The influence of B heteroatom concentrations on the physiochemical properties of N, B-co-doped biochar for peroxymonosulfate activation in ciprofloxacin removal. (February 2023) - Choong, Zheng-Yi
Abstract: N, B-co-doped biochars with varying boric acid (BA):urea mass ratio were prepared by two-step calcination of sawdust (NB-BC-x, where x = 1, 2, and 3 corresponds to the BA:urea mass ratio of 0.025:1, 0.05:1, and 0.1:1, respectively) and characterized. Generally, B doping prior to N doping can improve N doping because the presence of oxidized B during N doping can interact with NH3, facilitating N doping. The performance of NB-BCs in PMS activation for ciprofloxacin (CIP) removal was evaluated and it was found that the k app increased in the order of: N-BC (0.010 min −1 ) < B-BC (0.016 min −1 ) < NB-BC-2 (0.031 min −1 ) < NB-BC-3 (0.039 min −1 ) < NB-BC-1 (0.053 min −1 ). Due to its large specific surface area and synergistic interaction between N and B moieties, NB-BC-1 presented the best PMS activator, achieving CIP removal of ∼45 and ∼80 % by adsorption and degradation in 60 min, respectively. Further performance study using NB-BC-1 revealed that the k app increased with increasing catalyst loading and PMS dosage. Meanwhile, higher pH can reduce the CIP removal efficiency due to the electrostatic repulsion between NB-BC-1 and PMS. It was also demonstrated that NB-BC-1 can be reused and regenerated after deactivation using thermal treatment at 500 °C. From the chemical scavengers and electrochemical studies, it can be deduced that NB-BC-1 activates PMS through both radical and nonradical pathways. Lastly, the degradation pathway of CIP was also proposed by identifying the degradation intermediates and their toxicity were accessed. Overall, this study showed that NB-BC-1 can potentially be used as a PMS activator for wastewater treatment. Graphical abstract: Unlabelled Image Highlights: N, B-co-doped biochar (NB-BC) was prepared using two-step calcination method. The presence of oxidized B can facilitate N doping in the second doping step. CIP removal of 80 % can be achieved in 60 min by NB-BC via PMS activation. NB-BC can activate PMS through both radical and nonradical pathways. The CIP degradation pathways were proposed based on detected intermediates.