聚丙烯/蒙脱土纳米复合材料研究进展

聚合物/蒙脱土纳米复合材料具备特殊的结构和形态。显示出优异的物理化学性能，因此具有重要的科学意义，本文详细介绍聚丙烯/蒙脱土纳米复合材料的制备，制备过程热力学与动力学及其结构和性能，并对其应用前景进行了展望。     

聚丙烯/蒙脱土纳米复合材料的研究进展

介绍了聚丙烯/蒙脱土纳米复合材料的制备原理及插层方法。并对国内外的研究进展进行了综述，讨论了蒙脱土对聚丙烯结晶性能的影响。蒙脱土的加入聚丙烯有异相成核的作用。另外介绍了聚丙烯/蒙脱土纳米复合材料中蒙脱土对聚丙烯力学性能的影响。其力学性能随蒙脱土含量的增加先增加后下降。     

聚丙烯/蒙脱土纳米复合材料流变性能的研究

采用毛细管流变仪研究了聚丙烯(PP)／蒙脱土纳米复合材料的流变性能。结果表明：PP／蒙脱土纳米复合材料的流动特性与常规PP相似，为典型的假塑性流动；其非牛顿指数随温度提高而增大，在220℃时，复合材料的非牛顿性小于PP，在260℃时，复合材料的非牛顿性大于PP；复合材料的表观粘度低于PP，粘流活化能大于PP。     

改性纳米蒙脱土对废水中Cr(Ⅵ)的吸附行为研究

以纳米蒙脱土(MNT)、溴化十六烷基吡啶(CPB)和EDTA为原料,采用溶胶-凝胶法,制备了CPB-MNT(C-M)和CPB-EDTA-MNT(C-E-M)吸附剂,采用XRD、SEM、N2吸附-脱附和FTIR进行表征,考察其对Cr(Ⅵ)的吸附行为,并研究了吸附等温方程和吸附动力学。结果表明,经改性后,CPB和EDTA成功进入蒙脱土层间,使层间距由0.95 nm分别增大到1.69 nm和2.12 nm,单位吸附量由4.02 mg/g分别增大到7.11 mg/g和11.91 mg/g;相同条件下,对Cr(Ⅵ)去除率C-E-M(99.19%)C-M(59.25%)MNT(32.5%);C-E-M吸附模拟废水中Cr(Ⅵ)符合拟二级动力学和Langmuir方程,极限吸附量和Langmuir常数分别是44.41 mg/L和0.731 2;吸附机理主要是物理吸附和化学吸附。C-E-M吸附剂用于处理含Cr(Ⅵ)废水具有巨大的前景。     

改性纳米蒙脱土对废水中Cr(Ⅵ)的吸附行为研究

以纳米蒙脱土(MNT)、溴化十六烷基吡啶(CPB)和EDTA为原料,采用溶胶-凝胶法,制备了CPB-MNT(C-M)和CPB-EDTA-MNT(C-E-M)吸附剂,采用XRD、SEM、N2吸附-脱附和FTIR进行表征,考察其对Cr(Ⅵ)的吸附行为,并研究了吸附等温方程和吸附动力学。结果表明,经改性后,CPB和EDTA成功进入蒙脱土层间,使层间距由0.95 nm分别增大到1.69 nm和2.12 nm,单位吸附量由4.02 mg/g分别增大到7.11 mg/g和11.91 mg/g;相同条件下,对Cr(Ⅵ)去除率C-E-M(99.19%)>C-M(59.25%)>MNT(32.5%);C-E-M吸附模拟废水中Cr(Ⅵ)符合拟二级动力学和Langmuir方程,极限吸附量和Langmuir常数分别是44.41 mg/L和0.731 2;吸附机理主要是物理吸附和化学吸附。C-E-M吸附剂用于处理含Cr(Ⅵ)废水具有巨大的前景。     

聚丙烯/蒙脱土纳米复合材料研究

本文综述了聚丙烯／蒙脱土纳米复合材料的特点、制备方法,并对复合材料的结构表征方法作了介绍。     

聚丙烯/接枝物/蒙脱土纳米复合材料的制备

采用熔融插层法制备聚丙烯／接枝物（PP－g－MAH）／有机蒙脱土（org-mont）纳米复合材料，用X射线衍射法（XRD）检测复合材料层间距的变化，用示差扫描量热法（DSC）研究其非等结晶动力学，并考察了纳米复合材料的力学性能。结果发现，非极性PP大分子链很难直接插入蒙脱土片层，引入适量的接枝物是制备聚丙烯基纳米复合材料的关键。适当用量的蒙脱土和接枝物可使PP的结晶温度和结晶速率提高，分别在10％、20％时出现最大值。随接枝物用量的增加，纳米复合材料拉伸强度先增加后减小，10％时最大，比纯PP增加了14％，“V”缺口冲击强度和纯PP相近。可以得出，org-mont含量为2％，接枝物含量为10％时，纳米复合材料的综合性能最佳。     

聚丙烯/蒙脱土纳米复合材料的湿热老化性能

用熔融插层法制备了2种聚丙烯/蒙脱土(PP/OMMT)纳米复合材料,考察了在90℃的水中进行0~80 d不同时长的湿热老化后的产物特征。添加少量纳米化蒙脱土的PP表面形貌被破坏时间可延长20 d左右,比纯PP拉伸强度保持率提高67.5%,冲击强度保持率提高12.4%。PP、PP/OMMT复合材料湿热老化的损伤主要是环境中的水分子的直接物理作用,其中PP/季铵型OMMT纳米复合材料优良的抗湿热老化能力是其较高的结晶度、剥离性纳米化OMMT片层对水分子和热的物理阻隔效应以及OMMT与PP间较强的相互作用的共同结果。     

聚丙烯/蒙脱土复合材料的热重分析

利用热重分析技术对聚丙烯和含4%蒙脱土的聚丙烯蒙脱土(PP/OMMT)复合材料的热分解行为进行了研究。运用Qzawa法计算了PP和PP/OMMT复合材料的热分解动力学参数,并用Coats-Redfem法研究了热分解动力学机理。结果表明,PP和PP/OMMT复合材料的热分解一步完成;OMMT的加人,使得PP的初始失重温度较高;失重22%以前,复合材料的活化能大于纯PP,失重率大于22%后,复合材料的活化能低于PP。失重率在30%一80%时,PP和PP/OMMT热分解反应的机理函数分别为Valensi方程(n=1/2)和Mampel Po~法则,对应机理为二维扩散和幂函数法则。     

聚丙烯／蒙脱土纳米复合材料研究进展

简要介绍了蒙脱＋（MMT）的结构、插层原理和表面修饰方法,并介绍了聚丙烯（PP）／MMT纳米复合材料的制备原理和方法。综述了PP／MMT纳米复合材料的国内外研究进展。     

改性高粱秸秆对Cr(Ⅵ)吸附性能的研究

研究了改性高粱秸秆对Cr(Ⅵ)的吸附性能,结果表明,改性高粱秸秆对水溶液中Cr(Ⅵ)具有很好的吸附作用。常温下,用0.15g改性高粱秸秆,对20mL pH为2.5,ρ[Cr(Ⅵ)]为20mg/L的溶液,振荡吸附100 min,Cr(Ⅵ)的去除率可达98.11%。改性高粱秸秆对水溶液中Cr(VI)的吸附符合Freundlich吸附等温方程和Langmuir吸附等温方程,说明该吸附过程以单分子层物理吸附为主。     

弱碱性离子交换纤维对六价铬吸附性能的研究

以一种腈纶基弱碱性离子交换纤维为材料,探讨了纤维型式(氯型、氢氧型)对吸附量和再生性能的影响.考察了溶液pH、温度对氯型纤维吸附量的影响,并进行相应的动力学实验.结果表明:转为氯型的纤维吸附与再生性能明显优于相应的氢氧型纤维,该纤维在pH 2～3时吸附性能最好,温度越高吸附量越大.吸附过程符合准二级动力学模型(R2＞0.998),吸跗在30 min内基本达到平衡.纤维对六价铬的吸跗容量可达376 mg·g-1(pH=2,G=300 mg·L-1),明显高于国外商品化的Fiban A-1离子交换纤维(152.9 mg·g-1);且经100次含铬电镀废水吸附再生循环后,六价铬去除率与纤维质量基本保持不变.     

EDTA改性凹凸棒土及其对六价铬离子的吸附效果研究

采用微波辐射的方法成功地将乙二胺四乙酸(EDTA)修饰到凹凸棒土表面,通过傅里叶红外光谱、扫描电子显微镜等对修饰效果进行表征。研究表明:EDTA改性后的凹凸棒土能较好地去除重金属废水中的Cr~(6+)。且在溶液体系条件为中性或弱碱性,EDTA与凹凸棒土配比在一定范围内时,其对Cr~(6+)去除率可稳定在90%以上。     

A Study in the Adsorption Behaviors of Cr (VI) on Crosslinked Cationic Starches

The adsorption behaviors between Cr (VI) and crosslinked cationic starch with quaternary ammonium group were investigated in various conditions. The adsorption processes are found to be dependent on the initial pH of the solution, the dose of the absorbents, initial concentration of Cr (VI), and adsorption temperature. The adsorption reaches equilibrium in a short time, and follows the Langmuir isotherm. The adsorption capacity increases with the increasing cationic groups. The adsorption thermodynamics study shows that adsorption processes are exothermic, and lower temperature is favorable to the adsorption of Cr (VI).     

Comparison Between the Cr(VI) Adsorption by Hydrotalcite and Hydrotalcite-Gibbsite Compounds

Cr(VI) adsorption from aqueous solutions on Mg-Al hydrotalcite and Mg-Al hydrotalcite-gibbsite with Al/(Al+Mg) ratios (R) of 0.3 and 0.6 (MgAlHT_{R = 0.3} and MgAlHTG_{R = 0.6}) was investigated as a function of the pH and chromium concentration. The results showed that the maximum Cr(VI) adsorption by Mg-Al compounds do not depend on the value of R at pH 7. In addition, the chromate equilibrium sorption capacity for MgAlHTG_{R = 0.6} is at least 4.8 times higher than that for MgAlHT_{R = 0.3} at pH 5. The Cr(VI) maximum capacities of MgAlHT_{R = 0.3} and MgAlHTG_{R = 0.6} at pH 7 were similar, 6.5 and 6.8 mgCr(VI)/g, respectively.     

Adsorption of Cr(VI) using thermally activated weed Salvinia cucullata

Cr(VI) removal studies were carried out by using activated carbon obtained from waste weed, Salvinia cucullata. Effects of various parameters, such as pH, contact time, temperature, adsorbate concentration, adsorbent dose and particle size of the adsorbent on percentage of adsorption were studied. The adsorption studies were carried out at an agitation speed of 600 rpm to minimize the film diffusion. The adsorption kinetics followed dual rate; it was fast during a first stage and then it was reduced. The equilibrium was achieved in 12 h. The kinetics increased with decrease in pH. Adsorbate and adsorbent concentration also influenced the kinetics. The adsorption process was endothermic in nature. The reaction kinetics followed pseudo-second-order kinetic equation. Empirical rate equation developed, which explained the effect of various adsorption parameters, was studied. Theoretical numbers of stages were calculated based on the results. Intra-particle diffusion was found to be the rate-controlling step. Optimization studies were also carried out to establish the upper and lower breakthrough points.     

焙烧水滑石的制备及其吸附Cr(VI)的研究

通过共沉淀法制备Mg-Al水滑石,考察制备温度、pH值、离子比等因素对水滑石吸附Cr(VI)的影响,探讨最佳制备条件。再将水滑石进行焙烧,通过控制变量法考察投加量、吸附时间、pH值、温度和初始浓度对LDO吸附Cr(VI)的影响。结果表明,最佳制备条件pH约为9、离子比为3∶1、制备温度为70℃;LDO最佳的吸附条件为固液比为0.3%、时间为120 min、pH约为6、温度为35℃,最大吸附量为26.432 mg/g;LDO吸附Cr(VI)的过程更符合Langmuir吸附等温式和准二级动力学模型。     

Adsorption of Cr (VI) Oxyanions onto Modified Wood Pulp

A new adsorbent was prepared from wood pulp (WP) after reaction with epichlorohydrin and dimethylamine in the presence of pyridine and N,N-dimethylformamide (DMF). The adsorption of Cr (VI) from aqueous solutions by the so-prepared wood pulp adsorbent (WP-A) was investigated. Various factors affecting adsorption, such as pH, adsorbent concentration (1–5 g/L), agitation time (5–60 min), and Cr (VI) concentration (50–700), were taken into consideration. The adsorption of Cr (VI) onto (WP-A) was found to be pH-dependent and maximum adsorption was obtained at pH 3. The adsorption data obeyed Langmuir and Freundlich adsorption isotherms. The Langmuir adsorption capacity (Q_max) was found to be 588.24 mg/g. Freundlich constants, K_F and n, were found to be 55.03 and 2.835, respectively.     

Adsorption thermodynamics and kinetics of Cr(VI) on KIP210 resin

Series of resin selection experiments were carried out and the KIP210 strong base anion exchange resin was confirmed to have the maximum equilibrium adsorption capacity to remove Cr(VI) from wastewater. The adsorption thermodynamics and kinetics of Cr(VI) on KIP210 resin were investigated completely and systematically. The static experiments were performed to study the effects of various parameters, such as shaking speed, resin dosage and pH during the adsorption process. The results indicate that the effect of external diffusion is eliminated at 160 rpm, the best pH value is 3.0 and the removal percentage of Cr(VI) increases with the increase of the resin dosage. The adsorption of Cr(VI) on KIP210 agrees well with the Langmuir isotherm and the adsorption parameters of thermodynamics are ΔH = 26.5 kJ mol⁻¹, ΔS = 126.7 J mol⁻¹ K⁻¹ and ΔG < 0. It demonstrates that the adsorption of Cr(VI) on KIP210 is a spontaneously endothermic physisorption process. Moreover, the adsorption process can be described well by a pseudo-second-order kinetic model and the activation energy is 30.9 kJ mol⁻¹. The kinetic analysis showed that the adsorption rate is controlled by intraparticle diffusion. The resin is successfully regenerated using the NaOH solutions.