Secondary adsorption of nitrobenzene and m-nitrophenol by hexadecyltrimethylammonium-montmorillonite thermo-XRD-analysis

In the present research we studied the effect of the solvent used, whether it was polar water or a non-polar organic solvent (n-hexane or n-hexadecane), on the basal-spacing and bulk structure of the sorbate-sorbent complexes obtained by the secondary adsorption of nitrobenzene and m-nitrophenol by two types of organo-montmorillonites. X-ray measured basal spacings before and after thermal treatments up to 360°C. The organo-clays were synthesized, with 41 and 90% replacement of the exchangeable Na⁺ by hexadecyltrimethylammonium (HDTMA), with mono-and bilayers of HDTMA cations in the interlayer space, labelled OC-41 and OC-90, respectively. After heating at 360°C both organo-clays showed spacing at 1.25–1.28 nm, due to the presence of interlayer-charcoal, indicating that in the preheated organo-clays the HDTMA was located in the interlayer. The thermo-XRD-analysis of Na-clay complexes showed that from organic solvents both sorbates were adsorbed on the external surface but from water they were intercalated. m-Nitrophenol complexes of both organo-clays obtained in aqueous suspensions contain water molecules. Spacings of nitrobenzene complexes of OC-41 and OC-90 and those of nitrophenol complexes of OC-41 showed that the adsorbed molecules were imbedded in cavities in the HDTMA layers. Adsorption of m-nitrophenol by OC-90 from water and n-hexane resulted in an increase of basal spacing (0.21 and 0.29 nm, respectively) suggesting the existence of a layer of nitrophenol molecules sandwiched between two parallel HDTMA layers.     

Thermal properties of poly(lactic acid)/organo-montmorillonite nanocomposites

Poly(lactic acid)/organo-montmorillonite nanocomposites were prepared by melt intercalation technique. Maleic anhydride-grafted ethylene propylene rubber (EPMgMA) was added into the PLA/OMMT in order to improve the compatibility and toughness of the nanocomposites. The samples were prepared by single screw extrusion followed by compression molding. The effect of OMMT and EPMgMA on the thermal properties of PLA was studied. The thermal properties of the PLA/OMMT nanocomposites have been investigated by using differential scanning calorimeter (DSC) and thermo-gravimetry analyzer (TG). The melting temperature (T _m), glass transition temperature (T _g), crystallization temperature (T _c), degree of crystallinity (χ_c), and thermal stability of the PLA/OMMT nanocomposites have been studied. It was found that the thermal properties of PLA were greatly influenced by the addition of OMMT and EPMgMA.     

Gemini表面活性剂改性有机蒙脱土的制备及其对甲基橙的吸附性能

分别以1,2-亚乙基-双(十二烷基二甲基溴化铵)(12-2-12)和1,2-亚乙基-双(十六烷基二甲基溴化铵)(16-2-16)为插层试剂,通过离子交换法合成了不同阳离子交换量的有机蒙脱土12-2-12-MMT和16-2-16-MMT。FTIR、XRD和TG-DTG分析表明,随着阳离子交换量的增大和Gemini表面活性剂碳链的增长,改性蒙脱土的层间距增大。考察阳离子交换量、时间、p H和温度等对甲基橙吸附性能的影响,结果表明,1.0CEC的12-2-12-MMT和16-2-16-MMT在20℃、p H=3、6 h对甲基橙吸附的效果最好;且同一吸附条件下16-2-16-MMT对甲基橙吸附性能明显优于12-2-12-MMT,有机蒙脱土对甲基橙的吸附动力学符合准二级动力学方程,热力学符合Langmuir吸附等温式。     

季铵盐插层蒙脱土及其去除海洋卡盾藻的研究

利用插层法制备了5种季铵盐改性的蒙脱土,通过FTIR、XRD和DTG等表征表明5种季铵盐已成功插入蒙脱土中;随后以中国典型赤潮藻海洋卡盾藻(Chattonella marina)为研究对象,考察了5种季铵盐改性蒙脱土的除藻效果。发现以双溴化十四烷基二甲基乙基溴化铵改性的蒙脱土在用量为8mg·L-1时,24h内对海洋卡盾藻的去除率最高,可达100%,而未改性蒙脱土在相同条件下除藻率仅为5.64%;除藻效果与除藻剂的结构有密切关系,在官能团相同时,链长数为14的脂肪族季铵盐除藻率最高,24h可达67.03%;在链长数相同时,含吡啶官能团的季铵盐比脂肪族季铵盐除藻率高,24h为33.62%,且随时间延长明显提高。渗溢性评估实验显示,改性蒙脱土经72h浸泡后表观插层率从71.9%降低到69.6%,表明除藻剂在水体中基本不释放。