Document Type : Review Articles
physical chemistry faculty of science Al-Azhar university
hydrogeochemistry department desert research center
Physical chemistry department faculty of science Alazhar univercity
In this study, converting exhausted resin with no commercial value into a promising activated carbon as adsorbent with the aid of mineral acids H2SO4 (S-AC) and H3PO4 (P-AC), and base NaOH (OH-AC). This is achieved by mixing the exhausted resin with concentrated sulphoric acid, phosphoric acid and powdered sodium hydroxide separately. The properties of prepared activated carbon were characterized using SEM and FT-IR techniques. The adsorption parameters, including contact time, adsorbent dosage, initial concentration and solution pH as well as solution temperature were investigated. Adsorption models, kinetic and thermodynamic studies were performed to explore and predict the adsorption of Zn(II) onto the activated carbons from aqueous solutions and groundwater. Participation of OH-, COO-and SO3- groups in the adsorption of zinc ions was confirmed by FT-IR analysis. Also, SEM images showed that morphological surface changes happened after the adsorption processes occurred. The data obtained show that, increasing the carbonization temperature to 900°C reduced the removal percentage of Zn2+ significantly by S-AC but showed surprisingly little effect on the selectivity of P-AC and OH-AC adsorbent. pHPZC value for S-AC, P-AC and OH-AC at 450oC was 4.3, 5.5 and 7.1, respectively. Consequently, S-AC (450oC) has excellent adsorption properties than the other carbons. The optimum contact time was 300min using S-AC (450oC), the best dosage, initial concentration and pH are 0.4g, 50mg/l and 4, respectively. This study indicates the potential of S-AC to be applied as an economically viable and efficient adsorbent for the removal of Zn(II) from groundwater by batch technique. The Elovich model with a higher correlation coefficient value, R2 = 0.9864 proves a better choice in the adsorption process of Zn(II) ions from polluted solutions and groundwater. The adsorption obeys Freundlich isotherm model and the Zn(II) adsorption reaction process is considered as chemisorption process due to electrostatic interaction.