不同修饰模式高岭土的表征及对CrO42-的吸附

为了研究不同修饰模式高岭土对CrO_4~(2-)的吸附效果,并分析外界条件对CrO_4~(2-)吸附效果的影响,采用DTAB(十二烷基三甲基溴化铵,简写为DT)分别对15%、30%和60%BS-12(十二烷基二甲基甜菜碱,简写为BS)高岭土进行复配修饰,探索不同BS-12和BS+DT复配修饰模式高岭土的表面特征及其对CrO_4~(2-)的吸附特征,并对比不同p H值和温度条件下的吸附差别。结果表明:高岭土经BS-12和BS+DT修饰后,TOC含量均表现为疏水修饰模式疏水修饰和离子交换共存模式离子交换模式;不同修饰模式高岭土层间距d001无显著变化,但相比原土(CK)均增大;不同修饰模式高岭土的比表面积SBET随疏水修饰的增强而减小。BS+DT修饰高岭土对CrO_4~(2-)的吸附量均比CK和BS-12修饰的土高,Henry模型拟合证明疏水修饰模式高岭土对CrO_4~(2-)保持着良好的吸附能力,且随着疏水修饰比例的增强,土样对于CrO_4~(2-)的结合能力增强。温度范围10~30℃内,CK对CrO_4~(2-)吸附量增加5%以上,不同BS-12修饰土的吸附量增加了1.4%~3.7%。15%、30%和60%BS+DT复配修饰土对CrO_4~(2-)吸附量降低了5.4%~7.2%。p H值在4~10范围内,随着p H值增大,各修饰土样对CrO_4~(2-)的吸附量均逐渐减小。

Surface characteristics and CrO42- adsorption of kaolin with different modification

Modified minerals have enhanced surface and thus adsorption. In this study, surface characteristics and CrO2-4 adsorption of kaolin under different modification were examined at various pH and temperature. Dodecyl trimethyl ammonium bromide(DTAB)was used to modi-fy 15%, 30%and 60%BS-12(Dodecyl dimethyl betaine)pre-modified kaolin. Results showed that:TOC content was hydrophobic>hy-drophobic and ion exchange>ion exchange modifications for BS-12 and BS+DTAB modified samples. The interlayer spacing in different modified kaolin had no significant variation, but was all greater to different extent than that of the original(CK). The specific surface area of different modified kaolin decreased with increasing hydrophobic modification. Adsorption of CrO2-4 on BS-12 kaolin was greatly improved af-ter co-modification with DTAB. Henry model fitting proved that kaolin modified with hydrophobic substance had enhanced adsorption ca-pacity for CrO2-4 , which increased with increasing hydrophobic ratios. When temperature increased from 10 to 30℃, the adsorption capacity for CrO2-4 was increased by more than 5%on CK and by 1.4%~3.7%on BS-12 modified kaolin, but was reduced by 5.4%~7.2%on 15%, 30%and 60%BS+DTAB modified kaolin. Increasing pH from 4 to 10 decreased the adsorption capacity for CrO2-4 on all modified kaolin.