 30:6,583-609] discloses nano-adsorbents for the removal of metallic pollutants from water and wastewater.
Mostafa Khajeh Ali and RezaGolzary, 2014 [Biomolecular Spectroscopy, Volume 131, 15 October 2014, Pages 189-194] discloses the synthesis of zinc oxide nanoparticles–chitosan for extraction of methyl orange from water samples: Cuckoo optimization algorithm–artificial neural network.
The patent application no.CN101717529A discloses chitosan composite material and a method for preparing the same. The method mainly solves the technical problems of poor biocompatibility or antibacterial property of the conventional chitosan composite material. The technical scheme comprises the following key points: the chitosan composite material is a nano silver/nano zinc oxide/chitosan composite material prepared from a silver compound, the chitosan and a zinc compound, wherein the silver compound is 0.1 to 5 mass percent of the chitosan; and the zinc compound is 1 to 30 mass percent of the chitosan. The method for preparing the chitosan composite material comprises the following steps of: dissolving the chitosan and the compounds of silver and zinc with acid solution; spray drying the solution into small granules or drying the solution to form a film on clean glass in a spin coating way; dipping the small granules or the film in hot diluted alkaline solution so as to transform zinc ions in the chitosan into nano-scale zinc oxide; reducing silver ions into nano-scale silver under the effects of the chitosan and illumination; and washing the product with distilled water and drying the washed product so as to obtain the required nano silver/nano zinc oxide/chitosan composite material. The product of the invention is characterized by high antibacterial property and light color and the like. The preparation method has the advantages of environmental friendliness, simple process flow, low preparation cost and the like.
Though there are several reports in the literature for the chitosan zinc-oxide nanoadsorbents but there is no report for the chitosan zinc-oxide nanoadsorbent coated sand filter bed for dairy industry wastewater treatment. Keeping in view of the above facts, the need of an hour is to develop a suitable technology for recycling a reasonable quantity of the wastewater produced in

the dairy industry without affecting the overall economy. Therefore, the present inventors have developed the chitosan zinc-oxide nanoadsorbent coated sand filter bed for efficient dairy industry wastewater treatment which overcomes the drawbacks of the prior art effluent treatment systems.
OBJECTS OF THE INVENTION
The primary object of the present invention is the development of chitosan zinc-oxide nanoadsorbent coated sand filter bed for dairy industry wastewater treatment.
The other object of the present invention is the development of method for synthesis of chitosan zinc-oxide nanoadsorbent coated sand filter bed for dairy industry wastewater treatment.
The other object of the present invention is the development of effluent treatment system/plant having the chitosan zinc-oxide nanoadsorbent coated sand filter bed for treatment of dairy industry wastewater.
Further object of the present invention is the development of method for treatment of dairy industry wastewater by using chitosan zinc-oxide nanoadsorbent coated sand filter bed.
The other object of the present invention is the development of chitosan zinc-oxide nanoadsorbent coated sand filter bed which are very much effective in treatment of dairy industry wastewater and cost-effective.
The other object of the present invention is the development of chitosan zinc-oxide nanoadsorbent coated sand filter bedwhich are easy to use with little technical expertise.
The other object of the present invention is the development of chitosan zinc-oxide nanoadsorbent coated sand filter bed which are safe and practical to use.
Still another object of invention is to develop CZOCS filter bed packed laboratory scale column and is performance evolution through kinetic adsorption studies.
SUMMARY OF THE INVENTION
Chitosan zinc oxide (CZnO) nanoadsorbent was synthesized by chemical precipitation method and characterized by using SEM, EDS, XRD, FT-IR and DSC. Maximum per cent reduction efficiency of BOD using chitosan zinc oxide coated sand (CZOCS) filter bed was found at optimized CZnO coating dosage of 1.5 M, contact time of 120 min, pH of 6 and initial concentration of 50 mg/L. Similarly, maximum per cent reduction efficiency of COD using

CZOCS filter bed was found at optimized CZnO coating dosage of 1.5 M, contact time of 120 min, pH of 6 and initial concentration of 50 mg/L. Break through points, exhaustion point, break through capacity, exhaustion capacity and degree of column utilization were determined for optimized at CZOCS filer bed depth. Kinetic models of Thomas, Yoon-Nelson and Adams-Bohart models were used in fixed bed column adsorption study. Effect of filtration time and bed height on breakthrough points for BOD adsorption using CZOCS filter bed was found maximum breakthrough capacity (BTC) of 143.00 mg/g, exhaustion capacity (EC) of 143.50 mg/g and degree of column utilization (DCU) of 99.65% at 40 cm bed height. Effect of filtration time and bed height on breakthrough points for COD adsorption using CZOCS filter bed was resulted maximum BTC of 183.25 mg/g, EC of 185.75 mg/g and DCU of 98.65% at 40 cm bed height. Thomas model was found best fitted model for adsorption of BOD and COD using CZOCS filter bed at 30 cm bed height. The benefit cost ratio of development of CZOCS filter bed was found to be 1.23:1.
BRIEF DESCRIPTION OF FIGURES
Fig.1. Describes a flow diagram of existing dairy effluent treatment plant (ETP) with sampling points.
Fig.2. Describes a chemical reaction followed for synthesis of chitosan zinc-oxide (CZnO) nanoadsorbent.
Fig.3. Describes a scanning electron microscope (SEM) image of chitosan zinc-oxide (CZnO) nanoadsorbent.
Fig.4 Describes a elemental detection sensor spectrum (EDS) of chitosan zinc-oxide (CZnO) nanoadsorbent.
Fig.5. Describes a topography image of chitosan zinc-oxide (CZnO) nanoadsorbent.
Fig.6. Describes diffractogram results of standard ZnO, chitosan and synthesized chitosan zinc-oxide (CZnO) nanoadsorbent.
Fig.7. Describes FT-IR spectrum results of the standard ZnO, chitosan and synthesized chitosan zinc-oxide (CZnO) nanoadsorbent.
Fig.8. Describes differential scanning calorimeter (DSC) thermogram results of the chitosan zinc-oxide (CZnO) nanoadsorbent.
Fig.9. Describes a scanning electron microscope (SEM) image of chitosan zinc-oxide coated sand (CZOCS) filter bed.
Fig.10. Describes a elemental detection sensor spectrum (EDS) of chitosan zinc-oxide coated sand (CZOCS) filter bed.
Fig.11. Describes a diffractogram results of chitosan zinc-oxide coated sand (CZOCS) filter bed.

Fig.12. Describes thermo gravimetric analysis results of chitosan zinc-oxide coated sand (CZOCS) filter bed.
Fig.13. Describes results of chitosan zinc-oxide (CZnO) nanoadsorbent coating dosage and contact time on per cent reduction efficiency of BOD (at pH 7 and initial BOD concentration of 100 mg/L).
Fig.14. Describes results of the effect of pH on per cent reduction efficiency of BOD (at CZnO nanoadsorbent coating dosage of 1.5 M, contact time of 120 min and initial BOD concentration of 100 mg/L).
Fig.15. Describes results of the effect of initial BOD concentration on per cent reduction efficiency of BOD (at CZnO nanoadsorbent coating dosage of 1.5 M, contact time of 120 min and pH 6).
Fig.16. Describes the results of the effect of chitosan zinc-oxide (CZnO) coating dosage and contact time on per cent reduction efficiency of COD (at pH 2 and initial COD concentration of 200 mg/L).
Fig.17. Describes the results of the effect of pH on per cent reduction efficiency of COD (at 1.5 M chitosan zinc-oxide (CZnO) coating dosage, 120 min contact time and initial COD concentration of 200 mg/L).
Fig.18. Describes the results of effect of initial COD concentration on per cent reduction efficiency of COD (at 1.5 M CZnO coating dosage, 120 min contact time and pH 2).
Fig.19. Describes the experimental setup view of the column adsorption study of nanoadsorbents coated sand filter bed.
Fig.20. Describes the results of effect of filtration time and bed height on breakthrough curves (BTCs) for BOD adsorption using CZOCS sand filter bed (at 1.5 M CZnO coated sand, initial BOD concentration of 500 mg/L and pH 6).
Fig.21. Describes the results of effect of filtration time and bed height on breakthrough curves (BTCs) for COD adsorption using CZOCS sand filter bed (at 1.5 M CZnO coated sand, initial COD concentration of 3000 mg/L and pH 6.).
Fig.22. Describes the results of effect of chitosan zinc-oxide coated sand (CZOCS) filter bed height on adsorption capacity of BOD at 20% break through and 95% exhaustion points.
Fig.23. Describes the results of effect of chitosan zinc-oxide coated sand (CZOCS) filter bed height on adsorption capacity of COD at 20% break through and 95% exhaustion points.
Fig.24. Describes the results of linear plots of Thomas model for BOD adsorption by using CZOCS at different bed height (at 1.5 M CZOCS, initial BOD concentration of 500 mg/L and pH 6).
Fig.25. Describes the results of linear plots of Yoon and Nelson model for BOD adsorption by using CZOCS at different bed height (at 1.5 M CZOCS, initial BOD concentration of 500 mg/L and pH 6).
Fig.26. Describes the results of linearised form of Adams-Bohart model for BOD adsorption by using CZOCS at different bed height (at 1.5 M CZOCS, initial BOD concentration of 500 mg/L and pH 6).

Fig.27. Describes the results of linear plots of Thomas model for COD adsorption by using CZOCS at different bed height (at 1.5 M CZOCS, initial COD concentration of 3000 mg/L and pH 6).
Fig.28. Describes the results of linear plots of Yoon and Nelson model for COD adsorption by using CZOCS at different bed height (at 1.5 M CZOCS, initial COD concentration of 3000 mg/L and pH 6).
Fig.29. Describes the results of linear plots of Adams-Bohart model for COD adsorption by using CZOCS at different bed height (at 1.5 M CZOCS, initial COD concentration of 3000 mg/L and pH 6).
STATEMENT OF THE INVENTION
Method for development of chitosan zinc-oxide nanoadsorbent coated sand filter bed for dairy industry wastewater treatment comprising:
a. synthesis of Chitosan zinc oxide (CZnO) nanoadsorbent;
b. dissolving the different dosages of synthesized Chitosan zinc oxide (CZnO)
nanoadsorbent at step (a) in acetic acid;
c. mixing of the above solution of step (b) with effective amount of activated sand
and then stirred continuously to form CZnO sand mixed template solution;
d. calcination of the CZnO sand mixed template solution obtained at step (c) at 200
ºC within heating rate at the 5 ºC per minutes and maintained at that temperature
for 120 min to form the Chitosan zinc-oxide coated sand (CZOCS) filter bed and
then cooled to room temperature; and
e. washing the obtained Chitosan zinc-oxide coated sand (CZOCS) filter bed with
distilled water to remove loose precipitates to get the Chitosan zinc-oxide coated
sand (CZOCS) filter bed for dairy industry wastewater treatment.
Method for the synthesis of Chitosan zinc oxide (CZnO) nanoadsorbent comprises:
a. dissolving zinc oxide in acetic acid and nitric acid;
b. the chitosan is added into the above solution of step (a) and stirred for 3 h at 500
rpm;
c. then the above mixture of step (b) is subjected to sonication for 15 min and the pH
of the solution is increased upto 10 by adding sodium hydroxide solution drop

wise to form the precipitate of Chitosan zinc oxide and this precipitate is kept in water bath at 60 °C for 3 h;
d. the precipitated Chitosan zinc oxide at step (c) is filtered and washed with
distilled water and then dried in a hot air oven at 50 °C for 24 h; and
e. then the dried Chitosan zinc oxide obtained at step (d) is subjected to reduction of
the particle size to get the Chitosan zinc oxide nanoadsorbent.
The concentration of zinc oxide is 3.75 g and is dissolved in 500 mL of 1% acetic acid, to this solution 50 mL of 60% HNO3 is added. The effective amount of chitosan added is 5 g. The nano size is obtained by using high speed cryo ball mill. The dosage of chitosan zinc oxide nanoadsorbent ranges between 0.5 to 2 M and preferably 1.5 M. The activated sand is formed by sieving the 5 kg of sand by using 300 µ sieve and washed twice with distilled water, then washed sand is soaked with 5L of 1M HCl solution for 12 h, soaked sand is then rinsed with distilled water and finally activated by keeping the rinsed sand in hot air oven at 105 ºC for 24 h. The effective amount of activated sand used is 1 kg.
Effluent treatment system for the treatment of wastewater from dairy industry comprising Chitosan zinc-oxide nanoadsorbent coated sand filter bed filled in column and which is provided with the effluent reservoir along with dosing pump and also influent reservoir. The column is fixed bed column.
Method for treatment of dairy industry wastewater comprising the Chitosan zinc-oxide nanoadsorbent coated sand filter bed.
DETAILED DESCRIPTION OF THE INVENTION
The wastewater samples required for the experiments were collected from Karnataka Milk Federation (KMF-Nandini), Ballary, Karnataka (India). The dairy industry has an effluent treatment plant (ETP) suitable for processing capacity of two lakh liters per day. The ETP has seven sampling points viz., wastewater inlet to ETP (P1), equalization tank (P2), primary clarifier (P3), aeration tank (P4), secondary clarifier (P5), chemical oxidation tank (P6), sand and activated carbon filter (P7). For the present experiment, the effluent samples were collected at the end of each sample collection point as shown in Fig. 1. BOD load of wastewater was found to be 1005.16, 976.50, 861.68, 676.50, 658.66, 463.50 and 331.66 mg/L at sampling points of P1, P2, P3, P4, P5, P6 and P7. Similarly, COD load of wastewater samples collected at each sampling

points were found to be 10737.87 mg/L at P1, 9878.87 mg/L at P2, 8650.08 mg/L at P3, 5015.77 mg/L at P4, 4733.14 mg/L at P5, 2755.40 mg/L at P6 and 711.80 mg/L at P7.
Fig. 2 represents the chemical reactions followed for synthesis of Chitosan zinc oxide nanoadsorbent. 3.75 g of zinc oxide was dissolved in 500 mL of 1% acetic acid, to this solution 50 mL of 60% nitric acid was added. Then 5 g of chitosan was added to this solution and stirred for 3 h at 500 rpm by using magnetic stirrer. Sonication was performed by using ultrasonicator for 15 min and the pH of the solution was increased upto 10 by adding 4M sodium hydroxide solution drop by drop. After reaching pH 10 precipitate of CZnO was formed and this precipitate was kept in water bath at 60 °C for 3 h. The precipitate was filtered and washed with distilled water and dried in a hot air oven at 50 °C for 24 h. Synthesized CZnO particle size was reduced to nano size using high speed cryo ball mill and preserved in an airtight glass container for further use.
SEM images of standard chitosan and standard ZnO were showed round and smooth surface morphology. Rough surface and rod like formations were observed in synthesized CZnO nanoadsorbent (Fig. 3). Variations were observed in the surface morphology among standard chitosan, standard ZnO and synthesized CZnO nanoadsorbent. This might be due to increased NaOH concentration during synthesis of CZnO and increased the interaction between chitosan and ZnO. EDS shown the characteristic peaks of zinc (59.98%), chlorine (0.43%) and carbon (39.60%) as shown in Fig 4. These characteristic peaks might be due to ZnO was cross linked between chitosan and NaOH.
Fig. 5 shows the topography image obtained by using AFM for CZnO nanoadsorbent which indicates the height (Y axis) and width (X axis) of the particles. Surface roughness value of 6.75 nm was obtained due to the rough surface area of the CZnO nanoadsorbent. The 2D micrograph showed the rod like structure of ZnO, thereby imparting larger surface area of CZnO. This might be due to enhanced porosity and owing to increased one sided dimensions of the CZnO particles. All these characteristics are expected to enhance the adsorption capacity of CZnO lead to very high values.
Diffractogram of standard ZnO, chitosan and synthesized CZnO nanoadsorbents are depicted in Fig. 6. A definite line broadening of the XRD peaks indicated the material consists of particles in nano scale range. The diffraction peaks of CZnO indicated the nano crystalline nature and identical to the hexagonal phase with Wurtzite structure. The CZnO peaks at angle (2θ) was around 19.80°, 33.18°, 34.47°, 36.29°, 47.53°, 48.38°, 56.57°, 62.86º, 66.42º, 67.95º and 69.08° correspond to the reflection from 4.48°, 2.81°, 2.69°, 2.59°, 2.47°, 1.91°, 1.87°, 1.62°, 1.47°, 1.40°, 1.37° and 1.35° crystal planes, respectively. All the diffraction peaks are in good agreement with those of hexagonal wurtzite structure of ZnO (JCPDS card 36-1451, 1986). This indeed revealed that, it was successful formation of nano sized chitosan/ZnO. As seen in the

XRD patterns, the straight base line and sharp peaks of standard ZnO, chitosan and CZnO were merged with each other at 47.57°, 47.53° and 48.38° 2-theta angle. This indicated that, the CZnO composite was a well crystalized material compared with separated ZnO nano particles.
The FT-IR spectra of standard ZnO, chitosan and synthesized CZnO nanoadsorbent are depicted in the Fig. 7. The FT-IR spectra of CZnO showed bands at 3365.78 and 2881.65 cm-1 due to the stretching vibration mode of NH2 and OH groups. The peaks at 2428.38 and 1788.01 cm-1 were typical of carboxylic acid O-H stretching vibration, while the band at 1647.21 and 1560.41 cm-1 were due to the amide I group (N-H bend). The transmission peak at 1340.53 cm-1 is attributed to the C-H deformation. The special broad peaks at 1151.50 and 1026.13 cm-1 are attributed to the vibration mode of the alkoxy C-O. In comparison with chitosan, the broader and stronger peak shifted considerably to lower wave number at 3477 cm-1, which indicated strong attachment of ZnO to the amide groups of chitosan molecules. The transmission peaks at 2918, 2860 cm-1 are due to asymmetric stretching of CH3 and CH2 of chitosan polymer. A new broad absorption band at the range of 580-400 cm-1 was found in the FT-IR spectra of CZnO nanoadsorbent, which were ascribed to the vibration of C-H and C-O groups. The reason for the above phenomena was the formation of hydrogen bond between ZnO and chitosan. This result indicated that, the CZnO composite was prepared successfully without damaging the crystal structure of ZnO core.
DSC thermogram of CZnO nanoadsorbent is shown in the Fig. 8. The CZnO exhibited first transition at 80-100 °C due to moisture vaporization and second highest transition showed endothermic peak at 240 to 260 ºC at nearly corresponding to its melting point. This might be due to transition peak of the native chitosan is in the range of 200-450 ºC and it is associated with the decomposition of chitosan. Based on these results, the calcination temperature of 200 ºC was selected for preparation of CZnO nanoadsorbent coated sand filter bed.
CZOCS filter bed was developed according to following methodology. Five kilogram of sand was sieved by using 300 µ (0.3 mm) sieve and washed twice with distilled water. Then, sand was soaked with 1M HCl solution (5 L) for 12 h. Soaked sand was rinsed with distilled water and activated by keeping the washed sand in hot air oven at 105 ºC for 24 h. Different dosages (0.5, 1, 1.5 and 2 M) of synthesized CZnO nanoadsorbent were dissolved in 2% acetic acid (1000 mL) using magnetic stirrer at 1000 rpm for 30 min. Then, 1 kg of activated sand was added into prepared CZnO solution. The resultant solution was stirred for 24 h at 1000 rpm using laboratory stirrer. CZnO sand mixed template solution was calcinated in muffle furnace at 200 ºC within heating rate at the 5 ºC per minutes and maintained at that temperature for 120 min. Calcinated samples were cooled to room temperature at the rate of 10 ºC/min. Coated sand was washed four times with distilled water to remove loose precipitates. It was then dried at room temperature and used for further experiments.
Surface morphology of uncoated sand and CZnO nanoadsorbents coated sand filter bed are depicted in Fig.9. Nanoadsorbents coated sand filter bed found to be significantly rough surface and larger cracks. This might be due to the binding between chitosan, zinc oxide, iron oxide and

graphen oxide species on the layer-structure of sand (Fig. 10). Rough surface of CZOCS had confirmed the presence of Zn on the surface.
EDS spectrum of CZOCS is depicted in Fig.10. The characteristic peaks of C, O and Zn were found to be weight per cent of 25.96, 28.51 and 45.54 were confirmed in the EDS spectra. These characteristic peaks might be due to ZnO was cross-linked between chitosan and NaOH. The results of the XRD reveal that, high intensity diffraction peak (Fig.11) of activated sand found at 2-theta angle of 26.96º. XRD pattern of CZnO showed the presence of sharp peaks corresponding to the zinc blend crystal structure. The XRD profile of sand (SiO2) and CZnO depicts the presence of sharp diffraction peaks, those positions fully matched with the bare week peaks of CZOCS. The presence of weak XRD peaks in the CZOCS can be attributed to the nature of small amount of ZnO. The XRD patterns of activated sand, CZnO and CZOCS were matched exactly at 2-theta angle of 70.26°. This might be due to the presence of the presence of CZnO on the surface of the CZOCS filter bed.
The TGA thermogram of CZOCS is shown in the Fig.12. The CZOCS exhibited first transition for weight loss from 34.44 to 172.39 ⁰ C. This might be due to moisture vapourization. The second highest transition showed endothermic peak from 172.39 to 598.23 ºC at nearly corresponding to its melting point of CZnO. This might be due to transition peak of the native chitosan is in the range of 200-450 ºC and it is associated with the decomposition of chitosan.
Effect of CZnO nanoadsorbent coating dosage and contact time on per cent reduction efficiency of BOD (at pH 7 and initial BOD concentration of 100 mg/L) is illustrated in Fig.13. The % RE of BOD increased from 40.14±0.30 to 95.22±0.71% with the beginning of the contact time from 20 to 120 min. This could be attributed to large number of vacant binding sites (as a result of grafting the extra functional groups) were available for adsorption during the initial stages. After reaching the plateaus, the equilibrium is achieved at 95.22 mg/L of BOD adsorbed by CZOCS filter bed. The experiment was continued up to 3 h of contact time to obtain equilibrium concentration at the solid/liquid interface. There is no change in BOD removal was observed when the time is prolonged than the 3 h contact time.
Increased pH from 2 to 6 led to increased % RE of the BOD from 57.24±0.26 to 90.03±0.39% (Fig. 14). In the acidic conditions, the % RE of BOD was found to be low. This might be due to presence of a high number of H+ ions causing increased hindrance to the diffusion of organic (contributing to BOD) ions. From the figure it is analyzed that, pH of 6 was found to be optimum for the maximum % RE of BOD (90.03±0.39%). Hence, this optimized pH value of 6 was used for the rest of the experimental work. Further increased pH from 8 to 12, per cent reduction efficiency of the BOD decreased from 89.18±0.38 to 84.27±0.36. This might be due to above pH of 6 the positive charge on the chitosan surface decreased and it became insoluble, this was negatively affected the treatment process and decreased the % RE of BOD.

Effect of initial BOD concentration on per cent reduction efficiency of BOD is depicted in Fig.15. Initial BOD concentration increased from 50 to 300 mg/L, the % RE of BOD decreased form 94.44± 0.41 to 64.89±0.28%. This might be due to more organic substances are adsorbed on the surface of the CZnO nanoadsorbent coated sand filter bed. Thus distribution coefficient decreases. This suggested the limiting number of absorption sites available for absorption at higher initial concentration of the BOD.
Effect of CZnO nanoadsorbent coating dosage and contact time on per cent reduction efficiency of COD (at pH 2 and initial COD concentration of 200 mg/L) is illustrated in Fig. 16. From the figure it is noticed that, the % RE of COD increased from 47.47±0.35 to 84.55±0.63% with the beginning of the contact times from 20 to 120 min and CZnO nanoadsorbent coating dosages from 0.5 to 1.5 M. In the initial stages, the % RE of the COD by the CZOCS increased rapidly due to the abundant availability of active binding sites on the adsorbent, and with gradual occupancy of these active sites, the adsorption became less efficient in the later stages. The equilibrium status can be achieved after 120 min at 1.5 M.
The % RE of COD at different pH values is shown in Fig. 17. The pH will affect the surface charge of CZnO and affect the stabilization of the suspension. The COD reduction was found to be highest at pH of 6. At this pH the % RE of COD was 85.44±0.57%. The optimum pH for the effective removal of COD is 6 and the COD removal is not effective above pH 6. This might be due to the weak interaction between the amino groups of chitosan and oppositely charged ions present in the effluent. Furthermore, CZnO will lose its charge and chitosan become deprotonated at higher pH.
Effect of initial COD concentration on per cent reduction efficiency of COD (at 1.5 M CZnO coating dosage, 120 min contact time and pH 6) is presented in Fig.18. The % RE of COD was found to be increased with an increase in the initial COD concentration, and after reaching saturation level, it remained almost constant. The COD reduction decreased from 85.08±0.64 and 59.56±0.44% when the initial COD concentration increased from 50 to 300 mg/L. The % RE of COD is high at lower initial substrate concentration, and the rate of adsorption of the organic ions increased progressively due to the increasing driving force. However, at 200 mg/L of initial COD concentration, the CZnO coated sand reached their saturation points. Thus, the ratios of the initial number of organic molecules to the available adsorption sites of the CZnO coated sand filter bed decreased accordingly.
A fixed bed column study is important to predict the column breakthrough, which determines the operation life span of the bed and generation time. Furthermore, in order to obtain basic engineering data, it is essential to study the continuous flow system. Adsorption capacity from column study gaves accurate scale-up information than the batch adsorption study. Hence, there is a need to perform dynamic studies using fixed bed columns.

Dynamic flow adsorption experiments were conducted in a polyvinyl chloride (PVC) column of about 3 cm internal diameter and 50 cm length (Fig. 19). The column provided with four sampling points at 10 cm bed height and each bed heights were underlined by 2 cm of glass wool. Addition of glass wool was made to improve the flow distribution. The bed height of the column was maintained upto 40 cm. The column was packed with the nanoadsorbent coated sand filter bed without any air gaps. Top and bottom end of the column was covered with end cap filled with 2 cm of glass wool to prevent the flowing of adsorbent out from the column outlet. At each 10 cm height, the tap connections were made to collect filter samples at an interval of one hour. The influent was pumped from the reservoir into the column by dosing pump in an up-flow direction. The up-flow operation was chosen to increase the contact time and to avoid channeling of the influent. Flow rate of 10 mL/min was maintained in the column by using dosing pump. Samples were collected at every one hour from the column. The parameters considered in fixed-bed column adsorption study for adsorption of organic pollutants by using nanoadsorbent coated sand filter beds are listed in Table 1.
Table 1. Parameters considered in fixed-bed column adsorption study for adsorption of BOD and COD by using CZOCS filter bed
Adsorbent Pollutant Z (cm) pH C0 madsorbent(g) Qy(mL/min) Qt (h) ��(L)
10 6 500 118.00 10
20 6 500 236.00 10
BOD 51 30.60
30 6 500 354.00 10
CZOCS 40 6 500 472.00 10
(1.5 M) 10 6 3000 115.18 10
20 6 3000 230.36 10
COD 43 25.80
30 6 3000 345.54 10
40 6 3000 460.72 10
Z = Bed height (cm); C0= Influent concentration (mg/L); madsorbent = Mass of adsorbent (g);
Qy= Influent flow rate (mL/ min); Qt = Total flow time of influent (h); ��= Total volume of
influent sent (L)
Fig. 20 shown the break through curves (BTCs) obtained from BOD adsorption on CZOCS filter bed for different bed heights of 10, 20 30 and 40 cm, with constant flow rate of 10 mL/min, 1.5 M CZnO coated sand, initial BOD concentration of 500 mg/L and pH 6, respectively. The results revealed that, by increasing the bed height, the break through time sifted to increase. By increasing bed height from 10 to 40 cm, the per cent removal efficiency of BOD increased. This is supported by used CZOCS filter bed at different bed heights. Detected breakthrough time (tb) with increase in bed height is an expected result. As the bed height is increased, the exhaustion time increased. Hence, break through capacity, exhaustion capacity and degree of column utilization were increased. This might be due to the higher adsorbent loading, the contact time increased and in turn increases the “sweep efficiency”. As a result, more adsorbent surface are

exposed to flow and increase in the removal efficiency of BOD. Further, higher breakthrough time gives better intra-particle diffusion phenomena and higher will be the adsorption capacity of column.
The effect of filtration time and bed height on breakthrough curves (BTCs) for COD adsorption by CZOCS filter bed at different bed heights of 10, 20, 30 and 40 cm with constant flow rate of 10 mL/min, 1.5 M CZnO nanoadsorbent coated sand, initial COD concentration of 3000 mg/L and pH 6 were illustrated in Fig.21. Breakthrough and exhaustion times were increased with increasing the bed height. The breakthrough and exhausting times were increased from 1 to 11.85 h and 1 to 33 h at 10 cm bed height, 11.85 to 15.29 h and 33 to 34.19 h at 20 cm bed height, 15.29 to 25.03 and 34.19 to 37.16 h at 30 cm bed height, 25.03 to 30.26 h and 37.16 to 40.96 at 40 cm bed height, respectively. As the bed height increases, the COD in influent had more time to contact with adsorbent that resulted in higher COD removal efficiency. The slope of breakthrough curve decreased with increasing bed height, which resulted in a broadened mass transfer zone. High COD uptake was observed at the highest bed height due to an increase in the surface area present in the CZOCS filter bed, which provided more binding sites for the adsorption. Hence, break through capacity, exhaustion capacity and degree of column utilization were increased.
Effect CZOCS filter bed height on adsorption capacity of BOD at 20% break through and 95% exhaustion points are depicted in Fig. 22. The adsorption capacity of BOD at 20% break through point (qB) increased from 313.84 to 1078.48 mg/g with increasing the bed height from 10 to 40 cm. This might be due to the lower bed height (10 cm) was saturated faster than the higher bed height (40 cm) and shortened the mass transfer. Similarly, adsorption capacity of BOD at 95% column exhaustion point (qE) increased from 611.04 to 1089.63 mg/g with increased bed heights. This is attributed to increase in availability of adsorption sights at higher bed heights for BOD adsorption and intra-particle diffusion of the organic species occurred simultaneously with the dominance of bed heights.
Effect CZOCS filter bed height on adsorption capacity of COD at 20% break through and 95% exhaustion points are depicted in Fig. 23. The value of adsorption capacity of COD at 20% break through point (qB) increased from 2779.58 to 7095.08 mg/g with increase in bed height from 10 to 40 cm. As the bed height increases, the influent had more time to contact with adsorbent that resulted in higher adsorption capacity. Similarly, adsorption capacity of COD at 95% column exhaustion point (qE) increased from 4512.29 to 5600.81 mg/g with increased bed heights from 10 to 40 cm. This might be due to increase in surface area of adsorbent in the presence of nano particles, which provided more active sites at higher bed heights.
Linear plots of Thomas model for BOD adsorption by using CZOCS at different bed height are depicted in Fig. 24. The bed height increased from 10 to 40 cm, the value of qo increased from 661.60 to 1584 mg/g, while the value of KTh decreased from 39.63 to 34.43 L/min mg. The

increase in qo can be explained due to an increase in the surface area of the CZOCS filter bed, which provided more binding sites for the adsorption. The KTh decreased with increased bed height indicating the reduced reaction rate which was ascribed to longer contact time for higher bed height.
Linear plots of Yoon-Nelson model for BOD adsorption by using CZOCS at different bed height are depicted in Fig.25. The Yoon-Nelson constant (KYN) decreased from 0.198 to 0.155min-1 and Time required for 50% adsorbate breakthrough (�) increased from 15.61 to 34.98 min with a subsequent increase in bed height from 10 to 40 cm. This might be due to increased bed height would increased the capacity because additional spaces will be available for the pollutants molecules to be adsorbed on these unoccupied areas. Furthermore, increasing bed height will give a sufficient contact time for these molecules to be adsorbed on the adsorbent surface. A proportional relationship was seen between Yoon-Nelson constant and bed height.
Linear plots of Adams-Bohart model for BOD adsorption by using CZOCS at different bed height are shown in Fig.26. The values of the kinetic constant (KAB) decreased from 66.05 to 11.23 L/mg min and saturation concentration (N0) increased from 13.20 to 58.95 mg/L with increased bed heights from 10 to 40 cm. This might be due to the Adams-Bohart model is based on surface reaction theory and assumes that equilibrium is instantaneous. Hence, the adsorption rate is proportional to both the residual capacity of the adsorbent and bed heights.
Linear plots of Thomas model for COD adsorption by using CZOCS at different bed height are depicted in Fig. 27. The bed height increased from 10 to 40 cm, the value of qo increased from 4710 to 7021 mg/g, while the value of KTh decreased from 7.54 to 5.39 L/min mg. The increase in qo can be explained due to the existence of greater number of binging sites, a higher contact time for adsorption at higher bed heights. The values of KTh decreased with increasing bed height indicating the reduced reaction rate which was ascribed to longer contact time for higher bed height.
Linear plots of Yoon-Nelson model for COD adsorption by using CZOCS at different bed height are depicted in Fig.28. The Yoon-Nelson constant (KYN) decreased from 0.226 to 0.181 min-1 and time required for 50% adsorbate breakthrough (�) increased from 18.08 to 33.44 min with increase in bed height from 10 to 40 cm. This might be due to the bed is saturated in less time for smaller bed heights, the smaller bed height corresponds to less amount of adsorbent.
Linear plots of Adams-Bohart model for COD adsorption by using CZOCS at different bed height are shown in Fig.29. The values of the kinetic constant (KAB) decreased from 67.08 to 12.74 L/mg min and saturation concentration (N0) increased from 29.95 to 53.58 mg/L with increased bed heights from 10 to 40 cm. This might be due to decrease in the solute concentration and broadened mass transfer zone.

Based on the statistical parameters best fitted model was selected. Highest R2 and Adj-R2 value, lowest SSE and RMSE value, the model in terms called as a best fit model. Thomas and Yoon-Nelson models were found to be best fitted model for adsorption of BOD and COD using CZOCS filter bed at 20 cm bed height.
CZnO nanoadsorbent was coated to the sand and conformed the CZnO morphology, elements present, coating roughness on the surface of the sand, crystalline nature of coated sand, CZnO functional groups existence on the surface of the sand and thermal stability of CZOCS filter bed. The maximum per cent reduction efficiency of BOD by using CZOCS filter bed was found at optimized CZnO coating dosage of 1.5 M, contact time of 120 min, 6 pH and initial concentration of 50 mg/L. Similarly, maximum per cent reduction efficiency of COD using CZOCS filter bed was found at optimized CZnO coating dosage of 1.5 M, contact time of 120 min, 6 pH and initial concentration of 50 mg/L.
The total cost for the production of CZOCS filter beds @ 3 kg per day for 270 days was found to be Rs. 35,93,068.46/-.
Effect of filtration time and bed height on breakthrough points for BOD adsorption using CZOCS filter bed was found maximum BTC of 143.00 mg/g, EC of 143.50 mg/g and DCU of 99.65 % at 40 cm bed height. Effect of filtration time and bed height on breakthrough points for COD adsorption using CZOCS filter bed was resulted maximum BTC of 183.25 mg/g, EC of 185.75 mg/g and DCU of 98.65 % at 40 cm bed height.
From the column performance study it was concluded that, adsorption capacity at 20% breakthrough and adsorption capacity at 95% exhaustion were increased with increasing bed height. Evaluation of kinetic models in fixed bed column adsorption study suggested that, Thomas and Yoon-Nelson models were found to be best fitted models for CZOCS filter bed for adsorption of BOD and COD at 20 cm bed height.

We Claim,
1. Method for development of chitosan zinc-oxide nanoadsorbent coated sand filter bed for
dairy industry wastewater treatment comprising:
a. synthesis of Chitosan zinc oxide (CZnO) nanoadsorbent;
b. dissolving the different dosages of synthesized Chitosan zinc oxide (CZnO)
nanoadsorbent at step (a) in acetic acid;
c. mixing of the above solution of step (b) with effective amount of activated sand
and then stirred continuously to form CZnO sand mixed template solution;
d. calcination of the CZnO sand mixed template solution obtained at step (c) at 200
ºC within heating rate at the 5 ºC per minutes and maintained at that temperature
for 120 min to form the Chitosan zinc-oxide coated sand (CZOCS) filter bed and
then cooled to room temperature; and
e. washing the obtained Chitosan zinc-oxide coated sand (CZOCS) filter bed with
distilled water to remove loose precipitates to get the Chitosan zinc-oxide coated
sand (CZOCS) filter bed for dairy industry wastewater treatment.
2. Method as claimed in claim 1 wherein the synthesis of Chitosan zinc oxide (CZnO)
nanoadsorbent comprises:
a. dissolving zinc oxide in acetic acid and nitric acid;
b. the chitosan is added into the above solution of step (a) and stirred for 3 h at 500
rpm;
c. then the above mixture of step (b) is subjected to sonication for 15 min and the pH
of the solution is increased upto 10 by adding sodium hydroxide solution drop
wise to form the precipitate of Chitosan zinc oxide and this precipitate is kept in
water bath at 60 °C for 3 h;

d. the precipitated Chitosan zinc oxide at step (c) is filtered and washed with
distilled water and then dried in a hot air oven at 50 °C for 24 h; and
e. then the dried Chitosan zinc oxide obtained at step (d) is subjected to reduction of
the particle size to get the Chitosan zinc oxide nanoadsorbent.
3. Method as claimed in claim 2 wherein the concentration of zinc oxide is 3.75 g and is dissolved in 500 mL of 1% acetic acid, to this solution 50 mL of 60% HNO3 is added.
4. Method as claimed in claim 2 where in the effective amount of chitosan added is 5g.
5. Method as claimed in claim 2 wherein the nano size is obtained by using high speed cryo ball mill.
6. Method as claimed in claim 1 wherein selected dosage of chitosan zinc oxide nanoadsorbent ranges between 0.5 to 2 M and preferably 1.5 M.
7. Method as claimed in claim 1 wherein activated sand is formed by sieving the 5 kg of sand by using 300 µ sieve and washed twice with distilled water, then washed sand is soaked with 5L of 1M HCl solution for 12 h, soaked sand is then rinsed with distilled water and finally activated by keeping the rinsed sand in hot air oven at 105 ºC for 24 h.
8. Method as claimed in claim 1 wherein the effective amount of activated sand used is 1 kg.
9. Chitosan zinc-oxide nanoadsorbent coated sand filter bed prepared by the method as claimed in any of the preceding claims.
10. Effluent treatment system for the treatment of wastewater from dairy industry comprising Chitosan zinc-oxide nanoadsorbent coated sand filter bed of claim 9 filled in column and which is provided with the effluent reservoir along with dosing pump and also influent reservoir.

11. Effluent treatment system for the treatment of wastewater from dairy industry as claimed in claim 10 wherein the column is fixed bed column.
12. Method for treatment of dairy industry wastewater comprising the Chitosan zinc-oxide nanoadsorbent coated sand filter bed of claim 9.