Process for the removal of arsenic and chromium from water

Abstract

The present invention provides low cost and highly effective method for the removal of arsenic and Cr(III&VI) from contaminated water using zinc peroxide nanoparticles (20±5 nm) capped with glycerol/PVP/TEA upto the permissible range of drinking water. As Arsenic and chromium occurs naturally in the earth's crust. When rocks, minerals, and soil erode, they release arsenic and chromium into groundwater. Arsenic and chromium occurs naturally in varying amounts in groundwater in various parts of country from ppb level to ppm level. The average concentration of arsenic and chromium as per USEPA standard in drinking water it is 10 parts per billion and 0.05 ppm (50 ppb) respectively. In drinking water the level of chromium is usually low as well, but contaminated water may contain the dangerous Cr(III&VI). Although Cr(III) is an essential nutrient for humans and shortages may cause heart problems, disruptions of metabolisms and diabetes. But the uptake of too much Cr(III) can cause health effects as well, for instance skin rashes. Cr(VI) is known to cause various health effects Skin rashes, upset stomachs, respiratory problems, weakened immune systems, kidney and liver damage and lung cancer The persons who are drinking water having upto 50 ppb of arsenic and 0.05 ppm chromium over for many years could experience skin damage or problems with their circulatory system, and may have an increased risk of getting cancer. Keeping the above facts we developed a cost effective nanoparticles for the removal of Arsenic and Cr(III&VI) from potable water upto potable range.

1 . A process for the removal of arsenic and Cr(III&VI) from contaminated water using zinc peroxide nanoparticles comprising treating the contaminated water containing arsenic and chromium with the nanoparticles of zinc peroxide in a ratio (w/v) ranging from 8:1 to 12:1 (mg/ml), having the concentration of arsenic, Cr(III&VI) contamination below 50 ppm in water, at ambient temperature, for a period of 5-10 min, followed by filtration to obtain the desired low concentrated contamination permissible drinking water. 
     
     
         2 . A process as claimed in  claim 1 , wherein the zinc peroxide nanoparticles used have size below 50 nm. 
     
     
         3 . A process as claimed in  claim 1 , wherein the amount of zinc peroxide used for the removal of arsenic and Cr(III &VI) is preferably in the range of 225-250 mg per 25 ppm of arsenic and Cr(III &VI) contaminated water. 
     
     
         4 . A process as claimed in  claim 1 , wherein the zinc peroxide nanoparticles are prepared by the process comprising the following steps:
 a) dissolving zinc acetate in ammonium hydroxide to obtain a solution mixture having pH in the range of 9-11;   b) adding glycerol/PVP/TEA to the solution mixture obtained in step (a) in a ratio of zinc acetate to glycerol in the range of 2:0.5 to 6:1(w/w), PVP in the range of 10:0.25 to 10:1 (w/w) and TEA in the range of 1:1 to 1:0.5 (w/w) with respect to zinc acetate respectively;   c) adding a polar organic solvent to the solution Mixture obtained in step (b), under stirring, at ambient temperature in the range of 25-30° C., followed by adding equimolar quantity of hydrogen peroxide with respect to zinc acetate to obtain the desired nanoparticles of zinc peroxide.   
     
     
         5 . A process as claimed in  claim 4 , wherein the weight ratio of zinc acetate to glycerol used is preferably in the range of 2:0.5 to 3:1. 
     
     
         6 . A process as claimed in  claim 4 , wherein the weight ratio of zinc acetate to PVP used is preferably in the range of 10:0.5 to 10:1 (w/w). 
     
     
         7 . A process as claimed in  claim 4 , wherein the weight ratio of zinc acetate to TEA used is preferably in the range of 1:1 to 1:0.5 (w/w). 
     
     
         8 . A process as claimed in  claim 4 , wherein yield of ZnO 2  nanoparticles obtained is in the range of 98-99% with respect to the starting material. 
     
     
         9 . A process as claimed in  claim 1 , wherein the ZnO 2  nanoparticles removes arsenic, Cr(III) and Cr(VI) each from 50 ppm to 0.1, 0.14, and 0.18 ppm, respectively without disturbing the pH of water. 
     
     
         10 . A process as claimed in  claim 1 , wherein the ZnO 2  nanoparticles removes arsenic, Cr(III) and Cr(VI) each from 30 ppm to 0.03, 0.07 and 0.08 ppm, respectively without disturbing pH of the water. 
     
     
         11 . A process as claimed in  claim 1 , wherein the ZnO 2  nanoparticles removes arsenic, Cr(III) and Cr(VI) each from 25 ppm to less than the detection limit of AAS-HG in case of arsenic and 0.01 in case of Cr(III) and Cr(VI) without disturbing pH of the water. 
     
     
         12 . A process as claimed in  claim 1 , wherein the ZnO 2  nanoparticles removes arsenic and Cr(III&VI) each from 20 ppm to less than the detection limit of AAS-HG and FAAS/GFAAS respectively without disturbing pH of the water. 
     
     
         13 . A process as claimed in  claim 1 , wherein the ZnO 2  nanoparticles removes arsenic and Cr(III&VI)each from 15 ppm to less than the detection limit of AAS-HG and FAAS/GFAAS respectively without disturbing pH of the water. 
     
     
         14 . A process as claimed in  claim 1 , wherein the ZnO 2  nanoparticles removes arsenic and Cr(III&VI) each from 10 ppm to less than the detection limit of AAS-HG and FAAS/GFAAS respectively without disturbing pH of the water. 
     
     
         15 . A process as claimed in  claim 1 , wherein the ZnO 2  nanoparticles removes arsenic and Cr(III&VI) each from 5 ppm to less than the detection limit of AAS-HG and FAAS/GFAAS respectively without disturbing pH of the water. 
     
     
         16 . A process for the removal of arsenic and Cr(III&VI) from contaminated water, substantially as herein described with reference to the examples and drawings accompanying this specification.