Strong Acid Cation Exchange Research Articles

Effect of the porous structure of polymer on the kinetics of Ni2+ exchange on hybrid inorganic-organic ionites

Hybrid organic-inorganic ion exchangers are obtained by incorporating amorphous zirconium hydrophosphate into the gel of strong acidic cation exchange resin. Hybrid organic-inorganic ion exchangers are obtained by modifying strong acidic cation exchange resin with amorphous zirconium hydrophosphate. The synthesized materials are studied by standard porometry contact. It is found that raising the inorganic component content to 34 wt % diminishes the microporosity of the samples and simultaneously enhances the of meso- and macropore volume. Experiments establish that modification of a polymer matrix lowers the self-diffusion coefficient of Ni2+ from 8.1 × 10−12 to 2.4 × 10−12–4.1 × 10−12 m2 s−1; nevertheless, an inorganic ion exchanger minimizes the inhibitory effect of co-ions on the Ni2+ → H+ exchange rate. One possible mechanism for of filling of the matrix by with particles of zirconium hydrophosphate is discussed.

Enhanced conductivity detection of common inorganic anions in electrostatic ion chromatography using water eluent.

To enhance the conductivity detection sensitivity of common anions (Na-anions) in electrostatic ion chromatography (EIC) by elution with water, a conductivity enhancement column packed with strong acid cation exchange resin in the H-form was inserted between an octadecyl silane (ODS)-silica separation column modified with zwitterionic surfactant (CHAPS: 3-{(3-cholamidopropyl)-dimethylammonio} propanesulfonate) and a conductivity detector. Specifically, the Na-anion pairing is converted to H-anion pairing after the EIC separation and then detected sensitively by the conductivity detector. The effects of conductivity enhancement and suppression in the EIC by the enhanced conductivity detection were characterized for the common strong acid anions such as SO4(2-), Cl(-), NO3(-), I(-) and ClO4(-) and weak acid anions such as F(-), NO2(-), HCOO(-), CH3COO(-) and HCO3(-). For the conductivity enhancement effect in the EIC, it is found that the conductivity of measured for all strong acid anions (Na-anions) was enhanced according to the theoretical conductivity predicted for H-anions and that of the measured for weak acid anions was suppressed depending on their pKa of H-anions. For the calibration linearity in the EIC, the strong acid anions were linear (r2 = 0.99 - 1.00) because the degree of dissociation is almost 1.0 over all the concentration range and that of the weak acid anions was non-linear because the degree of dissociation decreased by increasing the concentration of the weak acid anions. In conclusion, the EIC by enhanced conductivity detection was recognized to be useful only for the strong acid anions in terms of conductivity detection and calibration linearity.

An evaluation of a hybrid ion exchange electrodialysis process in the recovery of heavy metals from simulated dilute industrial wastewater

Hybrid ion exchange electrodialysis, also called electrodeionization (IXED), is a technology in which a conventional ion exchange (IX) is combined with electrodialysis (ED) to intensify mass transfer and to increase the limiting current density and therefore to carry out the treatment process more effectively. It allows the purification of metal-containing waters, as well as the production of concentrated metal salt solutions, which could be recycled. The objective of this paper was to investigate the ability of the IXED technique for the treatment of acidified copper sulphate solutions simulating rinsing water of copper plating lines. A single-stage IXED process at lab-scale with a small bed of ion exchanger resin with a uniform composition was evaluated, and the treatment performance of the process was thoroughly investigated. The IXED stack was assembled as a bed layered with the ion exchanger resin (strong acid cation-exchange Dowex™) and inert materials. The stack configuration was designed to prevent a non-uniform distribution of the current in the bed and to allow faster establishment of steady-state in the cell for IXED operation. The influence of operating conditions (e.g. ion exchanger resin with a cross-linking degree from 2 to 8% DVB, and current density) on IXED performance was examined. A response surface methodology (RSM) was used to evaluate the effects of the processing parameters of IXED on (i) the abatement yield of the metal cation, which is a fundamental purification parameter and an excellent indicator of the extent of IXED, (ii) the current yield or the efficiency of copper transport induced by the electrical field and (iii) the energy consumption. The experimental results showed that the performance at steady-state of the IXED operation with a layered bed remained modest, because of the small dimension of the bed and notably the current efficiency varied from 25 to 47% depending on the conditions applied. The feasibility of using the IXED in operations for removal of heavy metals from moderately dilute rinsing waters was successfully demonstrated.

Preparation and Characterization of Novel Nano-ZnO/Polystyrene Resin Composite

A nano-ZnO/polystyrene resin composite was prepared by adsorption nano-ZnO predecessor (Zn2+) onto macroporous strong acid cation exchange resin, denoted as D001, followed by chemical precipitation. The framework FT-IR spectrums showed new adsorption bands at ca. 1615 cm-1 and ca. 530 cm-1 were observed in ZnO@D001 compared to D001, and vibration peak shift in D001 was found from 1001 cm-1 to 1080 cm-1 in ZnO@D001. The specific surface area declined a litte, but pore volume and average pore diameter declined a lot when nano-ZnO immobilized onto D001. All of above results demonstrated the nano-ZnO particles immobilized on the inner nano-pores/channels of D001 successfully. The coefficient of volume and surface resistance (ρV, ρS) values of ZnO@D001 were lower than 104 Ω•m, indicating its excellent antielectrostatic ability.

Characterization of poly(vinylchloride) (PVC) based cation exchange membranes prepared with ionic liquid

In this study, poly(vinylchloride) (PVC) based heterogenous strong acidic cation exchange membranes were prepared by the solution casting technique by using suspension polymerized polyvinylchloride (S-PVC) and emulsion polymerized polyvinylchloride (E-PVC) as binders, dioctyl phthalate (DOP) and ionic liquid (IL) tetradecyl(trihexyl)phosphoniumdecanoate as plasticizers and ion exchange resin as functional group agent. The main goal of this work was to evaluate the effects of polymer binder type, plasticizer type and bider/plasticizer ratio on pyhsicochemical, morphological and electrochemical properties of the prepared membranes. Physicochemical characterization consisted of water contents, dry and wet densities, porosities, ion exchange capacities of membranes and isotherm studies. Scanning Electron Microscopy (SEM) analysis was used to perform morphological characterization. Water contents of the membranes were found between 30% and 40% while density values were in the 0.7–1.2g/cm3 range. Porosities were found between 0.2 and 0.4 and ion exchange capacities changed between 1.2 and 2.8meq Na+/g-dry. Electrochemical characterization included transport numbers of membranes determined by the membrane potential method. Transport number for the membranes prepared with dioctyl phthalate (DOP) was found to be around 0.5 whereas this figure was 1.0 for the membranes prepared with IL. Diffusivity values of Na+ ions across the membrane were calculated by using the Donnan dialysis method and found in order of magnitude-5.

Sorption Behavior of Strong Acid Cationic Exchange Fiber for Indium

In (III) was quantitative adsorption by strong acid cationic exchange fiber (SACEF) in the medium of pH=2.50 sulphuric aicd. The statically saturated sorption capacity of SACEF was 153.8 mgg-1. 0.5 molL-1 H2SO4 could be used as an eluant. The elution efficiency was 99%. The SACEF could be regenerated and reused without apparent decrease of sorption capacity. The sorption rate constant was k287K=0.09379 gmg-1min-1, k300 K=0.1159 gmg-1min-1, k321 K=0.4046 gmg-1min-1 and k350 K=0.6678 gmg-1min-1, respectively. The apparent sorption activation energy of SACEF for In (III) was 28.28 kJmol-1.The sorption behavior of SACEF for In (III) obeyed the Freundlich isotherm. The enthalpy change was H=5.67 kJmol-1.

Using strong acid–cation exchange resin to reduce potassium level in molasses vinasses

Molasses-based distilleries are one of the most vulnerable to pollution industries, which always generate large volumes of high strength vinasse. Recently, one of the most effective re-applications/reuse of vinasse is concentrating the molasses vinasse to prepare as fodder additive for animal food. However, the dosage of molasses vinasse to be added as animal feed is always limited because of the unexpectedly high potassium content in molasses vinasse. In present study, potassium ions were firstly extracted from molasses vinasses using a strong acid–cation exchange resin, and then desorbed from the resin and dissolved into the eluate by H 2SO 4 solution as the strong acid–cation exchange resin was regenerated. Finally, evaluation to recycle and reuse the mother liquor (once-used eluant), after extracting K 2SO 4 crystals from the eluant, was investigated. Results indicated that using the mother liquor to elute the resin column which absorbing K + from molasses vinasse was a potential means for industrial production of potassium salt. Meanwhile, the molasses vinasse which has removed most potassium ions might be used as animal feed.

Study on the Synthesis of Isoamyl Acetate Catalyzed by Strong Acidic Cation Exchange Resin

Isoamyl acetate was synthesized from isoamylol and glacial acetic acid with strong acidic cation exchanger as catalyst. The effects of reaction conditions such as acid-alcohol ratio, reaction time, catalyst dosage to esterification reaction have been investigated and the optimum reaction conditions can be concluded as: the molar ratio of acetic acid to isoamylol 0.8:1, reaction time 2h, 25 % of catalyst (quality of acetic acid as benchmark). The conversion rate can reach up to 75.46%. The catalytic ability didn’t reduce significantly after reusing 10 times and the results showed that the catalyst exhibited preferably catalytic activity and reusability.

Determination of Manganese in Food Grade FeSO<sub>4</sub>•7H<sub>2</sub>O by Solid Phase Extraction and Flame Atomic Absorption Spectrometry

A new method for the determination of manganese in food grade FeSO4•7H2O samples by flame atomic absorption spectrometry (FAAS) after solid phase extraction was developed. The research showed that when coexistent amount of iron was greater than or equal to 100 times of manganese, the relative error of direct determination of manganese by FAAS was greater than or equal to +5%. Firstly, Fe2+ was oxidized to Fe3+ by HNO3. Fe3+ was masked by EDTA. Mn2+ ions were then adsorbed by strong acid cation exchange fiber (SACEF) in pH 1.5 sample solution for 10 minutes and eluted by 2.5 mol/L HNO3 for 15 minutes. Iron and manganese can be effectively separated by this method. Under the optimum conditions, the adsorption capacity of SACEF to Mn2+ ions was attained to be 9.27 mg•g-1. The detection limit of the method was 0.032 μg•mL-1. The proposed method was used for determination of manganese in three batches of FeSO4•7H2O samples. The contents of manganese were 325 μg/g, 823 μg/g, 772 μg/g respectively. The recoveries were in the range of 96.1%~103 % and RSDs (n=5) were less than 3.0%.

Study on Direct Hydration of Camphene to Isoborneol by Cation Exchange Resins

The direct hydration of camphene to isoborneol has been studied in the presence of strong acidic cation exchange resins as catalyst. The effect of various parameters such as temperature, catalyst loading, mass ratio of the reactants, and reaction time on the conversion of camphene was investigated to optimize the reaction conditions. Based on the optimized reaction conditions, a novel pilot-scale jet reactor was used to study the direct hydration of camphene. The kinetic studies of direct hydration reaction have been discussed in detail. A pseudo-homogeneous (PH) model was used to correlate the experimental data in the temperature range from 353.15 K to 383.15 K. The kinetic parameters were evaluated, which made the calculated results in excellent agreement with the experimental results.

Removal of Ni(II) ions from aqueous solutions using fixed-bed ion exchange column technique

Ion exchange represents an efficient technique for removing of heavy metals from wastewater effluents. Limited number of studies focuses on fixed bed performance for metal removal. In this study, the removal of Ni 2+ from synthetic wastewater using a strong acidic cation exchange resin in a fixed bed columns was investigated. The experiments were conducted at different pH (3–7) and initial heavy metal concentrations (1.8, 2.8 and 3.8 g Ni/L). Investigation of the regeneration effect on the resin was conducted. The removal efficiency and rate of removal are shown on the breakthrough curves and the kinetic study of the process was determined. The Thomas model was applied to follow the exchange dynamics, the results from experimental work were compared to those using Thomas model, it is shown that the calculated breakthrough curves agreed well with the measured ones. The metal level in the treated wastewater was examined using the atomic absorption spectrophotometer to show that the Ni 2+ concentration complies with the standard environmental regulations limits.

COMBINATION OF REVERSE OSMOSIS AND ELECTRODEIONIZATION FOR SIMULTANEOUS SUGAR RECOVERY AND SALTS REMOVAL FROM SUGARY WASTEWATER

An integrated membrane system combining reverse osmosis (RO) and electrodeionization (EDI) is used for simultaneous sugar concentration and salts removal from a synthetic dilute sugar solution as a model of sugar-containing wastewater. The RO system uses a thin film composite RO membrane (Saehan CSM, RE1812-60). Meanwhile, the EDI stack has two diluted compartments, one concentrated compartment, one anode compartment, and one cathode compartment. Commercially available cation exchange membrane (MC-3470) and anion exchange membrane (MA-3475) are used as ionic selective barriers of the EDI stack. Both diluate and concentrate compartments are filled with mixed ion exchange resins (purolite strong acid cation exchange, C-100E and strong base type I anion resins, A-400). Two different operation modes, i.e. RO-EDI and EDI-RO, were assessed. The experimental results show that the observed sugar rejection of RO membrane is more than 99.9% and there is no sugar loss in the EDI stack. This indicates that the hybrid process allows almost total sugar recovery. In addition, significant reduction of salts content from the concentrated sugar solution is obtained. From permeate flux and permeate purity points of view, however, the EDI-RO configuration seems superior to the RO-EDI configuration. It should be emphasized that scale formation on the membrane surface of the concentrate compartment side has to be controlled.

Catalytic conversion of cellulose into 5-hydroxymethylfurfural in high yields via a two-step process

As a key renewable chemical for plastics and fine chemicals, the preparation of 5-hydroxymethylfurfural (5-HMF) from biomass is an important research topic. Cellulose, although abundant in nature, is difficult to convert to 5-HMF in good yields due to its recalcitrant and heterogeneous nature. In this work, we show an efficient two-step process for converting microcrystalline cellulose into 5-HMF with ionic liquids under mild conditions. In the first step, high glucose yields of above 80% could be obtained from the cellulose hydrolysis by a strong acidic cation exchange resin in 1-ethyl-3-methyl imidazolium chloride ([EMIM][Cl]) with gradual addition of water. In the second step, the resin was separated from the reaction mixture and CrCl3 was added which lead to a 5-HMF yield of 73% based on cellulose substrate. The strategy can allow practical conversion of biomass into bio-derived products.

Kinetics and molecular orbital calculations of desulfonation of strong acid cation-exchange resin

This paper deals with the desulfonation properties of some strong acid cation-exchange resins. The sulfate concentration in solution is continuously increased when a strong acid cation-exchange resin is mixed with water. The leaching of sulfate results from the desulfonation of the fixed group, and the amount of leached sulfate depends on the counter ion charge, the crosslinking degree and the exchanger matrix. The effects of the counter ion charge on the desulfonation rate suggested that the counter ion induces the nucleophilic attack of a water molecule on the sulfo group. This interpretation was supported by semiempirical molecular orbital calculations for the C 6H 5SO 3 −M m+ (M m+ = Na +, Mg 2+ and Al 3+) systems, and the transition state of the Na + system was successfully predicted by DFT calculations. The crosslinking degree influenced the desulfonation rate, which can be related to the decreasing hydration number of each counter ion in the resin phase with the increasing crosslinking degree. Furthermore, different exchanger matrices produced the differences in the rates, which may be derived from the electron-density donation from the exchanger matrix to the sulfo group. The desulfonation is governed by the electron-density of the sulfur atom and the water activity in the solid phase.

Kinetics and optimization of L-tryptophan separation with ion-exchange chromatography

Adsorption and desorption of L-tryptophan (L-trp) on strong acid cation exchange resin were investigated in a fixed-bed column. L-trp was effectively adsorbed onto the resin HZ-001, with the loading capacity and break- through time determined. Four kinetic models, including Adams-Bohard, Wolborska, Thomas, and Yoon-Nelson models, were adopted to determine the kinetic parameters of adsorption and to predict the breakthrough curves. The results showed that the models used described the breakthrough well. Desorption of L-trp from the column bed was performed using aqueous ammonia as the eluant. Optimum procedure was obtained with 2.0 M aqueous ammonia at the elution velocity of 6 BV/h. Five cycles of adsorption-elution-regeneration were conducted to evaluate the column reutilization.

New technological root for regenerating demineralized water plants for safe environment

The experiments in this work were subjected to lab-scale ion exchangers unit, consists of two kinds of ion exchangers (strong acid cation exchanger and weak base anion exchangers). The experimental investigation was directed at studying a new method for regenerating the strongly acidic cation exchanger in the demineralized water unit using one concentration of sulfuric acid (5%) directly without any precipitation problems. Experiments show that using sulfuric acid in the regeneration is equally efficient as that of hydrochloric acid solution in the production of dematerialized water (110 bed volume). The first objective of this study was to use sulfuric acid solution instead of hydrochloric acid solution because it is cheaper and non corrosive. The other benefits could be gained from the effluent (sodium hydroxide solution) which comes out of the anion exchanger columns instead of disposing them. Key words: Cation exchanger, anion exchanger, backwash, regeneration, rinsing.

Kinetic study of the direct hydration of turpentine

A study of turpentine direct hydration was carried out, using macropore and strong acidic cation exchange resin Amberlyst 15 wet as catalyst. During the hydration process, the isomerization of α-pinene also took place under the catalytic condition. The effects of different parameters such as agitation speed, catalyst type, catalyst loading, mass ratio of the reactants, temperature and the reusability of catalyst on the conversion of turpentine and the yield of α-terpineol were investigated to obtain the optimal reaction conditions in a stirred-tank reactor. Based on these optimized conditions, the experiment was conducted in a new pilot-scale jet reactor to achieve an excellent performance. Kinetics of the direct hydration reaction was also performed in the temperature range 328.15–348.15 K. A pseudohomogeneous (PH) model was used to explain the reaction rate equation and to determine the reaction rate constants and reaction activation energy.

Extraction of CO2from Seawater and Aqueous Bicarbonate Systems by Ion-Exchange Resin Processes

Ion-exchange resins in dynamic seawater and model bicarbonate systems were studied to determine their feasibility and practicality for extracting large quantities of carbon dioxide from seawater for use as a carbon feedstock for fuel synthesis. The capacity and selectivity of both a strong acid cation-exchange resin and a strong base anion-exchange resin revealed that the cation-exchange resin total carbon dioxide recovery (0.32 mg/g of resin) was far superior to the anion-exchange capacity (0.07 mg/g of resin). In addition, the ease of regeneration of the cation-exchange resin was demonstrated using deionized water as a possible substitute for strong acids. The laboratory-scale data are used to estimate the full industrial-scale feasibility of a carbon-capture process by these approaches.

Kinetics Study of Direct Hydration of Dihydromyrcene in a Jet Reactor

A novel pilot-scale jet reactor was applied to study the direct hydration of dihydromyrcene (DHM) with H2O using strong acid cation exchange resins (SACER) as catalysts. The effect of various parameters such as liquid circulation flow rate, temperature, catalyst loading, and mass ratio of the reactants was studied in detail. The equilibrium constants of the direct hydration were calculated on the basis of the activities that were predicted using UNIFAC group contribution method. A pseudohomogeneous (PH) model was used to correlate the kinetic data in the temperature range from 353.15 to 383.15 K. The estimated kinetic parameters make the calculated results in excellent agreement with the experimental results, indicating that the PH model gives a good representation of the kinetic behavior for the direct hydration of DHM.

The immobilization of hydrophilic ionic liquid for Cr(vi) retention and chromium speciation

The immobilization of N-methylimidazolium (Nmim) onto PVC surface forms bonded hydrophilic ionic liquid 1-chlorovinyl-3-methylimidazolium chloride (PVC-NmimCl), which entails anion exchange nature and positively charged surface, facilitating favorable retention of Cr(VI) with a retention capacity of 23.2 mg g−1 for Cr(VI) at pH 5.6. A novel on-line solid phase extraction approach for the separation and preconcentration of Cr(VI) is developed in a sequential injection system with a PVC-NmimCl mini-column, and an extra mini-column of strong acidic styrene type cation exchange resin is incorporated for pre-eliminating Cr(III) in sample solution before entering the PVC-NmimCl mini-column. The retained Cr(VI) is effectively recovered with elution by 0.2 mol l−1 NH4NO3 solution, and the eluate is quantified by electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICP-MS). With a sample volume of 2000 μl, a complete retention of Cr(VI) is obtained, giving rise to an enrichment factor of 23.4 and a sampling frequency of 9 h−1. A linear range of 0.01–1.0 μg l−1 for Cr(VI), along with a detection limit of 3 ng l−1 and a RSD of 2.9% at 0.5 μg l−1 is obtained. Total chromium in a certified reference material of reverine water (GBW08608) is determined after oxidation, which results in good agreement between the certified and the found values. The procedure is further demonstrated for chromium speciation in tap water and snow water samples.