气凝胶在气体吸附净化中的应用研究进展

气凝胶(Aerogels)是一种以空气为介质的轻质多孔性凝聚态物质,由胶体粒子或高聚物分子相互聚集构成独特的纳米多孔三维网络结构。气凝胶的颗粒相和孔隙尺寸均为纳米量级,具有相当高的比表面积和孔隙率、可调控的开放孔隙结构、易于化学修饰的表面以及多样化的种类和形态,其气体吸附量可比同等条件下活性炭吸附量高两个数量级,因此在气体吸附净化领域逐渐受到人们的广泛关注。目前,气体吸附净化领域研究较多的气凝胶主要是SiO_2气凝胶和炭气凝胶。此外,近年来对金属氧化物气凝胶以及SiC气凝胶、石墨烯气凝胶、生物质基气凝胶等新型气凝胶的气体吸附应用也有相应的研究报道。吸附材料对目标气体需要同时具有较高的吸附容量和良好的选择性吸附能力。气凝胶的高比表面积和多孔性质提供了众多的吸附位点,但仅依靠自身物理吸附作用的吸附量有限,对目标气体的选择性不高,在实际吸附应用中,往往由于共存气体组分的竞争吸附影响对目标气体的吸附性能。因此,为了进一步提升气凝胶的吸附容量,提高对目标气体的选择性,研究人员围绕气凝胶修饰改性进行了大量的研究探索工作,并取得了一定的进展。目前,气凝胶吸附净化研究报道的目标气体主要是温室气体CO_2和大气中主要的污染物挥发性有机化合物(VOCs)。针对目标气体的不同可分别通过氨基功能化、氮掺杂等方法引入碱性位点或通过引入非极性官能团对气凝胶进行疏水改性,以提升气凝胶对CO_2或VOCs的吸附量和选择性。所采用的修饰改性方式主要有以下两种:一是在湿凝胶形成后或超临界干燥后通过嫁接、浸渍等手段对气凝胶表面进行功能化改性,通过引入特定的官能团或活性组分提升气凝胶对目标气体的吸附量和选择性;另一种是在溶胶-凝胶反应过程中引入功能化前驱体,在分子或纳米尺度上赋予气凝胶网络特定的性能,进而有效平衡活性组分稳定性和对目标气体的吸附性能。此外,对于炭气凝胶,还可通过活化进一步增大比表面积,改善孔隙结构和表面化学性质,从而实现对目标气体污染物吸附性能的优化。本文归纳了各类气凝胶在CO_2与VOCs吸附净化方面的研究进展,介绍了气凝胶的制备过程和结构特点,讨论并对比了不同气凝胶对目标气体的吸附性能与吸附机理,总结了当前气体吸附净化研究中对气凝胶进行修饰改性的主要方法,最后指出提高气凝胶的结构稳定性和吸附速率、设计可同时吸附多种目标气体的气凝胶、缩短制备周期并降低成本是未来研究工作的重点。     

Selectivity of Hydrophilic and Hydrophobic TiO2 for Organic‐Based Dispersants

The effects of the surface chemistry of TiO₂ powders on the dispersion performance of various dispersants are studied. Four common dispersants (oleic acid, oleylamine, oleyl phosphate, and tris‐(2‐butoxyethyl) phosphate) with different functional groups (carboxyl (–COOH), amino (–NH₂), phosphate (–P(=O)(OH)₂), and –P(=O)) are investigated for their potential to disperse hydrophilic and hydrophobic titania (TiO₂) powders. The outcomes, based on adsorption kinetics, adsorption isotherms, rheologies, and theoretical calculations, indicate that the hydrophilic TiO₂ is more sensitive to the chemistry of dispersants as compared to the hydrophobic TiO₂. However, the relative dispersion efficiencies of the dispersants are not found relevant to the adsorption kinetics, which is dominated by the adsorption amount. In addition, hydrogen bonding between –OH groups of the phosphate‐based dispersants dominates their dispersion ability for TiO₂.     

Mn掺杂对Al-ZnO吸附剂H2S常温脱除性能的促进作用

采用共沉淀法制备了一系列ZnO、Al-ZnO和x-Mn-Al-ZnO吸附剂,在常温条件下测试样品的H2S脱除性能。通过N2物理吸附、X射线衍射（XRD）、扫描电子显微镜（SEM）、X射线光电子能谱（XPS）对吸附剂进行表征,考察其形貌结构及表面物理化学性质。脱硫性能测试结果显示,随着Mn含量的增加,脱硫性能呈现先增大后减小,再增大再减小的趋势,两个极值点分别出现在0.02Mn-Al-ZnO和0.08Mn-Al-ZnO。结合表征结果发现,不同Mn掺杂量对Al-ZnO吸附剂的脱硫性能表现出不同的促进作用机制。0.02molMn掺杂主要是提高Al-ZnO吸附剂的比表面积至171.4 m2/g,进而促进其H2S脱除性能;随着Mn掺杂量增加,其比表面积下降,但更多的Mn进入ZnO晶格导致Mn和Zn之间相互作用增强,进而促进脱硫性能;然而随着Mn掺杂量进一步增加,吸附剂比表面积继续下降,并且生成ZnMn2O4晶相,导致脱硫性能的下降。0.08Mn-Al-ZnO脱硫性能最佳,在25 oC,空速3000 h-1,H2S浓度1000 ppmv条件下,穿透硫容为7.21g S/100 g sorbent。本研究表明,不同Mn掺杂量会导致吸附剂的形貌结构、晶相和表面物化性质不同程度的变化,而由不同影响因素主导的x-Mn-Al-ZnO吸附剂表现出脱硫性能的差异。     

改性膨润土对活性染料废水的处理研究

通过对膨润土的改性，大大提高了膨润土对染料废水的去除效率。改性膨润土吸附剂在投加量为4～5g/L时．处理活性染料脱色率可达95％以上，处理实际印染废水CODcr去除率可达52％。     

Water‐insoluble polymers with ability to remove metal ions

Crosslinked poly[3‐(methacryloylamino)propyl]dimethyl(3‐sulfopropyl)ammonium hydroxide‐co‐2‐acrylamido glycolic acid [P(MAAPDSA‐co‐AGCO)] was synthesized by radical polymerization and tested as an adsorbent under competitive and noncompetitive conditions for Cu(II), Cd(II), Hg(II), Zn(II), Pb(II), and Cr(III) by batch and column equilibrium procedures. The resin–metal ion equilibrium was achieved before 1 h. The resin showed a maximum retention capacity value for Hg(II) at pH 2 of 1.084 meq/g. The recovery of the resin was investigated at 20°C under different concentrations of HNO₃ and HClO₄. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3679–3685, 2004     

Influence of pH and Ionic Impurities on the Adsorption of Poly(acrylic) Dispersant onto a Zinc Oxide Surface

We have studied the properties of aqueous suspensions of ZnO powders with different purities. Our results suggest that powder purity determines the amount of dispersant necessary to form a stable aqueous suspension as well as the maximum adsorption capacity of the dispersant: the higher the positive surface charge of the as-received ZnO powders, the higher the amount of dispersant adsorbed onto the metal oxide surface. The surface charge of the ZnO particles in suspension is affected by the concentration of zinc as well as sulfate ions, which are the major impurities in the supernatant. The pH of the aqueous ZnO suspensions increases with increasing concentration of poly(acrylic) dispersant until the maximum adsorption capacity is attained. Further additions of dispersant do not increase the pH because of a buffer formation with impurity ions.     

MN500阳离子交换树脂填充聚醚砜膜吸附剂对氨氮吸附的研究

以聚醚砜(PES)为膜的基质材料,以微米级粉末状阳离子交换树脂(MN500)为功能性颗粒,采用相转化的方法,制备了MN500离子交换树脂填充PES膜吸附剂,研究MN500树脂填充PES膜吸附剂对水中氨氮的吸附性能,考察了树脂填充量对膜吸附剂纯水通量影响,以及振荡时间、料液pH对氨氮吸附性能的影响.结果表明:与MN500离子交换树脂相比,MN500离子交换树脂填充膜吸附剂对氨氮的吸附容量较大;在静态条件下,膜吸附剂对水中氨氮的吸附容量为40 mg/g;在膜吸附剂吸附的初始阶段(0～90 min),吸附容量随时间快速上升,此后趋于平缓;当pH值大于8时,膜吸附剂对氨氮的吸附容量显著增加.     

Formation of porous structure of semicokes from pyrolysis of Turkish coals in different atmospheres

Activated carbons were obtained from Turkish coals by one-step steam pyrolysis process. The effect of the water vapor on the yield of the solid, liquid and gas products was studied. The presence of steam during pyrolysis-activation process contributes to distillation of low molecular weight products and reacts with the coal and the volatile products obtained during the pyrolysis. These processes lead to an increase in the yield of liquid and gas products and a decrease in the solid yield. The resulting carbons are determined to have good adsorption characteristics.     

硅胶嵌入多孔纸基对苯蒸气吸附性能

苯蒸气作为一种典型的有害VOC污染物，研究对其的高效净化处理具有重要意义。纸基材料是一种密度小、孔隙率高、机械强度高的多孔材料，分析以木浆纤维纸、陶瓷纤维纸作为多孔基材，通过多次硅溶胶浸泡的方法制得硅胶嵌入多孔纸基吸附材料样片。通过扫描电镜SEM研究两种纸基材料表面的形貌及结构，采用重量法蒸气吸附仪对不同上胶次数的两种基材样片进行吸附性能测试。测试结果表明：木浆纤维纸和陶瓷纤维纸6次上胶率高达3.38 g/g和8.66 g/g; 0.1分压苯蒸气下30 min样片吸附量即可达到最大吸附量的80%；两种硅胶嵌入多孔纸基样片吸附容量在0.8分压苯蒸气下均超过100 mg/g；在4次上胶时样片表现出最佳的苯蒸气吸附性能。此外，通过对实验结果进行分段拟合得到吸附特征曲线。     

In situ preparation of magnetic Fe3O4.Cu2O.Fe3O4/cryogel nanocomposite powder via a reduction–coprecipitation method as adsorbent for methylene blue water pollutant

Magnetic nanocomposites have attracted great attention as adsorbents for the removal of water pollutants, which respond to an external magnet that is used to remove both pollutants and composite nanomaterial traces from water. They are environmentally friendly and effective adsorbents for water treatment. In this respect, a simple in situ preparation method was used to prepare cryogel powder composite based on Fe₃O₄.Cu₂O.Fe₃O₄ nanomaterials. The ionic cryogel based on 2‐acrylamido‐2‐methylpropane sulfonate sodium salt and styrene sulfonate sodium salt was prepared by crosslinking polymerization at low temperature. The new magnetic nanoparticles based on Fe₃O₄.Cu₂O.Fe₃O₄ were successfully prepared inside the cryogel networks by a simple reduction–coprecipitation method based on reaction of Fe³⁺ with sodium sulfite and Cu²⁺ in the presence of hydroxylamine and ammonia solution. The thermal stability, accurate Fe₃O₄.Cu₂O.Fe₃O₄ content, magnetic properties, crystal lattice structure, particle sizes and morphology of the prepared cryogel composite were evaluated. The optimum conditions such as pH, contact time, adsorbate concentrations, adsorption equilibrium and adsorption kinetics were investigated to determine the efficiency of the prepared composite as an adsorbent to remove toxic methylene blue (MB) pollutant from aqueous solution. The data for MB adsorption confirmed the high ability of the prepared composite to remove more than 4.696 mmol L^?1 of MB from water during 6 min. The regeneration and reuse experiments showed excellent data for the synthesized new dye as an effective adsorbent for water treatment. © 2018 Society of Chemical Industry