Steel slag as a cost-effective adsorbent for synergic removal of collectors, Cu(II) and Pb(II) ions from flotation wastewaters

Abstract

Flotation reagents and heavy metal ions always coexist in mineral flotation wastewaters, arousing serious environmental issues or having deleterious effects on mineral flotation. In this work, the steel slag was adopted as a cost-effective adsorbent to synergically remove butyl xanthate (BX), diethyl dithiocarbamate (DDTC), Cu(II) and Pb(II) ions. At the steel slag dosage of 12.0 g/L, Cu(II) and Pb(II) concentrations decreased from 4.0 mg/L to below 10.0 μg/L, and the removal of COD reached 54.33%. The removal efficiency of COD increased from 11.36% to 57.49% as Cu(II) and Pb(II) concentrations rose from 0 to 8.0 mg/L, revealing the promotion effects of metallic ions on collector adsorption. The maximum uptake capacity of steel slag reached 110.45 and 160.48 mg/g for Cu(II) and Pb(II), respectively. The collector adsorption capacity of steel slag increased nearly two magnitudes after modifying with the uptake of Cu(II) or Pb(II) ions. The SEM/EDS, XPS and FTIR analysis indicated that steel slag could be in-situ modified to generate copper or lead hydroxides and oxides during the removal of Cu(II) and Pb(II) ions. Subsequently, these precipitates acted as reactive sites for chelating BX and DDTC to form indissolvable metal-collector chelates. Owing to in-situ modification of steel slag by uptaking metallic ions, the adsorption was potentially feasible for treating flotation wastewaters.