Adsorption of Organic Pollutants From Wastewater Using Biochar: A Mechanistic Study on Competitive Adsorption Behavior

This study investigates the adsorption of methyl orange (MO), methylene blue (MB), and acetaminophen (ACT) using biochars produced from Douglas fir and Miscanthus at different temperatures and with different post-pyrolysis treatments that added surface functional groups. Compounds were adsorbed separately and in mixtures to examine the competitive nature of the adsorption processes. MO is known to interact with MB and ACT, whereas MB and ACT are not likely to interact due to both having electron-donating groups. When comparing the biochar adsorption capacities for these compounds when alone and mixed, biochars with both hydroxyl and carbonyl surface functional groups had higher adsorption capacities for the tested compounds when they were in mixed solutions. Biochars with only hydroxyl groups exhibited competing adsorption mechanisms and poorer adsorption capacities of aromatic compounds in complex solutions. This provides an understanding of how competing adsorption mechanisms of aromatic compounds by biochars vary depending on the dominant adsorption mechanisms of the biochar, which will allow for more effective real-world applications for water purification in the future.