聚合氯化铝的盐基度与水解形态

聚合氯化铝(PAC)是国际上近年来发展较快的高效水处理剂之一。与传统药剂相比,具有用量少、成本低、净化水质优、使用方便等一系列特点,目前正迅速取代传统水处理药剂。随着聚合氯化铝的广泛应用,其形态结构成为人们日益关注的焦点。已有研究表明,絮凝剂的凝聚效率很大程度上取决于混     

高浓度高Alb含量聚合氯化铝的制备及其水解行为研究

高浓度高Alb含量聚合氯化铝的制备及其相关性质研究一直是国内外学者研究的热点和前沿问题.本文首先采用化学法合成出AlT=0.2 mol·L-1,Alb高于85%的低浓度高Alb含量的聚合氯化铝,并在热侧温度55℃,冷侧温度20℃条件下进行膜蒸馏浓缩,首次成功地制备出总铝浓度AlT=2.52mol·L-1,Alb含量高达88%的高浓度高Alb含量的聚合氯化铝溶液.其次,对两种高Alb含量的低浓度和高浓度的聚合氯化铝新产品进行了水解特性研究,分别考察了稀释倍数、pH和稀释时间等因素对溶液中聚铝形态分布的影响.结果表明,稀释刚一开始时,Alb下降比较明显,但随着稀释倍数的增大,Alb含量降低较为缓慢,但在整个稀释过程中Alb含量仍能保持在70%以上;溶液的pH在碱性范围内对聚铝形态有一定影响,在碱性范围内,随着pH的增加,Alb含量逐渐增加,Alb、Alc含量逐渐减少,在酸性和中性较宽的范围内能够保持较高的Alb含量和较低的Alb含量;稀释时间对铝形态的影响较小,Alb聚合形态能够保持较长时间的稳定性.实验结果表明我们所制备的高浓度高Alb含量聚合氯化铝具有相当的化学稳定性.     

铝形态分析的研究进展

介绍了铝形态分析的意义,环境和生物体系中铝存在的形式,综述了铝形态分析时采用的连续静态浸提法、铝-试铁灵逐时络合比色光度法、酸碱电位滴定、电化学分析、色谱分析、核磁共振及计算机拟合等分析方法(1984—2009年间),引用文献65篇。     

土壤和沉积物重金属形态分析研究进展

人类社会的发展进程导致土壤和沉积物中的重金属含量远远超过背景值,具有严重的潜在威胁隐患。然而,由于重金属的流动性、毒性以及生物累积性会对环境造成深远影响,重金属形态分析已然成为环境研究的重要一环。目前最具代表性的形态提取方法为 Tessier 法和 BCR 三步法,上述方法为标准物质研制、重金属污染评估、生态修复以及生物有效性风险等问题提供了有效解决方案,但也有着各自的局限性。本文总结了目前常用的元素形态提 取分析方法,系统对比论证,讨论了重金属形态分析方法未来可能出现的问题和发展方向,以期为土壤及沉积物重金属污染研究提供思路与支撑。     

砷形态分析技术研究进展

总结了近年来砷形态分析的分离、检测以及联用技术的研究进展,提出了今后在砷形态分析工作中应关注的主要问题.     

环境中锑的分布、存在形态及毒性和生物有效性

由于自然过程及人类活动的影响,锑及其化合物在环境中普遍存在,环境中锑的污染也日益严重.近年来,国外对锑污染的研究日益重视.锑不是植物必需的,但能够被植物根系吸收.已有证据表明锑对生物及人体产生毒性.本文主要对环境中锑的分布和存在形态,及对动物和人体的毒性和对生物有效性研究进展进行评述。     

凝胶色谱法分离聚合氯化铝中Al13形态的特性研究

采用缓慢滴碱法制备聚合氯化铝(PAC)溶液, 并采用Bio-Gel P-100型凝胶层析法将溶液中铝形态进行了分离. 采用常规的化学方法(Al-Ferron逐时络合比色法)和Al²⁷Al-NMR法对分离过程中收集的各级分进行了测定. 在分离过程中通过改变洗脱速度, 洗脱液离子强度和pH值等实验条件来研究影响分离的各因素. 实验结果表明, 在层析分离过程中除被分离物的分子尺寸之外, 分子电荷对分离也会产生相应的影响. 降低洗脱流速、提高洗脱液离子强度, 以及调节合适的pH值都能提高分离效率. 通过对实验条件的优化, 可以分离得到大量高纯Al₁₃形态(即 AlAl_b含量为100%的产品), 可占被分离PAC产品总量50%以上.     

环境中锑的形态分析研究进展

评述了环境样品中痕量锑的形态分析概况及近年来的发展趋势,主要包括分光光度法、电化学方法、原子光谱法和色谱法等。     

环境中无机铬形态分析研究进展

本文对近年来环境分析化学中的一个重要分支－环境中无机铬的形态分析进展及有关分析方法的现况和发展趋势进行了概述。     

土壤中砷形态分析研究进展

本文评述了近年来国内外土壤中砷形态分析的主要研究方法,包括联用分析法、分级提取法和同步辐射X-射线线吸收光谱法。联用分析法包括气相色谱联用法、毛细管电泳联用法和高效液相色谱联用法。重点介绍了目前应用范围较广的高效液相色谱-等离子体质谱(HPLC-ICP-MS)联用法和高效液相色谱-氢化物发生-原子荧光光谱(HPLC-HG-AFS)联用法。同步辐射X-射线线吸收光谱法近几年发展迅速,是最具发展潜力的形态分析方法。     

Enhancing electrochemical preparation of polyaluminum chloride by a magnetic field

A novel effective method for preparing polyaluminum chloride (PAC) with high content of Al₁₃ polymer through conventional electrolysis coupled with rare earth Nd-Fe-B magnetic field was introduced. The content of Al₁₃ polymer in PAC synthesized by this method was highly influenced by the electrobath voltage (E), the magnetic flux density (B), the current density (i) and the distance between the two adjacent electrodes (d_adj). A total aluminum concentration (Al_T) in the PAC solution of 0.8 mol l⁻¹ was obtained when the E, B and i was 2.2 V, 0.4 T and 3.2 A dm⁻², respectively. The optimum d_adj and circulating flow (Q_f) were 20 mm and 23.7 l h⁻¹. With accelerated mass transfer rate by external magnetic field and high Q_f, this process had the advantages of forming more Al(OH)₄⁻ as the precursor of Al₁₃ polymer and inhibiting the concentration polarization more obviously than conventional electrolysis process. Under the optimum conditions, the amount of Al₁₃ polymer in PAC accounted for 82.3% of the Al_T (Al_T = 0.8 M, basicity = 2.2), which was higher than that of PAC prepared by other methods.     

Investigation of dynamic processing on aluminum floc aggregation: Cyclic shearing recovery and effect of sulfate ion

The floc formation and re-aggregation potential and the effects of sulfate on coagulation by AlCl3, polyaluminum chloride (PAC), and Al13 species using a photometric dispersion analyzer (PDA) are in- vestigated. It is found that the recovery level from shearing is the highest for the Al13 species. This is likely a result of increased collision efficiency due to more effective charge neutralization. The ex- perimental results show that sulfate has a significant effect on coagulation and promoting aggregation of hydrolyzed species for the Al13 species. It results in significant improvement of the coagulation effi- ciency through an electrostatic patch effect. The results further indicate that zeta potential of the parti- cle suspension is not the only indicator for the coagulant efficiency when precipitate formation sig- nificantly improves coagulation.     

Characterzation and separation of Al13 species using gel-filtration chromatography

A polyaluminum chloride (PAC) sample was prepared using a slow alkaline titration method. The Bio-Gel P-100 gel column chromatographic technique was used to separate and characterize the various forms of aluminum present in the prepared PAC solution. The effluents from a gel column were monitored using online chemical method: Al-Ferron timed complexation spectrophotometry and by 27Al nuclear magnetic resonance (NMR) spectroscopy. Effects of different experimental conditions such as eluent flow rate, ionic strength and pH on separation of Al13 were investigated. Experimental results indicated that molecule size exclusion was not the only parameter affecting the column chromatographic separation efficiency of Al13 but molecule charge as well. Reducing the eluent flow rate, increasing the ionic strength and suitable pH resulted in increase in the separation efficiency. Experimental results clearly indicated that by varying the experimental conditions, it is possible to produce pure Al13 species using a gel column chromatographic technique.     

Preparation and characterization of polyaluminum chloride containing high content of Al13 and active chlorine

This paper introduces a new electrochemical method for preparation of polyaluminum chloride (PACl) which contains high content of Al₁₃ and active chlorine and presents integrated properties of flocculation with oxidation. E-PACl (PACl prepared by electrolysis process) samples were successfully prepared in an electrochemical reactor, which used Ti/RuO₂–TiO₂ anodes and Ti cathodes. Anode potential was the key electrochemical parameter that needed to be controlled at 1.5 V to ensure the maximal current efficiency of main reactions in electrolysis process. Analyses by ferron colorimetric method and ²⁷Al NMR spectroscopy indicated that Al₁₃ was the predominant species in the final product when total Al concentration (Al_T) was in the range of 0.1–1.5 mol/L. The amount of active chlorine was in inverse proportion to Al_T. Contents of the most active component, Al₁₃ and active chlorine could respectively reach 90.9% and 5650 mg/L with Al_T = 0.51 mol/L and basicity (B, OH/Al molar ratios) = 2.23 in the liquid product of PACl (E-PACl2). In E-PACl2, the sulfate precipitate of Al₁₃ was the unique material detected by X-ray diffraction patterns and clusters of small spheres that might be the aggregates of Al₁₃ were observed on the surface of its air-dried sample by atomic force microscopy. Results of dynamic light scattering showed that the particle size distributions of E-PACl were related with the Al species distributions and ageing time. The active chlorine in E-PACl2 performed well on disinfection of raw water.     

钙对铝水解聚合反应及聚合铝物化特性的影响

The polyaluminum chloride containing Ca was prepared by adding Ca before and after the aluminium polymerization, respectively. The effects of Ca on the hydrolysis and polymerization of aluminum, the characteristic of aluminum species, the ζ potential and viscosity of PAC were also studied. The experimental results show that the introduction of Ca retards the formation of Al precipitates during the hydrolysis and polymerization of aluminum and increases the contents of Al_m and Al₁₃ in PAC. Aluminum species can complex with Ca to form heteronuclear hydroxo complexes, which decreases the chemical shifts of Al_m and Al₁₃ in NMR. The ζ potential and the viscosity of PAC increase with the rise of Ca/Al molar ratio. Comparing with adding Ca after the aluminium polymerization, there are much more Al-Ca heteronuclear hydroxo complexes formed by adding Ca before the polymerization, which leads to a more obvious influence of Ca/Al molar ratio on the ζ potential and the viscosity of PAC.     

Characterization and separation of Al_(13) species using gel-filtration chromatography

Polyaluminum chloride (PAC) coagulant has been developed and widely used in water and wastewater treatment industry since the 1980s[1]. PAC is normally made by partial hydrolysis of acid aluminum chloride solution using slow alkaline titration method. However, this method would result in many different Al species. Among these Al species, it seems that tridecamer (Al13O4(OH) 724 , often denoted by Al13) is the most effective and stable polymeric Al species for water and wastewater treatme…     

Transition-metal-free trifluoromethylthiolation and difluoromethylthiolation of thiols with trifluoromethanesulfonyl chloride and difluoromethanesulfonyl chloride

Triphenylphosphine-mediated metal-free trifluoromethylthiolation and difluoromethylthiolation of thiols by CF₃SO₂Cl and CHF₂SO₂Cl to synthesize trifluoromethyl disulfides and difluoromethyl disulfides, respectively, was achieved at room temperature. Iodine generated in situ from iodide facilitated this reaction via the formation of iodotriphenylphosphonium iodide which could serve as a reducing agent in this transformation. Readily available reagents and mild reaction conditions without transition-metals allow this protocol to be more practical than traditional methods.     

聚碱式氯化铝制备实验探索

通过改进的制备方案,在常温下成功制备聚碱式氯化铝。无论在制备方法上还是在净水效果上,改进后的聚碱式氯化铝的制备方案都优于现有教材采用的实验方案。     

形态分布计算软件的设计及在大学化学教学中的应用

介绍了一种简单的配位平衡体系形态分布计算程序的设计方法,给出了程序中拟牛顿法解方程组的算法,并以铁（Ⅲ）-草酸盐配合物体系作为实际例子,给出了该程序计算所得的铁（Ⅲ）-草酸盐主要配离子形态的分布系数曲线。该软件设计有利于学习“大学化学”课程中复杂的配位平衡计算原理与方法,也为涉及到配合物平衡体系的化学研究提供帮助。     

Isopiestic measurements on aqueous mixtures of sodium chloride and strontium chloride

Isopiestic measurements have been made on NaCl–SrCl₂ mixtures at 25°C over the ionic strength range 0.6–6 mole-kg^–1. The results are interpreted in terms of current mixed-electrolyte treatments. The mixing behavior in this system is comparatively simple, but the Pitzer treatment is still clearly superior to the other treatments.