CHROMIC-ACID RECOVERY FROM CHROME PLATING RINSE WATER BY ION-EXCHANGE

Abstract

The regeneration of an anion bed saturated with dichromate ions by treatment with NaOH solution was studied in connection with the treatment of chrome plating rinse water by ion exchange. Column experiments were conducted to obtain an Cr(VI) elution curve and OH- breakthrough curve. The parametric effects of bed height, NaOH feed concentrations, and flow rate on the performance of regeneration were investigated. It was found that for a bed height of 70 cm and NaOH feed concentration of 1.5 to 2 mol/L with a flow rate of 100-150 mL/hr, up to a maximum concentration of 100 g/L of CrO3 could be obtained. Under the above operating conditions, the regenerant consumption is about 1.65 mole of OH- per mole of Cr(VI) recovered and the resin utilization is about 80%. An attempt is made to employ a simple analytic equation to correlate the OH- breakthrough and Cr(VI) elution data. The results of this work may be useful in the design and operation of systems for recovery and reuse of chromic acid by ion exchange in the chrome electroplating process.