Department of Applied Chemistry, University of Johannesburg, Doornfontein 2028, Johannesburg, South Africa; DST-CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa.
Int J Biol Macromol. 2016 Jul;88:66-80. doi: 10.1016/j.ijbiomac.2016.03.032. Epub 2016 Mar 17.
The objective of this work was to study the isotherm and kinetic models for the adsorption of methylene blue (MB) onto a TiO2 nanoparticle (TiO2NP)-containing hydrogel nanocomposite (HNC) of polyacrylamide-grafted gum ghatti (PAAm-g-Gg). The grafting of PAAm onto Gg was conducted using N,N'-methylene-bis-acrylamide (MBA) as a crosslinker, and different weight percentages of TiO2NPs were incorporated into the hydrogel matrix during the grafting reaction. The graft co-polymerization and the formation of the HNC were confirmed using FTIR, XRD, BET, SEM, TEM and EDS analyses. The adsorption of MB was studied in batch mode and it was found to be highly dependent on solution pH, ionic strength temperature and adsorbent loading. The MB-adsorption process followed the pseudo-second-order rate model and Langmuir adsorption isotherm with a maximum adsorption capacity of 1305.5mgg(-1). Thermodynamic studies revealed that the adsorption of MB onto the HNC surface was spontaneous, endothermic and through a process of physisorption. The results also showed that the HNC was much more effective for the adsorption of cationic dyes than anionic dyes, and it retained its original adsorption capacity for five successive cycles of adsorption-desorption. In conclusion, the hydrogel nanocomposite showed huge potential for remediating industrial wastewater polluted by toxic cationic dyes.
本工作旨在研究 TiO2 纳米颗粒（TiO2NP）负载的聚丙烯酰胺接枝田菁胶（PAAm-g-Gg）水凝胶纳米复合材料（HNC）对亚甲基蓝（MB）的吸附等温线和动力学模型。采用 N,N'-亚甲基双丙烯酰胺（MBA）作为交联剂，将 PAAm 接枝到 Gg 上，并在接枝反应过程中向水凝胶基质中加入不同重量百分比的 TiO2NP。通过傅里叶变换红外光谱（FTIR）、X 射线衍射（XRD）、BET、扫描电子显微镜（SEM）、透射电子显微镜（TEM）和能谱分析（EDS）对接枝共聚物和 HNC 的形成进行了确认。采用间歇法研究了 MB 的吸附，发现其高度依赖于溶液 pH 值、离子强度、温度和吸附剂的负载量。MB 的吸附过程符合拟二级动力学模型和朗缪尔吸附等温线，最大吸附容量为 1305.5mgg(-1)。热力学研究表明，MB 在 HNC 表面的吸附是自发的、吸热的，通过物理吸附过程进行。结果还表明，HNC 对阳离子染料的吸附比阴离子染料更有效，并且在五个连续的吸附-解吸循环中保留了其原始的吸附能力。总之，水凝胶纳米复合材料在修复受有毒阳离子染料污染的工业废水中具有巨大的潜力。
