LEAD TREATMENT ALTERNATIVES BY CHEMICAL PRECIPITATION


Kabdasli I. , Tünay O. , Teymur P.

FRESENIUS ENVIRONMENTAL BULLETIN, cilt.26, ss.527-532, 2017 (SCI İndekslerine Giren Dergi) identifier

  • Cilt numarası: 26 Konu: 1
  • Basım Tarihi: 2017
  • Dergi Adı: FRESENIUS ENVIRONMENTAL BULLETIN
  • Sayfa Sayıları: ss.527-532

Özet

Heavy metals are among the most important pollutants due to their effects on living organisms. While hydroxide precipitation is the most common, efficient and practical method for the control of heavy metals, its performance is not adequate for a few heavy metals. Lead is among these exceptions. While a broad literature is available for hydroxide precipitation, sources for lead control by chemical precipitation are rather limited. In this paper lead control by chemical precipitation using lead sulfate, lead carbonate and lead hydroxide is theoretically and experimentally investigated and results are comparatively evaluated. A wide range of initial lead concentrations between 10-4 and 2x10(-3) M was considered for the evaluation. The results were tested through a series of experiments. Results of the study indicated that hydroxide precipitation could reduce the lead concentration down to 17 mg/L which is not sufficient for attaining the present discharge limitations. Lead sulfate precipitation is found to be an appropriate method as a pretreatment and lead recovery at the source. Sulfate precipitation works in acid pH and its highest performance could be obtained at high lead concentrations of 10(-3) to 2x10(-3) M using excess sulfate concentration. The minimum residual lead concentration reached was 3.5 mg/L at pH 5 and for sulfate dose of twofold that of stoichiometric. The carbonate precipitation is the best method as the final and polishing treatment of lead ensuring meeting the discharge standards. The method is applicable at reasonable high pH and enables suitable operation as the performance remains practically unchanged between pH 8 - 9. The best performance was obtained as 0.12 to 0.22 mg/L residual lead at pH 8 - 9 for all initial lead concentrations.