稻壳灰对水中低浓度Pb(Ⅱ)的吸附特性

Adsorption Characteristics of Low Concentration Pb( Ⅱ) from Water to Rice Husk Ash

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p H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~θ<0、ΔH~θ>0和ΔS~θ>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。

In order to remove low concentration Pb（Ⅱ） in water by rice husk ash（ RHA）, RHA before and after adsorption is analyzed by Fourier transform infrared spectroscopy （FTIR）, the adsorption characteristics of low concentration Pb（Ⅱ） from water are investigated by static adsorption. The results show that there are multiple groups on the RHA surface, and some polar groups participate in Pb （Ⅱ） adsorption; the adsorption capacity increases as the solution pH increases. At the initial concentration of 20.0 mg/L and temperature was 25℃, the best dose of RHA is 1.8 g/L and the removal rate of Pb（Ⅱ） is 98.1%; Na（ Ⅰ ） and Ca（Ⅱ） in solution can binder the adsorption of Pb（Ⅱ） , and the effect of Ca（Ⅱ） is more obvious than Na（ Ⅰ ）. The analysis shows that the adsorption isotherms at different temperatures are fitted to Freundlich Equation better, which indicates polymolecular layer adsorption, increasing temperature is favorable for adsorption. ΔGθ〈0 and ΔHθ〉0 indicates that the adsorption is a spontaneous, entropy increasing and endothermic process. The kinetic experimental data of the adsorption fitted to the pseudo-second-order equation, the adsorption may be controlled by surface adsorption and intraparticle diffnsion better.