Waste to resource recovery: mesoporous adsorbent from orange peel for the removal of trypan blue dye from aqueous solution

In this study, mesoporous material developed from orange mesocarp was characterized (using TGA, SEM, EDX, FTIR, and BET) and applied for the adsorption removal of trypan blue dye from aqueous solution. The produced and characterized mesoporous material has the following BET properties: BET surface area (328.870 m 2 /g), total pore volume (0.1981 cm 3 /g), micropore volume (0.1342 cm 2 /g), pore diameter (2.138 nm), and average pore size (5.839 nm). The EDX profile of the sample indicated the presence of some heteroatoms (S, O, and N), which are functional entities in the provision of competitive adsorption sites. The removal efficiency of the mesoporous adsorbent for the trypan dye was evaluated as 97.10%. The extent of adsorption increased linearly with concentration, the period of contact, and adsorbent dosage but inversely with pH. Analysis of results obtained from kinetic models (pseudo-first and second orders, Elovich and intraparticle diffusion models) and adsorption isotherm models (Langmuir, Freundlich, Temkin, Elovich, and BET isotherms) strongly suggested chemisorption mechanism. The pseudo-second-order and the Langmuir models were the best descriptors that generated strong agreement between experimental and theoretical data. A synergy between information obtained from FTIR analyses and computational chemistry simulations confirmed that the sites for the adsorption of the dye are in the sulfate oxygen atoms. Experimental and theoretical data were useful in proposing the mechanism of adsorption of the dye on the mesoporous surface. The study provides useful information that gives hope to the efficient recovery of resources from orange peel wastes and for the remediation of dye contaminated water.