Adsorption of anionic textile dyes, phosphate and nitrate from aqueous solution by using boron industry waste in batch and continuous systems

In the first chapter of this thesis, the adsorption of Acid Red 183 (AR183) and Reactive Blue 4 (RB4) from single and binary solutions onto a waste material (BA) from boron industry was studied by batch and continuous (column) systems. In the batch system for single and binary solutions, the effects of operating variables such as solution pH, initial dye concentration and contact time were investigated. The adsorption capacities of AR183 and RB4 in single dye solution were found to be 8.1×10-5 mol/g and 6.42×10-5 mol/g, respectively. Due to competitive adsorption, the adsorption capacities of AR183 and RB4 in the binary dye solutions were reduced to 5.19×10-5 mol/g and 3.44×10-5 mol/g, respectively. The adsorption process for single and binary mixtures followed pseudo-second order kinetics and the isotherm fitted well to the Langmuir isotherm model. In continuous (column) system experiments, the adsorption of AR183 and RB4 from single and binary solutions was fitted well by the Thomas model. The breakthrough and exhaustion time of each dye decreased with increasing flow rate and decreased in the presence of the other dye molecule. The thermodynamic parameters such as free energy (?G), entropy change (?S) and enthalpy change (?H) were obtained showing exothermic nature of dye adsorption on BA.In the second chapter of the thesis, the adsorption of phosphate and nitrate ions from aqueous solution onto BA and calcined BA was investigated by batch and continous (column) systems. The adsorption of phosphate and nitrate ions onto BA and calcined BA was examined with respect to contact time, calcination temperature, pH, adsorbent dosage and temperature. The physical and chemical properties of the BA and calcined BA, such as specific surface area, zeta potential and calcinations temperature, play important roles in phosphate and nitrate adsorption. Three simplified kinetics models, namely, pseudo-first order, pseudo-second order, and intraparticle diffusion models were tested to investigate the adsorption mechanisms. The kinetic adsorption of phosphate and nitrate on BA and calcined BA follows a pseudo-second order model. The intraparticle diffusion model results show that the intraparticle diffusion is not only the rate controlling step but also boundary layer diffusion may control the rate of adsorption. The adsorption data have been analyzed using Langmuir isotherm, Freundlich isotherm, Dubinin-Radushkevich isotherm models. The results indicate that the Langmuir model provides the best correlation of the experimental data. Thermodynamic parameters such as enthalpy, entropy, and Gibb?s free energy changes were also calculated and it was found that the adsorption of phosphate and nitrate ions by BA and calcined BA was a spontaneous and exothermic process. In the continuous system for the adsorption of phosphate and nitrate ions, the effects of operating variables such as flow rate, bed height and initial solution concentration were investigated. In continuous system studies, it was found that the saturation time and the adsorption capacity were decreased with increasing flow rate and increased with increasing bed height. The continuous system studies showed that the saturation time was decreased with increasing inintial solution concentration. The results indicate that the column adsorption for phosphate and nitrate ions was in agreement with the batch experimental data. The Thomas model was used to describe the behavior of the continuous (column) adsorption process, and it was found that the theoretical and experimental adsorption capacity values were in a good accordance with each other.Keywords : Adsorption, Boron Industry Waste, Isotherm, Kinetic, Thermodynamic.