Biochar wastewater treatment is gaining attention as scientists search for cheaper and greener ways to clean polluted water. Oil sands process-affected water (OSPW) contains harmful organic pollutants called acid-extractable organics (AEOs), mainly naphthenic acids, which can threaten aquatic life and environmental health. Activated carbon is often used to remove these pollutants, but its high cost limits large-scale use. In this study, Bhuiyan et al. investigated whether biomass-derived biochar could provide a more affordable and sustainable alternative.
Materials and Methods
The researchers prepared biochar from several biomass sources, including wheat straw, pulp mill sludge, switchgrass, mountain pine, hemp shives, and aspen wood. These biochars were tested using real oil sands wastewater collected from Alberta, Canada. To better understand adsorption performance, some biochars were modified by either removing metals through acid washing or increasing metal content using iron impregnation.
The treated wastewater was analyzed to determine how much organic pollution remained after adsorption. Multiple characterization techniques were also used to study biochar properties and explain pollutant removal behavior.
Results
Among all tested materials, wheat straw biochar performed best, removing around 21% of harmful organics. Surprisingly, surface area was not the main factor controlling adsorption. Aspen wood biochar had the highest surface area but showed very poor adsorption performance.
Instead, the study found that iron (Fe) and aluminum (Al) content played the most important role. Biochars containing higher levels of these metals showed stronger adsorption. When metals were removed from wheat straw biochar, adsorption decreased. In contrast, adding iron improved adsorption performance.
The researchers explained that these metals act as binding sites that attract and hold harmful organic molecules on the biochar surface. This mechanism helped explain why some low-surface-area biochars performed better than more porous materials.
Conclusion
This study highlights an important lesson for biochar wastewater treatment: larger surface area does not always guarantee better pollutant removal. Instead, metal-rich biochar containing Fe and Al may offer a more effective and sustainable option for treating contaminated wastewater. Agricultural biomass, especially wheat straw, could therefore become a valuable low-cost material for future water remediation technologies.
Reference
Bhuiyan, T. I., et al. (2017). Adsorption of acid-extractable organics from oil sands process-affected water onto biomass-based biochar: Metal content matters. Chemosphere, 168, 1337–1344..
Reference
Bhuiyan, T. I., et al. (2017). Adsorption of acid-extractable organics from oil sands process-affected water onto biomass-based biochar: Metal content matters. Chemosphere, 168, 1337–1344.
