Electrochemical filtration system using hybrid materials between graphene oxide and metal organic framework for dichloroacetic acid reduction in water

Abstract

Haloacetic acids are potential human carcinogens, but they are not efficiently removed by conventional water purification systems. Electrochemical filtration-oxidation process is promising because it can adsorb and degrade pollutants simultaneously. However, stability and efficiency of anodic filter requires improvement. Here, abatement effectiveness of dichloroacetic acid (DCAA) in water via an electrochemical filtration process using graphene oxide (GO)–metal organic frameworks (MOFs) anodic filter was extensively elaborated. It is anticipated that MOFs can enhance stability of the filter; hence either MIL-53(Al) or NH₂MIL-53(Al) was added to form the hybrid filter. GO had a greater DCAA uptake (∼40.5 mg/g) than MOFs. At electro-filtration, adsorption played a dominant role when the GO-based membrane was used (reduction of 73–79 %), while composite membranes composed of GO and MIL-53 (Al) (GO:MIL-53(Al)) membrane showed a greater reduction than GO:NH₂MIL-53 (Al) membrane. The effectiveness of GO membrane dropped substantially to ∼18 % after reuse. Under applying DC current (1.83 mA/cm²), the DCAA reduction by GO:MIL-53 (Al) and GO:NH₂MIL-53(Al) membranes became similar to the GO membrane. Compared with GO membrane, composite membranes had better reusability for the DCAA reduction. The role of indirect oxidation was elaborated. While maintaining the same ionic strength of different background ions (i.e. Na₂SO₄ and NaCl), SO₄^• was found to be the predominant radical for DCAA reduction. Overall, this research offers insight into importance of MOFs in the composite membranes and DC current supply in DCAA reduction and suggestion for reusability improvement.