The contamination of water by synthetic dyes such as methylene blue (MB) has become a serious environmental issue. Using cost-effective and environmentally sustainable adsorbents from agricultural byproducts is a viable solution. This study aims to assess the potential use of olive mill solid waste (OMSW) for the adsorption of MB from aqueous solutions. OMSW was characterized by its ash content, volatile matter, fixed carbon, elemental composition (C, H, N, O, S), pH, point of zero charge (pH pzc ), surface morphology, surface area, pore characteristics, and functional groups to evaluate its suitability for the adsorption of MB. The effects of pH, contact time, initial MB concentration, and temperature were investigated in batch experiments. It was found that the adsorption capacity increased considerably as pH increased, reaching 73 mg/g at pH 10. To better understand the adsorption mechanism, the kinetic, mass transfer, and isotherm data were analyzed using standard models. The pseudo-second-order model well fitted the kinetic data, suggesting that surface interactions are likely the predominant adsorption mechanism. The mass transfer analysis reflected that the adsorption process influenced by both the film and intraparticle diffusion. The Langmuir isotherm model showed the best fitting to the isotherm data, suggesting that MB was adsorbed as a monolayer on a homogeneous surface with a maximum adsorption capacity of 101.01 mg/g. The thermodynamic behavior was also investigated, and the calculated parameters indicated that the adsorption process was spontaneous, exothermic, and mainly governed by physical interactions. The reusability experiment demonstrated that OMSW was found to be reusable for MB removal. Overall, these findings illustrate that OMSW can be effectively used as a sustainable and cost-effective adsorbent to remove MB from water. • Olive mill solid waste demonstrated promising potential for the adsorption of methylene blue form aqueous solutions. • The surface functionality of OMSW was evaluated by thorough characterization. • The pseudo-second-order kinetic model and Langmuir isotherm model fitted the kinetic and isotherm date. • The thermodynamic parameters confirmed the exothermic and spontaneous nature of adsorption. • The multiple-treated OMSW exhibited good reusability performance.
Kasasbeh et al. (Fri,) studied this question.