Synthesis of zeolite/geopolymer composite for enhanced sequestration of phosphate (PO) and ammonium (NH) ions; equilibrium properties and realistic study.

Zeolite impeded geopolymer (Z/G) was synthesized from natural kaolinite and diatomite. The structure (Z/G) was characterized as an enhanced adsorbent for PO and NH ions from aqueous solutions, groundwater, and sewage water. The synthetic Z/G structure exhibits sequestration capacities of 206 mg/g and 140 mg/g for PO and NH, respectively which are higher values than the recognized results for the geopolymer and other adsorbents in literature. The sequestration reactions of PO and NH by Z/G are of Pseudo-Second order kinetic behavior considering both the Chi-squared (χ) and correlation coefficient (R) values. The sequestration reactions occur in homogenous and monolayer forms considering their agreement with Langmuir behavior. The Gaussian energies (12.4 kJ/mol (PO) and 10.47 kJ/mol (NH)) demonstrate the operation of a chemical sequestration mechanism that might be involved zeolitic ion exchange process and chemical complexation. Additionally, these reactions are exothermic processes of spontaneous and favorable properties based on thermodynamic studies. The Z/G structure is of significant affinity for both PO and NH even in the existence of other anions as Cl, HCO, SO, and NO. Finally, the structure used effectively in the purification of groundwater and sewage water from PO and NH in addition to nitrate, sulfate, and some metal ions.