Isothermal Crystallization Kinetics and Melting Behavior of Poly(ethylene terephthalate)/Attapulgite Nanocomposites Studied by Step-scan DSC

The crystallization kinetics of poly(ethylene terephthalate)/attapulgite (AT) nanocomposites and their melting behaviors after isothermal crystallization from the melt were investigated by DSC and analyzed using the Avrami method. The isothermal crystallization kinetics showed that the addition of AT increased both the crystallization rate and the isothermal Avrami exponent of PET. Step-scan differential scanning calorimetry was used to study the influence of AT on the crystallization and subsequent melting behavior in conjunction with conventional DSC. The results revealed that PET and PET/AT nanocomposites experience multiple melting and secondary crystallization processes during heating. The melting behaviors of PET and PET/AT nanocomposites varied in accordance with the crystallization temperature and shifted to higher temperature with the increase of AT content and isothermal crystallization temperature. The main effect of AT nanoparticles on the crystallization of PET was to improve the perfection of PET crystals and weaken its recrystallization behavior.     

Synthesis of Polypropylene/Attapulgite Nanocomposites and Their Crystallization Behavior Studied by Step-Scan DSC

Attapulgite (AT) was modified by grafting with butyl acrylate (BA) via polymerizations initiated by Gamma radiation. Polypropylene (PP)/AT nanocomposites were synthesized via melt extrusion in a twin-screw extruder. Fourier transform infrared (FTIR) spectroscopy and thermogravimetry (TG) were used to assess the structure of the hybrid materials and the dispersion of AT was verified by transmission electron microscopy (TEM). The crystallization kinetics of PP/AT nanocomposites were investigated by differential scanning calorimetry (DSC) and analyzed by using the Avrami method. The isothermal crystallization kinetics showed that the addition of AT increased both the crystallization rate and the isothermal Avrami exponent of PP. Step-scan differential scanning calorimetry (SDSC) was used to study the influence of AT on the crystallization and subsequent melting behavior. The results revealed that PP and PP/AT nanocomposites experienced multiple melting and secondary crystallization processes during heating. The melting behaviors of PP and PP/AT nanocomposites varied with the variation of crystallization temperature and AT content.     

以硫代乙酰胺/凹凸棒石复合物为载体的钙离子选择性电极

报道了以硫代乙酰胺/凹凸棒石有机无机复合物为载体的新型钙离子选择性电极的研制. 探讨了该有机无机复合物中硫代乙酰胺与凹凸棒石的组成比例、增塑剂用量、被测溶液pH 等因素对钙电极性能的影响. 结果表明新制钙电极对溶液中的钙离子有较好的近能斯特响应, 响应斜率为15.2 mV·decade^-1, 最低检出下限为1.0×10^-6 mol·L^-1. 新制钙电极具有很好的稳定性, 其可应用在溶液pH=6.0～10.0 范围内. 新电极对常见阳离子表现出好的抗干扰性. 利用红外、紫外、相关电导率实验等方法研究了有机无机复合物型电活性物质的结构及所制钙电极的工作机理.     

氨浓度对氨蒸发法制备Pd-Cu/凹凸棒土催化剂常温CO氧化性能的影响

以凹凸棒土(APT)作载体,采用氨蒸发法制备了Pd-Cu/APT催化剂,以CO氧化为探针反应,在连续流动微反应装置上,考察了初始氨浓度对催化剂CO常温催化氧化性能的影响。通过N₂-physisorption、XRD、FT-IR、TEM和H₂-TPR等手段对催化剂的结构和性质进行了表征。结果表明,在较低或过高氨浓度条件下,制备的Pd-Cu/APT中Cu物种均主要以CuO为主,仅有少量Cu₂(OH)₃Cl;适宜的氨浓度有利于稳定Cu₂(OH)₃Cl物相的形成,其薄片状的形貌特征、良好的分散状态以及与Pd物种间较强的相互作用,显著提高了CO催化氧化性能。在空速6 000 h^-1、CO体积分数1.5%、水蒸气体积分数3.3%的反应条件下,Pd-Cu/APT催化剂表现出优异的CO室温催化氧化活性和稳定性。     

凹凸棒黏土固载AlCl3的制备、表征及其催化水杨酸乙酰化活性

以凹凸棒黏土（ATP）为载体,采用回流吸附法制备了AlCl3负载型固体酸催化剂AlCl3/ATP,并将其用于催化阿司匹林合成反应。 利用红外光谱、X射线粉末衍射、比表面（BET）、能谱(EDS) 和Hammett指示剂等测试技术对催化剂结构、组成和酸强度进行了表征。 以催化合成阿司匹林收率为考察指标,对影响其催化性能的凹土酸处理浓度、热活化温度、催化剂用量和AlCl3负载量进行优化,并比较了载体和负载前后催化剂的催化性能。 结果表明, ATP经10 mol/L盐酸室温酸化12 h,300 ℃热活化2 h后对AlCl3的负载量达1.18 mmol/g,当AlCl3/ATP用量为水杨酸质量的5%时,其催化阿司匹林合成反应收率达92.5%,高于未负载的AlCl3催化剂及载体本身,且该催化剂重复使用多次仍可保持相当的活性。     

Chemically modified attapulgite with asparagine for selective solid-phase extraction and preconcentration of Fe(III) from environmental samples

A new method that utilizes asparagine modified attapulgite as a solid phase extractant has been developed for preconcentration of trace Fe(III) prior to the measurement by inductively coupled plasma optical emission spectrometry. Characterization of the surface modification was performed on the basis of Fourier transform infrared spectra. The separation/preconcentration conditions of the analyte were investigated, including the pH value, the shaking time, the sample ?ow rate and volume, the elution condition and the interfering ions. At pH 4, the new adsorbent had relatively high capacity and enrichment factor compared to other methods reported so far. The adsorbed Fe(III) was quantitatively eluted by 2 mL of 0.5 mol L⁻¹ HCl. Common coexisting ions did not interfere with the separation. The detection limit of the method was 0.19 μg L⁻¹. The relative standard deviation was 3.4% (n = 8) which indicated that the method had good precision for the analysis of trace Fe(III) in solution samples. The method was validated using two certified reference materials and has been applied for the determination of trace Fe(III) in biological and natural water samples with satisfactory results.     

以天然凹凸棒石为原料合成Fe/Ti-ZSM-5沸石分子筛及其催化裂化性能

以天然凹凸棒石为硅源、铁源和钛源,一步合成了Fe/Ti-ZSM-5分子筛.X射线衍射、扫描电镜和N₂吸附等温线测定结果表明,所合成的样品具有良好的结晶度和较大的比表面积;NH₃程序升温脱附和H₂程序升温还原结果表明,该样品具有强的酸性和氧化还原性能.更为重要的是,与常规方法制备的ZSM-5沸石相比,Fe/Ti-ZSM-5在催化裂解原料油(LGO,加拿大)的测试中,丙烯的产率提高0.21%,总轻烯烃的产率提高0.33%.由此可见,Fe与Ti物种在ZSM-5沸石分子筛中的存在有利于提高轻烯烃的产率,有望在石油炼制过程中提高烯烃产率.     

凹凸棒黏土负载纳米TiO2-Fe3O4吸附剂的制备及Cr(Ⅵ)的脱除

采用溶胶-凝胶法、一锅反应法制备了负载纳米TiO₂和Fe₃O₄的凹凸棒黏土(TiO₂-Fe₃O₄-ATP)吸附剂,并进行了模拟废水中Cr(Ⅵ)的吸附及脱附性能的研究。 通过扫描电子显微镜(SEM)、X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)和EDS等分析方法对ATP负载纳米TiO₂-Fe₃O₄前后结构进行了表征,考察了物料配比及吸附时间、pH值、温度、投加量和初始质量浓度对Cr(Ⅵ)吸附率的影响。 结果表明,吸附剂在Ti元素含量与负载总量的摩尔比为3：4时吸附效果最佳。 当吸附剂质量为0.6 g,Cr(Ⅵ)离子初始质量浓度小于0.8 mg/L时,pH=6,温度20 ℃,吸附剂对Cr(Ⅵ)的吸附率为79.8%。 TiO₂-Fe₃O₄-ATP吸附剂对Cr(Ⅵ)离子吸附满足Freundlich模型。 在20~40 ℃ 条件下,吸附过程ΔG<0、ΔS=-43.55 J/(mol·K)、ΔH=-14.36 kJ/mol,表明该吸附是个自发、熵减、放热的过程。 吸附过程符合准二级动力学模型,吸附速率控制步骤以表面化学反应为主。 TiO₂-Fe₃O₄-ATP吸附剂在循环使用4次后,吸附率仍能达到65%以上。     

有机凹凸棒土对二氯苯酚的吸附研究

本研究采用超声法用十六烷基三甲基溴化铵改性凹凸棒土制得了有机凹凸棒土(HDTMA-凹凸棒土),并采用XRD和FT-IR对其结构进行了表征。通过吸附实验研究了HDTMA-凹凸棒土对水溶液中二氯苯酚的吸附性能和吸附机理。结果表明:经有机改性后,HDTMA+成功进入到凹凸棒土的层间,HDTMA-凹凸棒土对二氯苯酚的吸附量比未改性凹凸棒土增大了近20倍。Freundlich方程能够较好的描述吸附等温线。二氯苯酚在HDTMA-凹凸棒土上主要是焓推动为主的物理吸附过程,且吸附过程放热。     

Synthesis and applications of novel attapulgite-supported Co(II)-imprinted polymers for selective solid-phase extraction of cobalt(II) from aqueous solutions

A simple and reliable approach using surface imprinting technique combined with chitosan incorporated sol-gel process was established to synthesise a novel Co(II)-imprinted polymer (Co-IIP) with attapulgite as the support material. Then the prepared polymer was characterised by using fourier tranmission infrared spectra (FT-IR) and scanning electron microscopy (SEM), and the imprinting mechanism of Co-IIP was proposed. Batch experiments studies were performed to evaluate the adsorption kinetics, selective recognition, adsorption isotherm, desorption and regeneration characters of Co-IIP. Results showed that Co-IIP offered fast kinetics for the adsorption and desortion Co²⁺ under the optimum conditions. The adsorption and selective recognition Co²⁺ were both followed the order Co-IIP?>?attapulgite?>?NIP. Moreover, Langmuir adsorption isotherm fitted well for the experimental equilibrium data of Co-IIP, and the maximum adsorption capacity of Co-IIP was 31.5?mg?g^?1. Furthermore, Co-IIP could be reused four times with only about 13.42?～?16.17% regeneration loss, and the enrichment factor was more than 10.0. The developed method was also successfully applied to the determination of trace Co²⁺ in river sediments with satisfactory results. The relative standard deviation of the method (RSD) and the detection limit (3σ) were 1.35% and 0.0263, respectively.