Al-intercalated acid activated bentonite beads for the removal of aqueous phosphate

The separation of fine spent sorbents from treated water after remediation is a major difficulty associated with phosphate wastewater treatment technology. In this study, a novel aluminium-pillared acid activated bentonite powder (Al-ABn) and alginate immobilized aluminium-pillared acid activated bentonite beads (Al-ABn-AB) were synthesized and used for the removal of aqueous phosphate. The phosphate removal behaviour of adsorbents were evaluated by batch experiments as a function of various parameters such as pH, initial concentration, contact time, temperature, adsorbent dose and presence of coexisting ions. The sorption isotherm studies by Langmuir model showed 12.87 and 11.11 mgP/g maximum phosphate uptake capacity for Al-ABn and Al-ABn-AB, respectively. The kinetic studies confirm that the adsorption of phosphate by Al-ABn and Al-ABn-AB follows a pseudo-second-order model. The feasibility of Al-ABn-AB was also assessed in continuous mode in fixed bed column and the loading capacity obtained was 4.55mg/g. The adsorption capacity of Al-ABn-AB beads remained at relatively high even after four regeneration cycles. Furthermore, the applicability of the synthesized adsorbents towards real municipal wastewater confirmed that novel synthesized Al-ABn and Al-ABn-AB are the promising adsorbents for the removal of phosphate from contaminated water.