Simultaneous removal of ammonia and phosphate using green synthesized iron oxide nanoparticles dispersed onto zeolite

Since elevated levels of common nutrients, such as ammonia and phosphate, in natural water bodies (lakes and rivers) can lead to significant deterioration of pristine water ecosystems due to eutrophication, new and cost-effectiveness remediation strategies are urgently required. This work investigated the feasibility of using green synthesized iron oxide nanoparticles dispersed onto zeolite by eucalyptus leaf extracts (EL-MNP@zeolite), to simultaneously remove ammonia and phosphate from aqueous solutions. SEM and XRD both showed that EL-MNP@zeolite had better stability and dispersity than unsupported zeolite. At an initial concentration of 10 mg L^-1 each for the two co-existing ions the synthesized material removed 43.3% of NH₄⁺ and 99.8% of PO₄^3-. Removal of co-existing NH₄⁺-PO₄^3- was impacted by the ratio of zeolite to EL-MNP, temperature, initial ion concentration and solution pH. Under optimium conditions the maximum adsorption capacity of EL-MNP@zeolite for NH₄⁺ and PO₄^3- was 3.47 and 38.91 mg g^-1, respectively. For both ions' adsorption followed a pseudo-second-order kinetic reaction, confirming that the removal of ammonia and phosphate by EL-MNP@zeolite was via chemisorptions, where interaction between NH₄⁺-PO₄^3- and EL-MNP@zeolite may be through either electrostatic adsorption or ligand exchange. Overall these results indicated that EL-MNP@zeolite had significant potential as a nano-remediation strategy to simultaneously remove cationic ammonium and anionic phosphate from wastewaters.