Hydrogel 3D network derived and in-situ magnetized Fe@C for activation of peroxymonosulfate to degrade ciprofloxacin

Hydrogels possess 3D network with abundant reactive groups, and can bind with active metal ions within their confined 3D structure for fabricating functional materials. In this study, a chitosan grafted polyacrylic acid (CTS-g-PAA) hydrogel was prepared for loading Fe2+, which was then converted into magnetic Fe@C via subsequent pyrolysis process. In Fe@C activated peroxymonosulfate (PMS) (Fe@C/PMS) system, the degradation behaviors of ciprofloxacin (CIP) were systematically investigated, including influencing parameters, reactive oxygen spe-cies (ROSs), degradation mechanism and potential eco-toxicity of degradation intermediates. The results showed that CTS-g-PAA supported, in-situ derived magnetic Fe@C had not only stable catalytic ability at pH 3.0-9.0, but also high degradation efficiency in the presence of inorganic Cl- and HCO3- (5-20 mM) as well as organic humid acid (10 and 20 mg/L). Under the optimized conditions, the degradation efficiency of CIP could reach to 96.84 % within 1 h. In Fe@C/PMS system, the main ROSs involved free radicals SO4 center dot-, center dot OH, O-2(center dot-) and non-free radical O-1(2). Through free radical quantitative experiments, the concentration of SO4 center dot- and (OH)-O-center dot at 60 min was determined respectively to be 11.84 mu M and 0.14 mu M, proving the dominant role of SO4 center dot- . By HPLC-MS analysis, the degradation products were proposed via four degradation pathways, including hydroxylation, defluorination and decarboxylation, as well as the ring opening of quinolone and piperazine. Finally, the potential eco-toxicity of CIP and its degradation intermediates was evaluated by using ECOSAR method based on quantitative structur-e-activity relationships analysis.

Automated summary

In this study, a chitosan grafted polyacrylic acid hydrogel was prepared and used to fabricate magnetic functional materials. The degradation behaviors and mechanism of ciprofloxacin were systematically investigated using this new material as a catalyst and peroxymonosulfate as an activator. The results showed that the prepared hydrogel had stable catalytic ability and high degradation efficiency under different conditions.