title: Use of modified clays for removal of phosphorus from aqueous solutions.
abstract: Phosphorus (P) removal from aqueous solutions was investigated using modified bentonite, calcite, kaolinite, and zeolite with FeCl3, CaCl2, and NaCl. The maximum sorption capacity of P was obtained by modified adsorbents with Fe(3+) ions (Fe-adsorbents). The results showed that P sorption capacity by Fe-adsorbents (bentonite (1.31 mg g(-1)), calcite (1.97 mg g(-1)), kaolinite (1.31 mg g(-1)), and zeolite (1.58 mg g(-1))) was improved by ∼467, 107, 409, and 427 %, respectively, compared to unmodified adsorbents (bentonite (0.28 mg g(-1)), calcite (1.82 mg g(-1)), kaolinite (0.32 mg g(-1)), and zeolite (0.37 mg g(-1))). Sorption isotherms were well described by the Freundlich model. Desorption experiments showed that the desorption capacity was in order of unmodified adsorbents > modified adsorbents with Na(+) ions (Na-adsorbents) > modified adsorbents with Ca(2+) ions (Ca adsorbents) > Fe-adsorbents. Effect of pH and ion strength was also investigated. At different pH, changes in the ionic strength had little effect on the adsorption. Results showed that double-layer model (DLM) could model P adsorption onto modified adsorbents over a wide range of pH and varying ionic strength. According to the scanning electron microscopy (SEM) images and saturation indices (SIs), high P removal by adsorbents was partly due to the P precipitation.
authors.affiliation: Department of Soil Science, College of Agriculture, Bu-Ali Sina University, Hamedan, Iran. sm_moharami@yahoo.com.
authors.forename: Somayeh
authors.initials: S
authors.lastname: Moharami
authors.affiliation: Department of Soil Science, College of Agriculture, Bu-Ali Sina University, Hamedan, Iran.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Jalali
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry*; D001546:Bentonite / Q000737:chemistry; D000077215:Clay; D004784:Environmental Monitoring; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008962:Models, Theoretical; D009994:Osmolar Concentration; D010758:Phosphorus / Q000302:isolation & purification*; D012996:Solutions; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D017641:Zeolites / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D007477:Ions; D012996:Solutions; D014874:Water Pollutants, Chemical; D001546:Bentonite; D017641:Zeolites; D010758:Phosphorus; D000077215:Clay
keywords: Adsorption; Desorption; Modified adsorbents; Phosphorus removal; Thermodynamic parameters