Xing Gao,Weiying Feng,Hanxiao Zhang,Nanyan Weng,Shouliang Huo
Harmful cyanobacterial blooms in eutrophic water bodies have frequently occurred worldwide and become a major environmental concern. Therefore, it is imperative to develop a stable and efficient algaecide to solve this issue. In this study, our purpose was to investigate the efficacy and mechanism of a newly developed Cu 2+ doped Fe 3 O 4 @Biochar magnetic composite (Cu-Mag-BC) in in-situ inactivation of Microcystis aeruginosa ( M. aeruginosa ) . We successfully synthesized the Cu-Mag-BC by coating Cu 2+ onto Fe 3 O 4 @Biochar. Cu-Mag-BC exhibited superparamagnetic behavior and was uniformly impregnated by Cu 2+ . Cu-Mag-BC (5 mg/L), rapidly inactivated chlorophyll-a (Chl-a) in M. aeruginosa with low Fe and Cu leaching, during which time the OD 264 value and malondialdehyde (MDA) content increased, while the activities of superoxide dismutase (SOD) and catalase (CAT) first increased and then decreased, due to oxidative stress induced by over-generated reactive oxygen species (ROS). Quantitative results showed that ·O 2 − and ·OH were the main ROS species produced from Cu-Mag-BC. Inactivation efficiency was maintained at approximately 80 % after three consecutive runs and total Chl-a removal efficiency reached 2.84 g/g, indicating good reusability and stability. A possible inactivation mechanism is proposed; amino groups and adipose chain were the primary oxidation sites. Thus, Cu-Mag-BC shows potential as a candidate for simultaneously inactivating harmful cyanobacteria and preventing secondary pollution.
Xiaoxue Yang,Kun Luo,Zhoujie Pi,Peng Shen,Puyu Zhou,Li He,Xiaoming Li,Qi Yang
A novel nanocomposite CeO 2 /Fe 3 O 4 /biochar (BC) was prepared using a straightforward, solvent-free mechanical ball milling method. Comparatively to the material prepared by chemical co-precipitation (77.14 %) and raw BC (33.64 %), CeO 2 /Fe 3 O 4 /BC prepared by ball milling achieved better tetracycline (TC) removal (94.35 %) under the optimal condition (TC concentration 10 mg·L -1 , catalyst dose 0.5 g·L -1 and pH 9.01). Ball milling not only reduced the particle size, but also increased the surface area of composite, which was favorable to the adsorption of TC on CeO 2 /Fe 3 O 4 /BC. Meanwhile, the number of oxygen-containing functional groups in as-prepared nanocomposite increased after ball milling, which could serve as the bridge of electron transfer to enhance TC degradation. Dissolved oxygen (DO) was activated by CeO 2 /Fe 3 O 4 /BC to produce reactive oxygen species (ROS) for the TC degradation. X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) characterization indicated that the enhanced oxygen activation should be attributed to the presence of Ce 4+ /Ce 3+ and Fe 3+ /Fe 2+ redox pairs and persistent free radicals (PFRs) in CeO 2 /Fe 3 O 4 /BC. Desorption experiments suggested that the adsorption and degradation induced by ball-milled CeO 2 /Fe 3 O 4 /BC were accounted for about 79.8 % and 20.2 % of total TC removal, respectively. This study revealed that the organic pollutants removal by BC-based nanocomposite is not alone contribution of the adsorption and the degradation behavior during this process should be concerned.
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