为利用稻壳灰去除水中低浓度Pb(Ⅱ)，对吸附前后的稻壳灰进行傅里叶变换红外光谱（FTIR）分析，采用静态吸附法考察了稻壳灰对水中低浓度Pb(Ⅱ)的吸附特性。结果表明，稻壳灰表面存在多种基团，部分极性基团参与了Pb(Ⅱ)的吸附；随着pH的升高吸附量增加；当Pb(Ⅱ)初始浓度为20 mg/L、温度为25℃时，稻壳灰去除Pb(Ⅱ)的最佳投加量为1.8 g/L，去除率为98.1%；溶液中Na(Ⅰ)、Ca(Ⅱ)的存在会抑制稻壳灰对Pb(Ⅱ)的吸附，相同浓度的Ca(Ⅱ)对吸附的抑制比Na(Ⅰ)更明显。分析结果显示，Freundlich方程能够更好的地拟合不同温度的吸附等温线，该吸附存在多层吸附，温度升高有利于吸附。吸附热力学研究表明，ΔG?<0、ΔH?>0和ΔS?>0，说明该吸附是自发、熵增的吸热过程。准二级方程能够很好地拟合稻壳灰吸附Pb(Ⅱ)的动力学数据，可能是由表面吸附和颗粒内扩散共同控制。
Abstract
In order to remove low concentration Pb(Ⅱ) in water by rice husk ash(RHA), RHA before and after adsorption was analyzed by Fourier transform infrared spectroscopy (FTIR), the adsorption characteristics of low concentration Pb(Ⅱ) from water were investigated by static adsorption. The results showed that there were multiple groups on the RHA surface, and some polar groups participated in Pb(Ⅱ) adsorption; the adsorption capacity increased with increasing the solution pH; at the initial concentration of 20.0 mg/L and temperature was 25℃, the best dose of RHA was 1.8 g/L and the removal rate of Pb(Ⅱ) was 98.1%; Na(Ⅰ) and Ca(Ⅱ) in solution could hinder the adsorption of Pb(Ⅱ), and the effect of Ca(Ⅱ) was more obvious than Na(Ⅰ). The analysis showed that the adsorption isotherms at different temperatures were fitted better to Freundlich equation, which indicated polymolecular layer adsorption, increasing temperature was favorable for adsorption. ΔG?<0, ΔH?>0 and ΔS?>0 indicated that the adsorption was a spontaneous, entropy increasing and endothermic process. The kinetic experimental data of the adsorption fitted better to the pseudo-second-order equation, the adsorption was maybe controlled by surface adsorption and intraparticle diffusion.
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