Effective degradation of atrazine by spinach-derived biochar via persulfate activation system: Process optimization, mechanism, degradation pathway and application in real wastewater

Herein, biochar derived from spinach remnants was prepared for the first-time for the utilization in persulfate (PS) activation to effectively degrade atrazine. Characteristics of the prepared biochar were explored using advanced analyses. Control experiments implied the efficient activation of PS in the presence of the synthesized biochar. The highest degradation of atrazine (99.8%) could be attained at atrazine concentration of 7.2 mg/L, PS concentration of 7.7 mM, biochar dose of 1.88 g/L and reaction time of 120 min. The prepared biochar displayed a high recyclability performance attaining degradation ratios of 98.2, 96.53, 96.4, 92.8 and 88% in five sequential cycles under the optimum conditions. The degradation mechanism was explored showing that sulfate radicals were the prime reactive species in the degradation system. The degradation intermediates were specified, and the degradation pathways were propositioned. The highest REs in agrochemical industrial wastewater reached 80.21 and 83.43% of atrazine and TOC after 2 h. NH3 (348.4 mg/L) was reduced to 168.3 mg/L (RE: 51.7%) while level of NO3 (94.7 mg/L) was increased by 98.8% (188.3 mg/L) in the treated effluent due to oxidation of NH3 to nitrite and then nitrate. Extension of reaction time could contribute to achieving full mineralization of the real wastewater due to the residual PS after 120 min. The effectiveness and low-cost of biochar@PS system as well as its high performance in degrading real wastewater support the efficiency of the prepared biochar to be applied on an industrial scale.