Photocatalytic Cr(VI) reduction over MIL-88A(Fe) on polyurethane sponge: From batch to continuous-flow operation

MIL-88A(Fe)@sponge (MS) was synthesized by a dip-coating method, which displayed efficient photocatalytic Cr(VI) reduction efficiency under both low power LED UV light and real solar light irradiation. It was observed that MS (0.2 g/L) could remove 100% Cr(VI) (10 mg/L) by adding 0.4 mmol/L tartaric acid (TA) without adjusting pH (pH 5.05) within 6.0 min and 3.0 min under UV light and real solar light irradiation, respectively. Besides, the photo-induced e− and radicals (O2•− and CO2•−) were found to play the momentous roles in the MS/TA/UVL/Cr(VI) system by the scavenger experiments and electron spin resonance (ESR) tests. MS was also filled into a fixed-bed reactor to test the possibility of long-term Cr(VI) reduction operation in TA/UVL system. As expected, the results revealed that MS could still maintain 100% activity up to 60 h. These results demonstrated that MIL-88A(Fe) might be the potentially efficient catalyst for large-scale wastewater treatment in the near future.