Low-Cost Biochar Adsorbents for Wastewater Remediation: Case Studies on Ibuprofen, Sulfamethoxazole, and Diclofenac

Drugs such as ibuprofen, sulfamethoxazole, diclofenac, and pharmaceutical vitamins are increasingly appearing in surface and groundwater, and they are often insoluble in standard wastewater treatment methods. This review discusses low-cost biochar adsorbents, i.e., those produced from agricultural and industrial biomass, and the impact of production methods, physicochemical properties, and surface engineering on determining their efficacy in pharmaceutical remediation. It provides a general overview of the feedstocks (crop residues, forestry wastes, sludges), pyrolysis, and hydrothermal routes, demonstrating how greater pyrolysis temperatures tend to enhance the surface area, porosity, and aromaticity at the expense of polar functional groups responsible for hydrogen bonding. The major adsorption processes include pore filling, van der Waals force, pi interactions, hydrogen bonding, electrostatic interaction, ligand exchange, and surface complexation, associated with the biochar characteristics (surface area, functional groups, mineral content, charge) and the drug characteristics (size, pKa, hydrophobicity). Case studies report large capacity ranges (tens of mg/g to >1000 mg/g for engineered composites), with adsorption typically at pseudo-second-order reaction and Langmuir/Freundlich curves. Practical considerations, including pH, co-contaminants, biochar dosage, and regeneration approach, have significant impacts on removal efficiency. The review reveals regeneration strategies (thermal, chemical, and biological), life-cycle, and other co-benefits, such as carbon sequestration and waste feedstock recycling. Several gaps exist, from inconsistent materials standardizations to pilot-scale validation and LCA information. The standardized testing, scalable production, and built-in treatment systems will play key roles in addressing these issues, transforming biochar from a promising lab adsorbent into a practical and sustainable wastewater technology.