Photocatalytic Cr(VI) reduction over MIL-101(Fe)–NH₂ immobilized on alumina substrate: From batch test to continuous operation

MIL-101(Fe)–NH₂ was hydrothermally immobilized on porous alumina substrate to fabricate MIL-101(Fe)–NH₂@Al₂O₃ (MA) photocatalyst via a reactive seeding (RS) method. The as-prepared MA photocatalyst can accomplish 100% Cr(VI) reduction efficiency up to 20 cycles with the synergistic effect of oxalic acid upon the irradiation of white light. The influences of co-existing inorganic ions in simulated tanning wastewater on Cr(VI) reduction were evaluated via a Box-Behnken design of response surface methodology. The as-prepared MA photocatalyst can overcome the difficulty and challenge concerning the recovery and recyclability of traditional powder MOFs photocatalysts. Furthermore, a continuous fixed-bed device based on MA photocatalyst was designed, which can achieve a rapid and efficient Cr(VI) reduction under white light in lab experiment and under the real solar light in field experiment. This work provides the possibility for the continuous photocatalytic Cr(VI) reduction operation in the fixed-bed reactor.