铁锰氧化物/硅藻土复合物的制备及其对磷的吸附性能研究

Preparation and adsorption phosphate property of Fe-Mn oxide/diatomite composite

采用氧化还原共沉淀法制备铁锰氧化物/硅藻土复合物,考察原料配比、反应温度、焙烧温度及溶液pH值、离子强度对该复合物吸附磷性能的影响,同时开展吸附等温线、XRD和IR等分析。结果表明,2. 5 g硅藻土与1. 0 mmol锰、3. 0 mmol二价铁、3. 0 mmol三价铁制备的复合物在20℃、pH值为6时对磷的吸附量为10. 84 mg/g,较硅藻土提高约3. 6倍;沉淀反应温度对复合物吸附性能影响很小,焙烧温度400～500℃有利于复合物对磷的吸附;吸附量随溶液pH值的增大而减小,pH值较低时吸附作用主要是静电吸引和内层络合,pH值较高时减弱的静电吸引和内层络合与有利于吸附的内层络合共吸附综合作用,表现为吸附量减小;吸附等温线符合Langmuir方程,饱和吸附量34～37 mg/g,与D-R方程、R-P方程有较好相关性,平均吸附能9. 9～11. 3 kJ/mol,复合物具有微孔结构,有单层也有多层吸附。

Fe-Mn oxide/diatomite composite was prepared by oxidation reduction and coprecipitation techniques.The effects of raw material ratio,reaction temperature,calcination temperature and solution pH on adsorption phosphate property of composite were investigated with an analysis based on adsorption isotherm,XRD and IR.The results indicate that adsorption capacity of composite prepared from 2.5 g diatomite,1.0 mmol manganese,3.0 mmol ferric iron and 3.0 mmol iron(Ⅱ) is 10.84 mg/g under the condition of 20℃ and pH equal to 6,increasing 3.6 times compared with diatomite.Precipitation reaction temperature is negligible and calcination of 400 ~ 500℃ is beneficial to adsorption.Adsorption capacity decreases with increase of p H,and inner-sphere complexing and electrostatic attraction on surface are jointly driving force for adsorption of phosphorus at lower p H.At high pH,innersphere complexing and electrostatic attraction decrease,co-adsorption with inner-sphere complexing promotes adsorption,and the total effect is the declining of phosphorous adsorption.Adsorption isotherms are well consistent with Langmuir and D-R equation and R-P equation,the saturation adsorption capacities are 34 ~ 37 mg/g and the average adsorption energies are 9.9 ~ 11.3 kJ/mol,revealing single and multiple layers adsorption with the coexistence of physical and chemical actions.