Use of chitosacoated olive paste wastes in cationic dye removal

Today, environmental problems have reached a serious level on a global scale with the increasing population, industrialization, and construction activities. The waste generated in this process makes it challenging to protect natural resources and increases environmental pressure. Therefore, the recovery and reuse of waste stand out as an inevitable solution for the sustainability of natural resources. In this context, various recovery methods were investigated in this thesis using olive pulp (pomace), a natural waste product. Agricultural wastes, such as pomace, have the potential to harm the environment if not correctly utilized. Wastewater containing dyes is formed especially as a result of textile and similar industrial activities and poses serious threats not only to human health but also to the entire ecosystem. Such wastewater is usually discharged into the receiving environment after undergoing various pre-treatment and secondary treatment processes. However, in cases where traditional methods are insufficient, the need for more effective, low-cost, and environmentally friendly treatment technologies is increasing daily. In this context, the adsorption process stands out as an alternative method due to its high removal efficiency, ease of application, and economic nature. In this thesis, chitosan and glutaraldehyde-coated pomace (GA@Kt-Pr) and pomace char (GA@Kt-PÇ) were used as bioadsorbents for the first time in the removal of a basic dye called methylene blue (MM). Characterization of both adsorbents was performed using FT-IR, FE-SEM-EDX, BET, and particle size analysis. In addition, various parameters affecting the adsorption process (pH, adsorbent dose, initial dye concentration, contact time, and temperature) were investigated. The obtained adsorption data were analyzed according to the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. As a result of the evaluations, it was determined that the Langmuir isotherm represented the most suitable model for both adsorbents. According to the Langmuir model, the theoretical maximum adsorption capacity (qmax) of GA@Kt-Pr and GA@Kt-PC adsorbents at 25°C was calculated to be 104,16 mg/g and 52,35 mg/g, respectively. When evaluated in terms of kinetics, the experimental data obtained were compared with the pseudo-first-order, pseudo-second-order, and intraparticle diffusion models; accordingly, it was concluded that the adsorption process of both adsorbents showed the best fit with the pseudo-second-order kinetic model. In addition, the changes in thermodynamic parameters, including free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°), were calculated using data obtained from studies conducted at different temperatures. As a result of these calculations, it was understood that the adsorption process was spontaneous, exothermic, and thermodynamically applicable.