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CLAY-POLYMER COMPOSITES FOR THE DECONTAMINATION OF PESTICIDE INDUSTRIAL EFFLUENTS

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2015
V. T. Gajbhiye
DIVISION OF AGRICULTURAL CHEMICALS INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI
CLAY-POLYMER COMPOSITES FOR THE DECONTAMINATION OF PESTICIDE INDUSTRIAL EFFLUENTS
CLAY-POLYMER COMPOSITES FOR THE DECONTAMINATION OF PESTICIDE INDUSTRIAL EFFLUENTS
Ph.D

After industrial revolution, the effluent related pollution problems increased tremendously. Large volume of water is being utilised in the industries for various processes and washing purposes which in turn lead to the generation of large amounts of waste waters containing toxic substances such as heavy metals, pesticides, dyes, organic chemicals and other pollutants. When these effluents are released into the water bodies without proper treatment, they pose serious environmental concerns. Among those industries, pesticide industry is a major culprit in the environmental pollution problem. The wastes generated from the pesticide industries are very toxic and needed to be treated effectively. Various treatment processes are employed in the pesticide industrial effluent treatment plants. Among those techniques, adsorption is an important method for the removal of pesticides from water. Various adsorbents have been exploited for the removal of pesticides from waste water. Clay polymer composites are new area of adsorbents which should be exploited for its pesticide adsorption capacity. Several polymers are utilised for the preparation of composites. Most of them are synthetic ones increasing the concerns for environmental pollution and cost of production. The natural polymers are also reported to be used in the preparation of composites. Nano organoclays are also widely used in decontamination studies because of its high adsorption capacity. So the present study was carried out to prepare and utilise the natural polymer-nanoorganoclay composites for the decontamination of pesticide industrial effluent. A multiresidue method has been standardised for the analysis of nine selected pesticides, atrazine, butachlor, carbendazim, carbofuran, imidacloprid, isoproturon, pendimethalin, thiophanate methyl and thiamethoxam, using LC-MS-MS. The LOD for the pesticides ranged between 0.0001 and 0.0002 µg/mL and LOQ between 0.0003 µg/mL and 0.06 µg/mL for the selected pesticides. The method recovery was found to be more than 80% at different fortification levels. Three natural polymers, cellulose, carboxy methyl cellulose and chitosan, were used for the preparation of composites. Screening of clays was carried out to select the best one for the preparation of clay polymer composites. among the clays, normal bentonite, nanobentonite, nanobentonite modified with 25-30 wt % octadecylamine (ODA), nanobentonite modified with 35-45 wt % dimethyl dialkyl (C14-C18) amine (DMDA) and nanobentonite modified with 15-35 wt % octadecylamine and 0.5-5 wt% aminopropyltriethoxysilane (ODAAPS), DMDA showed the maximum adsorption of pesticides (42.8 to 99%) and was selected for the preparation of composites. for the comparison purpose, normal bentonite and nanobentonite were also utilised for the preparation of composites. Clay polymer composites were prepared by solution intercalation method by maintaining the polymer to clay ratio of 1:2. Among the prepared composites, 1:2 CMC-DMDA was found to be the best and detailed adsorption study was carried. Favourable adsorption of the pesticides on the composite was observed. The pesticides showed higher adsorption at basic pH. In order to improve the pesticide removal efficiency of the composites, the polymer to clay ratios were varied and screened. As the clay amount 104 increased, the pesticide adsorption was also increased. 1:5 CMC-DMDA composite showed the maximum adsorption of pesticides (55.0 to 99.7%). For further improvement in the removal efficiency of the composites for atrazine, mixed clay composites were prepared using CMC and combinations of organoclays, DMDA and ODAAPS. When ODAAPS was used instead of DMDA in 1:5 composite, the removal efficiency for atrazine was improved from 55.0% to 60.9%. Further improvement in the overall pesticide removal efficiency was observed when 1:2.5:2.5 CMC-DMDA-ODAAPS was used (64.9-99.9%). The natural polymer composite 1:2.5:2.5 CMC-DMDA-ODAAPS was found to be the better than the synthetic ones prepared from poly acrylic acid (1:2.5:2.5 AA-DMDA-ODAAPS) and poly acrylamide (1:2.5:2.5 AM-DMDA-ODAAPS). Detailed adsorption study was carried out using 1:2.5:2.5 CMC-DMDA-ODAAPS and the data were fitted into different isotherms. Thiophanate methyl showed the maximum adsorption capacity and the adsorption of pesticides on the composite was found to be favourable and followed physisorption process. The composite was further utilised for the decontamination of pesticides. As the composite dose increases, the adsorption of pesticide also increases. The prepared composites were characterised by infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), Scanning electron microscopy (SEM) and Electron dispersive X-ray (EDX) analysis and Transmission electron microscopy (TEM). The basal spacing was increased when the composite was prepared by incorporating CMC and clays. Intercalation of polymer into the clay layers is confirmed. The composites formed were found to be flaky. Pesticide industrial effluent collected from the nearby industry was characterised by GC-MS and LC-MS-MS. The before treatment sample was found to contain only one pesticide, thiamethoxam at a concentration level of ~50 µg/mL. So the effluent was fortified with other pesticides at the same level and decontamination study was carried out using the prepared composite. The effluent treatment using the composite dose of 5g (thrice) gave the highest removal efficiency for the selected pesticides (72.9 to 100.0%). Efficient regeneration of the used composite was obtained by acetone washing followed by thermal regeneration at 200°C. Even after second reuse, the composite was able to maintain 57 to 97% of its pesticide removal efficiency. The pesticides generated during the regeneration process can be effectively degraded by using 2N NaOH. The prepared composite can be utilised at some stages of the

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