Recycled niobium felt as an efficient three-dimensional electrode for electrolytic metal ion removal

An electrolytic process for the removal of lead from aqueous solutions using a flow-through cell with a recycled niobium felt is proposed. The operational conditions for the reactor were optimised as a function of the solution flow rate and the electrolytic removal of Pb(II) was used to characterise the mass transport properties of the niobium felt electrode. The three-dimensional cathode was made from continuous niobium tips resulting from niobium ingots machining. The performance and figures of merit of the niobium felt were studied using different flow rates. In the experiments lead concentration dropped from 50 mg l−1 to 0.5 mg l−1 (99% removal) in electrolysis time ranging from 94 to 150 min, depending on the flow rate. Dimensionless Sherwood and Reynolds numbers were correlated to characterise the mass transport properties of the niobium felt, and they were fitted to the equation Sh=22.9(Re)0.43(Sc)0.33.