Highly efficient removal of Cu(II), Zn(II), Ni(II) and Fe(II) from electroplating wastewater using sulphide from sulphidogenic bioreactor effluent

摘要

A bench-scale, stirred-tank batch precipitator was used to assess the selective removal of Cu~(2+), Zn~(2+), Ni~(2+) and Fe~(2+) from acidic electroplating wastewater using sulphide from a sulphidogenic bioreactor effluent. At pH ≈ 1.7, >99% of Cu was selectively precipitated, over Zn, Ni and Fe, from the wastewater as pure CuS by recycling H2S from the bioreactor effluent via N_2 sparging, resulting in a Cu effluent concentration <0.4 mg/L. The rate of Cu precipitation increased from 1.6 to 6.4 mg Cu/(L·min) when the pH of the bioreactor effluent decreased from 7.5 to 5.5. Experiments focusing on the precipitation of Zn, Ni and Fe from the wastewater devoid of Cu (at pH ≈ 1.7), using sulphide-rich bioreactor effluent, achieved ~85-97% precipitation efficiency for Zn, ~25-92% for Ni, and ~2-99% for Fe, depending on the initial sulphide/metal molar ratio. The sulphide/metal ratio of 1.76 was found to be optimal for the precipitation of Zn, Ni and Fe with sulphides and, to a lesser extent, with hydroxides, resulting in residual metal concentrations of 1 mg Zn/L, 3 mg Ni/L, and 0.5 mg Fe/L. These findings suggest the potential of waste biogenic sulphides for the selective recovery of valuable metals from acidic metal-rich industrial wastewaters.