Modulated fenton-like activity via peroxymonosulfate activation by CoxNiy-LDH: Mechanism of Co/Ni bimetallic synergy and application of catalytic membrane
Ningning Xiao, Aijing Zhang, Tao Li, Bing Hu, Ye Yang, Yingying Dong, Zhiwen Chen, Wendong Wang, Meiling Liu
Abstract
Metal-based layered double hydroxides (LDHs) are facile and efficient for peroxymonosulfate (PMS) activation. In this study, the PMS activation ability of Co x Ni y -LDHs was found controlled by both the numbers of Co active sites and the lamellar configuration. On one hand, the Co/Ni ratio modulated interlayer distance, specific area and porosity properties. On the other hand, Ni incorporation facilitated the Co 2+ /Co 3+ circulation to improve organics degradation efficiency. Consequently, Co 2 Ni 1 -LDH/PMS system achieved 99.2 % removal towards tetracycline (TC) and above 80 % removal towards multiple organics with accelerated reaction rate (k obs = 0.264 min −1 ), due to higher PMS activation efficiency. Density functional theory (DFT) revealed that increased adsorption energy and quantity of transferred electrons contributed to extend O-O bonds of PMS molecules to form SO 4 •− , •OH and 1 O 2 , which were chiefly responsible for decontamination. Co 2 Ni 1 -LDH/PMS system showed considerable environmental adaption ability in various ambient conditions (pH, coexisting anions and HA) and water matrices (tap water, river water and secondary effluent of wastewater treatment plant), maintaining the removal rate of over 90 %. More importantly, the Co 2 Ni 1 -LDH was loaded on PES membrane to build catalytic membrane system for TC wastewater purification. The stable removal efficiency (88 %–100 %), relatively high permeate flux (227.3 L/(m 2 ·h)) and low loading density (22.7 g/m 2 ) demonstrated the applicability of the catalytic membrane for water processing. This work systematically analyzed the synergetic mechanism between Co and Ni, providing inspiration for further study towards bimetallic LDHs.