1. A process for preparing Silica modified polymeric adsorbent from plastic waste, said process comprising: (a) Shredding of plastic waste into ambient size, (b) Dissolving the shredded plastic waste into an organic solvent, (c) Adding Silica Gel and stirring at 50°C -150°C to obtain extract without precipitation in the presence of solvent, and (d) Drying the said extract to obtain the silica modified polymeric adsorbent.

2. The process as claimed in claim 1 wherein the solvent is toluene.

3. The process as claimed in claim 1 wherein the temperature at step (b) is 90-110°C.

4. The process as in claim 1 wherein the said process occurs in single step without precipitation.

5. The process as claimed in claim 1 wherein the plastic waste is class or grade 7 plastic.

6. Silica modified polymeric adsorbent characterized by the XRD pattern as depicted in figure 3.

7. Silica modified polymeric adsorbent prepared by a process as claimed in claim 1.

8. Silica modified polymeric adsorbent for removal of arsenic from wastewater. Dated this the 31st day of May 2024.

Description:Field of the Invention
The present invention relates to novel Silica modified polymeric adsorbent and a process for preparing the same. The novel Silica modified polymeric adsorbent are prepared from waste plastic. It is used for the removal of Arsenic from wastewater.

Background of the invention
Plastics, being inexpensive and durable are preferred material for many domestic and industrial purpose. There are seven types of plastics, (a) Polyethylene Terephthalate (PET), (b) High-Density Polyethylene (HDPE) (c) Polyvinyl Chloride (PVC) Plastic, (d) Low-Density Polyethylene (LDPE), (e) Polypropylene (PP), (f) Polystyrene (PS) and (g) other plastics type. Some are easily recyclable; others need more sophisticated and intricate handlings in their recycling process. Even degradable and biodegradable plastics may persist for decades depending on local environmental factors, like levels of ultraviolet light exposure, temperature, presence of suitable microorganisms, etc. Out of these class 7 is most difficult to degrade and recycle. It is creating an alarming situation in terms of contamination of natural resources that ultimately produces a wide array of diseases like metabolic issues, respiratory disorders, skin and liver diseases, etc. in the recipients. Thus, there is a dire need to develop rational strategies to recycle symbol 7 plastic to reduce the degradation of natural resources and associated health
hazards in the recipients.

US6489373B2 discloses a process of decomposition and recovery of polyurethane resin. The process involves dissolving the polyurethane resin such as polyurethane foams discharged in a large amount as industrial wastes in a solubilizing agent containing a polyamine compound, a low molecular glycol or an amino alcohol, hydrolyzing the resulting solution with liquid water at 200 to 320° C., then recovering the polyamino compound and/or polyol compound thus formed.

Sha et al, in Energy Conversion and Management: X, Volume 13, January 2022, 100158 discloses the solvothermal upcycling of mixed plastic wastes: where in sub- and supercritical toluene is used for Depolymerization of waste plastics.

Bergerova et al in J Environ Health Sci Engineer 19, 1347–1360 (2021) discloses the use of polyurethane materials for Arsenic removal. The document uses Iron oxide hydroxide to increase the efficacy while present invention uses Silica. It also discloses that although polyurethane nanostructures have been found to be effective as relatively selective arsenic adsorbents, it is desirable to add them with another inorganic sorbent, which will further increase the adsorption efficiency.

Although the literature discloses various methods of the recycling on plastic waste, these processes are not energy efficient as they involve the use of extremely high temperature conditions which is expensive to achieve and sustain. Therefore, there is still a need for developing efficient process for the degradation of plastic and recycling them for use in some commercially useful article such as for removal of heavy metals from contaminated water. It is also important that the process occur at ambient temperature and with minimum use of energy. This would also help in achieving net zero operations.

Object of the invention
It is one object of the present invention to provide a novel Silica modified polymeric adsorbents derived from plastic waste, for removal of Arsenic from contaminated water.

It is another object of the present invention to provide an eco-friendly, one step process for the preparation of novel Silica modified polymeric adsorbents from plastic waste.

It is yet another object of the present invention to provide an eco-friendly, one step process for the recycling of plastic waste into economically useful articles.

It is yet another object of the present invention to provide a recycled product for the removal of Arsenic from contaminated water.

Summary of the invention
Accordingly, the present invention provides novel Silica modified polymeric adsorbent prepared from plastic waste.

In one embodiment, the present invention provides a process for preparing Silica modified polymeric adsorbent, said process comprising:
(a) Shredding of plastic waste into ambient size,
(b) Dissolving the shredded plastic waste into an organic solvent,
(c) Adding Silica Gel and stirring at 50 °C – 150 °C to obtain an extract, and
(d) Drying the said extract to obtain the silica modified polymeric adsorbent.

In another embodiment, the present invention provides Silica modified polymeric adsorbent from plastic waste, said process comprising:
(a) Shredding of plastic waste into ambient size,
(b) Dissolving the shredded plastic waster in toluene,
(c) Adding Silica Gel and stirring at 90°C – 110°C to obtain an extract without precipitation in the presence of solvent, and
(d) Drying the extract to obtain the silica modified polymeric adsorbent.

In another embodiment the present invention provides Silica modified polymeric adsorbent characterized by XRD pattern in accordance with FIG. 1.

In another embodiment the present invention provides Silica modified polymeric adsorbent for use in the removal of Arsenic from contaminated water.
Brief description of the drawings
Figure 1 shows the FTIR graph Si-PWPA and Si-PWPA-As before and after adsorption.
Figure 2 shows the FESEM images of (a) (b) Si-PWPA adsorbent before adsorption, (c) (d) Si-PWPA after adsorption of As(III), and EDX images of (e) (f) Si-PWPA adsorbent before adsorption, (g) (h) Si-PWPA after adsorption of As(III). Figure 2 [(e)-(h)] shows the corresponding EDX spectra, which shows elemental composition of the adsorbent Si-PWPA before and after adsorption of As(III).
Figure 3 shows the XRD graph of Si-PWPA and Si-PWPA-As.

Abbreviations:
PWPA refers to plastic waste derived polymeric adsorbent
Si-PWPA refers to Silica modified plastic waste derived polymeric adsorbent

DETAILED DESCRIPTION OF THE INVENTION WITH NONLIMITING EXAMPLES AND EMBODIMENTS
In the following detailed description of the invention, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be obvious to a person skilled in the art that the invention may be practiced with or without these specific details. In other instances, well known methods, procedures and components have not been described in details so as not to unnecessarily obscure aspects of the invention.

Furthermore, it will be clear that the invention is not limited to these alternatives only. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art, without parting from the scope of the invention.

Throughout this specification, unless the context requires otherwise the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of elements or steps but not the exclusion of any other element or step or group of elements or steps.

The present invention provides novel silica modified polymeric adsorbent prepared from plastic waste. The silica modified polymeric adsorbent of the present invention are also referred as Si-PWPA (Silica modified plastic waste derived polymeric adsorbent). Both terms can be used interchangeably. The Si-PWPA of the present invention have increased surface area and porosity which makes them ideal for the removal of heavy metals, in particular Arsenic, from contaminated water.

The present invention thus provides a novel method of recycling hazardous waste into economically useful article. It also provides a product and process which addresses the issue of water and land pollution.

In one embodiment, the present invention provides Silica modified polymeric adsorbent suitable for use in the removal of Arsenic from contaminated water. The said polymeric adsorbent is very effective in removing the Arsenic at ppm level. It can reduce more than 90% of Arsenic in about 40-80 minutes.

In one embodiment, the present invention provides a process for preparing Silica modified polymeric adsorbent from plastic waste, said process comprising:
(a) Shredding of plastic waste into ambient size,
(b) Dissolving the shredded plastic waste into an organic solvent,
(c) Adding Silica Gel and stirring at 50°C -150°C to obtain extract without precipitation in the presence of solvent, and
(d) Drying the said extract to obtain the silica modified polymeric adsorbent.

The solvent of the present invention is selected from Dimethyl sulphoxide (DMSO), Acetone and toluene.

In another embodiment, the present invention provides a process for the preparation of silica modified polymeric adsorbent (Si-PWPA) said process comprising:
(a) Shredding of plastic waste into ambient size,
(b) Dissolving the shredded plastic waster in toluene,
(c) Adding Silica Gel 60-120 Mesh (Grade – II) and stirring at 90°C – 110°C to obtain the extract without precipitation in the presence of solvent, and
(d) Drying the said extract to obtain the silica modified polymeric adsorbent.

In another embodiment the present invention provides Silica modified polymeric adsorbent characterized by XRD pattern in accordance with FIG. 1.

In another embodiment the present invention provides Silica modified polymeric adsorbent for use in the removal of Arsenic from contaminated water.

The Silica modified polymeric adsorbent of the present invention is highly porous and has large surface area for the removal of Arsenic waste from contaminated water. The structure of the modified polymeric adsorbent corresponds to modified polyurethane structure as confirmed by the instrumental analysis.

Examples:

Example 1: Preparation of Silica modified polymeric adsorbent.
Plastic wastes were shredded into 1x2 cm pieces. These shredded pieces were dissolved in toluene and silica was added to it. This was then stirred at 90 oC -110 oC temperature for 30-45 minutes. The extracted polymeric adsorbent was further dried in an oven at 90 oC -100 oC for 1 hour. After drying Silica modified polymeric adsorbent was obtained. This polymeric adsorbent was characterized by various spectroscopic and analytical methods such as FTIR, XRD, SEM, etc. Further, this adsorbent (Si-PWPA) was evaluated for the arsenic removal efficacy in the water samples.

Characterization of the polymeric adsorbent of the present invention:
Example 1 (a) Fourier transform infrared (FTIR)
FTIR spectra of polymeric adsorbents Si-PWPA and Si-PWPA-As before and after adsorption were recorded using Shimadzu Fourier transform infrared spectrophotometer. For understanding the nature of chemical bonding and the kinds of surface functionalities, the adsorbents used in this study were examined by FTIR. The range of wavenumber was of 4000 to 400 cm-1. Figure 1 shows the spectra before and after adsorption of As (III) on adsorbents. As shown in fig FTIR spectra of adsorbent showed an absorption peak at 2914 cm-1 which corresponds to the CH2 band. The peaks around 2846 and 793 cm-1 correspond to C-H stretching and bending vibration of polyurethane molecules. The vibrational frequency observed around 1084 and 1100 cm-1 exhibit Si-O bond in the crystal lattice of polyurethane. FTIR spectra showed that few peaks appeared after the adsorption of As(III) ions. The sharp peak at 1719 and 1257 cm-1 depict the C=O carbonyl group and C-O-C stretching respectively. The band observed at 1463 cm-1 after adsorption intensifies with a shift, is assigned to the As-N bending vibration, and confirms the loading of As(III) ions on the surface of the adsorbent. A change in intensity and appearance of peaks after adsorption at neutral pH confirms the adsorption of As(III) ions. Other bands observed around 724 and 660 cm-1 are vibrational related to symmetric and asymmetric vibrations of the adsorbent.
Example 1 (b) FE-SEM analysis
Field emission scanning electron microscope (FE-SEM) emission was used to determine the top and cross-sectional surface morphology and EDX for elemental composition of polymeric adsorbents Si-PWPA and Si-PWPA-As at 60 & 100 µm magnification. SEM and EDX images are shown in Figure 2. In Figure 2(a) (b), the pattern reveals the presence of flakes with porous morphology recommending high surface area available for the adsorption. Figure 2(c) (d) shows the agglomeration of As(III) clumped with the adsorbent, after the adsorption crystal like structure appears on the surface, as the figure exhibits the apparent morphological difference between surface of Si-PWPA before and after adsorption of As(III). A significant changes in the surface of the adsorbents specify that the adsorption is surface phenomenon.
Table 1 shows the weight % of the element silica (Si) and arsenic (As) before and after adsorption on the adsorbent Si-PWPA.
Table 1: Weight % of Si and As(III) before and after adsorption
Size
(µm) Element Atomic number Series Weight %
(wt %)
Before adsorption After adsorption
60 Si 14 K-series 0.87 0.88
As 33 L-series ---- 0.78
100 Si 14 K-series 0.76 1.16
As 33 L-series ---- 1.55

Example 1 (c) X-ray diffraction analysis.
X-ray diffraction (XRD) are used for studying the surface composition and morphology of adsorbents. For more understanding about chemical and physical composition XRD is a highly valuable. Figure 3 shows the XRD pattern of polymeric adsorbents Si-PWPA and Si-PWPA-As before and after adsorption of As(III). XRD patterns of the adsorbents were recorded using Bruker D8 Discover X-ray diffractometer over a range 2? angles from 1º to 90º in a step width of 1º and displayed peaks at about 2? = 20º. According to XRD studies, the silica interacted well with the adsorbent. The appearance of intense peak in the spectra specifies the amalgamation of silica component with adsorbent Si-PWPA. The XRD spectra showed sharp peaks at 20.9º and 21.96º of Si-PWPA and Si-PWPA-As respectively before and after adsorption of As(III) ions. A slight change was observed after the adsorption of As(III), the peak intensity of Si-PWPA slightly get increased. The statistics above show that adsorbent crystallinity has deteriorated.
Example 2: Evaluation of Arsenic removing efficiency:

As (III) doped water was taken in a beaker. pH was adjusted to 7 and a small piece of Silica modified polymeric adsorbent was added to it. The water was left for 120 minutes. The water was analyzed at regular intervals to quantify the amount of Arsenic.

Batch adsorption study of the adsorbent reveals impressive performance in arsenic removal with a maximum adsorption capacity of 166.66 mg/g at pH 7. Notably, Si-PWPA resulted in an augmented adsorption capacity towards As (III) ions with a maximum percentage removal of 98.78% in 90 minutes. The pseudo-second-order model fits well with kinetics data where the R2 value is 0.9995, for Si-PWPA. The recyclability of Si-PWPA for As (III) uptake showed consistent adsorption capacity up to five cycles thereafter a marked declination was recorded from 84.61% to 22.49% for As (III).

Table 2: Arsenic removal using PWPA and Si-PWPA
Adsorbent Initial
concentration of Arsenic As(III) concentration
________________________________________
30 min 40 min 60 min 80 min % reduction
at 90 min
Simple adsorbent
(PWPA) 10 ppm 6.7 5.5 4.9 4.5 67
Silica modified adsorbent
(Si-PWPA) 10 ppm 3.34 3.37 2.84 2.48

98.78

, Claims:We claim
1. A process for preparing Silica modified polymeric adsorbent from plastic waste, said process comprising:
(a) Shredding of plastic waste into ambient size,
(b) Dissolving the shredded plastic waste into an organic solvent,
(c) Adding Silica Gel and stirring at 50°C -150°C to obtain extract without precipitation in the presence of solvent, and
(d) Drying the said extract to obtain the silica modified polymeric adsorbent.

2. The process as claimed in claim 1 wherein the solvent is toluene.

3. The process as claimed in claim 1 wherein the temperature at step (b) is 90-110°C.

4. The process as in claim 1 wherein the said process occurs in single step without precipitation.

5. The process as claimed in claim 1 wherein the plastic waste is class or grade 7 plastic.

6. Silica modified polymeric adsorbent characterized by the XRD pattern as depicted in figure 3.

7. Silica modified polymeric adsorbent prepared by a process as claimed in claim 1.

8. Silica modified polymeric adsorbent for removal of arsenic from wastewater.
Dated this the 31st day of May 2024.