MIL-88A(Fe)/g-C3N4 composite and its catalytic membrane for tetracycline removal via peroxydisulfate activation: Performance, mechanism and toxicity evaluation

Abstract

Heterogeneous catalyst/persulfate advanced oxidation process has been widely used in antibiotic wastewater treatment. As-designed MIL-88A(Fe)/g-C3N4 composite catalyst firstly activated peroxydisulfate (PDS) to degrade tetracycline (TC) in this work. Activating PDS by MIL-88A(Fe)/g-C3N4 has a higher efficiency and rate toward TC degradation compared with MIL-88A(Fe) and g-C3N4. After 60 min, the optimal MIL-88A(Fe)/g-C3N4-5 activated PDS to degrade about 80% of TC in water. The existence of g-C3N4 increases the specific surface area and active Fe2+ content of MIL-88(Fe), promotes PDS adsorption and utilization, thus showing an excellent catalytic performance for PDS activation. MIL-88A(Fe)/g-C3N4 activated PDS oxidation process synergistically removed TC by free radicals (O2•−, •OH and SO4•−) with non-free radicals (1O2), and the effect of some important operating factors on TC removal, the TC degradation pathways and toxicity of TC intermediates were analyzed. Moreover, the MIL-88A(Fe)/g-C3N4-5 powdered catalyst was designed into a catalytic membrane, which could remove 96% of TC in a short time (<10 min). The cycle tests confirm that powdered MIL-88A(Fe)/g-C3N4 composite catalyst and its catalytic membrane have a good recyclability and stability, demonstrating that this catalyst possesses a practical application potential in the treatment of TC polluted wastewater.