Water-insoluble starch xanthate

To address this concern, several organic and inorganic reagents were evaluated as precipitants for heavy metals in a 10-34-0 (N-P2O5-K2O) fluid fertilizer and WPA. Trisodium trithiocyanuric acid (TMT-15), sodium polythiocarbonate (Thio-Red II), and sodium trithiocarbonate (5% Na2 CS3) precipitated arsenic, cadmium, copper, mercury, lead, and zinc from 10-34-0. Ammonium cyanurate was ineffective in removing cadmium from 10-34-0. Thio-Red II and 5% Na2CS3 precipitated mercury, lead, cadmium, copper, and chromium from WPA. A water-insoluble starch xanthate adsorbed mercury, copper, and lead from 10-34-0 and WPA. Sodium sulfide, sodium polysulfide, and potassium ferrocyanide were tested as inorganic precipitants. The polysulfide was twice as effective as the sulfide alone, and concentrations of less than 10 ppm of arsenic, cadmium, mercury, and lead were achieved in 10-34-0. Ferrocyanide reduced the concentrations of cadmium and nickel to less than 10 ppm in WPA. 

Starch Xanthate Adsorbents. Wing and coworkers (12) reported that insoluble starch xanthate was highly effective in adsorbing iron(II) and chromium(III) from synthetic waste water samples. For example, a pH 3.0 waste water with an initial iron(II) concentration of 27,920 mg/L was treated with the starch xanthate and after stirring for 2 h, the residual iron(II) concentration was found to be <1 mg/L. Similar results were obtained for chromium(III), where the chromium(III) concentration of a synthetic waste water sample at pH 3.2 was reduced from 26,000 mg/L to 3 mg/L after stirring for 2 h with the appropriate amount of starch xanthate. 

Starch xanthate. A water-insoluble synthetic polysaccharide made by reacting starch with sodium hydroxide and carbon disulfide biodegradable. 

WI Starch Xanthate. Research by Wing and others (22, 27-29) has shown that water-soluble (WS) starch xanthates, in combination with cationic polymers to form polyelectrolyte complexes, can effectively remove heavy metals from waste water. To eliminate the expensive cationic polymer and give a more economical method of heavy metal removal, further research by Wing and others (12,30-33) showed that xanthation of a highly crosslinked starch yields a water-insoluble (WI) product that is effective in removing heavy metals from waste water without the need for a cationic polymer. In more recent work, Tare and Chaudhari (34) evaluated the effectiveness of the starch xanthate (WS and WI) process for removal of hexavalent chromium from synthetic waste waters. 

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