Monovalent cation perm-selective membranes(MCPMs)"New developments and perspectives

As one of the most typical and promising membrane processes, electrodialysis(ED) technique plays a more and more significant role in industrial separation. Especially, the separation of monovalent cations and multivalent cations is currently a hot topic, which is not only desirable for many industries but also challenging for academic explorations. The main aim of the present contribution is to view the advances of a wide variety of monovalent cation perm-selective membranes(MCPMs) and their preparation technologies including(1) covalent crosslinking,(2) surface modification,(3) polymer blending,(4) electrospinning,(5) nanofiltration alike membrane,and(6) organic–inorganic hybrid. The relevant advantages and disadvantages with respect to some specific cases have been discussed and compared in detail. Furthermore, we elaborately discuss the opportunities and challenges of MCPMs, the fabricating strategies to take and the future perspectives.

Adsorption of sodium ions and hydrated sodium ions on a hydrophobic graphite surface via cation-π interactions

Using density functional theory computation, we show that sodium ions and hydrated sodium ions can be strongly adsorbed onto a hydrophobic graphite surface via cation-π interactions. The key to this eation-π interaction is the coupling of the delocalized π states of graphite and the empty orbitals of sodium ions. This finding implies that the property of the graphite surface is extremely dependent on the existence of the ions on the surface, suggesting that the hydrophobic property of the graphite surface may be affected by the existence of the sodium ions.

Adsorption equilibrium, kinetics, and dynamic separation of Ca2+ and Mg2+ ions from phosphoric acid–nitric acid aqueous solution by strong acid cation resin

The separation of Ca2+and Mg2+ions from phosphoric acid-nitric acid aqueous solution is very significant for the neutralization process of nitrophosphate fertilizer.This paper studied the adsorption equilibrium,kinetics,and dynamic separation of Ca2+and Mg2+ions by strong acid cation resin,and the effects of phosphoric acid and nitric acid on the adsorption process were investigated.The results reveal that the adsorption process of Ca2+and Mg2+ions in pure water on resin is in good agreement with the Langmuir isotherm model and their maximal adsorption capacities are 1.86 mmol·g-1 and 1.83 mmol·g-1,respectively.The adsorption kinetics of Ca2+and Mg2+ions on resin fits better with the pseudo-first-order model,and the adsorption equilibrium in pure water is reached within 10 min contact time,while at the present of phosphoric acid,the adsorption rate of Ca2+and Mg2+ions on resin will go down.The dynamic separation experiments demonstrate that the designed column adsorption is able to undertake the separation of metal ions from the mix acids aqueous solution,but the dynamic operation should control the flow rate of mix acid solution.Besides nitric acid solution was proved to be effective to completely regenerate the spent resin and achieve the recyclable operation of separation process.

Elements, Structure and Electrochemical Property of Carbon Derived from La^(3+) Adulterating Polystyrene Cation Exchange Resin

The polystyrene cation exchange resin was exchanged by La 3+ and then were carbonized to make resin carbon material. The electrochemical properties of the resin carbon material as the electrode of the lithium ion cell were investigated. The test results show that comparing with the polystyrene cation exchange resin without adulterating, the contents of hydrogen, oxygen and sulfur are changed obviously for the resin carbon material derived from the La 3+ adulterating polystyrene cation exchange resin. The contents of hydrogen and oxygen are increased, and the one of sulfur is decreased. The test results also indicate that it is more easily to form the stratum graphite minicrystal structure with bigger diameter for the La 3+ adulterating resin. According to the electrochemical test results, the electrode derived from La 3+ adulterating polystyrene cation exchange resin has much better electrochemical property, and the capacity of charge and discharge of the electrode is increased about 30 mAh·g -1 in average.

Cation mixing (Li_(0.5)Fe_(0.5))_2SO_4F cathode material for lithium-ion batteries

We study the crystal structure of a triplite-structured （Li0.5Fe0.5）SO4F with full Li＋/Fe2＋ mixing. This promising polyanion cathode material for lithium-ion batteries operates at 3.9 V versus Li＋/Li with a theoretical capacity of 151 mAh/g. Its unique cation mixing structure does not block the Li＋ diffusion and results in a small lattice volume change during the charge/discharge process. The calculations show that it has a three-dimensional network for Li-ion migration with an activation energy ranging from 0.53 eV to 0.68 eV, which is comparable with that in LiFePO4 with only one-dimensional channels. This work suggests that further exploring cathode materials with full cation mixing for Li-ion batteries will be valuable.

Elution Behaviour of Monocarboxylic Acids on a Cation-exchange Resin Column

The retention mechanism of monocarboxylic acids on a cation-exchange resin column was investigated. It was assumed that both Donnan membrane equilibrium and adsorption equilibrium were involved in the chromatographic process. On the basis of the proposed mechanism, an equation was derived for correlating distribution coefficient, Kd, dissociation constant, Aa, and adsorption equilibrium constant, K, of the analyzed acid. By this approach, retention data for some aliphatic acids under different operating conditions were predicted. Results are reasonably in agreement with experiment.

Novel Properties of Supramolecular Complexes Formed by Pairing Cationic Porphyrin and Anionic Metal-Oxo Cluster

MTBPyP (meso-tetrakis(4-N-benzylpyridyl)porphyrin, M=H-2, Zn) bearing positive charge has been shown to associate with SiW12O404- in water solution. The spectral evolution and Job's plots analyses reveal that the relatively stable aggregates contain equal numbers of MTBPyP4(+) and SiW12O404-.

Impact of Hydrogen Ion Concentration on Amino Acids Composition of Macadamia Protein: Approached Using Cation-Exchange Chromatography

In the present context, the objective of this study was to synthesize and analyze the content of AA of macadamia protein and the impact of hydrogen ion concentration (pH) on AA composition. The determination of AA mainly by cation-exchange chromatography was also investigated. Reproducible and reliable techniques for quantification and identification of AA usually require derivatization. However, techniques such as AA analyzer are composed of cation-exchange chromatography and other components can sideline the derivatization with significant accuracy. The present analysis revealed a higher concentration of essential amino acids especially acidic AA, Glu and Asp and basic AA, Arg than other AA in macadamia protein. The study constitutes first report of use of bubble chart for evaluation of AA and explaination of AAS. The results may elaborate that the degradation of AA of macadamia protein for extraction of pH 11 is caused by the impact of pH. Moreover, the nutritional values of AA present in macadamia protein could change for the better by adjusting pH of extraction.

SYNTHESIS AND APPLICATION AS POLYMER ELECTROLYTE OF HOMO- AND COPOLYMERS OF 3-(2-CYANO ETHOXY)METHYL- AND 3-(METHOXY(TRIETHYLENOXY))METHYL-3'-METHYLOXETANE

Two oxetane-derived monomers, 3-（2-cyano-ethoxy）methyl- and 3-（methoxy-（triethylenoxy））methyl-3＇- methyloxetane （COX and MTOX）, were prepared from 3-hydroxymethyl-3＇-methyloxetane. Their homo- and copolymerization in solution were carried out by the cationic ring-opening polymerization with BF3 · Et2O and 1,4-butanediol as co-initiator. The molecular weight and molecular weight distribution were determined using GPC so as to reveal the competition and interchange between active chain end （ACE） and activated monomer （AM） mechanism in the process. The reactivity ratios of the two monomers were calculated according to Kelen-Tudos using ^1H-NMR analysis. The influence of functional side chains in the monomers on the copolymerization behaviors was discussed in virtue of the reactivity ratio data. When doped with lithium salt LiTFSI, the ion conductivity of the homopolymer of MTOX reached 10^-3.58 S/cm at 30℃ and 10^-2.73 S/cm at 80℃, respectively, showing its potential to be used as polymer electrolyte for lithium ion battery.

采用自主研发的在线前处理系统同时分析脱硫废水中阴阳离子

电厂专用的全自动脱硫废水分析仪可以实现对超高浓度脱硫废水的自动化前处理以及分析,样品通过自动二步稀释,并与双系统离子色谱仪联用,对脱硫废水中的阴、阳离子同时进行检测。脱硫废水中阳离子主要有Na+、NH4+、K+、Mg2+、Ca2+,阴离子主要有F-、Cl-、NO3-、SO42-。本研究对仪器相关参数进行了验证,测试结果为,4种阴离子和5种阳离子的混合标准溶液在其线性关系内相关系数均大于0.999;4种阴离子的峰高和峰面积重复性RSD小于2.29%,5种阳离子的峰高和峰面积重复性RSD小于1.78%,实际样品中4种加标阴离子回收率在93.5%~100.2%之间;5种阳离子加标回收率在95.4%~103.8%之间。结果证明,该系统大大提高了分析效率,节省了人工成本,填补了市场空白。

盐酸改性凹凸棒石对铯离子的吸附性能研究

铯是重要的稀有金属元素,被人们广泛用于航天、医疗、特种玻璃等领域。近年来铯资源的分离提取技术及其应用得到了深入研究,其中吸附法作为最具潜力的分离提取方法之一,一直是该领域的研究热点。本研究采用盐酸对凹凸棒石改性,制备得到凹凸棒石吸附材料(ACH-3),并采用XRD、FT-IR、SEM、BET、XRF等表征手段研究ACH-3的结构特征。以ACH-3为吸附剂探究其对水溶液中铯离子(Cs^(+))的吸附性能,并进一步探讨了温度、初始pH、初始浓度以及吸附剂添加量对吸附性能的具体影响。实验结果显示,在25℃、pH=9和Cs^(+)浓度为200 mg/L的条件下,ACH-3对Cs^(+)的吸附量高达78.99 mg/g,超过凹凸棒石原矿吸附量(7.41 mg/g)的十倍。通过对吸附Cs^(+)前后光谱信息和动力学曲线分析,ACH-3对Cs^(+)的吸附归因于静电吸引与离子交换作用。

H_(2)S^(+)在A^(2)A_(1)(v1=1,v2=8,v3=0)激发态的光解动力学

振动激发在分子和离子的光解动力学中有着重要的作用:开展特定振动激发态分子离子的光解离动力学实验研究存在很大挑战,尤其是实现合频振动激发离子的量子态选择的制备.本文利用时间切片离子速度成像技术研究了H_(2)S^(+)离子经A^(2)A_(1)(v1=1,v2=8,v3=0)激发态解离生成S^(+)(4S)和H_(2)的光解动力学.实验结合多光子电离和共振激发技术制备了振动激发的H_(2)S^(+),获得了离子在357.02~358.38nm范围内六个光解波长下产物S^(+)的速度影像.根据实验影像,获得了产物的总平动能谱和不同转动态的角分布各项异性参数特别指出地是在很窄的光解能量范围内,转动产物H_(2)(J=1)和H_(2)(J=3)的分支比出现多次反转,该现象与A^(2)A_(1)态单一振动模式激发的H2S+离子的光解动力学行为有明显不同.该研究表明,合频振动激发的H_(2)S^(+)离子光解动力学中可能存在振动模式之间的协同效应.

膜法分离一/二价阳离子的研究进展

各类工业过程如水质软化、食用盐纯化、盐湖卤水提锂、酸和重金属资源回收等对一/二价阳离子高效分离的需求日益增长,近年来,针对上述分离体系的膜材料的研究取得了诸多进展。本文详细总结了针对一/二价阳离子分离的选择性阳离子交换膜、纳滤膜、支撑液膜和离子印迹膜的研究进展,重点梳理了相关膜材料的离子选择性优化思路和机理,对比分析了上述膜过程的特点和适用场景。基于此,作者认为,离子筛分精细化是膜分离技术的重要发展方向。在分子尺度明晰分离层的形成和演化机理,对于提高界面聚合反应可控度,实现在亚纳米尺度膜结构的精细调控至关重要。通过在膜基体内可控构建目标离子的特异性识别位点和传质通道,有望实现高选择性离子筛分。此外,具有本征规则孔道结构的新型分离膜材料,如MOFs、COFs、二维层状结构膜等,在精细筛分方面具有良好的发展潜力。

离子色谱法同时检测大气颗粒物PM_(2.5)中低级脂肪胺和常规阳离子

大气中存在大量的有机胺污染,其中低级脂肪胺是促进颗粒形成和生长成为PM_(2.5)的诱因,会对人体肾脏、心肺功能健康造成损害。而PM_(2.5)是大气中常见的颗粒污染物,是雾霾天气产生的主要原因,其成分非常复杂,测定其中的阳离子和低级脂肪胺,能直接监测环境大气质量,保护人体健康。本研究建立了抑制电导离子色谱法同时测定大气细颗粒物PM_(2.5)中4种低级脂肪胺(甲胺、二甲胺、三甲胺、乙胺)和5种常见阳离子(Na^(+)、NH_(4)^(+)、K^(+)、Mg^(2+)、Ca^(2+)),通过优化色谱条件,实现了K^(+)和甲胺、二甲胺和乙胺等难分离物质的有效分离,分析结果可用于评估空气中的颗粒物污染情况。本研究采用负载石英滤膜的中流量采样器采集大气中的PM_(2.5)颗粒物,裁剪1/2滤膜并剪碎于10 mL超纯水中超声提取2次共60 min,提取液过0.22μm滤膜后用离子色谱检测。比较了3种阳离子色谱柱IonPac^(TM) CS17、IonPac^(TM) CS16和SH-CC-9后,最终选用SH-CC-9阳离子分析柱(200 mm×4.6 mm)进行分离:柱温30℃,检测器温度35℃,进样量25μL,流动相为甲基磺酸(MSA)水溶液,流速为1.1 mL/min。在此色谱条件下,大气中可能存在的其他胺(N,N-二甲基甲酰胺、N,N-二甲基乙酰胺、丙胺、二乙胺、三乙胺、三乙醇胺、异丙胺)对目标离子没有影响。待测的4种低级脂肪胺和5种常见阳离子在各自相应的浓度范围内呈现良好的线性关系,线性相关系数(r)均不小于0.997,检出限(LOD)为0.02~1.90μg/L,定量限(LOQ)为0.07~6.32μg/L, 6个平行样品测定的相对标准偏差(RSD)小于2%,样品加标回收率为93.2%~104%。采用建立的方法对189个大气颗粒物PM_(2.5)样品进行检测,9种离子均有检出,其中Na^(+)、NH_(4)^(+)、Ca^(2+)等离子含量较多,4种低级脂肪胺含量少,但部分样品中乙胺含量偏高。结果表明,本研究建立的离子色谱方法前处理简单,灵敏度高,准确性好,可满足大气颗粒物PM_(2.5)中低级脂肪胺和常规阳离子同时定量检测的需求,能够快速处理大量样品,准确评价空气中颗粒物的污染程度,追溯污染来源,保护人类健康。

乙二胺改性聚苯乙烯树脂对水体中铅(Ⅱ)、铬(Ⅵ)的吸附研究

采用乙二胺对氯甲基化聚苯乙烯树脂进行改性,利用改性后的树脂去除溶液中的铅(Ⅱ)和铬(Ⅵ)。通过改变pH、时间、浓度和吸附剂投加量,确定最佳吸附实验条件,得到改性后的树脂对铅(Ⅱ)和铬(Ⅵ)的最大吸附容量分别为119.60mg/g和128.28mg/g。动力学研究表明,该模型符合Langmuir模型。

基于离子色谱法快速测定血清中钠、钾、钙、镁4种阳离子水平

目的建立并优化一种基于微波消解结合离子色谱法同时测定血清中钠、钾、钙、镁4种阳离子的方法,并对其性能进行评价。方法采用微波消解技术对血清样品进行前处理,使用离子色谱定量检测4种阳离子。参照美国临床和实验室标准协会(CLSI)发布的EP6-A和EP15-A3文件对建立的方法进行线性、精密度、加标回收率和正确度等性能验证。结果钠、钾、钙、镁4种离子的检测不精密度以变异系数(CV)表示,分别为0.10%~0.36%、0.15%~0.48%、0.22%~0.87%、0.21%~0.73%。4种阳离子的加标回收率均在97.3%~103.0%之间。参加RELA2020和RELA2021计划的分析结果偏差分别为-0.57%~-0.14%、-0.84%~-0.16%、-1.82%~-0.37%、-0.60%~0.34%,比对均通过。4种阳离子的检出限/定量限分别为0.0175/0.0583mmol/L、0.0005/0.0017mmol/L、0.0099/0.0329mmol/L、0.0011/0.0035mmol/L,表明经前处理后,其他杂质对测定无明显干扰。结论成功建立并优化了一种基于微波消解结合离子色谱法同时测定血清中钠、钾、钙、镁4种阳离子的方法。该方法精密度和正确度良好,操作简单,分析时间短,成本低,可用于临床血清电解质检测的质量改进。

通过Mo掺杂诱导低Li/Ni混排程度增强Li_(1.2)Ni_(0.13)Fe_(0.13)Mn_(0.54)O_(2)可逆容量与循环稳定性

富锂层状氧化物因能量密度高和成本低,有望成为下一代锂离子电池正极的重要候选材料.然而,富锂正极材料中阴离子氧化还原反应使晶格氧不稳定,导致电压衰减和不可逆容量损失.尽管铁代无钴富锂材料可以实现较少的电压衰减,但存在严重的阳离子混排和较差的动力学.采用一种简单易行的高价离子掺杂策略,在Li_(1.2)Ni_(0.13)Fe_(0.13)Mn_(0.54)O_(2)(LNFMO)中掺入Mo元素,拓宽了锂层间距,为Li^(+)的传输提供了更宽的通道,改善了Li^(+)的扩散动力学,有效抑制了阳离子混排,进一步稳定了层状结构.得益于此,Mo掺杂后的富锂材料表现出显著增强的电化学性能,在0.2 C电流密度下表现出209.48 mAh/g的初始放电比容量.1C下的初始放电比容量从137.02 mAh/g提高到165.15 mAh/g;循环300次后,仍有117.49 mAh/g的放电比容量,电压衰减由2.09 mV/cycle降低为1.66 mV/cycle.本文对Mo掺杂后的正极材料进行了系统表征并揭示了循环稳定的机理,为高性能富锂正极材料的设计提供了重要参考.

万通离子色谱仪测定雨水中阴阳离子的方法验证分析

检出限是测试仪器性能及评价一个分析方法的重要指标,依据《环境监测分析方法标准制修订技术导则》(HJ 168-2010)中有关方法验证相关的规定,利用万通离子色谱仪验证《大气降水中氟、氯、亚硝酸盐、硝酸盐、硫酸盐的测定离子色谱法》(GB 13580.5-1992)及《酸沉降监测技术规范(附录B离子色谱法对阳离子的测定)》(HJ/T 165-2004)中Na^(+)、NH_(4)^(+)、K^(+)、Mg^(2+)、Ga^(2+)五种阳离子和F^(-)、Cl^(-)、NO_(3)^(-)、SO_(4)^(2-)四种阴离子的研究方法,验证过程涉及线性关系、检出限、精密度、准确度及加标回收率5个项目,并对验证结果进行分析。

离子色谱法中降低可溶性阳离子空白值的对策

离子色谱法具有选择性好、灵敏度高、方便快捷的特点,常用于环境监测中阴阳离子的测定。自然界的化合物多为阴阳离子相互组合而成,因此阴阳离子伴随着颗粒物及水分会残留在实验室环境中,使用离子色谱法测定阴阳离子时常出现空白值偏高的现象,特别是可溶性阳离子。文章以美国戴安公司(DIONEX)ICS-900型离子色谱仪测定水中可溶性阳离子Na^(+)、NH_(4)^(+)、K^(+)、Mg^(2+)和Ca^(2+)为例,提出降低可溶性阳离子空白值的对策,供检测实验室参考。

氯化苯副产盐酸的精制工艺方法研究

利用树脂吸附和脱吸附原理,对氯化苯生产过程中产生的盐酸进行脱色和去除有机物,从吸附和脱附工艺流程、树脂配比、盐酸吸附定量等方面展开分析,设计相应模拟实验进行过程探索,形成了一套比较完善的氯化苯副产盐酸精制的工艺流程。