Removal of hardness in fermentation broth by electrodialysis

Lysine fermentation broth was desalinated by electrodialysis to reduce hardness concentrations as a pretreatment procedure for the purification and recovery of amino acids. Electrodialysis performance was investigated in terms of the rate of reduction in conductivity in dilute solutions and electrodialysis cell resistance for different ion exchange membranes at a constant current density. Among the membranes investigated in this study, membranes with high water content showed the better performance for hardness removal. Fouling experiments revealed that organics gave rise to fouling effects on the anion exchange membrane during demineralization of the lysine fermentation broth. The pulsed electric field with the half‐wave power enhanced the electrodialysis performances by mitigating membrane fouling in desalination of the lysine fermentation broth. This study successfully demonstrated the potential use of pulse power as an effective cleaning‐in‐place (CIP) method during electrodialysis of fermentation broth. © 2002 Society of Chemical Industry     

饮用水总硬度去除需求分析及控制目标探讨

饮用水总硬度及其所引起的"水垢"问题是近期人们关注的热点水质问题之一.论文基于我国水源水中总硬度的分布情况及离子组成比例,总结了Ca2+、Mg2+、典型阴离子、总溶解固体(TDS)对人体健康的影响.结合国内外针对总硬度限值的控制要求,综合饮用水主要用途、管道输送以及优质(舒适)水的供给需求等方面的内容,探讨了我国饮用水...     

Nanofiltration Membrane Process for the Removal of Arsenic from Drinking Water

The removal of arsenic from drinking water by nanofiltration membranes was investigated. Experiments were conducted with tap water to which arsenate and arsenite were added. Two types of nanofiltration membranes, i.e., NF‐90 and NF‐200, have been tested. The effect of various operating conditions, e.g., applied pressure, feed concentration, pH and temperature, were also investigated. The pH and arsenic concentration in the feed and the operating temperature are found to be decisive factors in determining the arsenic concentration remaining in the permeate. The level of removal of As(V) was higher than 98 % for both membranes, but that of As(III) was much lower. It can be concluded that by controlling the operating parameters, source water containing As(V) may be recovered as drinking water to EPA maximum contaminant level quality standards, but that water containing As(III) must undergo a pre‐oxidation treatment before passing through the nanofiltration membrane in order to maintain drinking water quality.     

Purification of glycerol/water solutions from biodiesel synthesis by ion exchange: sodium and chloride removal. Part II

BACKGROUND: Equilibrium studies were carried out with the aim of finding the basic design parameters for ion exchange plants using a glycerol phase obtained from biodiesel production. The uptake of sodium and potassium ions on a strongly acidic ion exchanger, Amberlite IR‐120, in the proton form from glycerol/water mixtures has been studied. The effect on the selectivity towards sodium of the percentage of water in glycerine/water mixtures on the macroporous resin Amberlite 252 has been analyzed. Finally, chloride removal by a strongly basic anionic‐exchange resin Amberlite IRA‐420 at three different temperatures has been studied. RESULTS: The strongly acidic ion exchanger Amberlite IR‐120 exhibits higher selectivity for potassium versus sodium ions. The ideal mass action law model was able to fit the experimental equilibrium data. The equilibrium data obtained at different percentages of water in the glycerine/water mixture indicate that as the water content increased the resin selectivity for sodium uptake is reduced. The selectivity of the anion exchange resin Amberlite IRA‐420 for chloride ions decreases with temperature. The ideal mass action law was accurate enough to fit the equilibrium data of the three systems and allowed the equilibrium thermodynamic properties to be obtained. CONCLUSIONS: These results confirm that macroporous resin Amberlite 252 could be a good choice to remove sodium ions from glycerol/water solutions with a high salt concentration and also that a strongly basic anionic‐exchange resin could be used for chloride removal. Copyright © 2009 Society of Chemical Industry     

Electrodialysis plant at Hatsushima

A commercial multistage batch system electrodialysis plant for desalination of brackish groundwater was installed at Hatsushima, Atami City in April 1973. The plant has three stages each of which is operated at a constant voltage. Each stage has a dialyzer which is provided with 150 pairs of ion exchange membranes having an effective area of 1 m² each. This plant is used for drinking water supply and has a capacity of 200 m³/day when the raw water has a saline concentration of 6,000 ppm TDS. The operation was very stable and easy, and it was possible to produce water of constant quality at all times regardless of fluctuations in the raw water concentration. The dialyzer was chemically cleaned for removal of deposits on membranes thereby reducing the maintenance cost by 62% without adversely influencing ion exchange membranes.     

Adsorption and desorption characteristics of zinc on ash particles derived from oil palm waste

Solid waste such as palm fibre and shell produced by the palm oil industry is used by palm oil mills as boiler fuel to produce steam for electricity generation. The ash produced after combustion creates a disposal problem for the palm oil industry. This study explored the potential of oil palm ash as an adsorbent material for removal and recovery of zinc ions from aqueous solutions. The equilibrium uptake of zinc was found to increase with solution pH in the range 3–6, yielding a maximum adsorption capacity of 0.163 mmol g^?1 of ash at a pH of 6. The affinity constant of oil palm ash was found to greatly exceed that of a commercial ion exchange resin, suggesting that oil palm ash may find potential application in treating dilute zinc‐containing waste streams. Four isotherm models were used to fit the constant pH equilibrium isotherms obtained at four different pH values. The entire data set was successfully simulated using two of the isotherm models: a Langmuir model with pH‐dependent parameters and an extended Langmuir–Freundlich model with pH‐independent parameters. The rates of adsorption and desorption for zinc were measured using a stirred‐batch contactor. The contact time required to reach apparent adsorption equilibrium was found to decrease with increasing adsorbent dosage. Both the rate and the extent of zinc desorption were affected by the pH of the desorbing solution. The adsorption and desorption rates were consistent with simple first‐order rate models. © 2002 Society of Chemical Industry     

地下水硝酸盐去除技术进展

硝酸盐是地下水中最常见的污染因子,给饮水安全带来了较大的威胁,因此世界上很多国家和地区都非常重视地下水硝酸盐脱除技术的研究与开发,取得了很多有价值的研究成果和应用经验。离子交换、反渗透和生物反硝化是研究和应用最广的地下水硝酸盐脱除技术。离子交换法具有投资小、运行管理简便的优点,比较适合中小规模供水需求,但其再生废液的处理或处置非常困难。反渗透法具有脱硝效果好、易于自动控制等优点,可满足各种规模供水需求,但反渗透会产生大量浓缩水,必须妥善处理或处置。在我国华北地区,反渗透浓缩水可用于浇灌农作物,其中较高浓度的硝酸盐是良好的氮肥。至于生物反硝化脱氮技术,虽然具有运行费用低的优点,但现阶段还不能很好地解决残留反硝化碳源和微生物代谢产物的二次污染问题,用此法生产的饮用水安全性还有待进一步评估。     

饮用水除氟技术研究进展

文章论述了饮用水的除氟方法,介绍了目前大规模使用的沉淀分离法,如混凝沉淀法、电凝聚法、电渗析法等,以及吸附分离法,如骨炭法、活性氧化铝法、沸石法、活性炭法、反渗透法、离子交换法等。文章阐述了各种除氟技术存在的优缺点,并对各种除氟技术的机理进行了详细的解析。此外,针对目前饮用水除氟技术,提出了几点建议。     

Photocatalytic nitrate reduction over metal modified TiO2

Photocatalytic removal of nitrates from water was examined using Cu, Fe and Ag containing titania based materials, and using a range of hole scavengers. In the presence of formic acid, complete nitrate removal was possible with all catalysts. All catalysts presented high activities and overall selectivites, with Ag containing catalysts in particular reaching residual levels of nitrite and ammonium below the EU guideline levels for drinking water. Some titania samples exhibited an induction period prior to the onset of nitrate removal and the size of the titania particles was found to influence the photocatalytic performance. An extended induction period for iron containing catalysts, which was absent during second and subsequent reaction tests, was attributed to a leaching of part of the Fe from the catalysts to reveal active sites of the titania support.     

Ion Exchange Properties of Pyridinium Molybdoarsenate

The ion exchange behaviour of pyridinium molybdoarsenate has been investigated with some uni- and bi-valent cations. The slopes of the isotherms are widely different for various cations suggesting that separation of these ions is feasible. Barrer's equation has been applied to the exchange reaction and various thermodynamic parameters, viz. interaction energy between the ions on surface, thermodynamic equilibrium constant and free energy change for the exchange process, have been evaluated. This exchanger is found to be highly specific for Tl⁺ ions and can be used for its removal from mixtures of various uni- and bi-valent cations.     

Removal of Nitrate from Ground Water by a Hybrid Process Combining Electrodialysis and Ion Exchange Processes

Abstract

In regions where agricultural activities are highly intensive, nitrate concentrations in ground water are usually above the permissible level for nitrate in drinking water. There are several physicochemical and biological treatment processes typically used to remove nitrate contamination from ground water. In this study, an electrodialysis‐ion exchange hybrid process was used for the removal of nitrate from ground water obtained from an agricultural area in the Western Anatolia religion in Turkey. Nitrate was effectively removed from the ground water. The effect of other ionic species such as chloride and sulfates on nitrate removal by electrodialysis has also been studied using deionized water that was dosed with selected anionic and cationic species.     

离子交换去除饮用水中有机物的研究进展

近年来国外去除饮用水中有机物的方法有混凝澄清、活性炭吸附、膜分离以及离子交换法等,其中离子交换法可有效地去除饮用水常规处理产生的消毒副产物--低分子有机物.进而从离子交换树脂的本身特征、水质特征和有机化合物特征3方面详细讨论了离子交换去除饮用水中有机物的影响因素.     

Effect of Process Parameters on Separation Performance of Nitrate by Electrodialysis

Abstract

The electrodialytic separation of nitrate from water was investigated as a function of feed characteristics such as applied voltage, feed flow rate, and nitrate concentration in the solution. The separation performance was evaluated in terms of percent removal of nitrate, process time, and energy consumptions. TS‐1‐10 electrodialysis equipment (Tokuyama) was used in experimental studies. During the unsteady state run of the ED system, both inlet and outlet concentrations of nitrate and conductivities of streams were measured at certain time intervals until the current drops to 0.01 A. It was obtained that the percent removal of nitrate from the solution increased when the concentration of nitrate in the feed solution increased. The operation time became shorter when a high potential was applied.     

Studies on defluoridation of water by coal‐based sorbents

Drinking water containing fluoride above a level of 1 mg dm^?3 is considered to be unsafe for human consumption. Higher intake of fluoride can cause potential health hazards. The conventional processes of fluoride removal from water are ion exchange, reverse osmosis and electro‐dialysis. However, the utility of these processes has been limited due to their expensive operation and subsequent disposal problem of the waste brine generated. Defluoridation of water samples by coal‐based sorbents was studied at different adsorbent dosages. First‐order adsorption rate constants using the Lagergren equation, the Freundlich adsorption isotherm, the Langmuir adsorption isotherm, film diffusion and pore diffusion coefficients have been evaluated for each system. The effect of pH on fluoride removal and the mechanism has also been discussed. Copyright © 2001 Society of Chemical Industry     

Drying of a system of multiple solvents: Modeling by the reaction engineering approach

Drying is a very important industrial operation in society. In drying, solute may dissolve in an aqueous solvent, a nonaqueous solvent or a mixture of solvents. Many mathematical models have been published previously to model drying of solute in water. The reaction engineering approach (REA) is known to be an easy‐to‐use approach. It can describe well many drying cases of water removal. Currently, no simple lumped model has been attempted to describe drying of porous materials containing a mixture of solvents. In this study, for the first time, REA is constructively implemented to model drying in a mixture of one aqueous and one nonaqueous solvent. The REA is applied here to model the drying of polyvinyl alcohol/methanol/water under constant and time‐varying environmental conditions. Similar to the relative activation energy of water, that of methanol is generated through one accurate drying run. For modeling the time‐varying drying, the relative activation energies are the same as those for modeling convective drying under constant ambient conditions but combined with the equilibrium activation energies at the corresponding humidity, methanol concentration, and temperature for each drying period. The REA is accurate to model drying of a solute in nonaqueous solvent as well as in a mixture of noninteracting solvents. In the future, spatially distributed REA for nonaqueous or mixtures of both aqueous and nonaqueous solvent will be explored for fundamental understanding and for practical application. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2144–2153, 2016     

Nanofiltration for drinking water treatment: a review

In recent decades, nanofiltration (NF) is considered as a promising separation technique to produce drinking water from different types of water source. In this paper, we comprehensively reviewed the progress of NF-based drinking water treatment, through summarizing the development of materials/fabrication and applications of NF membranes in various scenarios including surface water treatment, groundwater treatment, water reuse, brackish water treatment, and point of use applications. We not only summarized the removal of target major pollutants (e.g., hardness, pathogen, and natural organic matter), but also paid attention to the removal of micropollutants of major concern (e.g., disinfection byproducts, per- and polyfluoroalkyl substances, and arsenic). We highlighted that, for different applications, fit-for-purpose design is needed to improve the separation capability for target compounds of NF membranes in addition to their removal of salts. Outlook and perspectives on membrane fouling control, chlorine resistance, integrity, and selectivity are also discussed to provide potential insights for future development of high-efficiency NF membranes for stable and reliable drinking water treatment.     

An approach to formulating cold-water laundry products

Trilinear plots showing the performance of linear alkylbenzene (LAS), alcohol ether sulfate (ES) and alcohol sulfate (AS) mixtures are used to optimize surfactant active composition for maximum cold-water detergency. Superimposition of cost lines allows for estimating cost/performance. Results show that the composition of the optimally performing LAS/ES/AS mixture depends strongly on temperature, water hardness and cloth type. Under most conditions at low water hardness levels, optimum cost/performance is obtained by an all-LAS active composition. When water hardness exceeds the hardness removal capability of the builder, an LAS/ES blend is best. This paper was presented May 10, 1983, at the 74th Annual Meeting of the AOCS in Chicago, Illinois.     

Electrophoretic Deposition Forming of SiC-TZP Composites in a Nonaqueous Sol Media

Electrophoretic deposition (ED) was used to form uniform–structure green bodies with a thickness of about 3 mm of SiC whisker–tetragonal zirconia polycrystals (TZP) mixtures. A kinetic model for ED is presented. The model predicts the decrease of the forming rate as an exponential function of time. Diagrams of colloidal groups and electrochemical reactions of charged solid particles on the deposited electrode are proposed. The effects of applied electric field, viscosity, dielectric constant, amount of suspending agent, and zeta potential of the solid particles in Al(OC₃H₇)₃–C₃H₇OH–CH₃OH sol on ED processing are discussed.     

Synthesis of the cotton cellulose based Fe(III)-loaded adsorbent for arsenic(V) removal from drinking water

A novel macroporous bead adsorbent, Fe(III)-loaded ligand exchange cotton cellulose adsorbent [Fe(III)LECCA], is synthesized for selective adsorption of arsenate anions [As(V)] from drinking water in batch and column systems. As(V) adsorption on Fe(III)LECCA was independent of pH, especially in drinking water pH range. Film diffusive control mechanism will benefit As(V) exchange with Fe(III)LECCA whether in batch or in column experiments. When treating the tap water at 26.0 BV/h, the column still preserves 83% of the original saturation adsorption capacity of the As(V) aqueous solution. These results have indicated that Fe(III)LECCA has the potential to act as an adsorbent for the removal of As(V) from drinking water considering its availability, nontoxicity and cost-effectiveness.     

MIEX-DOC~离子交换树脂的饮用水除砷研究

对新型阴离子交换树脂MIEX-DOC的除砷性能进行了研究,考察了该树脂除砷容量、对三价砷[As(Ⅲ)]和五价砷[As(Ⅴ)]的去除能力、不同离子和水体pH值对树脂除砷[包括As(Ⅲ)和As(Ⅴ)]效率的影响。结果表明,MIEX-DOC树脂对人工配制高砷水(0.1mg.L-1)的除砷容量约为0.0051mg.mL-1;对As(Ⅲ)和As(Ⅴ)的去除能力相当;常见的共存离子对树脂除砷效率有抑制或促进影响;不同pH值下,MIEX-DOC树脂除砷效率不同,但对0.1mg.L-1的高砷水的除砷效率均达到50%以上。对农村高砷水的实地中试研究表明,当源水砷浓度约为0.1mg.L-1时,出水砷浓度低于0.05mg.L-1,达到《生活饮用水卫生标准》(GB 5749-2006)的农村小型集中式供水和分散式供水水质指标。成本分析结果表明,采用国产MIEX-DOC净水设备的除砷效果与进口设备相当,但除砷成本较低(0.56元.t-1),在我国农村高砷饮用水处理中有一定应用潜力。