Biochar-surface oxygenation with hydrogen peroxide

• Biochar-surface oxygenation was demonstrated with H2O2 treatment.
• Higher cation exchange capacity was found in H2O2 treated biochar.
• FT-IR revealed an increase of oxygen functional groups in H2O2 treated biochar.
• The H2O2 treatment led to apparently reduced biochar methylene blue adsorption.
• Surface oxygenation did not significantly alter the biochar bulk property.

Biochar was produced from pinewood biomass by pyrolysis at a highest treatment temperature (HTT) of 400 °C. This biochar was then treated with varying concentrations of H2O2 solution (1, 3, 10, 20, 30% w/w) for a partial oxygenation study. The biochar samples, both treated and untreated, were then tested with a cation exchange capacity (CEC) assay, Fourier Transformed Infrared Resonance (FT-IR), elemental analysis, field water-retention capacity assay, pH assay, and analyzed for their capacity to remove methylene blue from solution. The results demonstrated that higher H2O2 concentration treatments led to higher CEC due to the addition of acidic oxygen functional groups on the surface of the biochar, which also corresponds to the resultant lowering of the pH of the biochar with respect to the H2O2 treatment. Furthermore, it was shown that the biochar methylene blue adsorption decreased with higher H2O2 concentration treatments. This is believed to be due to the addition of oxygen groups onto the aromatic ring structure of the biochar which in turn weakens the overall dispersive forces of π–π interactions that are mainly responsible for the adsorption of the dye onto the surface of the biochar. Elemental analysis revealed that there was no general augmentation of the elemental composition of the biochar samples through the treatment with H2O2, which suggests that the bulk property of biochar remains unchanged through the treatment.