LEAD REMOVAL FROM FOUNDRY WASTE BY SOLVENT-EXTRACTION

Solvent extraction is used to reduce lead concentrations from millpond wastewater solids, a type of foundry process waste. Toluene and tolue ne mixed with di-(2-ethyl-hexyl) phosphoric acid (HDEHP) have been tri ed as leaching solvents. Toluene is ineffective as a solvent in extrac ting lead, but the toluene-HDEHP mixture effectively removes lead from solid foundry waste. The effects of the HDEHP concentration, the cont act time, and the amount of solvent used on lead extraction have been investigated. The mass transfer process is rapid: contact time of 1/2 hour has been found to be sufficient to accomplish the leaching proces s. The concentration of HDEHP significantly impacts lead removal. The optimum concentration of HDEHP is determined to range from 0.05 to 0.1 mel/l. The Toxicity Characteristic Leaching Procedure (TCLP) test of the treated samples gives leachable lead in much lower quantities than those found in the untreated samples. Thus the solvent extraction pro cess appears to be an effective method to significantly reduce the lea d content of millpond wastewater solids.