Adsorption of a Leather Dye on Mesoporous Struvite Obtained From Swine Wastewater

Struvite powder obtained from swine wastewater was used as adsorbent to remove an azo leather dye from aqueous solution. The material was characterized by X-ray diffraction, surface area, and atomic force microscopy. The sample presented a single phase having a mesoporous structure and surface area of 35.63 m2 g−1. Langmuir and Freundlich isotherm models were fitted to the adsorption data and both satisfactorily represented the process. The maximum adsorption capacity was 38.14 mg g−1. From the analysis of thermodynamic parameters such as free energy of adsorption (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) it was verified that the adsorption process is very fast, spontaneous, and exothermic in nature, with weak forces acting.