酸活化对甘肃会宁凹凸棒石微观结构及亚甲基蓝吸附性能的影响

Effects of Acid Activation on the Microstructure and Adsorption Capacity for Methylene Blue of Attapulgite Clay from Huining of Gansu

用不同质量分数的HCl、H2SO4和H3PO4对甘肃会宁凹凸棒石黏土进行了酸活化处理。利用红外光谱(FTIR)、X射线衍射(XRD)、扫描电镜(SEM)、X射线荧光光谱(XRF)、BET比表面分析和Zeta电位等表征手段,系统考察了酸活化处理对凹凸棒石微观结构、理化性能以及对亚甲基蓝吸附性能的影响。结果表明,用质量分数为2.5%的酸处理就可除去白云石和碳酸盐,显著降低MgO和CaO含量。经3种酸处理后,随着酸质量分数的增加,凹凸棒石样品的比表面积、外比表面积、微孔比表面积和微孔体积均先增加后降低,比表面积分别在5%HCl和5%H3PO4和15%H2SO4处理时达到最大值。酸活化作用使凹凸棒石表面电荷更负,不同酸作用强弱依次为HCl、H2SO4、H3PO4。酸活化样品较原土均具有更高的亚甲基蓝吸附量,其中15%HCl酸活化后凹凸棒石黏土吸附量最大,为89.48 mg/g,较原土提高54.2%。

Attapulgite clay from Huining of Gansu was acid-activated using a series of HCl, H2SO4 and H3PO4 solutions with different concentrations. The effects of acid-activation on the microstructure, physico-chemical properties of attapulgite were characterized by fourier transform infrared spectra （FTIR）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, Brunauer-Emmett-Teller （BET）, X-ray Fluorescence spectrometry （XRF） and Zeta potencial techniques, and the adsorption capacity of the acid-activated attapulgite for methylene blue were also evaluated. Results indicate that the acid-activation with 2.5% acid can remove the dolomite and carbonate and decrease the contents of MgO and CaO. The specific surface area, external specific surface, micropore specific surface area and micropore volume of the acid-activated attapulgite were initially increased and then decreased with increasing the concentration of acid, and the best specific surface area was achieved at the concentrations of 5% HC1 and 5% H3PO4, and 15% H^SO4. Acid-activated treatment enhanced the negative charge of the attapulgite with the order of acid activity of HCI〉H2SO4〉H3PO4. The acid-activation of attapulgite enhanced the adsorption capacity for methylene blue in contrast to the raw attapulgite clay, and the highest adsorption capacity 89.48 mg/g was achieved after being activated with 15% HCl, which enhanced by 54.2% compared with the raw clay.