Exchange Reaction Characteristics of Anion Exchange Resin for Diclofenac Sodium

Aim To study the exchange reaction characteristics of anion exchange resin for diclofenac sodium. Methods The drug-resin complexes were prepared by a batch method with diclofenac sodium as the model drug and the strong anion exchange resin (201 × 7) as the carrier. The effects of different forms (OH~ - and Cl~ - ) of the strong anion exchange resin, the particle size of the resin, and the reaction temperature on the exchange behavior were described. The exchange kinetic profiles were fitted. The related exc...

A more precise method to evaluate kinetic leakage of anion exchange resin used in condensate polishing of power plant

Sulfate mass transfer coefficient(MTC) is a sensitive parameter to evaluate the kinetic leakage of anion exchange resin used in condensate polishing system of thermal and nuclear power plant.However,a sufficiently precise determination method has not been well established.In this paper,the final expression of sulfate MTC derived based on plug flow reactor model is the same as Harries' model,which is widely acknowledged in this field.In the determining system we constructed,in-situ calibration of the concentration of sulfate and its cation conductivity was conducted and sulfate MTCs of four typical strongly basic anion exchange resin samples were determined.The systematic error is 8.26% and the calibrated curve used for quantifying sulfate is obtained.The repeatability and reproducibility standard deviation are 0.05×10^(-4) m·s^(-1) and 0.07×10^(-4) m·s^(-1) respectively,which are lower than previous works.By controlling test condition accurately,this study has developed a more precise sulfate MTC determining method.This method provides a basis for further research.

THE EFFECT OF IONIC STRENGTH ON THE UPTAKE OF TAURINE ON A STRONG-BASIC ANION EXCHANGE RESIN

Studied the effect of ionic strength on the uptake of taurine on a strong-basic anion exchange resin The batch phase equilibrium experiments of taurine on the anion exchange resin D290 were conducted at different ionic strength, and then the amounts of uptake of taurine on the resin at different pH were determined. The ion exchange mechanisms of taurine on the anion exchange resin at different pH were discussed. Experimental results showed that with increase of the ionic strength of solution, the adsorbed amount of taurine on the resin D290 decreased; Adding small amounts of NaOH or HCl into the system of taurine aqueous solution/D290 anion resin would nfake the amount of taurine taken up on the resin to decrease due to the competition uptakes of hydroxyl ion with taurine or the decrease in the amount of absorbable zwitterions of taurine in the solution and excluding the cations of taurine from the anion resin.

Selective removal of nitrate by using a novel macroporous acrylic anion exchange resin

An anion exchange resin NDP-5 has been prepared successfully and applied on the selective removal of nitrate from SO_4^（2-）/ NO_3^- binary co-existence system.The composition and morphology of NDP-5 were confirmed by FT-IR and SEM.The NDP-5 resin exhibits the completely different behavior on the adsorption capacity,adsorption kinetic and the effect of the completing anion in the absence or presence of sulfate,compared to D213.And,the resultants of kinetic are well fitted by the pseudo-first-order and pseudo-second-order models.These results are very important to develop novel resins with great features.

Adsorption of Ce(IV) in nitric acid medium by imidazolium anion exchange resin

N-methylimidazolium functionalized anion exchange resin in NO3 form （RNO3） was prepared and used for adsorption of Ce（Ⅳ） in nitric acid medimn. The adsorption amount increased with shaking time increasing and the adsorption equilibrium was obtained within 180 rain. Ce（Ⅳ） was partially reduced to Ce（Ⅲ） and the reduction percent of Ce（Ⅳ） increased with shaking time increasing. But RNO3 was more stable than other resins due to the high resistance to oxidation. A little increase of adsorption amount was found with concentration of HNO3 increasing. However, the reduction percent of Ce（Ⅳ） decreased with the increase of HNO3 concentration. The addition of NaNO3 decreased the adsorption amount of Ce（Ⅳ） on RNO3 due to the competitive anion exchange reaction. Ce（Ⅳ） was adsorbed on RNO3 in the form of Ce（Ⅳ） anion nitrato-complex. RNO3 and Ce（Ⅳ）-loaded RNO3 were characterized by fourier transform infrared （FT-IR） and thermogravimeric analysis （TGA）. Ce（Ⅳ） could be easily separated from RE（Ⅲ） solution by RNO3.

Effect of dissolved organic matter on nitrate-nitrogen removal by anion exchange resin and kinetics studies

The effects of dissolved organic matter （DOM） on the removal of nitrate-nitrogen from the model contaminated water have been investigated utilizing the strong base anion exchange resins. With the increase of gallic acid concentration from 0 to 400 mg/L, the adsorption amount of nitrate-nitrogen on the commercial resins, including D201, Purolite A 300 （A300） and Purolite A 520E （A520E）, would significantly decrease. However, the presence of tannin acid has little impact on nitrate-nitrogen adsorption on them. Compared to D201 and A300 resins, A520E resin exhibited more preferable adsorption ability toward nitrate-nitrogen in the presence of competing organic molecules, such as gallic acid and tannin acid at greater levels in aqueous solution. Attractively, the equilibrium data showed that the adsorption isotherm of nitrate-nitrogen on A520E resin was in good agreement with Langmuir and Fretmdlich equations. The rate parameters for the intra particle diffusion have been estimated for the different initial concentrations. In batch adsorption processes, nitrate-nitrogen diffuse in porous adsorbent and rate process usually depends on t1/2 rather than the contact time. The pseudo first- and the second-order kinetic models fit better for nitrate-nitrogen adsorption onto A520E resin. The observations reported herein illustrated that A520E resin will be an excellent adsorbent for enhanced removal of nitrate-nitrogen from contaminated groundwater.

Selection of magnetic anion exchange resins for the removal of dissolved organic and inorganic matters

Four magnetic anion exchange resins （MAERs） were used as adsorbents to purify drinking water. The effect of water quality （pH, temperature, ionic strength, etc.） on the performance of MAER for the removal of dissolved organic matter （DOM） was also investigated. Among the four studied MAERs, the strong base resin named NDMP- 1 with high water content and enhanced exchange capacity exhibited the highest removal rate of dissolved organic carbon （DOC） （48.9% removal rate） and UV-absorbing substances （82.4% removal rate） with a resin dose of 10 mL/L after 30 rain of contact time. The MAERs could also effectively remove inorganic matter such as sulfate, nitrate and fluoride. Because of the higher specific UV absorbance （SUVA） value, the DOM in the raw water was found to be removed more effectively than that in the clarified water by NDMP resin. The temperature showed a weak influence on the removal of DOC from 6 to 26℃, while a relatively strong one at 36℃. The removal of DOM by NDMP was also affected to some extent by the pH value. Moreover, increasing the sulfate concentration in the raw water could decrease the removal rates of DOC and UV-absorbing substances.

Adsorption Mechanisms of Heavy Metal Ions from Drinking Water by Weakly Basic Anion Exchange Resins

Heavy metal micro-contaminants can be removed from water sources such as rivers and lakes using variations of conventional treatment technologies. Weakly basic anion exchange resins offer the best ability to remove trace amounts of heavy metals with high selectivity. This paper discusses how weakly basic resins adsorb heavy metals using two different approaches. The removal of mercury, cadmium, and lead ions is based on the fundamental theory of coordination chemistry. The mechanism is not ion exchange but extractive adsorption of heavy metal salts. However, the marked preferential adsorption of chromate by weakly basic anion exchange can be explained using the traditional theory of ion exchange. A lab-scale study produced positive results for the removal of trace amounts of heavy metal ions from drinking water.

Adsorption behavior of benzenesulfonic acid by novel weakly basic anion exchange resins

Two novel weakly basic anion exchange resins（SZ-1 and SZ-2） were prepared via the reaction of macroporous chloromethylated polystyrene-divinylbenzene（Cl-PS-DVB） beads with dicyclohexylamine and piperidine, respectively. The physicochemical structures of the resulting resins were characterized using Fourier Transform Infrared Spectroscopy and pore size distribution analysis. The adsorption behavior of SZ-1 and SZ-2 for benzenesulfonic acid（BA） was evaluated, and the common commercial weakly basic anion exchanger D301 was also employed for comparison purpose. Adsorption isotherms and influence of solution p H, temperature and coexisting competitive inorganic salts（Na2SO4and Na Cl） on adsorption behavior were investigated and the optimum desorption agent was obtained.Adsorption isotherms of BA were found to be well represented by the Langmuir model.Thermodynamic parameters involving ΔH, ΔG and ΔS were also calculated and the results indicate that adsorption is an exothermic and spontaneous process. Enhanced selectivity of BA sorption over sulfate on the two novel resins was observed by comparison with the commercial anion exchanger D301. The fact that the tested resins loaded with BA can be efficiently regenerated by Na Cl solution indicates the reversible sorption process. From a mechanistic viewpoint, this observation clearly suggests that electrostatic interaction is the predominant adsorption mechanism. Furthermore, results of column tests show that SZ-1possesses a better adsorption property than D301, which reinforces the feasibility of SZ-1for potential industrial application.

Isolation of Uranium by Anionic Exchange Resins

A separation methodology to isolate natural uranium from its radioactive daughters： Th, Ra, Bi, Pb, Pa and Po, was developed using an only one anion exchange resin and varying concentrations of HC1 solutions. Three types of anion exchange resins were tested and the separation process was followed by gamma and alpha spectrometry. Uranium can be quantitatively isolated from its descendants using Dowex IX8 （20-50 mesh） or Amerlite IRA （100 mesh） resins in three steps： using 4 and 8 mol/L-1 HCI and water to recover uranium. The method is easy, quick, and inexpensive.

A STUDY ON THE KINETICS OF EXCHANGE REACTIONS OF W（Ⅵ） OR Mo（Ⅵ） WITHIN MACROPOROUS ANION EXCHANGE RESIN（D290） PHASE

The exchange behaviors of WO_4￣(2-) MoO_4￣(2-), H_2 W_(12) O_(40)￣(6-) and Mo8 O_(26)￣(4-) anions within macrOPorous exchange resin (D290) phases have been studied.The values of diffusion constant (B), inner diffusion coefficient (D), retarted time (td) half - exchange-period (t1/2), and activation energy (△E) were found from the kinetic analyses. A new method to separate W(Ⅵ) and Mo (Ⅵ) from each other was also suggested.

Control strategies for disinfection byproducts by ion exchange resin,nanofiltration and their sequential combination

Disinfection byproducts (DBPs) are emerging pollutants in drinking water with high health risks. Precursor reduction before disinfection is an effective strategy to control the formation of DBPs. In this study, three types of anion exchange resins (AERs) and two types of nanofiltration (NF) membranes were tested for their control effects on DBP precursors, DBPs, and total organic halogen (TOX). The results showed that, for AER adsorption, the removal efficiencies of DBP precursors, DBPs, and TOX increased with the increase of resin dose, and the strong basic macroporous anion exchange resin (M500MB) had the highest removal efficiencies. For NF, the highest removal efficiencies were achieved at an operating pressure of 4 bar, and the membrane (NF90) with a smaller molecular weight cut-off, had a better control efficiency. However, AER adsorption was inefficient in removing dissolved organic carbon (DOC);NF was inefficient in removing Br− resulting in insufficient control of Br-DBPs. Accordingly, a sequential approach of AER (M500MB) adsorption followed by NF (NF90) was developed to enhance the control efficiency of DBPs. Compared with single AER adsorption and single NF, the sequential approach further increased the removal efficiencies of DOC by 19.4%–101.9%, coupled with the high Br− removal efficiency of 92%, and thus improved the reduction of cyclic DBPs and TOX by 3.5%–4.9%, and 2.4%–8.4%, respectively;the sequential approach also reduced the cytotoxicity of the water sample by 66.4%.

Determination of rhenium and osmium by ICP-MS for galena and sphalerite

Digestion with aqua regia in a Carius tube and separation of Re with anion exchange resin is commonly employed for Re–Os dating of molybdenite and pyrite.However, the recovery of Re is extremely low when this routine anion exchange method is applied to galena,causing difficulty in Re–Os dating of galena. In this study,we investigated the mechanism of Re loss during sample preparation and tested a revised procedure for Re–Os dating of galena and sphalerite.

ELUTION OF TUNGSTEN BY SODIUM COMPOUNDS AND ACCELERATION EFFECTS OF COEXISTENT COUNTER IONS IN MIXED ELUANT

The elution of WO ions by NaOH. NaNO3 NaCl and NH4Cl on strong basicanion exchange resins in quaternary ammonium form I and the adsorption properties after elution were studied. In addition, the elution curse, the permeation curveand the exchange capacities of operation were presented. The eluate containingtungsten with high content and excessive eluant of low content were obtained by employing the process of eluting using mixed solution of NaCl and NaOH. It's possible to obtain Na2WO4. 2H2O with high purity by evaporating and crystallizing theeluate. The results of mixed elution showed that the diffusion coefficients of Cl-.OH- and WO ions in solution or exchange agent varied due to the coexistence ofcounter ions and then the exchange velocity of WO→Cl- and WOe→OH- wasaccelerated.

A HYDROGEN BONDING ASSISTED CATALYST SCREENED OUT VIA COMBINATORIAL CHEMISTRY STRATEGY

Possibilities for enhancement of catalytic reaction rate by combining phase transfer catalysis and hydrogen bonding of the catalyst with the substrate and reagent were studied. A phase transfer catalyst library with sixty polystyrene-supported quaternary ammonium salt catalysts was synthesized. The reduction of acetophenone by NaBH, was used as the probing reaction to select out the most active catalyst in the library by using iterative method, which was the gel-type triethanolamine aminating strongly basic anion exchange resin with the crosslinking degree of 2% A hydrogen bonding assisted catalytic mechanism was proposed to explain the high catalytic activity of the catalyst.

Removal of perfluorinated surfactants from wastewater by adsorption and ion exchange--Influence of material properties,sorption mechanism and modeling

Perfluorooctane sulfonate（PFOS） has attracted increasing concern in recent years due to its world-wide distribution, persistence, bioaccumulation and potential toxicity. The influence of sorbent properties on the adsorptive elimination of PFOS from wastewater by activated carbons, polymer adsorbents and anion exchange resins was investigated with regard to their isotherms and kinetics. The batch and column tests were combined with physicochemical characterization methods, e.g., N2 physisorption, mercury porosimetry, infrared spectroscopy, differential scanning calorimetry, titrations, as well as modeling. Sorption kinetics was successfully modelled applying the linear driving force（LDF） approach for surface diffusion after introducing a load dependency of the mass transfer coefficient βs.The big difference in the initial mass transfer coefficient βs,0, when non-functionalized adsorbents and ion-exchange resins are compared, suggests that the presence of functional groups impedes the intraparticle mass transport. The more functional groups a resin possesses and the longer the alkyl moieties are the bigger is the decrease in sorption rate.But the selectivity for PFOS sorption is increasing when the character of the functional groups becomes more hydrophobic. Accordingly, ion exchange and hydrophobic interaction were found to be involved in the sorption processes on resins, while PFOS is only physisorptively bound to activated carbons and polymer adsorbents. In agreement with the different adsorption mechanisms, resins possess higher total sorption capacities than adsorbents. Hence, the latter ones are rendered more effective in PFOS elimination at concentrations in the low μg/L range, due to a less pronounced convex curvature of the sorption isotherm in this concentration range.

Preparation of a novel magnetic resin for effective removal of both natural organic matter and organic micropollutants

A novel, bifunctional, hypercrosslinked, magnetic resin W2 was prepared using divinylbenzene （DVB） and glycidyl methacrylate （GMA） as comonomers in three steps （i.e., suspension polymerization, amination and post-crosslinking reactions）. To evaluate the adsorption of natural organic matter （NOM） and organic micropollutants （OMPs） on the obtained resin W2, two magnetic resins W1 （the precursor of W2 before post-crosslinking） and W0 （the precursor of W1 before amination） were chosen for comparison. The results indicated that W2 would be a promising material for the removal of both NOM and OMPs from aquatic environments.