高等学校化学学报

高等学校化学学报 ›› 2009, Vol. 30 ›› Issue (9): 1830.

• 研究论文 • 上一篇    下一篇

阳离子表面活性剂在膨润土上的有序化作用及吸附热力学

陈宝梁, 毛洁菲, 吕少芳   

  1. 浙江大学环境科学系, 杭州 310028
  • 收稿日期:2008-10-06 出版日期:2009-09-10 发布日期:2009-09-10
  • 通讯作者: 陈宝梁, 男, 博士, 教授, 博士生导师, 主要从事环境界面行为、控制与修复等方面的研究. E-mail: blchen@zju.edu.cn
  • 基金资助:

    国家自然科学基金(批准号: 20207007)和浙江省科技厅计划项目(批准号: 2006C33050)资助.

Organized Assemblies of Cationic Surfactant on Bentonites in Water and Their Thermodynamics

CHEN Bao-Liang*, MAO Jie-Fei, LÜ Shao-Fang   

  1. Department of Environmental Science, Zhejiang University, Hangzhou 310028, China
  • Received:2008-10-06 Online:2009-09-10 Published:2009-09-10
  • Contact: CHEN Bao-Liang. E-mail: blchen@zju.edu.cn
  • Supported by:

    国家自然科学基金(批准号: 20207007)和浙江省科技厅计划项目(批准号: 2006C33050)资助.

PDF (PC)

被引次数

20

摘要：

绘制了不同温度下溴化十四烷基吡啶(MPB)在膨润土上的等温吸附曲线, 探讨了MPB的吸附热力学及作用机理; 并用XRD, FTIR和UV固体漫反射表征了MPB在固相上的有序化作用. 研究结果表明, MPB的吸附热力学、作用机制及有序化过程取决于其在膨润土上的负载量. 不同负载量下标准吉布斯自由能ΔGm0<0, 表明为自发吸附过程, 但存在3个不同阶段. 在低负载量(<0.8CEC)时为吸热吸附[焓变ΔHm0=7.92 kJ/mol, 熵变ΔSm0≈110 J/(K·mol)], 以阳离子交换作用吸附为主; 在高负载量阶段为放热吸附[ΔHm0=-34.41 kJ/mol, ΔSm0≈-50 J/(K·mol)], 以脂肪链间的疏水性相互作用为主; 最大吸附量随温度的升高(278 K→328 K), 从2.8CEC降低为1.5CEC, 相应的ΔHm0=-9.74 kJ/mol. 在负载量由低到高的吸附过程中, 吸附态MPB的状态从无序“液态”逐渐演变为有序“固相”, 吸附过程从熵驱动(ΔSm0>0)过渡为焓驱动(ΔHm0<0).

关键词: 溴化十四烷基吡啶; 膨润土; 吸附热力学; 作用机理; 有序结构

Abstract:

Sorption of myristylpyridinium bromide(MPB) on a model mineral, bentonite, was investigated under different temperatures(278, 283, 298, 308, 318 and 328 K). The sorption thermodynamics and interaction mechanisms are discussed. The resultant complexes of MPB-mineral were characterized with XRD, FTIR and UV-Vis diffuse reflectance spectra to probe the organized assemblies of adsorbed-MPB. The thermodynamics, mechanism and organized process are dominated by the MPB-loadings. For the whole isotherms, the molar standard Gibbs free energy of adsorption(ΔGm0) is negative, suggesting that adsorption is a spontaneous process, but the assembled process divided into three stages: sorption was driven by cationic exchanged firstly, then controlled by hydrophobic interaction after cationic exchanged reach maximum level. At low MPB-loadings(<0.8 cmc), the principal contribution to the ΔGm0 of negative value(-25—-30 kJ/mol) is the maximum positive value of molar standard adsorption entropy(ΔSm0 is about 110 J·K-1·mol-1), whereas the molar standard adsorption enthalpy(ΔHm0) is negative(-7.92 kJ/mol). At high loadings, the main contribution to the ΔGm0 of negative value(-30—-20 kJ/mol) is the maximun negative value of ΔHm0(-34.41 kJ/mol), whereas the ΔSm0 is negative(about -50 J·K-1·mol-1). The saturated amount of MPB decreased from about 2.8CEC at 278 K to about 1.5CEC at 328 K, and the corresponding ΔHm0=-9.74 kJ/mol. With the increase of loading, the adsorbed-MPB transited from a disordered liquid-like state to an ordered solid-like state, and the spontaneous adsorption evolved from an entropy-driven process(ΔSm0>0) to an enthalpy-driven process(ΔHm0<0). These observations provide a theoretical base to further understanding the adsorption behavior of cationic surfactant to mineral and an engineered reference to synthesize surfactant-mineral complexes for environmental applications.

Key words: Myristylpyridinium bromide; Bentonite; Sorption thermodynamics; Interaction mechanism; Organized structure

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