Preparation and characterization of Al-, Fe- and Zr- pillared clays and their applications

Aluminum, iron, zirconium - pillared clays were prepared by using Montmorillonite KSF and K10 and used as inorganic fillers for synthesis poly(acrylic acid/ Aluminum and zirconium pillared clays) superabsorbent composites. Pillared clays and Al- KSF, Al-K10 and Zr-KSF based superabsorbents were characterized by XRD, FTIR, gas adsorption analysis, SEM and TGA. Pillaring process resulted in a strong increase in the d001 basal spacing. BET surface area analyses indicated that the surfaces areas of pillared clays were increased. The superabsorbents showed pH dependent and reversible swelling behaviors. Decreasing of swelling ratio was observed by increasing the content of Zr-KSF on the superabsorbent. The more crosslinking ratio of Al-K10 based superabsorbents was understood from less swelling character than Al-KSF based superabsorbents. XRD revealed that the layers of clay dispersed on the composite. FTIR analyses indicated that the shifts of stretching vibrations of O-Si-O tetrahedra and OH bands supported ester formation between acrylic network and pillared clay. Additionally, the efficiency of aluminum-pillared-layered K10 and KSF montmorillonites (Al-PILCs) for the removal of Trimethoprim (TMP) was investigated. The removal percentage was highly depended on pH. TMP and the adsorbent surface, both carrying positive charges at acidic pH values may explain the poor adsorption. Al-K10 exhibits higher removal capacity of TMP at lower adsorbent dosages in comparison with Al-KSF. Adsorption is increased by increasing temperature onto Al-KSF and increased by decreasing temperature onto Al-K10. From Dubinin?Radushkevich isotherm equation, the adsorption onto Al-KSF and Al-K10 can be explained by ion-exchange mechanism and physical adsorption type, respectively. Standard enthalpy value of the sorption indicates that adsorption is endothermic while the standard entropy suggests that randomness increases during adsorption. The results showed that Al-PILCs are potential useful adsorbents for the removal of TMP from wastewater treatment plants and fine inorganic fillers for synthesis of superabsorbent composites.