EVALUATION OF ECO-FRIENDLY POROUS CERAMICS FOR REMOVAL OF Zn2+ ION FROM AQUEOUS SOLUTIONS: KINETIC, EQUILIBRIUM AND THERMODYNAMIC STUDIES

In the last decade, access to clean water has become a challenge, because of the rapid population growth and enormous agricultural and industrial activities. There are numerous processes for removing dissolved heavy metals, including ion exchange, coagulation, precipitation and adsorption. Adsorption could be the most effective for this purpose because of the low cost, easy operation, and short duration time. Nowadays, porous ceramic materials are promising adsorbents for different heavy metal ions. Eco-friendly porous ceramics based on natural zeolite and bentonite clay were synthesized and adsorption capacity toward Zn2+ ions was investigated. The synthesis was performed using the foaming method without an organic binder. Hydrogen peroxide was used as the blowing agent, while sodium dodecyl sulfate was used as the foaming agent. The obtained green and sintered samples of porous ceramics were characterized in detail by different methods (TG/DTG, SEM, XRD, FTIR, XRF). Results showed that the foamed samples could be synthesized at room temperature and fully crystallized after being sintered at 800 °C. Total porosity of porous ceramic sample reached maximum value of 74.7%. The second-order model and Langmuir model best described the adsorption kinetic and isotherm data. The maximum adsorption capacity obtained using the Langmuir model was approximately 5.01 mg Zn2+/g. The thermodynamic parameters showed that adsorption is a spontaneous and endothermic process favored at higher temperatures. Overall, this study highlights the potential of porous ceramics based on natural zeolite and bentonite for the removal of heavy metals and provides insight into the mechanisms of the adsorption process.