Adsorption of boron from aqueous solutions using fly ash: Batch and column studies

In the present paper, boron removal from aqueous solutions by adsorption was investigated. Fly ash particle size used in adsorption experiments was between 250 and 400 μm. During the experimental part of this study, the effect of parameters such as pH, agitation time, initial boron concentration, temperature, adsorbent dosage and foreign ion on boron removal were observed. In addition, adsorption kinetics, adsorption isotherm studies and column studies were made. Maximum boron removal was obtained at pH 2 and 25 °C. Thermodynamic parameters such as change in free energy (ΔG°), enthalpy (ΔH°), entropy (ΔS°) were also determined. As a result of the kinetic studies, it was observed that the adsorption data conforms to the second degree kinetics model. In the isotherm studies, Langmuir and Freundlich isotherm models were applied and it was determined that the experimental data conformed to Langmuir isotherm model. Batch adsorbent capacity (qo) was calculated as 20.9 mg/g. The capacity value for column study was obtained by graphical integration as 46.2 mg/g. The Thomas and the Yoon-Nelson models were applied to experimental data to predict the breakthrough curves and to determine the characteristics parameters of the column useful for process design.