Activation of persulfate by lanthanum modified activated coke for tetracycline degradation

Abstract

Abstract Activated coke (ACO) has been applied in some wastewater treatment plants to advance the removal of micro-pollutants from secondary effluent. This work investigated the use of Lanthanum (La) to modify ACO (La-ACO) for enhancing the removal/degradation of micro-pollutants by activating peroxydisulfate (PDS). We report that the immobilization of La oxide on ACO significantly enhances the adsorption of tetracycline (TC) from aqueous solution as well as its persulfate-based catalytic oxidation. The pseudo-first-order Kapp value of the La-ACO/PDS process is 1.41 times that of adsorption and PDS oxidation alone, indicating an evident synergistic effect. Surface analysis confirms the introduction of La on ACO, while both La(OH)3 and La2O3 consist of La species on La-ACO. The pH values close to neutral are shown to improve the degradation of TC. Also, increasing reaction temperature improves the TC oxidation. The oxidizing species superoxide anion radical (O2·−) and active holes (h+) prove the predominant oxidizing species, while the contribution percentages of O2·− and h+ achieve 51.3% and 84.2% of the total degradation capacity, respectively. The inhibiting effect of SO42− and Cl− is insignificant, while the coexisting humic acid has actually improved the TC removal. Reusability test indicates the stable and continuable PDS catalytic ability.