MCM-41介孔材料的合成条件和特性对吸附镉离子的影响

以气相氧化硅为硅源,十六烷基三甲基溴化铵(cetyl trimethyl ammonium bromide,CTAB)为模板剂,分别在碱性氢氧化钠(NaOH),四乙基氢氧化铵,tetraethyl ammonium hydroxide,(C2Hs)4NOH(TEAOH)]和酸性介质条件盐酸(HCl)]T水热合成了MCM-41有序介孔材料MCM-41-N,MCM-41-T和MCM-41-H.用X射线衍射、氮气吸附-脱附等手段对比分析了合成的3种MCM-41介孔材料的物相、比表面积、孔径、孔体积等,发现酸性介质中合成的介孔材料的孔径最大.在此基础上,利用MCM-41介孔材料对比研究了处理含镉离子(Cd2 )废水的效果和机理,确定了不同介孔材料用量、不同初始pH值条件下MCM-41介孔材料对水中Cd2 的吸附率和吸附量.结果表明:介孔材料用量相同时,溶液pH值的增大有利于提高3种MCM-41介孔材料对水中Cd2 的处理效果.在pH值从7.0到8.0的过程中,其吸附率有1个突变,MCM-41-T的Cd2 吸附率从35.65%提高到62.15%;MCM-41-N的从38.80%提高到69.40%;MCM-41-H的从50.22%提高到73.47%.孔径最大的MCM-41-H对Cd2 的吸附效果最佳,最大吸附率为89.56%,最大吸附容量为8.57 mg/g.吸附溶液pH值的大小和介孔材料的孔径尺寸是决定吸附量大小的关键因素,因此,重点应通过优化合成工艺提高介孔材料的孔径.

EFFECT OF SYNTHESIS CONDITIONS AND CHARACTERISTICS OF THE MCM-41 MESOPOROUS MATERIALS ON ADSORPTION OF CADMIUM ION

The ordered mesoporous material MCM-41 was synthesized by a hydrothermal method using fumed silica,sodium hydroxide(NaOH)/tetraethyl ammonium hydroxide(TEAOH)/hydrogen chloride(HCl)and cetyl trimethl ammonium bromide(CTAB).The three synthesized mesoporous material MCM-41 samples as MCM-41-N,MCM-41-T and MCM-41-H were characterized by X-ray diffraction and N2 adsorption-desorption.The results show that mesoporous material MCM-41 synthesized in acid conditions has larger pore size than the two others.Moreover,mesoporous material MCM-41 samples were used to treat cadmium ion(Cd2 )-containing wastewater.The amounts of Cd 2 adsorbed onto mesoporous material MCM-41 samples were studied in different adsorbent amounts and with different pH values.The results show that the adsorption rate can be improved by increasing the pH value of the Cd2 -containing solution.When the pH value is from 7.0 to 8.0,the Cd 2 adsorption rate of the MCM-41-T is from 35.65%to 62.15%;the Cd2 adsorption rate of the MCM-41-N is from 38.80%to 69.40%;and the Cd 2 adsorption rate of the MCM-41-H is from 50.22%to 73.47%.The MCM-41-H synthesized in acid solution can reach to the highest adsorption rate(89.56%)and adsorption amount(8.57 mg/g)because it has the largest pore size.According to the results,the pore size of mesoporous material MCM-41 and the pH value of the initial Cd2 solution are the key factors that affect the adsorption rate.Therefore,the pore size of mesoporous ma-terial MCM-41 should be increased to improve the adsorption rate of Cd2 .