The coinage refractory wastewater treated by electrocatalytic-membrane process (ECMP) integrated with chemical- or electro-coagulation techniques

Abstract

Some industrial wastewater containing complicated contents (e.g., heavy metals and organics) and extensive concentration-variation cannot be well-treated by physical-chemical treatment processes. In order to obtain the feasible electrochemical technique, an electrocatalytic-membrane process (ECMP) was established to treat such wastewater from a mint factory in Taiwan. Wastewater samples with pollutants of Cu2+, Ni2+ and chemical oxygen demand (COD) were categorized into three types based on pH and concentrations. The complexity of wastewater is attributed that a verity of chemical reagents and manufacturing methods are employed to produce different kind of coins. In this study, each type of wastewater was treated by the ECMP and integrated with other techniques to find out the appropriate procedures. Results indicate that the sole ECMP can effectively remove the Cu2+, Ni2+, and COD when the wastewater is with relatively low pH (around 3–5), low COD (around 50 mg L−1), and high concentration of heavy metals (Cu2+ concentration over 500 mg L−1). However, the ECMP should combine with pH-adjustment to effectively remove the Cu2+, Ni2+, and COD when the wastewater is with very low pH (close to 1), high COD (over 200 mg L−1), and high concentration of heavy metals. In addition, the ECMP has to link the electrocoagulation (ECG) to decrease the Cu2+, Ni2+, and COD concentration when the wastewater is with neutral pH (around 7), middle-level COD (around 130 mg L−1), and low concentration of heavy metals (Cu2+ concentration around 1.0 mg L−1). Accordingly, the ECMP integrated with other treatment processes gains potential to treat refractory wastewater.