Abstract: In the process of oilfield exploitation, the extensive use of chemical agents leads to serious crude oil emulsification, which makes the produced liquid contain a large amount of crude oil that is difficult to remove. In order to treat oily wastewater efficiently, quickly and without secondary pollution, nanoscale zero-valent iron (nZVI) was supported on biochar prepared from spent mushroom substrate (SMS) to prepare a novel iron-carbon composite (SMS-nZVI), and its ability to treat high concentration of oily wastewater was comprehensively evaluated. The results of the indoor simulated removal of petroleum experiment show that, compared with SMS and nZVI, SMS-nZVI can remove petroleum quickly and effectively. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) nitrogen-adsorption and Fourier transform infrared (FTIR) were used to characterize the morphology, structure and properties of the composite. The results showed that SMS biochar can effectively prevent the agglomeration of nZVI, increase the overall specific surface area and enhance the adsorption capacity of the composite. Comparing with other biochar substrates, it was found that the iron-carbon composits prepared by spent mushroom substrate has a better petroleum removal effect than the traditional wheat straw biochar. By optimizing the experimental conditions, an operation process with the best petroleum removal effect was obtained: when the mass ratio of nZVI to biochar was 1:5, pH was 4, and the initial concentration of petroleum was 1000mg·L-1, the petroleum removal rate could reach 95% at 5h. After exposing SMS-nZVI to air for 30 days for natural aging treatment, SMS-nZVI can still maintain an oil removal rate of more than 62%, which indicates that the composite has good stability.

Key words: oily wastewater, nanoscale zero-valent iron (nZVI), spent mushroom substrate (SMS), SMS-nZVI composites