Remediation and Optimisation of Petroleum Hydrocarbon Degradation in Contaminated Water by Persulfate Activated with Bagasse Biochar-Supported Nanoscale Zerovalent Iron

In this study, biochar (BC) was prepared from bagasse and then successfully loaded with nanoscale zerovalent iron (nZVI) to produce BC-supported nZVI, termed nZVI@BC. Satisfactory results were obtained using a nZVI@BC-activated persulfate (PS), termed nZVI@BC/PS, to remediate total petroleum hydrocarbons (TPH)-contaminated water. The effects of three influencing factors—the dosage of nZVI@BC, DnZVI@BC, the concentration of PS, CPS, and the initial pH, pHi—on TPH removal were examined through single-factor and batch tests. The results show the following. Each factor considerably influenced the performance of the prepared nZVI@BC/PS reaction system in removing TPH. The TPH degradation process conformed to a first-order kinetic model. The response surface method (RSM) was used in tandem with a Box–Behnken design to optimise the variables involved in TPH degradation. The three influencing variables (i.e., DnZVI@BC, CPS, and pHi) were set in the range of 0.4–1.0 g/L, 20–160 g/L, and 2.21–9.42, respectively, during the experiment. An optimised quadratic model used to fit the experimental data displayed a high level of significance (p < 0.0001) with a very high regression value (R2 = 0.9906; adjusted R2 = 0.9786). Analyses of regression and variance revealed that the quadratic model sufficiently explains the TPH degradation rate. An electron paramagnetic resonance (EPR) spectroscopic analysis of the nZVI@BC/PS system revealed that SO4−·, ·OH, O2−·, and 1O2 participated in the activation and degradation processes. The results of this study show that nZVI@BC-activated PS systems possess great potential for applications in TPH-contaminated wastewater treatment and environmentally sustainable development.