Study Of Extraction Of Hexavalent Chromium Ions From Electroplating Wasterwater

As well knowen as the"beautician",Plating is the use of chemical method to plating varieties metals on the surface of metals or other materials.But during the plating process,it will produces many kinds of electroplating wastewater to make plating industry become one of the three plution industries. Plating wastewater has the characteristics of difficulty degradation, highly toxic and so on.Now, although these traditional treatments had mature application,they had many limitations, such as high cost, source waste, second polution.In this article,two extraction methods were applied in the treatment of electroplating wastewater inclouded Cr6+.Firstly,this study applies Bis(2-ethylhexyl)phosphate and tributyl phosphate as the extract, kerosene and trichoromethne as the diluent. Traditionl complex extraction was used to treat the extroplating wastewater. Bis(2-ethylhexyl)phosphate,kerosene were selected as the extractant,diluent.And the optimum composition of the extraction solvent mixture was 70vol% Bis(2-ethylhexyl)phosphate +30vol% kerosene.Many influencing factors were investigated in detail,including extractant concentraction,operating time,extract ratio and operating temperature and so on to get suitable optimum composition.And by changing the value of pH to recycle the membrane organic.Last, at 298K,0.2MHCL as the stripping is the optimum conditionSecondly, hollow finber supported liquid membrane with stripping dispersion (HFSLM-SD) was introduced to treat electroplating wastewater to decrease extraction solvent mixture loss.And combine extract and stripping process into one step.Polypropylene (PP) as the membrane material,D2EHPA as the carrier,kerosene as the diluent. The effects of stripping concentration,pressure,feed and stripping volume flows,packing ratio on the performance of HFSLM-SD have been investigated. In the condition of HCl concentration of 1.0 mol/L in strip phase, pressure of 0.053MPa, feed volume flow of 4.0L/h, stripping volume flow of 3.0L/h, the recovery of Cr6+ is up to 96%, when the operation continues 5 hours. The stability of the liquid membrane has also been evaluated. It was observed that organic phase was still maintained in the support membrane pore, and the recovery of Cr6+ was stable.Lastly,based on the optimization of operating conditions and the stability studies of HFSLM-SD extractioon of electroplating wastewater,analyses the electroplating wastewater extraction process.