Biochar Supported Nanoscale Zero-valent Iron Composites for the Removal of Petroleum from Wastewater

Considering the need for efficiently and rapidly treating oily wastewater while preventing secondary pollution,the nanoscale zero-valent iron(nZVI) was supported on biochar prepared by using a spent mushroom substrate(SMS),to produce an iron-carbon composite(SMS-nZVI). The ability of the SMS-nZVI to treat wastewater containing high concentration of oil was then comprehensively evaluated. The morphology, structure, and other properties of the composite were characterized by using scanning electron microscopy, transmission electron microscopy, the Brunauer-Emmett-Teller nitrogen sorption analysis, and the Fourier transform infrared spectroscopy. The results show that the biochar prepared by using the SMS can effectively prevent the agglomeration of nZVI and increase the overall specific surface area, thereby enhancing the absorption of petroleum by the composite. Experiments reveal that compared with the SMS and nZVI,the SMS-nZVI composite removes petroleum faster and more efficiently from wastewater. Under optimized conditions involving an nZVI to biochar mass ratio of 1:5 and a pH value of 4, the efficiency for removal of petroleum from wastewater with an initial petroleum concentration of 1000 mg/L could reach 95% within 5 h. Based on a natural aging treatment involving exposure to air for 30 d, the SMS-nZVI composite retained an oil removal rate of higher than 62%, and this result could highlight its stability for practical applications.