Application of FeMgMn layered double hydroxides for phosphate anions adsorptive removal from water

The development and application of new materials for phosphate removal are very important due to its increasing emissions from the activities of daily living and socially production which may lead to eutrophication. The FeMgMn layered double hydroxides (FeMgMn-LDH) have been synthesized via a co-precipitation method and their adsorption characteristics for phosphate were investigated in this study. Adsorption equilibrium could be fitted by the Dubinin-Kaganer-Radushkevich (DKR) and Langmuir models. FeMg2Mn-LDH has the largest phosphate removal capacity and the fastest adsorption kinetics among the three LDH with different Fe/Mg/Mn ratio. The maximum adsorption capacity of FeMg2Mn-LDH at 25 degrees C is 34.31 mg-P/g. The negative values of Delta G(0) and the positive value of Delta H-0 (6.725 kJ/mol) indicate that the phosphate adsorption process on FeMgMn-LDH is spontaneous and endothermic. The competition order of coexisting anions on phosphate adsorption with FeMgMn-LDH is CO32- -> SO42- -> NO3-. An ion exchange mechanism can be attested by the apparent adsorption energy (E) values and the change of Cl content. Moreover, the appearance of small particles on the SEM images of Phosphate-FeMgMn-LDH, and the results of FTIR and XPS spectra demonstrated that the formation of both outerand inner-sphere surface complexes via electrostatic attraction and monodentate/bidentate complexations. Overall, the as-prepared FeMgMn-LDH is a promising adsorbent for dephosphorization.

Automated summary

The development and application of new materials for phosphate removal is crucial, with FeMg2Mn-LDH showing the best phosphate removal capacity and fastest adsorption kinetics among different Fe/Mg/Mn ratio LDHs. The process is spontaneous and endothermic, with an ion exchange mechanism and the formation of surface complexes via electrostatic attraction and complexations.