水滑石类化合物及其制备、应用的研究进展

介绍了水滑石类化合物的结构和性质,综述了水滑石类化合物的制备方法及其在催化材料、红外吸收材料、紫外阻隔材料、阻燃抑烟材料、热稳定剂、生物医药材料、分离与吸附材料等方面的应用研究进展,并指出了当前水滑石类化合物制备与应用研究中存在的问题。     

水滑石类化合物及其制备、应用的研究进展

介绍了水滑石类化合物的结构和性质,综述了水滑石类化合物的制备方法及其在催化材料、红外吸收材料、紫外阻隔材料、阻燃抑烟材料、热稳定剂、生物医药材料、分离与吸附材料等方面的应用研究进展,并指出了当前水滑石类化合物制备与应用研究中存在的问题。     

新型环境矿物材料—水滑石应用研究进展

层状双金属氢氧化物结构和性质上的特殊性，使水滑石成为一种新型多功能无机材料，应用于多个领域。水滑石类材料也可作为吸附剂、催化剂载体和微粒乳化剂有效地用于环境污染防治，在实际应用方面已取得一系列研究成果。作为一种新型的环境矿物材料，其在环境污染控制领域呈现出良好的研究价值和应用前景。     

Mg-Al-Ce水滑石吸附去除水中的硼

用共沉淀法成功制备了镁铝铈水滑石(Mg-Al-Ce-HT), 采用不同分析手段对材料进行表征。通过静态吸附实验研究了Mg-Al-Ce-HT的吸附效率与初始pH、吸附剂剂量、初始硼酸浓度和接触时间的关系。当pH小于8.0时, 溶液的pH对硼吸附几乎没有影响, 当pH超过8.0时, 吸附容量降低。吸附剂的最佳用量为200 mg, 最大吸附容量为32.52 mg·g ^-1。 硼去除量在160 min内达到平衡。吸附等温线表明吸附过程是一个非自发的吸热过程。吸附数据与Langmuir模型拟合良好, 表明吸附是单层吸附。     

焙烧态水滑石吸附水中钒酸根的研究

采用共沉淀法合成了Mg/Al物质的量比为2∶1的水滑石(LDH),773K煅烧得到其煅烧产物(CLDH),研究了CLDH对钒酸根的吸附性能,分别考察了吸附剂用量、钒酸根浓度、吸附时间和温度等因素对钒酸根吸附效果的影响,并探讨了吸附热力学。结果表明,CLDH对钒酸根有很强的吸附能力,在293～313K温度范围内,CLDH的最大吸附量随着温度的升高而逐渐增大(79.8～92.9mg/g),吸附等温线很好地符合Langmuir方程(R20.999),吸附自由能(ΔG0)为-2.47～-3.81kJ/mol,是自发的物理吸附过程;CLDH吸附钒酸根为熵增过程,熵变为67.23J/(mol·K)。     

Mg-Al-Ce水滑石吸附去除水中的硼（英文）

用共沉淀法成功制备了镁铝铈水滑石(Mg-Al-Ce-HT),采用不同分析手段对材料进行表征。通过静态吸附实验研究了Mg-Al-Ce-HT的吸附效率与初始pH、吸附剂剂量、初始硼酸浓度和接触时间的关系。当pH小于8.0时,溶液的pH对硼吸附几乎没有影响,当pH超过8.0时,吸附容量降低。吸附剂的最佳用量为200 mg,最大吸附容量为32.52mg·g–1。硼去除量在160min内达到平衡。吸附等温线表明吸附过程是一个非自发的吸热过程。吸附数据与Langmuir模型拟合良好,表明吸附是单层吸附。     

水滑石除磷的吸附动力学研究

采用共沉淀法制备了Mg/Al水滑石,研究了不同Mg/Al物质的量比、材料用量、不同pH条件下Mg/Al水滑石吸附除磷的动力学特征,从而对吸附速率的控制过程进行分析。结果表明水滑石对磷的吸附能较好地符合准二级动力学方程、Elovich动力学方程和内扩散模型。n(Mg)/n(Al)=3是水滑石最理想配比,水滑石投加量越大,外扩散过程越慢;一定范围内pH的升高能促进水滑石对磷吸附速率和吸附容量的提升。     

镁铝水滑石纳米片可控制备及其吸附性能研究

在聚乙二醇(PEG)存在的条件下,通过一步水热法合成了晶相单一的六方片状镁铝水滑石层状双氢氧化物(LDH)。采用XRD、SEM、TEM、FT-IR、N2吸附、UV-Vis紫外-分光光度计和zeta电位仪等对产物进行了表征。考察了PEG活性剂对水滑石形貌及性能的影响。结果表明,添加活性剂改性后制备的六边形水滑石纳米片形貌规整均一,宽约几微米,厚度约为100~200 nm,纳米片间易形成交叉支撑结构,分散性好,比表面积为203.5 m2/g。在室温,焙烧后的Mg AlLDO对浓度为100 mg/L的刚果红30 min内去除率可达97%,饱和吸附量为243.5 mg/g。     

液-固体系水滑石、沸石、硅藻土对Cr(Ⅵ)吸附特性差异

采用静态吸附实验研究水滑石、沸石、硅藻土对Cr(Ⅵ)的吸附特性及其差异性;利用扫描电镜(SEM)、能谱仪(EDS)、红外光谱仪(FTIR)分析理化特性及其与吸附特性之间的关系。结果表明:水滑石和硅藻土对于Cr(Ⅵ)的等温吸附特性符合Freundlich模型,沸石符合Langmuir模型;水滑石、沸石、硅藻土的最大吸附量qm分别为8.62、12.57、6.32 mg·g~(-1),吸附动力学特性均符合伪二级动力学方程;3种吸附剂均为优惠吸附,均是自发的、吸热的、无序的;从理化特性来看,沸石具有最优吸附条件。     

以水滑石为前体的Co-Mn-Al复合氧化物的制备及表征

采用共沉淀法制备了n(Co)∶n(Mn)∶n(Al)=4∶0∶2、4∶1∶1、4∶2∶0的CO32-离子插层层状双金属氢氧化物(LDHs),经500℃煅烧4h得到相应的Co-Mn-Al复合过渡金属氧化物。利用X射线衍射(XRD)、X射线荧光光谱分析(XRF)、N2吸附脱附、透射电镜(TEM)技术对样品进行了表征。研究结果表明,Co-Mn-Al复合氧化物具有含Co尖晶石氧化物的结构特征,属于中孔材料,与Co-Mn-Al LDHs相比,其比表面积增大,孔容增加,孔径尺寸变小,且随着Mn与Al原子比的增加,样品结晶度及有序性均下降。     

Sorption study of an acid dye from an aqueous solution on modified Mg-Al layered double hydroxides

In this paper, experimental methods and results are reported on the removal of the dye Green Bezanyl-F2B (an acid dye) from MgAlCO(3) (HT) and from intercalated anionic surfactant, "sodium dodecylsulfate (SDS)", into the Mg-Al layered double hydroxides by the calcination-rehydration reaction using Mg-Al oxide precursors calcined at 773 K. Dodecylsulfate hydrotalcite was prepared by the calcination-rehydration method. The surfactant intercalation in the interlayer space of hydrotalcite was investigated by XRD and FT-IR spectroscopy where the resulting materials were found to be similar to those reported in the literature and were used to remove an acid dye from an aqueous solution. Equilibrium time and rate-determining step of the dye Green Bezanyl-F2B sorption were determined. Two simplified kinetic models were tested to investigate the sorption. The adsorption capacity data were also fitted to Langmuir and Freundlich equation as well. The sorption data fitted to the Langmuir model gave good values of the determination coefficient.     

手性阴离子柱撑水滑石的制备和表征

以水滑石Mg4Al2(OH)12CO3.4H2O为前体,采用返混沉淀方法进行插层组装制备了L-(-)-酒石酸、L-(-)-天冬氨酸、L-(-)-苹果酸柱撑水滑石(LDHs),用X射线衍射、红外光谱及差热分析表征了超分子结构手性层柱材料的结构,结果表明,3种手性酸根阴离子可以插入水滑石的层间完全取代CO32-,得到结晶度高、晶相单一且手性酸根阴离子在层间有序排列的超分子结构手性层柱材料。     

A comparison of corrosion inhibition of magnesium aluminum and zinc aluminum vanadate intercalated layered double hydroxides on magnesium alloys

The magnesium aluminum and zinc aluminum layered double hydroxides intercalated with NO ₃ ^- (MgAl-NO₃-LDH and ZnAl-NO₃-LDH) were prepared by the coprecipitation method, and the magnesium aluminum and the zinc aluminum layered double hydroxides intercalated with VO _x ^- (MgAl-VO _x -LDH and ZnAl-VO _x -LDH) were prepared by the anion-exchange method. Morphologies, microstructures and chemical compositions of LDHs were investigated by SEM, EDS, XRD, FTIR, Raman and TG analyses. The immersion tests were carried to determine the corrosion inhibition properties of MgAl-VO _x -LDH and ZnAl-VO _x -LDH on AZ31 Mg alloys. The results showed that ZnAl-VO _x -LDH possesses the best anion-exchange and inhibition abilities. The influence of treatment parameters on microstructures of LDHs were discussed. Additionally, an inhibition mechanism for ZnAl-VO _x -LDH on the AZ31 magnesium alloy was proposed and discussed.     

Ageing behaviour of unary hydroxides in trivalent metal salt solutions: Formation of layered double hydroxide (LDH)-like phases

The hydroxides of Mg, Ni, Cu and Zn transform into layered double hydroxide (LDH)-like phases on ageing in solutions of Al or Cr salts. This reaction is similar to acid leaching and proceeds by a dissolution-reprecipitation mechanism offering a simple method of LDH synthesis, with implications for the accepted theories of formation of LDH minerals in the earth’s crust.     

Sorption of an anionic dye by uncalcined and calcined layered double hydroxides: a case study

Layered double hydroxides (LDHs) with a Mg/Al molar ratio of 2:1 were synthesized by using a co-precipitation method and their calcined products (CLDHs) were obtained by heating Mg/Al-LDHs at 500 °C. Sorption of a weak acid dye, Brilliant Blue R (BBR), by LDHs and CLDHs indicated equilibrium time required for BBR sorption by CLDHs was less than 12 h, regardless of initial concentration of BBR, whereas BBR sorption by LDHs was longer than 20 h. Sorption capacity of CLDHs was much larger than that of LDHs. Therefore, CLDHs could be used to remove anionic dyes of relatively high concentrations while LDHs may only be used to remove anionic dyes of low concentrations. Isotherms for BBR sorption by CLDHs and LDHs were well described using the Freundlich and Langmuir equations, respectively. When the initial pH of BBR solutions was lower than 8.0, the final pH of the solution after sorption was enhanced and stabilized at 10.6–10.8. The effect of initial pH (<8.0) on BBR removal was negligible, which would be environmentally important for precipitation/co-precipitation of co-existing metal cations. The effects of both Cl⁻ and SO₄²⁻ on BBR sorption by CLDHs were minimal; but the presence of CO₃²⁻ markedly reduced BBR removal. Thermal regeneration for re-use of LDHs and CLDHs after BBR sorption was feasible only within the first two cycles, after which the regenerated materials suffered from a large loss in their sorption capacities.     

ZnAlTi型层状双氢氧化物光催化降解亚甲基蓝的性能研究

利用动态尿素水解法制备了3种不同比例的ZnAlTi型层状双氢氧化物,取部分样品分别在温度为500、600、700和900℃条件下煅烧4h,制得具有光催化性能的材料。研究催化剂不同摩尔比、催化剂用量、煅烧温度等不同因素对光催化降解亚甲基蓝过程的影响。结果表明,紫外光照射下,在反应温度为30℃、催化剂中Ti和Al的摩尔比为2、催化剂投加浓度为1.0g/L、亚甲基蓝初始浓度为10mg/L、煅烧温度为600℃的反应条件下,催化剂对亚甲基蓝的降解效果最好,光照反应12h后亚甲基蓝的降解率为94.4%。     

类水滑石的制备与改性及其在聚丙烯阻燃中的应用

采用共沉淀法制备了镁铝类水滑石（LDHs）前驱体,加入少量聚磷酸铵（APP）制得APP-LDHs,探讨了不同质量分数APP对LDHs晶体生长的影响;当APP在LDHs前驱浆液中添加量为0.8wt%时,将APP-LDHs与季戊四醇（PER）、硅烷偶联剂KH-550进行球磨混合,制备插层包覆改性的LDHs;通过XRD、FTIR、SEM和TG等对改性前后的LDHs进行了表征;采用极限氧指数（LOI）、垂直燃烧测试（UL-94）、缺口冲击和弯曲实验等方法研究了LDHs改性前后LDHs/聚丙烯（PP）复合材料的阻燃性能及力学性能的差异。研究结果表明：APP的加入,未显著影响LDHs的层板生长,但其层板堆叠受到抑制;SEM观察表明,所制备的LDHs为片状,且经插层包覆改性后的LDHs粉体形貌较为规整,颗粒粒径为100~250 nm;改性LDHs在较高温度下的热稳定性显著优于未改性的LDHs;当PP中加入质量分数为20%的LDHs及改性LDHs时,可抑制PP燃烧时产生的熔滴,并促使LDHs/PP复合材料表面形成炭层;改性LDHs/PP复合材料具有更好的阻燃性能,且其冲击强度、弯曲强度等力学性能下降不明显。     

Bromide ion removal from contaminated water by calcined and uncalcined MgAl-CO3 layered double hydroxides

A fundamental investigation on the uptake of bromide ion from contaminated water by calcined and uncalcined MgAl-CO3 layered double hydroxides (LDHs) were conducted in batch mode. The uptake capacity of calcined LDHs (CLDH) is higher than that of uncalcined LDHs, due to their different mechanisms which are confirmed by powder X-ray diffraction, FT-IR spectroscopy and TG-MS measurements. The former mechanism is based on the reconstruction of CLDH to Br-LDHs, whilst the latter is related to the surface adsorption. It has been found that the LDHs calcined at 500 degrees C with Mg/Al molar ratio of 4 represents the highest capacity to remove bromide ion from aqueous solution. The equilibrium isotherms of uptake of bromide by CLDH were well fitted by the Langmuir equation, and thermodynamic parameters such as Delta G0, Delta H0 and Delta S0 were calculated from Langmuir constants. The negative value of Delta H0 confirms the exothermic nature of adsorption. Three kinetics models were used to fit the kinetics experimental data, and it was found that the pseudo-second order kinetics model could be used to describe the uptake process appropriately. The value of Ea was calculated to be 79.9 kJ/mol, which suggests that the process of uptake bromide is controlled by the reaction rate of bromide with the CLDH rather than diffusion.     

Selective removal of heavy metal ions in aqueous solutions by sulfide-selector intercalated layered double hydroxide adsorbent

Remaining largely under-appreciated, a majority of metal ion sorbents are limited in their target selectivity. In this work, a 3D sulfide intercalated NiFe-layered double hydroxide (NFL-S) hierarchical sorbent has been synthesized for selective heavy metal removal. The intercalation of sulfurated groups in the interlayer of the layered double hydroxide (LDH) nanosheets endows NFL-S as a selective heavy metal ion filter; the selectivity of NFL-S for heavy metals is in the order of Pb²⁺ > Cu²⁺ ≥ Zn²⁺ > Cd²⁺> Mn²⁺, and NFL-S has high k_d values for Pb²⁺ (∼10⁶ mL/g) and Cu²⁺ (∼10⁵ mL/g). Scanning electron microscopy, X-ray photoelectron spectroscopy and powder X-ray diffraction were used to analyze the composition of the as-prepared nanoadsorbent. The selective adsorption behavior was systematically studied using batch experiments, and the performance was evaluated through kinetic and isotherm studies. Moreover, the adsorption mechanism of heavy metals by NFL-S through surface complexation was also investigated, which shows great potential for water decontamination.     

铁尾矿制备的分子筛MCM-41吸附剂对废水中Ni2+的吸附行为

以铁尾矿为原料制备出介孔分子筛MCM-41吸附剂,研究了其对废水中Ni2+的吸附行为.结果表明:MCM-41对Ni2+有良好的吸附性能,吸附率随溶液pH值的增加而增加,在pH值为7、吸附时间为80 min时吸附率达到85%以上;Ni2+在MCM-41上的吸附是一个吸热过程,且符合Langmuir吸附等温式,提高温度有利于吸附的进行.