Lead Removal in Fixed Beds by Recycled Iron Material

Abstract

A granular iron-bearing material recovered from surface finishing operations in cast-iron manufacturing is demonstrated to be an effective sorbent for removal of lead from wastewaters in laboratory-scale tests. Fixed-bed experiments indicate that lead removals are equal to or greater than those achieved by other sorbents such as activated carbon and prepared granular iron oxides on a mass per mass basis. State-of-the-art equilibrium and rate models have been shown to be useful for simulating adsorber performance and quantifying the effects of system variables in fixed-bed systems. For an influent lead concentration and pH of 10 ppm and 5.5, respectively, an empty bed contact time of ≥2.5 min provides for efficient use of the sorbent and yields a solid phase loading capacity of ∼40 mg/g at exhaustion. Minor differences were observed in the adsorptive properties of two different particle size fractions. Efforts to chemically regenerate the sorbent resulted in relatively low lead recovery and subsequent adsorption efficiency compared with investigations with ion exchange materials and activated carbons. However, the low sorbent usage rate and availability of the material should render the recycling and reuse of shot blast fines a cost-competitive process for fixed-bed treatment of metals such as lead in industrial and hazardous wastewaters.