The possibility of Cu(II), Ni(II) and Sn(II) removal from model solutions and real wastewater from the production of PCBs using Na2 CS3 for precipitation was presented in this paper. The testing was carried out on a laboratory scale using model and real industrial wastewater containing additives in the form of complexing compounds used in the production of PCBs (Na2 EDTA, NH3(aq), thiourea) and recommended by the USEPA (Na3 MGDA, Na4 GLDA). Application of Na2 CS3 in optimal conditions of conducting precipitation process was connected with obtaining wastewater containing low concentrations of metals (Cu 0.02 mg/L, Sn <0.01 mg/L, Ni <0.005 mg/L at pH 9.39 and Cu 0.07 mg/L, Sn <0.01 mg/L, Ni 0.006 mg/L at pH 7.79). Controlled application of Na2 CS3 by the use of a platinum redox electrode was also connected with obtaining treated wastewater containing low concentrations of metals (Cu 0.019 mg/L, Sn <0.05 mg/L, Ni <0.0098 mg/L at pH 9–9.5 and E= -142 mV in the laboratory scale and Cu 0.058 mg/L, Sn <0.005 mg/L, Ni 0.011 mg/L at pH 9.14 and E= +10 mV in the industrial scale). Changing the value of redox potential of treated wastewater by dosing Na2 CS3 made it possible to control the precipitation process on laboratory and industrial scale by the use of a platinum redox electrode. Controlled application of Na2 CS3 can be used to remove Cu(II), Ni(II) and Sn(II) from industrial effl uent containing chelating compounds like Na2 EDTA, NH3(aq), thiourea, Na3 MGDA and Na4 GLDA.
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