Selective removal of phosphate from wastewater using hydrated metal oxides dispersed within anionic exchange media

• Published in: Chemosphere (Oxford) Vol. 119; pp. 1353 - 1360
• Main Authors: Acelas, Nancy Y., Martin, Benjamin D., López, Diana, Jefferson, Bruce
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.01.2015
• Subjects: Adsorption; Copper - chemistry; Copper oxides; Diffusion; Diffusion rate; Exchange; Ferric Compounds - chemistry; Freundlich isotherm; Hydrated metal oxides; Intraparticle diffusion mechanism; Kinetics; Langmuir isotherm; Mathematical models; Media; Phosphates; Phosphates - analysis; Phosphates - isolation & purification; Pseudo-second order kinetics; Sulfates; Waste Water - chemistry; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - isolation & purification; Water Purification - methods; Zirconium oxides; Hydrated metal oxides; Intraparticle diffusion mechanism; Pseudo-second order kinetics; Langmuir isotherm; Freundlich isotherm
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2014.02.024

•The hybrid materials are more effective adsorbents for the removal of phosphate than the base resin.•HZrO and HFeO hybrid materials exhibited P removal of 83% and 70%.•The chemisorption is the determining step of the adsorption process.•Two or more steps occur and they are limiting the overall rate of adsorption.•The mechanism of phosphate adsorption on hydrated metal oxides (HMO) occur via a ligand exchange. Hydrated ferric oxide (HFeO), hydrated zirconium oxide (HZrO) and hydrated copper oxide (HCuO) were immobilized within a microporous anion exchange resin (IRA-400), forming hybrid media for enhanced phosphate removal from aqueous systems. Empirical data from batch kinetic trials fitted the pseudo second order mechanism for chemical adsorption and each media was rate limited by intraparticle diffusion overall. These models were also used to predict the adsorption rate constants and the equilibrium adsorption capacities, which ranged from 26.51 to 30.44mgPg−1, and from 24.15 to 27.90mgPg−1 of media for the calculated and experimental capacities, respectively. The phosphate adsorption behavior by the hybrid materials fit both the Langmuir and Freundlich adsorption isotherms (R2>0.94), and the maximum adsorption capacities were 111.1mgPg−1 for HFeO, 91.74mgPg−1 for HZrO and 74.07mgPg−1 for HCuO. The effect of competing ions such as sulfate reduced these capacities to 18.52mgPg−1 for HFeO and 18.97mgPg−1 for HZrO. Despite this decrease, HFeO was capable of reducing the phosphate in a real wastewater matrix by 83%, and the HZrO media was able to reduce it by 86%, suggesting that such hybrid media have the potential for application at full scale.