Parametric studies on the performance of anion exchange for nitrate removal

Ion exchange performance to remove nitrate in surface and underground water was studied experimentally in batch and continuous operation systems under various conditions. Data were collected by using commercially available strong-base anion-exchange resins of C1 and OH types. Equilibrium curves, obtained through the batch system and plotted as the concentration ratio versus run time, were used to evaluate the effects of temperature, resin type, and initial feed concentration on the equilibrium characteristics of nitrate. The selectivity coefficients of the resins were correlated as a function of temperature by using the Kraus-Raridon equation. Breakthrough curves, obtained through the continuous column system and plotted as the ratio of effluent to influent concentration versus solution volume passed through the experimental column, gave detailed results about the effects of the system parameters, such as temperature, resin type, feed concentration, volumetric flow rate, column diameter and height on the performance of the anion exchange to remove nitrate. The results of this study could be scaled up and used as a design tool for a water-purification system of real ground water and surface water treatment processes.     

Ammonia Removal from Aqueous Solutions by Iranian Natural Zeolite

Abstract

The capability of Iranian natural clinoptilolite for ammonia removal from aqueous solutions has been thoroughly studied. Both batch and continuous (column) experiments were carried out. The viability of this natural zeolite in reducing the leakage of ammonia to the environment through waste water streams was a main focus of this research. Through the batch experiments, the effect of process variables such as the size of zeolite particles, pH, and ammonia concentration of the feed solution on the kinetics of ammonia uptake were investigated. Ammonia removal occurred rapidly and within the first 15 minutes of contact time, a major part of ammonia was removed from the solution. An adsorption capacity about 17.8 mg NH₄ ⁺/g zeolite at feed ammonia concentration of 50 mg/L was obtained and the optimum range for pH was achieved about 5.5–7.6. The adsorption capacity of clinoptilolite in the continuous mode was about 15.16 and 15.36 mg NH₄ ⁺/g zeolite for the original and regenerated types of clinoptilolite, respectively, where feed ammonium concentration was 50 mg/L. Increasing the feed ammonium concentration to 100 mg/L did not reduce the capability of the column for its ammonium removal and up to a bed volume (BV) of 85, there was only less than 1 mg/L ammonium in the column outlet. Presence of cations such as Ca²⁺, Mg²⁺ and Na⁺ in the feed solution reduced the clinoptilolite adsorption capacity to about 11.68 mg NH₄ ⁺/g zeolite. Regeneration experiments were carried out using concentrated sodium chloride solutions, as well as tap water. Where tap water was used as the regenerant, gradual release of ammonium from exhausted clinoptilolite was observed.     

REMOVAL OF BORON FROM BALÇOVA-IZMIR GEOTHERMAL WATER BY ION EXCHANGE PROCESS: BATCH AND COLUMN STUDIES

In this study, the efficiency of boron removal from Balçova geothermal water provided by the Izmir Geothermal Energy Company, Turkey, has been investigated using boron selective ion exchange resins Diaion CRB 02 and Dowex (XUS 43594.00) by batch and column methods. The results of the column studies have been evaluated in terms of type of resin and feed flow rate, and the effects of particle size and temperature have been investigated using the results obtained from batch kinetic studies. The data from the kinetic studies have been evaluated using pseudo-first-order and pseudo-second-order kinetics models. In addition, the classical diffusion models have been used to evaluate the kinetic data obtained to understand the rate-controlling mechanisms.     

NEW CATION EXCHANGE RESINS BASED ON POLYVINYL ALCOHOL CONTAINING CARBOXYL GROUPS FOR THE REMOVAL OF SOME TEXTILE CONTAMINANTS FROM AQUEOUS SOLUTIONS

Two cation exchange resins having carboxyl contents, 628 and 424 meq/100 g sample were prepared by free radical polymerization of acrylic acid in presence of polyvinyl alcohol aqueous solution using methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The prepared resins were characterized by investigation of their potentiometric titration, durability, water solubility, and swellability. The removal of Cu²⁺ ions (in the form of copper sulfate) from aqueous solution using these resins was studied under different conditions, including resin particle size, copper sulfate concentration, time, pH, liquor to resin ratio (LR), agitation speed, and resin capacity. A comparison was also held among the removal of other cations, namely Ni²⁺ and Co²⁺, in their sulfate forms. The resins were also utilized in the removal of some basic dyes from their aqueous solutions.     

Static adsorption properties of Ni（Ⅱ）by IDA resin and U-shaped continuous countercurrent desorption

研究了亚胺基二乙酸型螯合树脂R604对模拟含镍废水中镍离子静态交换吸附性能的主要影响因素,包括废水浓度、pH值、温度等,还研究了吸附平衡态、吸附过程的动力学、热力学,并给出了相应的模型,这些模型均与实验结果有很好的符合度。最后研究了独创的U形解吸柱系统对吸附饱和树脂的解吸性能,探讨了树脂停留时间、解吸液树脂流量比对解吸率和金属浓缩液浓度在柱体内分布的影响。研究表明,亚胺基二乙酸型树脂在废水金属离子镍的去除中有着高效、独特的性能,连续逆流U形解吸系统能提高重金属浓缩液浓度,并大幅度节省解吸液用量,减少解吸时间。     

KINETICS OF ZINC REMOVAL FROM COBALT ELECTROLYTES BY ION EXCHANGE

ABSTRACT

The removal of trace zinc concentrations from the INCO (Port Colborne) cobalt advance electrolyte by solvent impregnated ion exchange was studied in column and batch tests. The resins OC 1026, SIR 272 and SIR 302 were compared in terms of zinc loading and selectivity.

The OC 1026 resin demonstrated superior zinc loading and selectivity characteristics, but retained significant amounts of cobalt. Cobalt loading was determined to be closely related to the electrolyte pHdrop across the column. Resin pre-treatment with the advance electrolyte at pH 3 acts to diminish the pH drop across the column, and hence reduced the cobalt retained. Results from batch tests were fitted to kinetic models to gain an insight into process mechanisms. It was found that pre-treatment enhanced the apparent diffusion coefficient inside the resin phase by nearly an order of magnitude, improved exchange kinetics by allowing a lower pH reduction during the loading process, and improved Co²⁺/Zn²⁺ exchange in a matrix of the cobalt complex. Breakthrough curve analysis was also undertaken to determine the rate determining steps in the column process.

Further work is needed in X-ray microprobe analysis of resin samples from various portions of the column after loading, to gain a better understanding of the column loading process. The use of zinc selective electrodes in batch tests could also be undertaken to obtain more accurate estimates of diffusion and mass transfer coefficients.     

Copper-selective chelating resins. II. Column extractions

Two chelating resins based on poly(glycidylmethacrylate-co-ethyleneglycol dimethacrylate) and two based on poly(styrene-co-divinylbenzene) have been used in small-scale column extractions of Cu(II) from sulphate solutions containing 1.0 mg l⁻¹ of metal ion at pH 5. Two of the resins bearing 2-aminomethylpyridine residues with saturation capacities up to ∼ 15 g Cu(II) l⁻¹ resin showed sharp breakthrough profiles and rapid exchange kinetics. The other two with higher ligand loading displayed shallow profiles and did not reach saturation capacity, indicating a significant proportion of the ligand groups to be inaccessible under the conditions employed. For a column of 10 ml bed volume, increasing the flow rate of the feed solution from 1 ml min⁻¹ progressively to 30 ml min⁻¹, using one of the more efficient resins, showed that above a rate of ∼ 5 ml min⁻¹ the bulk movement of ions through the column was too fast for all the resin-bound ligands to be accessed. As a result breakthrough moved to lower volumes and the working capacity dropped. No difference was found in the elution of all four resins with 1 M H₂SO₄ at a flow rate of 1 ml min⁻¹. In all cases Cu(II) was rapidly and efficiently eluted from the column.The selectivity properties of the two efficient resins in extracting Cu(II) ions from a solution containing a large excess of Zn(II) ions were also investigated. The effect of a 250-fold excess of Zn(II) proved negligible in both cases, and Cu(II) was rapidly and selectively extracted with a separation factor of ∼ 900: 1 in the case of the polystyrene-based resin, and ∼ 500: 1 in the case of the methacrylate-based species.In terms of kinetic performance and metal ion selectivity (in both loading and elution) the results of the batch extraction experiments were confirmed in these column tests, hence proving the predictive value of careful batch testing. On considering kinetic factors, capacity factors and metal ion selectivity factors, a resin carrying a 2-aminomethylpyridine group attached to a polymethacrylate backbone proved to be the optimum one.     

Efficient Removal of Hg(II) by Polymer-Supported Hydrated Metal Oxides from Aqueous Solution

Chelating PS-EDTA resins modified by metal (Fe, Al, and Zr) oxides were used as adsorbents to remove Hg(II) from aqueous solutions. The modified resins were characterized by BET, FTIR, and XPS. The amino, carboxylate, and the metal oxides on resins exhibited a synergistic effect for Hg(II) removal. It was observed that the modification of PS-EDTA resin not only increased the adsorption of Hg(II) but also accelerated the adsorption rate of Hg(II). The equilibrium data of Hg(II) were best described by the Freundlich isotherm, and the kinetics were found to follow the pseudo-second-order kinetic model. Also, thermodynamic parameters showed that Hg(II) adsorption was endothermic and spontaneous in nature. The increasing the concentration (0.1–2.0 g/L) of NaNO₃ in Hg(II) solution did not affect the adsorption of Hg(II). Moreover, the competitive adsorption indicated that the modified resins had higher selectivity towards Hg(II) over Cd(II), Pb(II), Zn(II), or Cu(II) in a binary system. All of the above results indicated that the modified resin was an efficient and reusable adsorbent for Hg(II) removal due to its simple preparation, high adsorption capacity, fast adsorption rate, ionic strength independence, high selectivity, and good reusability. These properties are of potential application in the fixed-bed continuous-flow column for Hg(II) removal from wastewaters.     

State of the Art Bifunctional Hydrogenation Heterogeneous Polymeric Catalyst

Polymeric bifunctional heterogeneous catalyst, Amberlyst? CH28 resin, enables low temperature (<140 °C) synthesis of 4-methyl-2-pentanone (MIBK). A single pot multireaction process achieved high yields (<65%) and selectivity (>90%) in batch and continuous processes. New Pd impregnated strong acid styrenic ion exchange resins were tested and a good statistical correlation of secondary products and MIBK yield was found. GC–MS and GC methods were used to identify reaction products.     

处理高浓度氨氮废水的阳离子交换树脂筛选

目前树脂种类繁多,给处理高浓度氨氮废水的树脂选型带来困难。根据离子交换理论,利用001×7、D61和D001三种阳离子交换树脂,模拟研究了氮肥厂废水（氨氮浓度为915 mg·L^-1）氨氮的吸附等温式,在30～50 min内三种树脂对氨氮的吸附基本可达到平衡,吸附等温线均符合Freundlich吸附模式;进而研究了这三种树脂对废水中氨氮吸附的选择性系数、工作交换容量和离子交换速率。结果表明,用D61树脂处理含高浓度氨氮的废水效果较为理想,可以相对较少的用量,使处理后水质达到相关排放标准的要求。     

Diesel Oil Removal by Froth Flotation Under Low Interfacial Tension Conditions II: Continuous Mode of Operation

Abstract

The objective of this study was to investigate the relationship between interfacial tension (IFT) and foam characteristics and the efficiency of diesel oil removal from water in a continuous froth flotation column. The effects of operational parameters, including surfactant concentration, salinity, oil-to-water ratio, foam height, air flow rate, and hydraulic retention time (HRT) on the oil removal were investigated in the continuous mode of a froth flotation operation and compared to batch operation results. Unlike the batch system, for the continuous system used in the present study, having only branched alcohol propoxylate sulfate sodium salt surfactant (C_14–15(PO)₅SO₄Na) and NaCl present in the solution yielded such poor foam characteristics that a stable froth which overflowed the flotation column could not be produced, so the addition of sodium dodecyl sulfate (SDS) as a froth promoter was used to improve the foam stability. Unlike the batch froth flotation system with only C_14–15(PO)₅SO₄Na, the continuous froth flotation with the mixture of C_14–15(PO)₅SO₄Na and SDS, it was not possible to find a SDS and a NaCl concentration at which both ultralow IFT and good foaming were both achieved. Foam formation, stability, and production rate were found to be crucial parameters to the froth flotation efficiency. The continuous froth flotation system offers a high diesel oil removal of 96% in the single stage unit. Demonstration of efficient operation in the continuous mode in this work is important to the practical application of froth flotation in large scale processing.     

Unconventional ion exchange resins and their retention properties for Hg2+ ions

Synthesis of two unconventional ion exchange resins and their behaviour on the mercury sorption experiments were investigated.The ion exchange resins were obtained by the quaternization reaction of 4-vinylpyridine:divinylbenzene copolymer, gel-type, by two ways namely, the nucleophilic substitution of the pyridine matrix with 2-chloroacetamide and the nucleophilic addition of protonated copolymer to acrylamide.Comparative sorptions of Hg²⁺ ions on the synthesized pyridine resins by batch experiments in mono- and binary system were analyzed. Mercury retention experiments aimed to study the influence of the solution concentration, contact time and solution pH. The removal of Hg²⁺ ions from aqueous solutions depends on the pH values, the amount of the retained mercury increased with the pH value.The studied strong base pyridine anion exchange resins presented a good selectivity for the Hg²⁺ ions during the competitive sorption of Hg²⁺/Cu²⁺, Hg²⁺/Zn²⁺ and Hg²⁺/Fe³⁺ at metal cations ratio of 1:1.     

Adsorption of Nickel(ll) and Cobalt(ll) from Aqueous Solutions on Levextrel Resin Containing Acidic Organophosphinic Extractant and Phosphorus-Based Chelating Resins: Comparative Study on the Selectivity of the Resins

Abstract

A comparative study was conducted on the adsorptions of cobalt(II) and nickel(II) from aqueous ammonium nitrate solutions on a Levextrel resin containing acidic organophosphinate extractant, Cyanex 272, as an active component and on chelating resins containing phosphorus-based acidic functional groups. It was found that the Levextrel resin has much higher selectivity for cobalt(II) over nickel(II) then the chelating resins. The origins of the low selectivity of the chelating resins are qualitatively discussed.     

Column sorption of divalent metals from sulfate solutions by extractant-impregnated macroporous resins

Column sorption of zinc and copper ions from single aqueous sulfate solutions using extractant-impregnated macroporous resins was experimentally studied at 298 K. The widely used di(2-ethylhexyl)phosphoric acid was selected as the extractant. The breakthrough curves were measured as a function of feed flow rate, feed pH and metal concentration in the feed solution, extractant concentration in the resin phase, and the type of resin. It was shown that feed pH and the type of resin played a rather important role in determining the shape of breakthrough curve. For a given type of resin bed, the saturated capacity was greater under the conditions of higher feed pH, higher concentrations of metal and extractant, and lower feed flow rate.     

亚胺基二乙酸树脂对金属镍的静态吸附及连续逆流U形解吸系统

研究了亚胺基二乙酸型螯合树脂R604对模拟含镍废水中镍离子静态交换吸附性能的主要影响因素,包括废水浓度、pH值、温度等,还研究了吸附平衡态、吸附过程的动力学,热力学,并给出了相应的模型,这些模型均与实验结果有很好的符合度,最后研究了独创的U形解吸柱系统对吸附饱和树脂的解吸性能,探讨了树脂停留时间、解吸液树脂流量比对解吸率和金属浓缩液浓度在柱体内分布的影响.研究表明,亚胺基二乙酸型树脂在废水金属离子镍的去除中有着高效、独特的性能,连续逆流U形解吸系统能提高重金属浓缩液浓度,并大幅度节省解吸液用量,减少解吸时间.     

Zirconium and Hafnium Separation,Part 2. Solid/Liquid Extraction in Hydrochloric Acid Aqueous Solution with Anion Exchange Resins

Abstract

Sorption behavior of zirconium and hafnium on different commercial anion exchange resins with different amine functions; ammonium (Amberjet 4200Cl), pyridine (PVP) and pyridinium (HPQ) was investigated in hydrochloric acid by both batch and column methods. Experiments were studied as a function of the concentration of hydrochloric acid. For all resins, zirconium was preferably extracted. The highest separation factors at equilibrium conditions were obtained by poly(vinyl‐pyridine) (PVP) with a hydrochloric acid concentration of 9.5 M. It was observed that a single contact of the loaded resins with pure water completely back extracted the metal ions from the resins. On the basis of the significant difference between distribution coefficients of Zr and Hf, the separation was performed on a glass column (25×160 mm), packed with the resin. The breakthrough curves showed a competitive sorption and desorption process between Zr and Hf for the three resins studied.     

The effects of amine additives and flow rate on the performance of mixed-bed ion exchange at ultralow concentrations

Experimental data were obtained to evaluate the effects of amine additives for pH control of solution and the volumetric flow rate of feed solution on the performance of mixed-bed ion exchange for the removal of ionic impurities in solution. The experiments were performed under various temperatures and cation resin ratios by using a continuous column system with NaCl solution. The breakthrough curves of ions, plotted as the ratio of the effluent to influent concentration versus run time or treated solution volume, give detailed results about the effects of the existence of the pH controller, such as ammonia and morpholine, and the variable flow rate on the fate of each ion in the units. The experimental results show that the morpholine breakthrough occurs earlier than the ammonia breakthrough and that the effect of ammonia on both sodium and chloride exchange rates is more significant than that of morpholine. The addition of ammonia in solution results in the decrease of cation resin capacity for the sodium removal much more than the addition of morpholine. The step changes in the flow rate affect significantly the shapes of sodium and chloride breakthrough curves. The effluent concentrations of sodium and chloride change according to the flow rate. However, the effect increases with decreasing operation capacity of cation resin, while it becomes serious around the breakthrough time of chloride and negligible after the time.     

离子交换树脂吸附法分离乙醇溶液中甘油的研究

通过实验探讨了离子交换树脂对乙醇溶液中甘油的吸附作用。实验结果表明,凝胶型树脂对甘油的静态吸附容量大于大孔型树脂,且一般随温度降低而增大;在所试验的几种树脂中,２０１×４（ＯＨ型）具有较大的动态吸附容量（３３．７ｍｇ甘油／ｍｌ湿树脂）。     

Affinity Dialysis–A Method of Continuous,Rapid Metal Ion Separation Using Dialysis Membranes and Selective,Water-Soluble Polymers as Extractants

Abstract

A membrane process utilizing dialysis and selective complexation by water-soluble polymers has been developed. This process, termed affinity dialysis, has been shown to selectively extract and concentrate both cations and anions in a manner similar to ion exchange or solvent extraction. The selective removal of calcium from sodium with selectivity of about 30, removal of chromate ion from dilute streams, and separation of transition metal ions such as Cu/Fe and Cu/Zn have all been successfully demonstrated. Effects of different polymers, polymer concentration, temperature, and flow rates have been studied. The effect of increased polymer concentration is to increase product concentration if appropriate changes in feed, polymer solution, and strip flow rates are made. A continuous polymer solution recycle and regeneration system has been constructed and operated with Cu/Zn and chromate/chloride feed streams. Removal of over 95% of the desired ion in one pass and concentration factors of product over effluent in excess of 100 have been achieved at feed flow rates of 24 gal/d. Product concentrations of greater than 3% from as little as 400 ppm feed have been demonstrated in a continuous process. In addition, the degree of polymer loss to the effluent stream has been shown to be less than 0.01%/d for a typical system. Metal removal from typical feeds is about 0.9 g/m² per 1000 ppm metal in the feed. It is expected that this technique may be useful in the separation of organic and biological materials, as well as for ionic species     

The mixed-bed ion exchange performance at ultralow concentrations 1. Variable feed concentration and incomplete mixing of resins

Experimental data were obtained to evaluate the performance of mixed-bed ion exchange for the cases of variable feed concentration and incomplete mixing of anion and cation resins observed in large scale industrial units. For variable feed concentration, step changes in feed concentration were arbitrarily introduced into a test column. For incomplete mixing, only anion resin was loaded in the upper 20% of the column and more cation resin in the lower portion. Feed concentrations of 5.0× 10⁻⁵−2.0×10^-4 M NaCl were used for the experiments, with flow rates of 0.665-7.0 ml/sec. The effluent from the column was collected periodically and analyzed using on-line/off-line ion chromatography. The step changes in feed concentration affect the breakthrough times of sodium and chloride. Sodium breakthrough curve is more sensitive to the step changes than chloride breakthrough curve. With the same volumes of cation and anion resins, incomplete mixing of resins increases the cation exchange rate slightly and decreases the anion exchange rate slightly. As the cation resin volume increases, the effect of the incomplete mixing of resins decreases. The breakthrough curves of both ions, plotted as the ratio of effluent to the influent concentration versus run time in hour, give some detailed results about the effects of the conditions.