Removal of guaifenesin and amprolium drugs from wastewater using ecofriendly low-cost biopolymer: adsorption isotherms, kinetics models and thermodynamic studies.

An environmentally safe, economic, yet simple approach was presented in this study for the removal of the traces of guaifenesin (GUA) and amprolium (AMP) drugs from wastewater using chitosan (CS) biopolymer. The removal capacity was investigated under several variables including pH, contact time, adsorbent dose, and drug capacity. The study of adsorption isotherm models demonstrates that Langmuir model is more likely to illustrate the adsorption process more than Freundlich with correlation coefficient (R²) of 0.984 and 0.994 with (q_m) of 2.78 and 1.33 for both GUA and AMP, respectively. Four kinetic models were assessed for the adsorption process. The results indicate that the adsorption system follows the pseudo-second-order model which was confirmed by its higher correlation coefficient (R² ≈ 0.99) for both GUA and AMP, suggesting that chemical adsorption is the rate-limiting step of the adsorption mechanism. Thermodynamic studies were carried out to determine ΔH°, ΔG°, ΔS°. The positive values of ΔH° and ΔG° indicated that the sorption of both drugs onto CS is an endothermic nonspontaneous and the system gained energy from an external source. [ABSTRACT FROM AUTHOR]