氨基膦酸改性硅胶在乙醇体系中对汞的吸附性能研究

Adsorption of Hg(Ⅱ) on Silica-gel Functionalized by Triethylenetetraminomethylenephosphonic Acid in Ethanol Solutions

采用异相合成法,以3-氯丙基三甲氧基硅烷为偶联剂,以硅胶为基质,通过胺化、膦酸化反应合成并表征了氨基膦酸改性硅胶SG-Cl-T-P,并进一步研究了氨基膦酸改性硅胶在无水乙醇体系中对金属离子的静态饱和吸附性能,重点研究了对Hg(Ⅱ)的吸附动力学、吸附热力学及竞争吸附。结果表明,氨基膦酸改性硅胶对Hg(Ⅱ)具有较好的吸附性能,25℃的静态饱和吸附容量为72.75mg.g-1。在无水乙醇的二元金属离子体系中,吸附剂对Hg(Ⅱ)具有较好的吸附选择性。等温吸附符合Langmuir经验式。吸附动力学结果表明,氨基膦酸改性硅胶在不同条件下对Hg(Ⅱ)的吸附属于液膜扩散机理,拟二级动力学方程能更好的描述吸附剂对Hg(Ⅱ)的吸附。根据动力学数据计算得到吸附热力学参数分别为:ΔG=-3.24kJ.mol-1(35℃),ΔH=29.25kJ.mol-1,ΔS=106.20J.K-1.mol-1。

Silica gel chemically modified by triethylenetetraminomethylenephosphonic acid（denoted as SG-Cl-T-P） was synthesized and characterized.Adsorption properties of SG-Cl-T-P for transition metal ions in ethanol solutions were studied and the research results revealed that SG-Cl-T-P has the best adsorption capacity for Hg（Ⅱ）.Furthermore,the adsorption results displayed that the adsorption selectivity of SG-Cl-T-P for Hg（Ⅱ） was relatively well in binary ions systems in ethanol solutions.The saturated adsorption capacity for Hg（Ⅱ） was 72.75 mg·g-1 when the initial solution concentration was 0.5 mmol·L-1 at 25 ℃.The Langmuir model was better than Freundlich model to fit the adsorption isotherms of SG-Cl-T-P for Hg（Ⅱ）.The kinetics data indicated that the adsorption process was governed by the film diffusion and followed pseudo-second-order rate model for SG-Cl-T-P.And the thermodynamic parameters ΔG,ΔH and ΔS were-3.24 kJ·mol-1（35 ℃）,29.25 kJ·mol-1,and 106.20 J·K-1·mol-1,respectively.