Study On Reclamation Of Hexavalent Chromium From Eletroplaing Wastewater By Ion-exchange

Electroplating wastewater has a large discharge quantity and carries a varied of heavy metals pollutants. The effect of conventional treatment for electroplating wastewater is stabilizing, but heavy metal in wastewater can not be retrieved, and resource is wasted. So it has a great value to study the stable and efficient technology for electroplating wastewater reusing treatment, In this theme two ion-exchange columns are used to treat electroplating wastewater from an electroplating factory in Guangdong Province. At the same time it realizes that the hexavalent chromium discharge reaches the nation criterion and retrieving hexavalent chromium.This study includes the following 5 parts:1 resin selection;2 treatment processes determination;3 regenerant dosage;4 regenerative way;5 resin exchange capacity and regeneration degree;6 recovery liquid component and recovery cost.This experiment mainly investigates several aspects as follows:the effects and mechanism of removing hexavalent chromium using ion-exchange; the effects of regenerant dosage for resin regeneration; the effects of resin regenerative way for the using effects of regenerated resin; the component of recovery liquid which contains hexavalent chromium.The experiment results show that: 1 Using D301 resin and double anion exchange column processes are good for the removal of hexavalent chromium. The regenerant dosage is small. 2 We use countercurrent regeneration processes. The first is water anti-washing, the second is regeneration solution backwashing, and then water anti-washing, the final is acid washing. According to the ways, when the regenerated exchange column is reusing the concentration of hexavalent chromium in the effluent is able to meet goals. If there is not the final acid washing, when the regenerated exchange column is reusing the initial hexavalent chromium concentration in the effluent exceeds criterion. 3 The previous effluent of regeneration liquid anti-washing contains high concentration hexavalent chromium and pH is neutral. The latter part of the effluent contains low concentration hexavalent chromium and pH is highly alkaline. Anti-washing of regeneration liquid is divided into two steps, the first is the latter effluent of last regeneration washes the resin, the second is the new regeneration solution washes resin. 4 We regard effluent of regeneration liquid anti-washing resin as recovery liquid. The recovery liquid mainly contains hexavalent chromium, and it can be reused in plating after appropriate treatment processes.The results show that achieving the closed cycle of hexavalent chromium and the concentration of hexavalent chromium in the effluent meeting discharge standards are feasible by using ion exchange processes.