去除水中腐殖酸的磁性焙烧态类水滑石制备与表征

采用共沉淀法一步合成系列类水滑石负载磁性粒子的颗粒,经煅烧得到磁性焙烧产物.利用焙烧产物吸附水中腐殖酸,得到磁性焙烧态锌铝类水滑石去除腐殖酸效果较好.考察了磁性焙烧态锌铝类水滑石制备条件对腐殖酸去除效果的影响,通过正交试验优化了制备条件.静态吸附实验表明:吸附剂投加量0.2 g/L, 30 min内20 mg/L腐殖酸去除率为97.96%.X射线衍射(XRD)、红外光谱(FT-IR)、热重-差热(TG-DSC)和比表面积(SSA)表征结果表明:一定量的磁性基质掺入并没有破坏锌铝类水滑石典型的层状结构;焙烧态产物为氧化物,磁性保持良好;比表面积达80.00 m2/g.磁性焙烧态锌铝类水滑石在水中因"记忆效应"而结构重建通过表面吸附和腐殖酸结构中小尺寸的官能团插层快速去除腐殖酸.     

镁铝水滑石焙烧产物对甲基橙溶液的吸附性能

本文研究了Mg-Al-LDHs焙烧产物(LDO)对甲基橙的吸附性能并讨论了焙烧温度和吸附温度对反应的影响.结合XRD表征结果得到450℃焙烧产物在吸附甲基橙溶液后,恢复为LDHs层状结构;其对甲基橙溶液的吸附主要是层间吸附,即甲基橙可进入Mg-Al水滑石层间;此外,还对吸附动力学进行了讨论,结果表明:LDO对甲基橙的吸附符合准二级动力学模型.     

镁铝型水滑石复合热稳定剂的研究

采用加热瞬间沉淀法制备镁铝水滑石,对所得产物进行FT-IR、XRD分析,用刚果红法测试镁铝水滑石单一作用以及和硬脂酸钙复合作用时对PVC热稳定性的影响.结果发现:水滑石单独作用时,占PVC 3％的水滑石效果最佳,PVC热稳定时间为37 min,热稳定温度为203℃.水滑石与硬脂酸钙复合作用时,水滑石占复合热稳定剂总量的80％时效果最佳,热稳定时间为51 min,热稳定温度为213℃,水滑石与硬脂酸钙有较好的协同作用.     

焙烧层状氢氧化镁铝吸附脱除水中苯酚的研究

用层状氢氧化镁铝的焙烧产物吸附水中苯酚,研究了吸附剂用量、吸附时间、温度、溶液pH值等条件对吸附性能的影响。结果表明,吸附主要发生在90min内,吸附量随着温度的升高而增加。溶液初始pH值对吸附影响较大,pH值在6～11范围内吸附效果较酸性时好。吸附符合Langmiur等温线,饱和吸附量为0.557mg/g。     

焙烧水滑石去除氯离子性能研究

利用水滑石 (LDH)焙烧后在一定条件下可重新吸收水和阴离子从而部分恢复层状结构的结构记忆效应 ,研究了 3种工业级LDH不同温度下的焙烧产物即焙烧水滑石 (CLDH)去除Cl-的行为。射线粉末衍射仪表征了它们的结构特征。CLDH对氯离子的去除实验表明 ,n(Mg)∶n(Al)比值为 3和 4的LDH在 5 0 0～ 6 0 0℃下焙烧的CLDH对氯离子的去除率达到 95 %以上 ,1gCLDH去除氯离子的最大量约 5 9 6mg。     

层状双金属氢氧化物的合成与应用

层状双金属氢氧化物（LDHs）是近来受到广泛关注的一类新型固体催化材料，具有碱性、氧化还原性和层间阴离子可交换性。本文综述了近年来层状双金属氢氧化物合成与应用方面的研究进展。主要包括LDHs及柱撑LDHs的合成方法，LDHs及其焙烧产物在碱催化、氧化还原催化和催化剂载体、功能材料、医药等领域的应用。     

镁铝二元水滑石焙烧产物对酸性紫90染料的吸附性能(英文)

研究了镁铝比为3:1的二元水滑石(layered double hydroxides)焙烧产物(MgAl–LDO,layered double oxide)对弱酸性染料酸性紫90(C40H27CrN8Na2O10S2,AV90)的吸附性能。X射线衍射和Fourier变换红外光谱的结果显示:由于水滑石的"结构记忆效应",在富水条件下,MgAl–LDO会吸附部分AV90阴离子进入水滑石层间,从而恢复为层状结构的MgAl–LDHs。研究结果表明:MgAl–LDO对AV90具有良好的去除效果,在298 K,pH=9.7条件下,MgAl–LDO对AV90去除率高达99.7%,吸附容量为999.78 mg/g。MgAl–LDO对AV90的吸附过程同时符合Langmuir和Freundlich等温吸附方程,并且是一个自发、放热的过程。动力学研究表明:该吸附动力学符合准二级动力学模型。吸附实验结果同时表明:MgAl–LDO吸附性能优于活性炭和二氧化硅等传统吸附剂,经三次回收利用的MgAl–LDO对AV90仍具有良好的吸附性能。     

酸性黄17在焙烧态Zn/Al水滑石上的吸附研究

研究了摩尔比为3:1的焙烧态水滑石(Zn/Al-LDO)对酸性黄17(AY17)的吸附。考察了AY17不同起始浓度C0、温度及p H值等因素对Zn/Al-LDO吸附AY17的影响,并探讨了吸附过程的动力学和热力学规律。实验结果表明:Zn/Al-LDO对AY17具有良好的去除效果,在25℃、p H=7条件下,0.5 g?L?1的Zn/Al-LDO对C0=50~200 mg?L?1的AY17去除率超过98%。动力学和热力学研究表明:Zn/Al-LDO对AY17的吸附过程均符合Langmuir和Freundlich等温吸附方程,且是一个自发、放热的过程。由D–R等温吸附方程计算的吸附自由能E为0.1474~1.6667 k J?mol?1,表明吸附过程为物理吸附。同时,该吸附过程符合准二级反应动力学模型。通过XRD、FT-IR及颗粒内扩散模型的实验数据进一步分析吸附机理,推断膜扩散和颗粒内扩散对Zn/Al-LDO吸附AY17起决定性作用。     

Partial Oxidation of Methane to Syngas over Calcined Ni–Mg/Al Layered Double Hydroxides

The catalytic partial oxidation of CH₄ to syngas was carried out over an Ni–Mg/Al mixed-oxide catalyst prepared from layered double hydroxide-type precursors. The catalysts were characterized by XRD, TPR, UV-DRS, XRF, BET and CHNS analysis. The effects of the catalyst composition and the calcination temperature on the catalytic performance and the extent of catalyst deactivation were investigated. Ni–Mg/Al oxide catalysts converted CH₄ into syngas efficiently with high selectivity. The catalyst performance was strongly related to the Ni particle size and the calcination temperature. The catalysts that were calcined at higher temperature exhibited a better catalytic performance. In conclusion, the NiAl₂O₄ spinel phase had a positive effect on the stability of the catalyst.     

镁铝水滑石及其复合体系对PVC热稳定性能的调控

采用比色法、热失重法等研究了不同镁铝摩尔比的水滑石(LDHs)对PVC糊热稳定性能的影响。结果表明,在镁铝比分别为2、3、4的样品中,镁铝比为2的LDHs对PVC的热稳定效果最佳;将其与传统的铅盐、有机锡稳定剂复配,均具有良好的协同效应,可以实现对PVC糊热稳定性能的控制。其中,PVC/Mg-AlLDHs/Sn以100∶1.5∶1.5(质量份数,下同)比例复合后的体系,不仅热稳定性能优于传统的的铅盐体系,而且具有较低的糊黏度及较好加工流变性能。     

国内外水滑石产品在农膜中的应用探索

对国产与进口水滑石产品在粉体分子结构、粒径、化学式、热性能及红外吸收等性能上的异同进行了比较。结果表明国产水滑石的分子结构特征、热性能、红外吸收性能与日本水滑石基本相同。将上述两种水滑石作为保温添加剂用于农膜生产后发现,两者的加工性、力学性能、透光率及实际应用时的流滴、消雾、保温、防老化功能也无明显差异,国产助剂的成本却大幅下降。但因国产水滑石的粒径稍大,影响到农膜的雾度值和红外线透过率与进口水滑石相比均略有上升。文章对制成的农膜在红外线透过率测试方面趋势不同的原因,以及水滑石在今后的研究方向进行了初步的探讨。     

Mg-Al水滑石的水热合成及晶面选择性生长

以MgO、Al(OH)3为镁源和铝源,采用一步水热法合成了镁铝水滑石(Mg-Al LDHs),考察了水热时间及水热温度对水滑石晶粒度和晶面选择性生长的影响规律.用XRD、SEM等对合成产物进行了表征.结果发现水热时间不变,升高水热温度,或水热温度不变,延长水热时间,LDHs的晶体结构均趋于完整,径厚比呈增大趋势;并且晶体沿a轴方向的生长速率比沿c轴方向的生长速率大,即[110]晶面的生长速率比[003]晶面的生长速率快.     

Adsorption of Anionic and Cationic Dyes from Aqueous Solution on Non-Calcined Mg-Al Layered Double Hydroxide: Experimental and Theoretical Study

Non-calcined Mg-Al layered double hydroxide (LDH) with Mg/Al molar ratio of 3:1 was synthesized using the co-precipitation method. Sorption of anionic (acid blue 25 - AB25, reactive blue 4 - RB4), and cationic (methylene blue - MB) dyes by Mg-Al LDH form aqueous solution was investigated. The effect of solution pH, initial concentration, and contact time were investigated by batch adsorption experiments. The adsorbed amount increases with decrease in pH solution for AB25 and RB4. The cationic dye (MB) solution was insensitive to pH variation and also exhibited a low performance in the kinetic equilibrium studies. While anionic dyes were almost completely extracted from the solution, 90% of the methylene blue remained in solution. The equilibrium data were well described using the Langmuir-Freundlich model for RB4, AB25, and MB dyes with maximum adsorption capacity of 328.90, 246.10, and 43.48 mg/g, respectively. Finally, the mechanism of adsorption involving the dyes and LDH was evaluated using the Monte Carlo approach in the NVT ensemble. The results suggest that molecular simulation can be used to preview quantitatively the dye uptake. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the supplemental file.     

水滑石在水泥基中的结构重建及其碳化分析

水滑石( LDHs)具有层间阴离子可交换性和结构记忆性的特点,可利用外掺水滑石( LDHs)吸附侵入水泥石中的二氧化碳,从而提高水泥基的抗碳化性能。通过X射线衍射可以观察煅烧水滑石( LDOs)在碳化环境下的结构重建情况,以及掺煅烧水滑石( LDOs)水泥砂浆的抗碳化行为。试验表明：500℃煅烧后的水滑石具备较强的结构重建能力,可在水泥水化环境下吸附二氧化碳并有效提高水泥基抗碳化性能。     

Ni-Fe层状双金属氢氧化物的制备及性能研究

采用水热法制备了Ni-Fe层状双金属氢氧化物(Ni-Fe LDHs),研究了反应温度、反应时间、镍铁比和柠檬酸三钠用量对Ni-FeLDHs生长的影响,并研究其对甲基橙和亚甲基蓝的吸附性能.利用X-射线衍射、扫描电镜和交变梯度磁强计等测试方法研究了工艺条件对Ni-Fe-LDHs形貌、粒径、结晶性和磁性能的影响.实验结果表明:延长反应时间或升高反应温度都不利于得到结晶性好的Ni-Fe-LDHs.镍铁比对样品的结晶性和形貌有重要影响;镍铁比为2∶1,样品的结晶性和磁性能最好,增加镍铁比,得到片层组装形成得花状结构;镍铁比为3∶ 1时,Ni-Fe-LDHs对甲基橙和亚甲基蓝表现出良好的吸附性.     

焙烧态镁铝水滑石对刚果红的脱色性能研究

采用单滴法合成了n(Mg)/n(Al)=3的镁铝水滑石Mg3Al-LDH及其焙烧态产物Mg3Al-CLDH,并对刚果红溶液进行了吸附脱色试验。XRD分析结果说明合成的Mg3Al-LDH样品具有水滑石的典型结构,Mg3Al-CLDH在吸附刚果红阴离子后重新恢复为水滑石的层状结构。相同条件下Mg3Al-CLDH对刚果红的脱色率高于Mg3Al-LDH。对质量浓度为100mg/L的刚果红溶液,当Mg3Al-CLDH投加量为0.7g/L,pH值为5～10时,室温下反应40min,脱色率可达99%以上。Mg3Al-CLDH重复再生4次循环利用,刚果红脱色率仍在90%以上。表明Mg3Al-CLDH能够有效吸附溶液中的刚果红阴离子,可用于水体中阴离子染料的脱色处理。     

室温固相结合水热处理制备纳米Mg-Al层状双金属氢氧化物

采用室温固相反应结合水热处理制备了纳米层状双金属氢氧化物(LDHs)。利用X射线粉末衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)、热重(TG-DTA)等分析方法对样品的物相、形貌、粒径、热稳定性进行了表征。研究结果表明经水热处理后,产品颗粒由不规则的团聚体转化为规则的六方形片状结构,改善了晶体结晶性能,生成了分散性良好的层状双金属氢氧化物。     

Uranyl Ion Uptake from Aqueous Solutions by Chemically Cross-linked Polyelectrolyte CAMA Hydrogels

Uranyl ion adsorption from aqueous solutions has been investigated by chemically cross-linked polyelectrolyte acrylamide/maleic acid (CAMA) hydrogels. CAMA hydrogels with various compositions were prepared from ternary mixtures of acrylamide (A), maleic acid (MA), and water by free radical polymerization in aqueous solution using multifunctional cross-linkers such as ethylene glycol dimethacrylate (EGDMA) and 1,4-butanediol dimethacrylate (BDMA). Uranyl ion adsorption from aqueous solutions was studied by batch sorption technique at 25°C. The effect of uranyl ion concentration and mass of adsorbent on the uranyl ion adsorption were examined. In the experiments of the sorption, L type sorption in the Giles classification system was found. Some binding parameters such as initial binding constant (K _i ), equilibrium constant (K), monolayer coverage (n), site-size (u), and maximum fractional occupancy (Ô) for CAMA hydrogel-uranyl ion binding system were calculated by using Langmuir linearization method. Finally, the amount of sorbed uranyl ion per gram of dry hydrogel (q) was calculated to be 3.29 × 10^?4 ? 15.87 × 10^?4 mol uranyl ion per gram for CAMA hydrogels. Adsorption of uranyl ion was changed range 8.17–48.10%.     

头孢吡肟插层水滑石的缓释性能

用共沉淀法将头孢吡肟(Cefepime)插层到含NO3–的Zn–Al水滑石(layered double hydroxides,LDHs)层间,组装得到杂化材料Cefepime-LDHs。X射线衍射结果表明:Cefepime-LDHs晶型良好,为典型的水滑石类层状材料,其层间距为2.18 nm。通过对Cefepime三维尺寸的理论模拟,推测该杂化材料中的Cefepime以沿长轴方向与层板呈一定角度倾斜的方式排布于水滑石层间。此外,与Cefepime相比,该杂化材料中层间药物的释放具有一定的缓释效果,缓释过程符合一级动力学及Higuchi扩散模型。     

Structure and Basicity of Mesoporous Materials from Mg/Al/In Layered Double Hydroxides Prepared by Separate Nucleation and Aging Steps Method

This paper presents the synthesis of mesoporous materials from hydrotalcite-like layered double hydroxides (LDHs) with the Mg^{2 +}/(Al^{3 +} + In^{3 +}) molar ratio of 3.0 on the brucite-like lattice and the interlayer carbonate anions, using a novel separate nucleation and aging steps method developed in our laboratory. The physicochemical properties of as-synthesized LDHs and resulting calcined products at 500C were investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), simultaneous thermogravimetric and differential thermal analysis (TG-DTA), ²⁷Al nuclear magnetic resonance (NMR) and low-temperature nitrogen adsorption-desorption experiments. The results indicate calcination of LDHs with a well-crystallized single phase and nanoscale crystallites leads to the formation of the type MgO-like phase, and the pore size distributions of uncalcined and calcined LDHs are mostly in the range of mesopores. Furthermore, calcined materials have higher surface areas, pore volumes, pore diameters and surface basicities than corresponding precursors. When used as solid base catalysts for the Knoevenagel condensation of ethyl cyanoacetate with benzaldehyde, the material with higher density of base sites on the surface also exhibited a higher catalytic activity. Particularly, calcined MgAlIn-LDH has highest density of base sites resulting in a highest catalytic activity, as points to an important role of indium as a modifier of the surface properties of solid base catalysts.