Classical and advanced isotherms to model the adsorption of drugs, dyes and metals on activated carbonaceous materials: a review

Water contamination is a major health issue that can be addressed by using carbonaceous materials to adsorb and filter pollutants, yet adsorption mechanisms need to be better understood to improve the adsorption efficiency. Here we review the models that are used to study the mechanisms of adsorption of drugs, dyes and metal ions on carbonaceous materials, with emphasis on classical and advanced isotherms. We discuss the fitting frequency, lignocellulosic and fossil fuel-derived adsorbents, biomass composition, activating agents, surface functions, the carbonization temperature, the medium temperature effect and the use of several isotherms to explain the same mechanism. The adsorption capacity can reach up to 2651 mg of contaminant per g of lignocellulosic materials and 1274 mg of contaminant per g of fossil materials. Isotherm validation commonly depends on several parameters. The adsorption on lignocellulosic carbonaceous materials is best described by the Langmuir isotherm. In contrast, adsorption on fossil materials is best described by the Redlich-Peterson isotherm. Advanced and classical isotherms are in good agreement in 44% of reports.