Hybrid Cation Exchange Research Articles

Synthesis and Characterization of Zirconium-Resorcinol Phosphate; A New Hybrid Cation Exchanger and Dye Adsorbent for Water Treatment

Synthesis and characterization of a new hybrid ion exchange material Zirconiumresorcinol Phosphate (ZrRP) is reported in this study. Synthetic conditions such as reactant concentrations and mixing volume ratio were varied to optimize the ion exchange properties of this material. The material has Na+ ion exchange capacity equal to 1.7 meq/g (dry). X-ray diffraction spectra suggest that it is amorphous in nature. This ion-exchanger was also characterization by SEM, IR and TGA-DTG. Various studies such as determination of ion exchange capacity, elution behaviour and pH titration has been performed for different metal ions such as K+, Ca2+, Sr2+, Mg2+, Ni2+, Cd2+. This material has potential application for removal of these ions from the aqueous systems. Effect of anionic (SDS) and nonionic (TX-100) surfactants has also been studied on the adsorption behavior of ZrRP. The material has been found to be selective for Mg2+and Cd2+. We also found that the material showed remarkable adsorption behavior towards some dyes like malachite green and methylene blue.

A novel selective hybrid cation exchanger for low-concentration ammonia nitrogen removal from natural water and secondary wastewater

Recently, the discharge of ammonia nitrogen from wastewater treatment plants into freshwater bodies has led to serious problems of eutrophication. Many new tertiary treatment systems have been developed to address this problem. This study introduces a novel ammonium-selective adsorbent (Cu-HCIX), a polymer-supported sorbent loaded with CuO microparticles within cation exchanger. Batch static adsorption tests were conducted to evaluate sorption capability. The static adsorption data agreed well with pseudo-second-order model and Langmuir model. Removal of low-concentration ammonium (1.0–10mgNL−1) was also investigated in fixed-bed column runs. The results indicate that both the adsorption capacity and selectivity of the Cu-HCIX were enhanced after dispersing CuO microparticles within the cation exchanger. Dynamic breakthrough data were observed to follow the Thomas model. The separation factors of Cu-HCIX, representation selectivity, for ammonium over other competitive cations, were approximately five times greater than the original exchanger. The high selectivity of Cu-HCIX for ammonium results from the introduction of dispersed CuO microparticles. The exhausted Cu-HCIX can be repeatedly utilized after regeneration by NaOH solution. Cu-HCIX shows considerable potential for removal of ammonium from surface freshwaters and secondary wastewater.

Integrated strong cation-exchange hybrid monolith coupled with capillary zone electrophoresis and simultaneous dynamic pH junction for large-volume proteomic analysis by mass spectrometry

A sulfonate–silica hybrid strong cation-exchange (SCX) monolith was synthesized at the proximal end of a capillary zone electrophoresis column and used for on-line solid-phase extraction (SPE) sample preconcentration. Sample was prepared in an acidic buffer and deposited onto the SCX-SPE monolith and eluted using a basic buffer. Electrophoresis was performed in an acidic buffer. This combination of buffers results in formation of a dynamic pH junction, which allows use of relatively large elution buffer volume while maintaining peak efficiency and resolution. All experiments were performed with a 50µm ID capillary, a 1cm long SCX-SPE monolith, a 60cm long separation capillary, and a electrokinetically pumped nanospray interface. The volume of the capillary is 1.1µL. By loading 21µL of a 1×10−7M angiotensin II solution, an enrichment factor of 3000 compared to standard electrokinetic injection was achieved on this platform while retaining efficient electrophoretic performance (N=44,000 plates). The loading capacity of the sulfonate SCX hybrid monolith was determined to be ~15pmol by frontal analysis with 10−5M angiotensin II. The system was also applied to the analysis of a 10−4mg/mL bovine serum albumin tryptic digest; the protein coverage was 12% and 11 peptides were identified. Finally, by loading 5.5µL of a 10−3mg/mL E. coli digest, 109 proteins and 271 peptides were identified in a 20min separation; the median separation efficiency generated by these peptides was 25,000 theoretical plates.

Synthesis, characterization and photolytic degradation activity of poly-o-toluidine–thorium(IV)molybdophosphate cation exchanger: Analytical application in metal ion treatment

A new hybrid cation exchanger poly-o-toluidine–thorium(IV)molybdophosphate (POT-TMP) has been synthesized using sol–gel method by the incorporation of inorganic precipitates of thorium(IV)molybdophosphate into the matrices of organic poly-o-toluidine. The product formation was optimized by varying the synthesis conditions at pH of 1.0. Ion exchange capacity, pH titration, effect of calcinations, chemical stability and distribution behavior of the exchanger were also studied. Activation energy calculated from Arrhenius plot using Broido equation was found to be 7.94KJmol−1 at 50°C. The distribution coefficient values of metal ions determined in different solvent media show the selectivity of the hybrid exchanger for Hg2+ and Pb2+ ions. The analytically important separations of metal ions have been successfully achieved using columns packed with this exchanger. The practical utility of the material was shown by qualitative as well as quantitative determination of Pb2+ and Hg2+ in the synthetic mixtures and industrial effluents. The limit of detection (LOD) evaluated for Pb2+ and Hg2+ was found to be 1.53 and 0.72μgL−1 respectively. The photocatalytic degradation of Congo red dye using the composite under natural sunlight shows that about 74% of Congo red dye was degraded within 8h of photo irradiation.

Development of bivalent cation selective ion exchange membranes by varying molecular weight of polyaniline

A novel hybrid cation exchange membrane (CEM) composed of a blend of polyvinylidene fluoride (PVDF), sulfonated PVDF(S-PVDF) and doped polyaniline (PANi) as additive was prepared. PANi was synthesized with different molecular weights to optimize the performance of membranes for water softening. The membrane properties such as thermal behavior, membrane structure, membrane morphology and miscibility, ion exchange capacity (IEC), permselectivity, water uptake, contact angle, cell resistivity, current efficiency and electrodialysis (ED) performance were evaluated. Addition of doped PANi increased the bivalent selectivity of the cation exchange membrane. The highest bivalent selectivity and best removal of Ca2+ and Mg2+ were achieved for PANi with Mw≈45,000gmol−1 and polydispersity index (PDI)≈3.2.

Selective Co(ii) removal from aqueous media by immobilizing silver nanoparticles within a polymer-matrix through a formaldehyde cross linking agent

A novel hybrid cation exchange resin was developed by encapsulating AgNPs within a macroporous phenol–formaldehyde cation exchanger for the removal of cobalt from aqueous solution.

Transport Properties of Novel Hybrid Cation-Exchange Membranes on the Base of MF-4SC and Halloysite Nanotubes

The diffusion permeability through new hybrid materials based on a Nafion-type membrane (MF- 4SC) and nanotubes of halloysite is investigated using the Nernst-Planck approach. A method of quantitative evaluation of physicochemical parameters (averaged and individual diffusion coefficients and averaged distribution coefficients of ion pairs in the membrane) of system “electrolyte solution—ion-exchange membrane—water”, which was proposed earlier, is further developed. The parameters of hybrid membranes on the base of MF-4SC and nanotubes of halloysite (5% wt and 8% wt) are obtained from experimental data on diffusion permeability of NaCl solutions using theoretical calculations. New model of three-layer membrane system can be used for refining calculated results with taking into account both diffusive layers. It is shown that adding of halloysite nanotubes into the membrane volume noticeably affects exchange capacity as well as structural and transport characteristics of original perfluorinated membranes. Hybrid membranes on the base of MF-4SC and halloysite nanotubes can be used in fuel cells and catalysis.

The effects of multi-functional groups from PVA and ternary multisilicon copolymer on diffusion dialysis

Ternary multisilicon copolymers are prepared from copolymerization of acrylic acid, sodium styrene sulfonate and γ-methacryloxypropyl trimethoxy silane, from which functional groups of –Si(OCH3)3, –COOH and –SO3Na are obtained respectively. The acidic –COOH groups may induce gel during copolymerization, and thus sufficient solvent needs to be used. The –Si(OCH3)3 groups can crosslink with polyvinyl alcohol (PVA) to yield cation exchange hybrid membranes.The membranes have the ion exchange capacity of 1.01–2.26mmol/g, water uptake of 39.1–59.7%, swelling degrees of 108–339% in 65°C water after 192h, and swelling degrees of 254–344% in 65°C alkaline solution after 60h. Membrane with proper ratios of multi-functional groups can sorb 1.4mol/L NaOH in 1.0mol/L NaOH solution. The membranes are used in diffusion dialysis (DD) process for alkali recovery from NaOH/Na2WO4 solution. The dialysis coefficients of NaOH (UOH) are in the range of 0.013–0.021m/h at room temperature, with the separation factors of 15–23. The high UOH values indicate the superiority of multi-functional groups. The –OH, –COOH and –SO3Na groups from PVA and multisilicon copolymer chains may have coupling effects on the transport of both Na+ and OH− ions.

A biopolymer-based hybrid cation exchanger pectin cerium(IV) iodate: synthesis, characterization, and analytical applications

Pectin cerium(IV) iodate (PcCeI) and cerium(IV) iodate (CeI) cation ion exchange materials were synthesized via sol–gel methods. The materials were characterized by using Fourier transform infrared spectroscopy, X-ray diffractometer, thermogravimetric analysis, and scanning electron microscopy. The ion exchange capacity (IEC), thermal stability, distribution coefficient (Kd), and pH titrations were investigated to recognize the cation exchange behavior of the materials. The IEC of pectin-cerium(IV) iodate (PcCeI and cerium(IV) iodate CeI were reported as 1.80 meq/g and 0.92 meq/g, respectively. The higher distribution coefficient values of 250.01 and 219.14 mg/L confirmed the selectivity of pectin-cerium(IV) iodate hybrid ion exchanger for As3+ and Zn2+. The antibacterial activity of synthesized ion exchangers was explored for E. coli bacteria and observed relatively higher for PcCeI as compared to CeI.

Surface modification of composite ion exchange membranes by polyaniline

The aim of this work is to develop new selective cation exchange membranes (CEMs) from bivalent to monovalent selectivity by surface functional groups. So, a novel hybrid cation exchange membrane was prepared by polymerization of polyaniline on a composite membrane, made of polyvinylidene fluoride (PVDF) and sulfonated PVDF (S-PVDF). Polyaniline was doped with different doping agents and their effect on total salt extraction and selectivity of bivalent to monovalent cations was evaluated. The chemical and morphological properties of hybrid membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Ion exchange capacity (IEC), transport number, ion conductivity and water uptake decreased after surface polymerization. Composite membrane has a good selectivity (∼2) for bivalent and excellent removal of both cations. The hybrid membrane, doped with pTSA has a very high selectivity for monovalent ions (∼7.1) and a high removal of monovalent ions.

Preparation of cation-exchange hybrid membranes with multi-functional groups and their performance on alkali recovery

Cation-exchange hybrid membranes have been prepared via the blending of sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) with poly(vinyl alcohol) (PVA), which is cross-linked with multisilicon copolymer of poly(acrylic acid-co-γ-methacryloxypropyl trimethoxy silane) (poly(AA-co-γ-MPS)). The SPPO phase, PVA phase, and multisilicon copolymer can provide the membranes with functional groups of –SO3Na, –OH and –COOH, respectively. Hence, multi-functional groups are formed within the hybrid membranes. The hybrid membranes have a short-term thermal stability of 234–260°C, tensile strength (TS) of 12–13 MPa, and elongation at break of 27–49%. Membrane stability in alkaline solution is much affected by the content of SPPO. The membranes are potentially applied in diffusion dialysis (DD) for alkali recovery (NaOH/Na2WO4). The dialysis coefficients of NaOH (UOH) are in the range of 0.0075–0.032 m/h, which are higher than those of commercial membranes and reported membranes. The separation factor can reach up to 21.2 at 25°C for the membrane containing 10 wt% SPPO. Meanwhile, the membrane shows relative stability during long-term DD process. Hence, the multi-functional groups are effective for the diffusion dialysis process.

Synthesis, characterization and electrical conductivity of Polyaniline-Sn(IV)tungstophosphate hybrid cation exchanger: Analytical application for removal of heavy metal ions from wastewater

A novel Polyaniline based hybrid cation exchange material has been synthesized by the simple sol–gel method. FTIR, TGA/DTA, XRD, SEM, and TEM have been done for characterization of the material. The preliminary study of the physicochemical properties (ion exchange capacity, pH titrations, effect of concentration and effect of temperatures etc.) was also carried out. The synthesized material has been favored by reproducible and granulometric nature. The material was found to be fairly stable in dilute solution of common acids, bases and most of the organic solvents. On the basis of distribution coefficients (Kd values), the material has been found suitable for some important quantitative binary separations (e.g. Cd2+–Pb2+, Zn2+–Pb2+, Er3+–Pb2+, Zn2+–Al3+, Cu2+–Al3+) on its columns. The limits of detection and quantification for Pb2+ ions were found to be 0.54μgL−1 and 1.8μgL−1 respectively. The electrical conductivity of the material was found to be in semiconductor region (10−4 to 10−3Scm−1). Based on experimental observations it was found to be suitable for the separation and determination of metal pollutants in water samples. The practical utility of the material has been established by the removal of Pb2+ ion from industrial wastewater.

Selective Sorption of Chromium from Tannery Wastes by Hybrid Cation Exchange Resin

Selective Sorption of Chromium from Tannery Wastes by Hybrid Cation Exchange Resin

Polyaniline modified organic–inorganic hybrid cation-exchange membranes for the separation of monovalent and multivalent ions

Organic–inorganic hybrid cation-exchange membranes (CEMs) were chemically modified by in situ polymerization of aniline in acidic medium using FeCl3 as an oxidizing agent. The presence of polyaniline (PANI) on the surface and inside membrane matrix was confirmed from PANI coating density and scanning electron microscopy. Membranes were characterized in details by estimating water uptake, ion-exchange capacity, fixed ion concentration, counter-ion transport number and membrane conductivity. The values of Na+ transport number across the membranes were unchanged, whereas the values of Zn2+ and Al3+ transport number were decreased after modification with PANI. The dense nature of PANI modified membranes was evaluated through an electro-osmotic study. The selectivity of PANI modified membranes towards Na+, Zn2+ and Al3+ ions was investigated by electrodialysis using single or binary mixture of electrolyte solutions (Na+/Zn2+ and Na+/Al3+). The current and separation efficiencies of CEM and PANI modified membrane (CEM/PANI-120) for Na+, Zn2+ and Al3+ were determined at varied applied current densities and electrolyte solution feed concentrations. The obtained values of current and separation efficiencies for CEM/PANI-120 membrane suggested the suitability of PANI modified membrane in electrodialysis selective separation of Na+ from the binary mixture (Na+/Zn2+ and Na+/Al3+) in aqueous solutions.

Polyelectrolyte complex/PVA membranes for diffusion dialysis

Polyelectrolyte complexes (PECs)/polyvinyl alcohol (PVA) membranes are prepared from PVA, anion exchange and cation exchange multisilicon copolymers, which contain plenty of functional groups of OH, N+(CH3)3/Si(OCH3)3, and SO3Na/Si(OCH3)3, respectively. The OH and Si(OCH3)3 groups can undertake sol–gel reaction to form crosslinking structure, while the N+(CH3)3 and SO3Na groups can be combined through electrostatic interaction.The PECs/PVA membranes exhibit improved thermal stability, swelling resistance and flexibility as compared with single anion or cation exchange hybrid membranes. The PECs/PVA membranes have the water uptakes (WR) of 25.3–70.4%, initial decomposition temperatures (IDTs) of 246–285°C, tensile strength of 23.1–33.8MPa, and elongation at break of 3.5–13.1%. The membranes can be potentially applied for both acid and alkali recovery through diffusion dialysis (DD) process. The separation factor (S) for HCl/FeCl2 mixture can reach up to 89.9, which is about five times higher than that of commercial DF-120 membrane (18.5 at 25°C). The dialysis coefficients of NaOH (UOH) are in the range of 0.014–0.019m/h, around 7–9 times higher than the value of commercial SPPO membrane (0.002m/h at 25°C). The membranes also show potential usefulness for industrial acidic and alkali wastes treatment.

Synthesis and characterization of polyacrylamide zirconium (IV) iodate ion-exchanger: Its application for selective removal of lead (II) from wastewater

Polyacrylamide zirconium (IV) iodate was synthesized using the sol–gel technique. The synthesis conditions such as reactant concentrations and temperature were changed to optimize the ion exchange properties of the hybrid organic–inorganic ion exchange material. Zirconium oxychloride (0.1M) was added to 0.1M potassium iodate in the presence of 0.4M acrylamide and heated at 70°C for 6h to yield the polyacrylamide zirconium (IV) iodate with maximum capacity. The ion exchange capacity was found to be 3.27meq/g for Pb(II). The hybrid material has been characterized on the basis of chemical composition FTIR, XRD, TGA-DTA, SEM and EDX studies. Sorption studies showed that the hybrid cation exchanger has a high selectivity to Pb(II) in comparison to other metal ions. Its selectivity was evaluated by performing some important binary separations like Hg(II)–Pb(II), Cu(II)–Pb(II), Ni(II)–Pb(II), Fe(III)–Pb(II) and Cd(II)–Pb(II). In addition, the selective separation of Pb(II) was also achieved from a synthetic mixture containing a large number of metal ions with a recovery of ∼98.5%. The proposed method was successfully applied for the selective removal of Pb(II) from wastewater samples.

Preparation of a Hybrid Cation-Exchange Monolith and Its Application for the Separation of Proteins by High Performance Liquid Chromatography

A hybrid cation-exchange monolith for high performance liquid chromatography (HPLC) was prepared by a one-pot synthesis with reverse-atom transfer radical polymerization, in which sodium bisulfite was used as the inorganic material, methyl methacrylate was used as organic material, 2, 2'-Azobisisobutyronitrile as initiator, and ferric trichloride as the inorganic catalyst. Moreover, sodium bisulfite was used to provide the sulfonic group. The conditions of polymerization were optimized. The chemical groups of the monolith were assayed by Fourier transform infrared spectroscopy; the morphology of monolithic material was investigated by scanning electron microscopy; the pore size distribution was determined by a mercury porosimeter; and the mechanical stability and permeability of the monolith were investigated by the back-pressure drop at several linear velocities. Finally, the monolith was used to separate human serum albumin from human plasma in conjunction with HPLC in 5 min, and the influences of buffer concentration and pH value on the elution of human serum albumin were investigated. In addition, the monolith was applied to separate lysozyme from egg whites in a short time (4 min) and separate a mixture of aromatic compounds.

Separations of lanthanides and actinides using novel hybrid ion exchange materials, M(IV) phosphonates

Zirconium diethylene triamine pentamethylene phosphonate and titanium diethylene triamine pentamethylene phosphonate, novel hybrid cation exchange materials of the class of tetravalent metal acid salts, synthesized by sol-gel method has been characterized by spectroscopy and thermal analysis. Distribution coefficient and breakthrough capacity for La3+, Ce3+, Pr3+, Nd3+, Sm3+ (lanthanides) and Th4+, UO22+ (actinides) have been studied. Based on the differential affinity/selectivity and elution behavior of various metal ions, a few binary and ternary metal ion separations have been carried out.

A simple and green preparation of PVA-based cation exchange hybrid membranes for alkali recovery

Here, a novel and green route for preparing cation exchange hybrid membranes is presented via polyvinyl alcohol (PVA) and 3-trihydroxysilyl-1-propanesulfonic acid (THOPS), during which aqueous media instead of organic solvents is used and sulfonation process is avoided. The resulting hybrid membranes have the water uptake (WR) of 38–86%, ion exchange capacities (IECs) of 0.70–1.56mmol/g, initial decomposition temperature (IDT) of 224–231°C, tensile strength (TS) of 13.3–40.7MPa, and favorable elongation at break (Eb) of 177–571%. The linear expansion ratio (LER) is in the range of 15–25% in water, while in the range of 18–27% in 1.0M alkali solution. Diffusion dialysis (DD) of NaOH/Na2WO4 system shows that the dialysis coefficients of NaOH (UOH) are in the range of 0.011–0.022m/h, with the separation factors (S) of 11.6–20.6. Consequently, apart from endowing the resulting hybrid membranes with desirable DD performances, the method employed herein is simple and environment-friendly particularly due to the avoidance of organic solvents and hazardous sulfonation agents.

PVA-based cation exchange hybrid membranes with multifunctional groups prepared from ternary multisilicon copolymer

Multisilicon copolymers are put forward as new types of crosslinking agents for preparing ion exchange hybrid membranes. Ternary multisilicon copolymer is prepared from copolymerization of maleic anhydride (MA), sodium styrene sulfonate (SSS) and γ-methacryloxypropyl trimethoxy silane (γ-MPS). The obtained copolymer is then crosslinked with polyvinyl alcohol (PVA) to yield cation exchange hybrid membranes. The membranes contain multifunctional groups including SO3Na, COOH and SiOH from the multisilicon copolymer and COH from PVA, which can form crosslinking structure through SiOSi, SiOC and (CO)OC bonding.The membranes have the tensile strength (TS) of 25.6–32.1MPa and elongation at break (Eb) of 68–161%. The swelling resistance at room temperature or 65°C increases with the dosage of multisilicon copolymer. The membranes are used in diffusion dialysis (DD) process for potential application in alkali recovery. The dialysis coefficients of OH− (UOH) are in the range of 0.011–0.019m/h at 20°C and 0.021–0.031m/h at 40°C, higher than those of commercial sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) membrane (0.002m/h at 25°C) or other PVA-based hybrid membranes. The DD performances cannot be well explained by the ion transport mechanism based on “three phase” membrane structure, or by the change of water uptake (WR), ion exchange capacity (IEC) and fixed group concentration (CR). The uniqueness of the membrane structure, as well as the presence of multifunctional groups has to be taken into account, which gives some insight as to future DD membrane design objectives.