Novel combined method of biosorption and chemical precipitation for recovery of Pb2+ from wastewater.

A novel combined biosorption-precipitation process has been designed and applied to recycle Pb2+ from low concentration lead containing wastewater. Pb2+ was firstly removed selectively from wastewater by pyromellitic dianhydride (PMDA) modified sugarcane bagasse (SB) fixed-bed column, and then, it was desorbed into the concentrated eluate and recycled by adding chemical precipitant. Adsorption performance of the column and optimum desorption and precipitation condition for Pb2+ were investigated in detail. Results showed that the as-prepared column could efficiently remove Pb2+ from aqueous solution and optimum condition for Pb2+ precipitation in eluate was at pH 3.0 and molar ratio of precipitant to Pb2+ of 5:1 by using Na3PO4 as precipitant. Recovery experiment illustrated that Pb2+ was selectively removed from wastewater containing ions of Pb2+, Zn2+, Cd2+, Ca2+, K+, and Na+ through competitive substitution adsorption on the modified SB, and mass ratio of the five metal ions in eluate was 96.8:0.7:0.7:0.7:0.5:0.5. Pb2+ in this concentrated and purified eluate solution was recycled efficiently by adding Na3PO4. The combined method had great potential in application of heavy metal recovery from wastewater.