Adsorption of metals in oil sands process water by a biochar/iron oxide composite: Influence of the composite structure and surface functional groups

In this work, anaerobic sludge from a wastewater treatment plant was used to prepare a sludge-based biochar/ iron oxide (B-FeOx) adsorbent. The B-FeOx adsorbent was successfully used to remove metals, including Cr, Cu, Se and Pb from oil sands process water (OSPW) for the first time. Compared with biochar or FeOx alone, a higher removal efficiency of Cr (80.79%+/- 3.44%), Cu (98.21%+/- 0.25%), Se (88.82%+/- 0.31%) and Pb (90.96%+/- 1.86%) was obtained using the B-FeOx composite. The high removal efficiency was attributed to the improved specific surface area and pore volume of the B-FeOx composite, which increased by about 5.9 and 5.7 times, respectively, when compared to biochar. In addition, functional groups in the composite, such as C-O, C = O, O-H, and some iron-bound functional groups, played an important role in the improvement of the removal efficiency of metals. Moreover, the adsorption process was best modelled by the pseudo-second order kinetic model and Langmuir model. Intraparticle diffusion modelling for adsorption of the four metals using B-FeOx composite resulted in two distinct regions: film and pore diffusion. This study provides the details of a low cost, effective, and environmentally friendly adsorbent for the removal of metals from real OSPW.

Automated summary

This study successfully developed a highly efficient B-FeOx adsorbent using anaerobic sludge, which significantly improves the removal efficiency of Cr, Cu, Se, and Pb metals from OSPW. The increased removal efficiency is attributed to the larger specific surface area and pore volume of the B-FeOx composite compared to biochar.