有机膨润土层间硅氧烷表面对亲水性芳香胺的吸附

用3种吡啶阳离子(氯化吡啶、溴化丁基吡啶、溴化十四烷基吡啶)改性制备高、低电荷的有机膨润土,研究其吸附亲水性芳香胺(苯胺和N,N-二甲基苯胺)的性能,并通过有机碳含量分析、粉末X射线衍射、N2-BET等手段表征了有机膨润土的结构,试图揭示有机膨润土层间硅氧烷表面的暴露程度与吸附性能之间的关系.结果表明,通过减少层间电荷和用较小分子尺寸的吡啶阳离子改性,能在膨润土层间暴露较大面积的硅氧烷表面,从而增强对亲水性有机物的吸附.如在六种吡啶盐改性的有机膨润土中,用最小分子尺寸的吡啶阳离子(氯化吡啶)改性的低电荷膨润土(L-HP)具有较大的内比表面积(145 m2·g-1)和孔容(0.082 mL·g-1),显示出较强的吸附性能,对水中20 mg·L-1的N,N-二甲基苯胺和苯胺的去除效率分别为85.6%和52.8%.研究结果为进一步开发新型高效有机膨润土吸附材料提供理论依据.     

Sorption kinetics and isotherm modelling of imidacloprid on bentonite and organobentonites

Bentonite was modified by quaternary ammonium cations viz. cetytrimethylammonium (CTA), cetylpyridinium (CP), rioctylmethylammonium (TOM) and pcholine (PTC) at 100% cation exchange capacity of bentonite and was characterized by X-ray diffraction, CHNS elemental analyser and Fourier transform infrared spectroscopy. The sorption of imidacloprid on organobentonites/bentonite was studied by batch method. Normal bentonite could adsorb imidacloprid only upto 19.31–22.18% while all organobentonites except PTC bentonite (PTCB), enhanced its adsorption by three to four times. Highest adsorption was observed in case of TOM bentonite (TOMB) (76.94–83.16%). Adsorption kinetic data were fitted to pseudo-first-order, pseudo-second-order and intraparticle diffusion models. For normal bentonite data were best fitted to pseudo-first-order kinetic, while for organobentonites fitted to pseudo-second-order kinetics. Sorption data were analysed using Freundlich, Langmuir, Temkin and Dubinin–Radushkevich isotherm models. Data were well fitted to Freundlich adsorption isotherm. Product of Freundlich adsorption constant and heterogeneity parameter (K_f.1/n) was in following order: TOMB (301.87) > CTA bentonite (CTAB) (152.12) > CP bentonite (CPB) (92.58) > bentonite (27.25). Desorption study confirmed hysteresis and concentration dependence. The present study showed that the organobentonite could be a good sorbent for removal of imidacloprid from natural water sample also. Percentage adsorption and Distribution coefficient (mL g^?1) value of different adsorbent was in following order: TOMB (74.85% and 297.54) > CTAB (55.78% and 126.15) > CPB (45.81% and 84.55) > bentonite (10.65% and 11.92).     

对硝基苯酚在阴-阳离子有机膨润土/水间的界面行为研究

用阴、阳离子表面活性剂改性制得一系列阴-阳离子有机膨润土,表征了有机膨润土的结构特征,研究了对硝基苯酚在阴-阳离子有机膨润土/水间的界面行为,并探讨了其吸附机理.结果表明:阴-阳离子有机膨润土的层间距和有机碳含量与改性时阴、阳离子表面活性剂的组成和配比有关;阴-阳离子表面活性剂在有机膨润土中形成了增溶(分配)作用较强的有机相,在一定配比下对水中有机污染物产生协同效应.     

阳-非离子有机膨润土对水中硝基苯的吸附作用

分别用阳离子表面活性剂CTMAB、非离子表面活性剂Triton X-100及其混合物改性膨润土制得一系列的单阳离子、单非离子、阳-非离子有机膨润土.比较了它们对水中硝基苯的吸附性能及机理.结果表明,有机膨润土吸附水中硝基苯的等温吸附曲线呈线性,主要为分配作用所致,分配作用的大小由有机膨润土有机碳含量决定,并与改性时表面活性剂的种类、组成及配比有关;阳-非离子混合表面活性剂改性的有机膨润土有机碳含量(foc)高于相应的单阳离子和单非离子有机膨润土有机碳含量的和,因此,阳-非离子有机膨润土对水中硝基苯的吸附能力显著增强.     

Sorption of BTEX mixtures to organobenonites

Organobentonites synthesized by replacing the metal ions in bentonite with cetyltrimethylammonium (CTMA) or tetramethylammonium cation(TMA) were investigated for their behaviors to sorb benzene, toluene, pxylene from water. The results served to distinguish the sorption mechanisms (adsorption or partition) of the two types of organobentonites. Bentonites modified with short-chain alkyl functional groups(e, g., TMA) sorb organic contaminants primarily by an adsorption process, in which the sorbed amount decreases with increasing steric hindrance of the organic compound and the process exhibits a competitive effect because of steric hindrance in multisolute systems. In contrast, the sorption of contaminants to organobentonites modified with long-chain alkyl groups (e. g., CTMA) occurs by partition process without exhibiting a competitive effect, and the additional organic compounds may induce a cosorptive effect. In the latter case, the measured distribution coefficients of organic compounds between organobentonites and water( log Kd ) are positively correlated with the octanol-water partition coefficients of the compounds (logKow) and the sorption process exhibits no competitive effect in multi-solute systems.     

有机膨润土吸附水中有机物的盐效应及其机理

实验室模拟研究了一系列双阳离子有机膨润土对水中不同浓度的对硝基苯酚的吸附性能.结果表明,土样有机碳含量越高,对硝基苯酚初始浓度越低,有机膨润土对其吸附性能越好.试验了多种无机盐对有机膨润土吸附性能的影响,发现盐效应与离子荷径比和膨润土改性表面活性剂有关.无机盐阳离子相同时,盐效应与阴离子荷径比成反比;无机盐阴离子相同时,与阳离子荷径比成正比.单阳离子有机膨润土的盐效应呈负效应,长短碳链比例相当的双阳离子有机膨润土的盐效应呈正效应.     

微波合成有机膨润土及其吸附水中有机物的性能

采用微波辅助合成法制备有机膨润土.试验表明,其最佳条件是表面活性剂(CPC)的用量为膨润土阳离子交换容量(CEC)的 80%～100%,微波能量为420J/mL.在微波的作用下,有机膨润土合成反应速度有较大提高,反应活化能从常规合成的44.83kJ/mol降低到5.23kJ/mol.与常规湿法合成的有机膨润土相比,微波法合成的 CPC 有机膨润土的层间距增加 12.8%,有机碳含量提高 32.5%,比表面积降低 33.9%,在废水处理过程中不易脱附,对酸性大红的吸附处理效率提高 50.89%.     

阴-阳离子有机膨润土协同吸附作用及其机理研究

合成并研究了一系列阴-阳离子有机膨润土对水中苯酚、苯的吸附作用及其机理.结果表明,阴-阳离子有机膨润土对水中有机物具有协同吸附作用,其作用大小与改性时所用表面活性剂的种类、组成、配比及有机物本身的性质有关;对苯酚的吸附符合Langmuir和Freundlich吸附等温式,是分配作用(partition)和表面吸附(adsorption)共同作用的结果,分配作用的贡献率随改性时阴离子表面活性剂加入量的增大而增大;对水中苯的吸附以分配作用为主,分配系数大于原土及单阳离子有机膨润土,且与有机碳含量呈正相关.     

经丁二酮肟修饰的改性皂土对废水中镍的吸附

采用十六烷基三甲基溴化铵(CTMAB)对皂土改性,用丁二酮肟(DMG)对其表面修饰,并制备了新型固态吸附剂.研究了该吸附剂对水中Ni2+的吸附行为.结果表明,该固态吸附剂对水中Ni2+具有较强的吸附能力.吸附量受介质pH值、温度和吸附时间的影响.其吸附行为符合Langmuir吸附等温模型和HO准二级动力学方程,吸附焓变(△H)为58.759kJ/mol,各温度下,吸附自由能变(△G)均＜0,熵变(△S)均＞0,该吸附反应为吸热的自发过程.吸附了Ni2+的丁二酮肟修饰改性皂土,可用0.1mol/L的HNO3溶液洗脱再生.     

阴-阳离子有机膨润土吸附水中苯胺、苯酚的性能

首次用阴、阳离子表面活性剂改性膨润土 ,制得一系列阴 -阳离子有机膨润土 ,表征了有机膨润土的结构特征 ;研究了阴 -阳离子有机膨润土吸附水中苯酚、苯胺等有机物的性能及影响因素 ,并初步探讨了其吸附机理 .结果表明 ,阴 -阳离子有机膨润土的层间距和有机碳含量与改性时阴、阳离子表面活性剂的组成和配比有关 ;阴 -阳离子表面活性剂在有机膨润土中形成了增溶 (分配 )作用较强的有机相 ,从而对水中的有机污染物产生协同去除效应 .