Acid precipitation coupled electrodialysis to improve separation of chloride and organics in pulping crystallization mother liquor

Inefficient separation of inorganic salts and organic matters in crystallization mother liquor is still a problem to industrial wastewater treatment since the high salinity significantly impedes organic pollutant degradation by oxidation or incineration. In the study, acidification combined electrodialysis (ED) was attempted to effectively separate Cl^- ions from organics in concentrate pulping wastewater. Membrane's rejection rate to total organic carbon (TOC) was 85% at wastewater intrinsic pH=9.8 and enhanced to 93% by acidifying it to pH=2 in ED process. Negative-charged alkaline organic compounds (mainly lignin) could be liberated from their sodium salt forms and coagulated in acidification pretreatment. Neutralization of the organic substances also made their electro-migration less effective under electric driving force and in particular improved separation efficiency of chloride and organics. After acid-ED coupled treatment (pH=2 and J=40 mA·cm^-2)[TOC] remarkably reduced from 1.315 g·L^-1 to 0.048 g·L^-1 and[Cl^-] accumulated to 130 g·L^-1 in concentrate solution. Recovery rate of NaCl was 89% and the power consumption was 0.38 kW·h·kg^-1 NaCl. Irreversible fouling was not caused as electric resistance of membrane pile maintained stably. In conclusion, acidic-ED is a practical option to treat salinity organic wastewater when current techniques including thermal evaporation and pressure-driven membrane separation present limitations.     

Preparation of mineral source water from deep sea water: Reduction of sulfate ion using selemion ASV membrane

Adopting a laboratory‐scaled electrodialysis (ED) process, we investigate the performance of a monovalent anion exchange permselective membrane in the reduction of the concentration of sulfate ions during the production of mineral source water from deep sea water (DSW). The dependence of the separation efficiency of anions on the operating time and the applied DC voltage is investigated based on a brine having salinity of about 15% prepared from DSW. The experimental results reveal that if the applied DC voltage is high, the change in the liquid volume during ED is dominated by the ions transported and the effect of electroosmosis. In addition, the amount of chloride ions transported correlates roughly linearly with the operating time, and the transport of sulfate ions is found to be blocked by chloride ions, presumably because of that the pore size of the permselective layer is close to the size of sulfate ions. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Preparation of polyelectrolyte complex membranes based on sodium cellulose sulfate and poly(dimethyldiallylammonium chloride) and its permeability properties

In this study, polyelectrolyte complex (PELC) membranes prepared by the simultaneous interfacial reaction between aqueous solutions of sodium cellulose sulfate (NaCS) as polyanion and poly(dimethyldiallylammonium chloride) (PDMDAAC) as polycation were proposed. The preparation conditions were optimized. The influence of two important factors, molecular weight (MW) of PDMDAAC and reaction time on the membrane formation procedure and permeability was investigated. Membranes with the preparation conditions as NaCS 3.5% (w/v), PDMDAAC (MW = 200–350 kDa) 7.0% (w/v), the reaction time 30 min, hold a favorable performance, and steady state in water flux experiment. To testify the feasibility of the membrane used in salt separation, membrane performances and selectivity of the inorganic salts as well as their relations to the preparation conditions, the operation parameters, the species of inorganic salts, etc., were investigated in the pressure‐driven experiments. The results showed that this single‐layer PELC membrane afforded higher rejections of divalent ions (SO) to that of monovalent ions (Cl⁻), which indicated the potential application of this membrane system in the salt rejection process. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

含吡啶基吸附材料的研究进展

介绍了含吡啶基吸附材料对金属离子、无机阴离子及有机污染物的吸附分离研究进展。吡啶环的氮原子具有较强的配位功能,能与多种金属离子形成络合物。这类吸附材料对金属离子显示出高的吸附容量和吸附选择性,其吸附金属离子后形成金属主体高分子,然后再利用金属离子与具有配位性能的无机阴离子、有机污染物通过路易斯酸-碱在水溶液中进行配体交换,从而达到吸附分离的目的。作为高分子交换配体(PLE),这类新型吸附材料将是今后发展的重点。     

Effects of applied potentials on permselectivity of ions through polypyrrole/porous-polypropylene composite membrane

A composite membrane was prepared by the combination of polypyrrole with a porous-polypropylene film, and its permselectivity was investigated. The permeability and selectivity of various sodium salts through the membrane were changed with an applied potential. The permeation of anions at the positive potentials was due to the migration through the positive sites of the polypyrrole layer, as well as the diffusion from the difference of concentration and potential. The contribution of the migration effect to the anion permeation was very large. The main factors dominating the permeation character of different anion species were the size and valence of the anions. The composite membrane worked effectively as a functional separation membrane to control the ionic permeability by potential application. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 647–653, 1998     

Separation of strong acids by electrodialysis with membranes selective to monovalent ions. An approach to modelling the process

In this work some mixtures of sulphuric and nitric acids have been separated and concentrated by selective electro-dialysis (SED) using heterogeneous membranes. Selective membranes can now be used for the separation of acids since anion exchange membranes with reduced transport number to multivalent ions are commercially available. The electric performance of the system has been analyzed and a correlation between current density, hydrodynamic parameters and concentration was established. The modelling of the SED experiments can be achieved with a good fitting for various membrane configurations of industrial interest. Experimental results show that at operation times lower than 40 minutes, the selective anion exchange membranes efficiently exclude the sulphate anions. The nitrate anions fall to zero concentration at 60 minutes of operation and then the sulphate anions begin to cross through the membrane.     

Electrically-switchable, permselective membranes prepared from nano-structured N-doped DLC

In this study, we report a fabrication of a conductive DLC through-hole membrane with highly ordered nanopore arrays by template synthesis using an anodic porous alumina and effects of intrinsic properties of DLC (a wide working potential range and low ion adsorption) on ion permselectivity when the membrane is applied to separate ions.We have successfully fabricated the conductive DLC membranes that have pore diameters ranging from 14 nm to 105 nm and show electrically tunable charge selectivity. With these membranes, fluxes of cations across the membrane can be reduced by applying positive potentials and can be increased by applying negative potentials. In the case of anions, a selectivity pattern opposite to cations was observed. Inside pore surfaces of the conductive DLC membrane could have excess charge by potentiostatically charging. This excess charge regulates ion transport across the membranes. The membranes reject ions of the same sign as excess charge and transport ions of the opposite sign. The permselectivity of the membrane can be reversibly switched from cation-permselective to anion-permselective by changing potentials applied to the membrane (because the signs of excess charge can be controllable by applied potentials).DLC membrane exhibited ion permselectivity even in an electrolyte solution including ions strongly adsorb to electrode surfaces such as Na₂SO₄ and HCl solutions. By using DLC membrane, ion permselectivity can be controlled in real samples commonly including adsorbing ions (that cannot be controlled with Au nanotubule membrane due to a specific adsorption to electrode surfaces).We could also demonstrate the permselectivity of target ions by controlling the potential applied to the membrane even in the mixed solution, which contains both cations and anions and is close to actual samples including ions aimed to be separated.     

Desalination of fish meat extract by electrodialysis and characterization of membrane fouling

Fish meat extract (FME) desalination via electrodialysis (ED) was performed and the changes of important parameters such as membrane stack potential, brix, pH, and electrical conductivity were examined for a quantitative evaluation. The change of electrical conductivity in diluted or concentrated solutions showed that the mineral ions contained in the FME could be effectively removed. The characterization of membrane fouling indicated that the organic/ inorganic components deposited, respectively, on the surfaces of anion/cation exchange membrane and resulted in the increase of membrane electrical resistance. Ion chromatograph (IC) analysis showed that the main mineral ions, such as Na⁺ and Cl⁺ ions contained in the FME, were removed about 82.3% at an average current efficiency of around 77.9% via ED. By considering the removal rate of mineral ions and current efficiency, the feasibility of FME desalination via ED was proved.     

The effect of lipophilic salts on surface charge in polymeric ion-selective electrodes

The effect of quaternary ammonium salts (QAS) structure and concentration in polymeric membranes on their performance in potentiometric Ion Selective Electrodes (ISEs) without ionophore is studied. The membranes with both symmetric: tetraoctylammonium bromide (TOAB), tetradodecylammonium bromide (TDDAB), tetraoctadecylammonium bromide (TODAB), and asymmetric: tridodecylmethylammonium chloride (TDMAC) and dimethyldioctadecylammonium chloride (DODMAC) quaternary ammonium salts were tested in very broad concentration range (1–10⁻⁴%). The observed ISEs responses could not be explained within the framework of the Phase Boundary Model, but could be easily understood semi-qualitatively with help of the simple Gouy–Chapman electrical double layer theory. The latter provides a straightforward link between the electrical potential on the membrane's surface and the corresponding surface charge density. Assuming that the electrical potential difference measured in ISEs originates from adsorption of surface active ions (tetraalkylammonium cations, QA⁺) and co-adsorption of anions present in the sample, the surface charge density was calculated using the Grahame equation. We postulate that the positive charge provided by adsorption of QA⁺ at the membrane's surface provides a constant positive charge density, dependent on the QAS surface activity and concentration. This positive charge is partially neutralised by anions originating either from QAS in the membrane, or from inorganic electrolyte in the contacting aqueous phase (sample). This process could explain the dependence of electrical potential difference measured in ISEs on the concentration and type of both QAS and inorganic anions present in the sample (the latter known as “Hofmeister pattern” in potentiometry). Also the pH sensitivity of ISEs with low-QAS content membranes can be explained in the framework of the proposed model by a competition for adsorption sites on the membrane surface between QAS and high surface activity of hydroxide ions.     

The possibility of the desalination of actual 1,3-propanediol fermentation broth by electrodialysis

Electrodialysis (ED) was employed to remove the organic and inorganic salts from actual 1,3-propanediol (PDO) fermentation broth. These salts cause many problems during the purification of PDO if not removed. Suitable operation parameters such as applied potential and the flow rate of streams were selected to ensure a stable and durative desalination process for PDO fermentation broth. Under these conditions, the membrane fouling can be alleviated effectively by changing pole and cleaning membranes so that further industrial production is possible. The experiment results show that about 90% of organic acid salts in PDO broth are removed by the ED process. In addition, a simulated diffusion PDO experiment proved that the diffusion of PDO results in its loss from fermentation broth and the loss ratio is less than 6% under the chosen operating conditions.     

固体支撑液膜的传质速率和应用研究

固体支撑液膜在湿法冶金和现代环境保护中应用十分广泛，是工业废水处理的一种有效的新技术，尤其对含有金属盐类的废水的处理有其独特的优势。在电镀废水和湿法磷酸除镉等领域中曾试用了支撑液膜系统，该系统具有处理能力大，溶剂损失不，除去有关离子的选择性好等特点。为了推广其应用，进一步进行了用三正十二烷基氯化铵固体支撑液膜处理含有锌和镉等的氯化物工业废水的研究，确定了其过程的传质速率，并讨论了分离废水中锌和镉等金属离子的可能性及基本条件。结果证明本方法适合于回收处理含有金属离子的废水，且分离效果好。     

Material Advancements in Fabrication of Mixed‐Matrix Membranes

The mixed‐matrix membrane (MMM) is a new membrane material for gas separation and plays a vital role for the advancement of current membrane‐based separation technology. Blending between inorganic fillers like carbon molecular sieves, zeolite, metal oxides, silica and silica nanoparticles, carbon nanotubes, zeolitic imidazolate framework, metal organic framework, and glassy and rubbery polymers etc. is possible. Due to mechanical, thermal, and chemical stability, these membranes achieve high permeability and selectivity as compared to pure polymeric materials. Despite of these advantages, the MMM performances are still below industrial expectations because of membrane defects and related processing problems as well as the nonuniform dispersion of fillers in MMMs. Material selection for organic and inorganic phases, preparation techniques, material advancements, and performance of MMMs are discussed. Issues and challenges faced during MMM synthesis as well as problem solutions are highlighted.     

模拟的发酵液组分对聚二甲基硅氧烷/陶瓷复合膜渗透汽化性能的影响

对所制备的聚二甲基硅氧烷（PDMS）/陶瓷复合膜进行了渗透汽化性能表征。通过在乙醇-水混合体系中添加不同的模拟发酵液组分;如葡萄糖（多羟基醛）、甘油（多元醇）、丁二酸（有机酸）、KCl（无机盐）;考察了各组分对复合膜渗透汽化性能的影响。研究发现：在333 K下;在乙醇浓度为65 g·L-1的混合物中添加不同浓度的第三组分;有机添加物对膜的渗透汽化性能没有明显影响;而无机盐的加入使膜的分离因子稍有提高。所制备的PDMS/陶瓷复合膜;在上述渗透汽化过程中表现出良好的稳定性和对乙醇的优先选择性;渗透通量和分离因子（醇/水）分别在4.5～4.7 kg·m^-2·h^-1、8.3～10.3之间。     

工业废水电渗析过程中膜污染研究进展

综述了工业废水电渗析体系膜污染类型、性质、影响因素等的研究进展. 无机污染主要是Ca2+, Mg2+或其他高价离子在离子膜表面或内部形成的结垢现象,原理是极化或溶液过饱和形成沉淀. 有机污染是由蛋白、腐植酸、表面活性剂及大分子有机物在离子膜表面沉积或渗透到膜内部而形成,原因主要是带负电荷的有机物与阴膜荷正电基团的静电作用及带苯环有机物与基膜的亲和作用,其次是有机物分子大小与膜的网络结构的作用. 膜污染形成及其性质与施加电流、共存组分、温度、pH值和运行时间等密切相关,可造成离子膜导电性、离子交换容量、水含量和极限电流密度等减小,且有机污染对电渗析性能的影响比无机污染更严重. 由有机物凝胶层形成的膜污染可用电渗析膜污染指数定量描述.     

Recovery of alpha-ketoglutaric acid from model fermentation broth using electrodialysis with bipolar membrane

ABSTRACT

A bipolar (BP) membrane electrodialysis (EDBM) was used to recover the alpha-ketoglutaric acid (AKG) from the model broth. A two-chamber EDBM membrane stack consisting of an anion exchange membrane and a BP membrane was used. The effect of the initial composition, applied current density, and pH of diluate on the efficiency of EDBM processes was investigated. The obtained results showed that the used membrane stack configuration allows complete separation of AKG from glucose and ethanol and simultaneous conversion of AKG salts to the acidic form. The scale-up of the EDBM process for model fermentation broth was also carried out.     

无机膜与有机膜分离技术应用特性比较研究

通过对无机膜和有机膜分离技术的概念类别、制备方法、应用领域、膜性能参数和膜清洗方法等多方面特性的比较分析,无杌膜在装填密度、制作成本及工业化应用等方面有待优化完善,但在耐污能力、运行稳定性和膜再生性能等方面却具有一定优势.     

膜法电容去离子技术用于水溶液中单/多价阴离子的分离

将电容去离子技术（CDI）与单价阴离子选择性交换膜结合构建新型膜法电容去离子膜堆（PSMCDI）,并探索其在单/多价阴离子分离中的应用。采用自制的测试装置,以Cl^-/SO₄^2-水溶液为模拟体系,并选择现有的两种商业化单价阴离子选择性交换膜（ASV和ACS）作为膜元件,系统地研究了各参数（PSMCDI种类、阴离子组成和浓度、pH、操作时间、电压和流速）对单价离子选择性的影响。结果表明,总阴离子去除量随着阴离子浓度的增加而增加,但是对于单价离子（Cl^-）选择性降低。随着操作时间的增加,单价离子（Cl^-）选择性也降低。对于ASV膜,在1.2 V的直流电压、10 min吸附时间和30 ml·min^-1进料流速的条件下得到1.6的单价阴离子去除选择性。同时,在相同条件下,ACS膜的单价阴离子去除选择性为1.4。     

Industrial wastewater desalination using electrodialysis: evaluation and plant design

Industrial processes usually generate streams enriched with high organic and inorganic components. Due to the complexity of these streams sometimes it is not quite straightforward to predict the performance of desalination technologies. Some technologies are available for the selective removal of salts from aqueous stream, but in general these technologies are applied in high value applications where salts are either the product or limit further purification of the final product is required. These technologies are, however, not widely used in low value applications like wastewater treatment. The aim of this article is to review, improve and perform the design of electrodialysis processes for relevant industrial wastewater applications. It is focused on the determination of the critical design parameters like membrane resistance, current efficiency and limiting current density through lab scale experiments and its further use for industrial scale first approximation design. In this article, the basic equations for design are reviewed and a practical approach to obtain the number of stacks required for a certain separation is introduced. An industrial wastewater stream has been used for lab batch experiment and its following continuous plant design. The results show that it is possible to separate monovalent ions in a high rate (more than 70 %) and divalent ions were less separated (less than 50 %). The energy required for the particular case was evaluated in a range from 6 to 11 kWh/m³ of feed stream depending on the water reclamation rate.     

分离膜材料和膜制备技术的研究进展

膜分离技术在工业中已得到广泛的应用,它是最有发展前途的分离技术之一。综合介绍了无机膜材料、有机膜材料、液膜的研究进展,并介绍了各种膜制备技术的研究状况,提出今后在膜材料和膜制备技术方面需要优先研究的课题。     

面向油水分离的无机膜制备及应用进展

膜技术是处理含油污水及含水油液的有效分离方法。无机膜材料由于可调变的表面性质和良好的稳定性,即使在苛刻的条件下,在分离油水方面表现出优异的分离性能。本文首先阐述了设计与制备油水分离膜的理论基础,包括分离过程中压力驱动力和膜表面特性对膜通量和选择性的影响;然后综述了当前国内外用于油水分离的无机膜的制备及其应用进展,重点介绍分子筛膜、金属氧化物/金属氢氧化物膜和氧化石墨烯膜等的研究,分析了在不同油水混合物中研究者们调控无机膜表面性能的策略,提出膜表面润湿性和膜结构是提高膜分离效率和抗污染性的关键;最后指出抵制含大量表面活性剂、碱液及有机聚合物种的乳化油对膜造成污染,是无机膜亟需解决的问题,并展望了无机膜在分离油水方面的发展方向。