Galvanostatic removal of Pb2+ ions from diluted solutions by the use of a membrane-less flow-through cell with stainless steel wool electrodes

Abstract

The removal of Pb2+ ions from dilute solutions was investigated under galvanostatic conditions using a membrane-less flow-through cell with stainless steel wool (SSW) electrodes. The response surface methodology (independent variables: electric current and volumetric flow rate) was used to find the optimal conditions for Pb2+ removal from 2 L of an aqueous solution of 50 mg L-1 Pb(NO3)2 in 0.10 mol L-1 NaNO3 + 0.10 mol L-1 H3BO3 (pH 4.8). The obtained response surfaces revealed that the volumetric flow rate (59-341 L h-1) does not substantially affect the Pb2+ removal process. On the other hand, the electric current increase led to higher Pb2+ removal, with significantly improved values of specific energy consumption and current efficiency when compared with those reported in the literature. For an experiment carried out in the optimum-condition region (70 mA and 200 L h-1), a Pb2+ conversion of 99.6% was attained after 90 min of electrolysis. The use of the membrane-less flow-through cell with SSW electrodes, besides being significantly more energy efficient, led to Pb2+ removal on both electrodes, but predominantly in the SSW anode, on which more than 95% of the Pb2+ ions were converted to PbO2.