Preparation and characterization of a novel mountain soursop seeds powder adsorbent and its application for the removal of crystal violet and methylene blue from aqueous solutions

Herein, a novel mountain soursop seeds powder (MSSP) adsorbent was employed to explore the adsorption mechanism of two relevant environmental pollutants: crystal violet CV and methylene blue MB. As a first assessment to investigate the adsorption mechanism and to analyze the performance of this adsorbent, the dye adsorption isotherms were measured at 298–328 K and pH 8. Experimental results demonstrated that this adsorbent was more effective to remove the CV dye compared to MB dye from aqueous solution, thus concluding that it could utilized for the treatment of dye polluted industrial effluents. To further interpret the adsorption mechanism and to obtain a new physicochemical vision, a successful phenomenological theoretical analysis via double layer adsorption model was detailed in this paper. At high equilibrium concentration, the adsorbed quantities at saturation were calculated and they followed this sequence: Qsat (CV-MSSP) > Qsat (MB-MSSP). This theoretical finding explained the highest adsorption for CV dye at different temperatures and characterized analytically its affinity for tested adsorbates. The geometry inclination of tested dyes on MSSP adsorbent surface was described in the paper by analyzing the bonded number of CV and MB dye molecules per site. It was demonstrated that these dyes were adsorbed via a mixed orientation. Based on the estimated concentrations at half-saturation, the calculated adsorption energies suggested that the adsorption of CV and MB on MSSP adsorbent was endothermic. A general analytical description of the dye adsorption mechanism showed that the density of receptor sites and adsorption energies followed the same trend as the adsorption capacity, then they can be considered as the factors that governed this separation process.