Upcycling of steel slag to activate persulfate for the degradation of chlortetracycline hydrochloride: Performance and mechanism

View large Download slide View large Download slide Close modal Steel slag has great potential as an Fe-based heterogeneous Fenton-like catalyst because of its high iron content and low cost. However, the iron compounds are often encapsulated by calcium or silicon compounds in the steel slag. Herein, steel slag powder was acid-modified with salicylic acid to remove some Ca–Si compounds and thus expose more iron active sites. The results showed that the calcium content significantly decreased from 36.33 to 20.54% after modification, and more transition metals of Fe and Mn with catalytic activities were exposed simultaneously. During the activation of peroxysulphate, the conversion of Fe(Ⅱ) to Fe(Ⅲ) occurs and large amounts of • OH and 1 O 2 are produced as the main reactive oxygen species. The removal rates of CTC and TOC are 93.42 and 46.05%, respectively, and a degradation process may also be inhibited by CO 3 2− , H 2 PO 4 − , and humic acid (HA). The degradation pathways of CTC mainly include both dechlorination and demethylation. In addition, salicylic acid-modified steel slag shows good repeated usability, and its removal ability is maintained at higher than 80% after four times of recycling. This study provides a new idea for designing an efficient and cheap catalyst to treat organic wastewater. A low-cost but high-efficiency catalyst for wastewater treatment was prepared. Efficient catalysts with more active metal sites are obtained by specific acid treatment. The catalyst provides a reference for how to prepare an efficient catalyst for treating antibiotic wastewater.