Pharmaceutical residues, particularly widely prescribed antibiotics like sulfamethoxazole and trimethoprim, continuously enter aquatic environments through untreated municipal wastewater, landfill leachates, and agricultural runoff. Persistent exposure to these active drugs at trace levels poses severe ecological threats and accelerates the global emergence of antibiotic-resistant bacteria and resistance genes. Traditional wastewater treatment systems frequently fail to break down or remove these complex chemical structures completely. Converting abundant agricultural residues and biological wastes into activated biochars offers an affordable, highly efficient, and environmentally sustainable adsorption alternative for cleaning polluted water.

Physicochemical characterization confirms that thermal pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More at 700 degrees Celsius paired with phosphoric acid activation creates highly effective structural properties in both white-rot fungus biochar and corncob biochar. Both materials preserve a high fixed carbon content exceeding 70 percent, yielding extensive surface pores and cavities that facilitate fluid movement. Advanced surface spectroscopy reveals abundant functional groups, including hydroxyl, carbonyl, and carbon-oxygen structures, which provide essential binding sites for capturing target antibiotic molecules. Additionally, elemental analyses confirm strong carbon retention, ensuring stable skeletal frameworks during water treatment operations.

Individual batch adsorption experiments demonstrate exceptional performance when each biochar is applied independently to synthetic water solutions containing environmentally realistic antibiotic levels. White-rot fungus biochar achieves maximum removal efficiencies of 99.5 percent for sulfamethoxazole and 89.8 percent for trimethoprim, delivering an adsorption capacity of 0.22 milligrams per gram for both pharmaceuticals. Corncob biochar similarly achieves impressive removal rates, eliminating 89.8 percent of sulfamethoxazole and 87.7 percent of trimethoprim. The rapid initial adsorption rate observed across both materials stems from a high abundance of open surface binding sites and strong concentration gradients driving mass transfer.

Detailed kinetic and equilibrium modeling demonstrates that antibiotic removal proceeds through a complex combination of physical and chemical mechanisms. Adsorption behavior fits pseudo-first-order, pseudo-second-order, and Elovich kinetic models, indicating that mass transfer, pore-filling, and chemical binding operate simultaneously. Furthermore, solution acidity strongly governs the process by altering the ionization state of the drugs alongside the net surface charge of the biochars. Trimethoprim removal peaks under neutral to slightly basic conditions driven by electrostatic attraction, while sulfamethoxazole binding relies heavily on strong hydrogen bonding across varying pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More levels.

Evaluating composite mixtures of white-rot fungus biochar and corncob biochar reveals an unexpected reduction in overall antibiotic filtration. Tested across various mixing ratios and contact times using a Taguchi experimental design, the combined biochar system achieves maximum removal efficiencies of only 65.56 percent for sulfamethoxazole and 27.37 percent for trimethoprim. This performance drop demonstrates an antagonistic interaction between the two materials. The smaller particle size of white-rot fungus biochar likely blocks the open structural pores of corncob biochar, reducing the total available surface area and active binding sites. Consequently, single-source biochar applications remain far superior for practical water treatment systems.

Source: Kaudza, C. (2026). Adsorptive removal of sulfamethoxazole and trimethoprim from aqueous solutions using white-rot fungus biochar, corncob biochar, and their composite mixtures (Master’s thesis, Jomo Kenyatta University of Agriculture and Technology).