Treatment of Wastewater from Wet Scrubbers in Secondary Lead Smelters for Recycling and Lead Recovery

The present study shows a method to recover lead metal from wastewater of wet scrubber in secondary lead smelter. The wastewater is loaded with 42,000 ppm of insoluble lead compounds (TSP) submicron in diameter. The technical background benefits the use of cationic polyfloc solution to flocculate these colloidal solids before press filtration. The polymer solution is injected in the wastewater stream in a countercurrent flow design. The study demonstrates the effect of polymer dose, temperature, pH, flow velocity of the wastewater and different filtration media on the filtration extent. Results indicated that filtration rate (ƒr), quality of purified water, purifying efficiency (ƒe) and floc diameter decrease regularly with increase in mass flow rate and velocity up to turbulence of 0.5 m.sec. Laminar flow is in favor of flocculation. Polyfloc concentration of 0.75 – 1.25 g/m wastewater is convenient. Increasing temperature of the wastewater and pneumatic pressure of filtration enhances ƒr. High pH value deforms floc formation and assists degradation of the filtration fabric. The overall efficiency of the method amounts to 93.2 %. Lead metal was recovered from the filtrate cake using carbon as a reducing agent at 900°C. Keywords—Wastewater, wet scrubbers, filtration, secondary lead.