Zeolite (ZSM-12) is a unique material obtained from the drinking water treatment plants' residual "alum sludge", as a result of using aluminum sulphate as a primary coagulant in the plants. Herein, alum sludge (AS) is initially dewatered and subjected for various calcination temperatures 400 °C, 600 °C and 800 °C and the corresponding materials are named as AS400, AS600 and AS800, respectively. Such calcination is provided to attain ZSM-12, which is considered a highly adsorptive material. The material characterization and morphology were investigated using scanning X-ray diffraction (XRD) and electron microscope (SEM) that confirm the presence of ZSM-12 and porosity of such prepared materials. Thereafter, such materials are introduced for phenol remediation from aqueous solution. The experimental data reveal that AS400 had the largest adsorption capacity (275 mg-phenol/g), in comparison to the commercial adsorbent materials during 2 h of isotherm time. Such a result confirms the suitability of alum sludge residue to be a good candidate for environmental remediation. Furthermore, adsorption isotherm models were applied, and the data are well-fitted to the Langmuir isotherm model. In addition, thermodynamic parameters are investigated which verify the physisorption adsorption process and exothermic nature with a spontaneous reaction system.
Keywords: adsorption isotherm; aluminum-based residue; phenol; sorption; statistical optimization.