Temperature effect on the mechanism of phosphate anions sorption by β-MnO2
Temperature effect on the mechanism of phosphate anions sorption by β-MnO2
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DOI：
10.1016/j.cej.2007.10.020
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发表时间：
2008-07
影响因子：
15.1
通讯作者：
S. Mustafa;M. I. Zaman;Sadullah Khan
中科院分区：
文献类型：
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作者：
S. Mustafa;M. I. Zaman;Sadullah Khan
已知储存水水库中过量的磷酸盐阴离子刺激藻类生长和工业中用于冷却目的的容器中的结垢。离子交换、活性炭吸附、化学沉淀和反渗透等技术已被用于去除。最近优选使用无机离子交换剂如氧化物/氢氧化物，这是由于它们在高温下对电离辐射的稳定性以及对特定阴离子和阳离子的高选择性。本文研究了β-MnO_2对磷酸盐的吸附，在pH = 3，5，7三种条件下，磷酸盐浓度（1.07-11.85×10 - 1 mmolL-1）和温度（293- 313 K）对吸附的影响。在pH值为3-7的范围内，磷酸盐的吸附量随温度的升高而降低。由质量作用定律方程推导出的Freundlich方程适用于吸附数据。背景电解质浓度的影响和FTIR研究表明，在所有的温度下的吸收过程的机制是外层复合物的形成。计算了热力学参数ΔH°、ΔS°和ΔG°值沿着计算了吸附热，结果表明，在低温和pH值较低的条件下，该固体更倾向于多电荷磷酸盐。
Phosphate anions excess in stored water reservoirs are known to stimulate algal growth and scaling in vessels used for cooling purposes in industries. Several techniques such as ion exchange, adsorption on activated carbon, chemical precipitation and reverse osmosis have been used for its removal. The use of inorganic ion exchangers like oxide/hydroxides has been preferred recently due to their stability at high temperature, to ionizing radiations and high selectivities for specific anion and cations. In the present investigation phosphate sorption on β-MnO2is studied as function of concentration (1.07–11.85×10−1mmolL−1) and temperature (293–313K) at three different pH values of 3, 5 and 7. The sorption of phosphate is found to decrease with the increase in temperature in the pH range 3–7. Freundlich equation derived from the Law of mass action equation was found applicable to the sorption data. Effect of background electrolyte concentration and FTIR studies showed that mechanism of uptake process was the formation of outer-sphere complexes at all the temperatures under investigation. The thermodynamic parameters such as ΔH°, ΔS° and ΔG° values along with isosteric heats of adsorption were calculated, which showed that the solid preferred the multiply charged phosphate at low temperature and pH.