The role of Mn oxide doping in phosphate removal by Al-based bimetal oxides: adsorption behaviors and mechanisms
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This study investigated the behaviors and mechanisms of phosphate adsorbed onto manganese (Mn) oxide-doped aluminum (Al) oxide (MODAO). The isotherm results demonstrated that the maximum amount of phosphorus (P) adsorbed onto MODAO was 59.8 mg/g at T = 298 K (pH 6.0). This value was nearly twice the amount of singular AlOOH and could increase with rising temperatures. The kinetic results illustrated that most of the P was adsorbed onto MODAO within 5 h, which was shorter than the equilibrium time of phosphate adsorption onto AlOOH. The Elovich model effectively described the adsorption kinetic data of MODAO because of its heterogeneous surface. The optimal solution pH for phosphate removal was approximately 5.0 because of electrostatic interaction effects. Meanwhile, the decrease in P uptake with increasing ion strength suggested that phosphate adsorption occurred through an outer-sphere complex. Phosphates would compete for adsorption sites on the surface of MODAO in the presence of fluoride ion or sulfate. In addition, the spectroscopic analysis results of Fourier transform infrared spectroscopy and X-ray photoemission spectroscopy indicated that removal mechanisms of phosphate primarily include adhesion to surface hydroxyl groups and ligand exchange.
KeywordsBimetal Adsorption Al oxide Mn oxide doped Phosphate
This work was supported by the Natural Science Foundation of China (grant no. 51208415), the Funds for Major Science and Technology Program for Water Pollution Control and Treatment (2012ZX07313-001-02), China Postdoctoral Science Foundation (grant no. 2012M511986), and Research Fund for the Doctoral Program of Higher Education of China (20126120120005).
- Freudlich HMF (1906) Ünber die adsorption in lösungen. Z Phys Chem 57(A):385–470, LeipzigGoogle Scholar
- Gong WX, Qu JH, Liu RP, Lan HC (2012) Adsorption of fluoride onto different types of aluminas. Chem Eng J 189–190:126–133Google Scholar
- Ho YS, Mckay G (1998a) Kinetic models for the sorption of dye from aqueous solution by wood. J Environ Sci Health Part B: Proc Saf Environ Prot 76(B):184–185Google Scholar
- Moulder JF, Stickle WF, Sobol PE, Bomben KD (1992) Handbook of X-ray photoelectron spectroscopy. Perkin-Elmer, NorwalkGoogle Scholar
- Nakamoto N (1986) Infrared and Raman spectra of inorganic and coordination compounds. Wiley, New YorkGoogle Scholar
- Ozcan AS, Erdem B, Ozcan A (2005) Adsorption of acid blue 193 from aqueous solutions onto BTMA-bentonite. Colloids Surf A 266:73–81Google Scholar
- Rudzinski W, Steele WA, Zgrablich G (1996) Equilibria and dynamics of gas adsorption on heterogeneous solid surfaces. Elsevier, AmsterdamGoogle Scholar
- Somusundurun P, Shrolri S, Huung L (1998) Thermodynamics of adsorption of surfactants at solid–liquid interface. Pure Appl Chem 70(3):621–626Google Scholar
- Sparks DL (1989) Kinetics of soil chemical processes. Academic, New YorkGoogle Scholar
- Weber WJ Jr, Morris JC (1963) Kinetics of adsorption on carbon from solution. J Sanitary Eng Div Proc Am Soc Civil Eng 89:31–59Google Scholar