Adsorptive removal of sulfonamides, tetracyclines and quinolones from wastewater and water using carbon-based materials: Recent developments and future directions

Antibiotics are widely used for treatment of diseases caused by bacteria. They reach the aquatic environment through urine and excreta. The dominant antibiotics that are commonly detected in aquatic environments include tetracyclines, sulfonamides and quinolones. This review critically analyzes the effectiveness of carbon-based materials (biochar and hydrochar) for removal of antibiotics from wastewater and water. Both biochar and hydrochar show excellent performance for adsorptive removal of antibiotics from the aqueous medium. However, the adsorption capacity of hydrochar is relatively higher than that of biochar, specifically for the removal of tetracyclines. Insights into removal mechanisms, solution chemistry, adsorption kinetics, isotherms, adsorbent regeneration and cost-analysis are provided. The key mechanisms associated in the adsorption of antibiotics onto biochar/hydrochar surfaces include π-π electron donor-acceptor interactions and H-bonding. Thermodynamics studies indicate the sorption process is mostly spontaneous and endothermic. In most cases, the adsorption data can best fit the pseudo-second-order kinetic and Langmuir isotherm models. Overall, biochar/hydrochar-mediated adsorptive removal of antibiotics from aqueous solution merits serious considerations from both economic and environmental perspectives. The key knowledge gaps and future research directions are highlighted to expand the scope of ongoing research on engineered biochar/hydrochar and modification of their physicochemical characteristics to achieve effective removal of antibiotics and their metabolites.