Study on hypochlorite degradation of aromatic polyamide reverse osmosis membrane

A serious limitation of most commercial polyamide reverse osmosis (RO) membranes is their sensitivity to chlorine attack. By studying the hypochlorite degradation of aromatic polyamide RO membrane, this work was to get some understandings in the prevention of membrane depreciation and develop membranes with improved chlorine resistance. Membrane performances, including water flux and salt rejection, were evaluated before and after hypochlorite exposure under different pH and concentration conditions. The results showed that chlorination destroyed hydrogen bonds in polyamide chains, causing a notable decline of membrane flux especially in acid environment; however, membrane performance was slightly improved after the treatment of alkaline hypochlorite solution for a certain time, which was probably due to the effect of amine groups in barrier layer. Based on the attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) characterizations and performance measurements, the results indicated that N-chlorination reaction of aromatic polyamide was also reversible, in other words, the N-chlorinated intermediate could be regenerated to initial amide with the alkaline treatment before ring-chlorination reaction. This conclusion provided several relative suggestions for membrane cleaning procedures. Finally, a method adopting surface coating was proposed to develop membranes with good chlorine resistance, and the preliminary results showed its potential for applications.     

Detector comparison for sulfur and chlorine detection with laser induced breakdown spectroscopy in the near-infrared-region

Laser-induced breakdown spectroscopy has been employed for the investigation of the sulfur and chlorine content of building materials. Both, chloride and sulfate ions are major damaging species affecting the stability and lifetime of a structure. Chlorine and sulfur are mostly detected in the VUV and the NIR. In case of building materials the main elements like calcium or iron have many strong spectral lines over the whole spectral range, so that trace elements can only be detected in spectral windows unaffected from these lines. With regard to a preferably simply, robust against dust and vibrations and portable setup only the NIR spectral features are used for civil engineering applications.

Most detectors, mainly CCD cameras have rapidly decreasing quantum efficiency in the NIR. Also the quantum efficiency of the photocathode of CCD-Detectors with image intensifier is decreasing in the NIR. Different CCD-detectors were tested with respect to high quantum efficiency and high dynamic range, which is necessary for simultaneous detection of weak spectral lines from trace elements and intense spectral lines from main elements.

The measurements are made on reference samples consisting of cement, hydrated cement, cement mortar and concrete with well-defined amounts of the trace elements. Experimental conditions are chosen for an optimum intensity of the trace element spectral lines. The detector systems are compared by limit of detections and the signal to noise ratio.     

氯参与的化学气相淀积金刚石的热力学分析

用非平衡热力学耦合模型研究了金刚石在CHCl体系中的生长,计算所得CHCl体系的金刚石生长的相图与大量实验结果符合良好.通过热力学分析讨论了氯的添加对提高金刚石薄膜生长速率及其质量的影响以及降低淀积温度的作用.     

A new sensitive and selective fluorescence method for determination of chlorine dioxide in water using rhodamine S

A new simple, selective and sensitive method for the determination of trace chlorine dioxide in water has been developed, based on the oxidation by chlorine dioxide to reduction the fluorescence of rhodamine dyes in ammonia-ammonium chloride buffer solution. Four rhodamine dyes systems such as rhodamine S, rhodamine G, rhodamine B and butyl-rhodamine B were tested. The rhodamine S system is the best, with a linear range of 0.0060-0.450 μg mL⁻¹ and a detection limit of 0.0030 μg mL⁻¹ ClO₂. It was applied to the determination of chlorine dioxide in synthetic samples and real samples, with satisfactory results. This method has good selectivity, especially, other chlorine species such as chlorine, hypochlorite, chlorite and chlorate do not interfere the determination. The mechanism of fluorescence reduction was also considered.     

新型低共熔溶剂的制备及其在分散液-液微萃取水样中臧红T和胭脂红的应用EI北大核心CSCD

建立了一种基于低共熔溶剂的旋涡辅助分散液-液微萃取和高效液相色谱连用检测水样中臧红T和胭脂红染料的方法。制备了一类分别由苄基三乙基溴化铵、苄基三丁基溴化铵、苄基三乙基氯化铵或苄基三丁基氯化铵(氢键受体)和正辛酸(氢键供体)组成的新型疏水性低共熔溶剂。最佳萃取条件为:选取苄基三丁基氯化铵和正辛酸(摩尔比为1∶2)制备的低共熔溶剂为萃取剂,萃取剂用量为75μL,萃取时间为1 min,溶液pH=7,NaCl浓度为3 mg/mL。在最优化条件下,检测臧红T和胭脂红的线性范围为4.8~1000 ng/mL;相关系数(R^(2))分别为0.9981和0.9987;检出限分别为1.5和1.8 ng/mL;定量限均为4.8 ng/mL。将该方法应用于实际水样中臧红T和胭脂红的测定,加标回收率为88.5%~113.6%,相对标准偏差均低于8.8%。     

Covariate model-based fault tree analysis for risk assessment in chemical process industries: A case study of a chlorine manufacturing facility

Fault tree analysis (FTA) is a promising quantitative technique for risk analysis in chemical process industries (CPIs). In FTA, a certain sequence of basic events (causes) leads to one specific Top event (critical event of interest). However, the conventional fault tree analysis has the limitations of staticity and uncertainty. The staticity in conventional FTA arises due to its inability to accommodate time-dependent characteristics of the process system. Whereas uncertainty primarily lies in the failure probability data of basic events. This paper proposes an innovative methodology that uses a time-dependent covariate model to update the failure probability values of major contributing basic events in FTA. A novel subclass of the family of phase-type distributions is used to model the covariates corresponding to the basic events. The newly developed methodology is applied for a case study in a chlorine manufacturing facility to estimate the chlorine release probability. The blockage in the pipeline was identified as the significant reason for chlorine release from expert opinion and sensitivity analysis. The results of the proposed model of FTA are compared with that of conventional FTA.     

电容去离子除氯电极的构建及其脱盐性能研究进展

电容去离子技术(Capacitive deionization,CDI)是一种新兴的脱盐技术,通过在电极两端施加较低的外加电场除去水中的带电离子和分子,由于其较低的能耗和可持续性而备受关注。基于储能电池领域近年来的迅猛发展,CDI电极材料实现了从以双电层作用机理为代表的碳材料到法拉第电极材料的跨越,使得脱盐性能有了大幅度提升。Na⁺的去除与Cl^-的去除同等重要,然而,CDI中针对氯离子高效去除的电极材料研究关注较少。本文从CDI装置的构型演变发展出发,系统地归纳与梳理了CDI中关于脱氯电极材料的分类,对比了不同类型脱氯电极材料的特点,并总结了Cl^-去除的机理,分别为基于双电层的电吸附、转化反应、离子插层和氧化还原反应。本文是首篇关于CDI阳极材料的进展综述和展望,为CDI除氯电极的后续研究提供理论基础和研究思路。     

海水电解面临的挑战与机遇：含氯电化学中先进材料研究进展

氢气是一种清洁高效的能源载体,通过海水电解规模化制备氢气能够为应对全球能源挑战提供新的机遇。然而,缺乏高活性、高选择性和高稳定性的理想电极材料是在腐蚀性海水中连续电解过程的一个巨大挑战。为了缓解这一困境,需要从基础理论和实际应用两方面对材料进行深入研究。近年来,人们围绕电极材料的催化活性、选择性和耐腐蚀性进行了大量的探索。本文重点总结了高选择性和强耐腐蚀性材料的设计合成与作用机制。其中详细介绍了多种电极材料(如多金属氧化物、Ni/Fe/Co基复合材料、氧化锰包覆异质结构等)对氧气生成选择性的研究进展;系统论述了各种材料的抗腐蚀工程研究成果,主要讨论了本征抗腐蚀材料、外防护涂层和原位产生抗腐蚀物种三种情况。此外,提出了海水电解过程中存在的挑战和潜在的机遇。先进纳米材料的设计有望为解决海水电解中的氯化学问题提供新思路。     

Circumventing the OCl versus OOH scaling relation in the chlorine evolution reaction: Beyond dimensionally stable anodes

The development of selective electrocatalysts for the chlorine evolution reaction (CER) is majorly restrained by a scaling relation between the OCl and OOH adsorbates, rendering that active CER catalysts are also reasonably active in the competing oxygen evolution reaction (OER). While theory predicts that the OCl versus OOH scaling relation can be circumvented as soon as the elementary reaction steps in the CER comprise the Cl rather than the OCl adsorbate, it was demonstrated recently that PtN₄ sites embedded in a carbon nanotube follow this theoretical prediction. Advanced experimental analyses illustrate that the PtN₄ sites also reveal a different reaction kinetics compared to the industrial benchmark of dimensionally stable anodes (DSA). A reverse Volmer–Heyrovsky mechanism was identified, in which the rate-determining Volmer step for small overpotentials is followed by the kinetically limiting Heyrovsky step for larger overpotentials. Since the PtN₄ sites excel DSA in terms of activity and chlorine selectivity, we suggest the Cl intermediate as well as the reverse Volmer–Heyrovsky mechanism as the design criteria for the development of next-generation electrode materials beyond DSA.     

离子色谱法测定水果及其树叶的含氯量

本文提出用离子色谱法测定水果及其树叶中氯含量的方法,在IC-PAK阴离子柱上,用4 mmol/L邻苯二甲酸(pH4.5)作流动相进行洗脱,电导检测器检测。方法简便、快速,灵敏、准确。氯的最小检出量为0.14μg,相对标准偏差为2.4%,回收率为99.4%。