Green rust-deposited MoS2 composites for the enhanced sequestration of EDTA-chelated Cu(II) from an aqueous solution

Abstract

EDTA-Cu(II) is usually observed in electroplating wastewater, and its removal is very challenging due to its easy dissolution, stability and difficult biodegradation characteristics. In this work, an excellent binary composite (MG) was prepared via the combination of green rust (GR) and MoS2 to remove EDTA-Cu(II) from an aqueous solution. Batch test results showed that the maximum capacity of EDTA-Cu(II) uptake by MG was 89.85 mg/g. Thus, up to 98.5% of EDTA-Cu (20 mg/L) was removed. The residual Cu content was lower than the discharge standard of China (0.5 mg/L); additionally, the leaching of Fe ions was lower than 22 mg/L under ambient conditions. MG could satisfactorily remove EDTA-Cu(II) from complex environments in one step and was only minimally affected by various experimental conditions (the presence of different salt ions, different ratios of EDTA organic groups, and different dissolved oxygen concentrations). The highly active MG composite has a wider pH range (pH = 3–7) for the efficient replacement reaction with EDTA-Cu(II) than for the replacement of common Fe(III) ions (pH = 2.7–5.2). GR deposited on MoS2 could not only effectively increase the surface reaction sites of MG composites but also enhance EDTA-Cu(II) removal performance through the mutual synergy between GR and MoS2. These experimental results suggest that MG holds promise for use in removing EDTA-Cu(II) from contaminated wastewater.