Engineered Algal Biochar for the Sequestration of Cu2+ from Aqueous Solution

Abstract

The provision of safe drinking water in low-income countries is problematic due to high levels of pollution and high cost of water treatment. While existing water treatment methods are efficient in removing most contaminants, they are expensive. Adsorption methods may be a cheaper and efficient alternative, given that feedstock for the fabrication of adsorbents are readily available, and they are easy to produce. The objective of this study was to synthesize and evaluate the performance of algae-derived adsorbents in removing Cu2+ form wastewater using batch experiments and fixed-bed columns. Algal biomass was pyrolyzed under limited oxygen to produce biochar (BC), which was separately activated using: (1) ferric chloride to form a Fe2O3-BC composite, and (2) KMnO4 and H2SO4 through a modified Hummer’s method to form HBC. Batch experimental data fitted well in both pseudo-first order (r2=0.965) and pseudo-second order (r2=0.946) kinetic models, and there was no significant difference (p=0.349). The Yoon-Nelson (r2=0.879) and Thomas (r2=0.891) models adequately described the experimental data, while the Adams-Bohart model had low fit (r2=0.673) in column studies. The results showed that the biosorbents were effective in removing Cu2+ from wastewater, with HBC having a higher affinity than Fe2O3-BC and BC. FTIR measurements after adsorption suggest that carbonyl groups played a key role in binding Cu2+ ions. Overall, valorizing algal biomass potentially helps towards solving the problem of algal blooms, while providing material for treating water. Further research should investigate the economic feasibility and up-scaling of the technology to field-scale.