Reducing the leachable lead content of used oil filter paper

Used automotive oil filter papers are typically contaminated with traces of lead and zinc particulates that may exceed the EPA toxicity characterization leaching procedure (TCLP) or the California soluble threshold limit concentration (STLC). The leachable lead and zinc content of oil filter paper may be reduced below hazardous waste levels by treatment with leach solutions comprised of metal complexing agents that dissolve a portion of the heavy metals. Further reduction of leachable lead and zinc in filter paper may be achieved by treatment with phosphate solutions to form insoluble metal phosphates. The resultant non‐toxic paper may be safely incinerated, while the leach “solubilizing” and phosphate “fixing” solutions are recycled. Lead and zinc are recovered from leach solutions by precipitation with sodium sulfide or polysulfide for beneficial use in lead/zinc smelter feedstock. The total levelized cost of treatment of filter paper to yield a non‐hazardous waste may range from $ 100–$ 300 per metric ton.