Electrochemical properties of polyethylene membrane modified with sulfonic and phosphonic acid groups

Ion-exchange membranes modified with sulfonic (-SO₃H) and phosphonic acid (-PO₃H) groups were prepared by radiation-induced grafting of glycidyl methacrylate (GMA) onto polyethylene (PE) films and sub-sequent sulfonation and phosphonation of poly(GMA) graft chains. The surface area, thickness and volume of grafted PE film increased with increasing grafting yield. The specific electrical resistance of PE membrane modified with the -PO₃H and -SO₃H groups decreased with increasing the ion-exchange capacity. The PE membrane modified with -PO₃H group had a lower specific electrical resistance than that of PE membrane modified with -SO₃H group.     

Usefulness of microporous hydrophobic polypropylene membranes after plasma-induced graft polymerization of acrylic acid for high-power nickel-cadmium batteries

Commercial microporous polypropylene (PP) membranes were modified by plasma-induced graft polymerization of acrylic acid (AAc) under UV irradiation. Under optimized conditions obtained membranes are hydrophilic and may be serviceable as separator in nickel-cadmium cell. Electrolytic resistance of modified membranes is evaluated and compared with that of commercial separators: conventional cellophane separation and hydrophilic polypropylene separation (Celgard 3501). This paper reports the maximum power test data for nickel-cadmium cells equipped with different separators. Cells with modified PP membrane show very good high-rate performance.     

Electrochemical modification of cation exchange membrane with polyaniline for improvement in permselectivity

A novel method of modification of cation exchange membrane for improved permselectivity is reported in this paper. Acrylic acid grafted fluorinated ethylene propylene copolymer membrane after sulphonation (FEP-g-AA-SO₃H) was used as the cation exchange membrane for modification. Polyaniline is deposited electrochemically on to the membrane. The deposition of polyaniline starts from the surface of the membrane and growth proceeds inside the membrane. The amount of polyaniline deposited depends upon the polymerization time. The presence of polyaniline is confirmed by FTIR, scanning electron microscopy, X-ray mapping, cyclic voltammetry and ion exchange capacity measurements. The electrodialysis experiments show improved permselectivity for divalent cations.     

低温等离子体引发丙烯酸在PET纳米纤维膜上的接枝聚合

介绍了低温等离子体引发丙烯酸（AA）表面接枝聚合对聚苯二甲酸乙二醇酯（PET）纳米纤维薄膜的改性研究。实验探索了放电时间和放电功率对薄膜润湿性的影响,在真空度60 Pa、AA气体流量3 L/min条件下,放电功率75～150 W范围内,放电时间60 s和放电功率150 W、放电时间30~60 s范围内,处理后薄膜的水接触角均为0°,结果说明了此改性PET纳米纤维膜具有超亲水性。通过扫描电镜、红外和力学性能等测试讨论了接枝处理前后薄膜的形态及性能的变化。实验结果表明气相低温等离子体接枝处理后,薄膜的断裂伸长率和断裂强度有一定的增强。低温等离子体引发AA表面接枝PET纳米纤维薄膜的方法有望成为电纺PET纤维膜表面改性的有效手段,具有积极的应用价值。     

Permeation of single and mixed gases through composite membranes prepared by plasma polymerization of fluorocarbon compounds

The permeations of simple permanent gases and their mixtures through plasma-polymerized composite membranes were studied. Composite membranes were prepared by the plasma polymerization of fluorocarbon monomers such as pentafluorotoluene (PFT) and pentafluoropyridine (PFP) onto porous Celgard. For pure gases, the permeability coefficients were mainly affected by diffusivity rather than solubility. The permeability coefficient decreased as the kinetic molecular diameter of the penetrant molecules increased, and the permeability coefficients were independent of pressure. For mixed gases, the permeability coefficient was not affected by the composition of penetrants for the whole range of composition.     

Thermotreatment and chemical resistance of porous alumina membrane prepared by anodic oxidation

Porous alumina membranes were prepared by anodic oxidation of aluminum in an aqueous solution of oxalic acid. The thermal and chemical stabilities of porous alumina membranes were investigated by thermal analysis and corrosion test. Alumina membranes prepared in oxalic electrolyte had fairly good thermal stability, but they reacted with boiling water to form boehmite, which blocked pores on the surface of the membrane. For acid and alkali resistance, the membranes were estimated to have chemical stability in aqueous acidic and alkaline solution at 1< pH < 12. On the other hand, pore size and its distribution were not changed at the time of thermal treatment. Polycrystalline alumina membrane obtained by thermal treatment for 3 h at 900 ‡C could suppress corrosion reaction and enhance their resistance in acid and alkaline solution.     

Surface modification of heterogeneous cation exchange membrane through simultaneous using polymerization of PAA and multi walled carbon nano tubes

Polyvinylchloride based heterogeneous cation exchange membrane was modified by using in situ polymerization of polyacrylic acid and multi walled carbon nano tubes simultaneously. Spectra analysis confirmed graft polymerization decisively. SEM images illustrated that grafted-PAA/MWCNTs filled the cracks in membrane by simple gel network entanglement. Ion exchange capacity was improved by PAA/MWCNTs grafting in modified membranes. Membrane water content was decreased by PAA grafting and then showed increasing trend by using MWCNTs in modifier solution up to 0.1%wt. Water content was decreased again by more MWCNTs loading ratio. Grafted-PAA membranes showed lower membrane potential, transport number, selectivity and flux compared to pristine membrane in sodium chloride ionic solution. These parameters were decreased more by using MWCNTs up to 0.1%wt in modifier solution and then showed increasing trend by more MWCNTs concentration from 0.1 to 0.3%wt. All mentioned parameters were declined again by more increase in MWCNTs content from 0.3 to 1.0%wt. Results exhibited lower membrane selectivity for the modified membranes compared to pristine ones in bivalent ionic solution. The grafted-PAA/MWCNTs modified membranes also showed lower electrical resistance compared to unmodified ones. Obtained results showed different behavior for permeability in bivalent ionic solution compared to monovalent type.     

氧化-还原引发法合成淀粉接枝丙烯酸高吸水性树脂

目的：研究以过硫酸铵、亚硫酸钠组成的氧化-还原引发剂“一锅法”合成淀粉接枝丙烯酸高吸水性树脂。方法：采用水溶液中引发聚合的方法。结果：在(NH4)2S2O8占0．30％，N，N’-亚甲基双丙烯酰胺占0．15％，中和度78％，引发温度40℃，丙烯酸占32％的条件下合成出有实用价值的高吸水性树脂。结论：“一锅法”简单易行，有工业价值。     

Mechanism and kinetics study on removal of Iron from phosphoric acid by cation exchange resin

Iron element is one of the main impurities in wet-process phosphoric acid and it has a significant impact on the subsequent phosphorus chemical products. This paper studied the feasibility of using Sinco-430 cation exchange resin for iron removal from phosphoric acid. The specific surface area and the total exchange capacity of resin were 8.91 m~2·g~(-1) and 5.18 mmol·g~(-1), respectively. The sorption mechanism was determined by FTIR and XPS and the results indicated that iron was combined with-SO_3 H in resin. The removal process was studied as a function of temperature, H_3 PO_4 content and mass ratio between resin and solution. The unit mass of resin to remove iron was 0.058 g·g~(-1) resin when the operating parameters were T = 50 ℃, H_3 PO_4 content = 27.61 wt%and S/L = 0.1, respectively. Kinetics study demonstrated that pseudo-second-order reaction model fits this study best and the calculated activation energy of overall reaction is 29.10 kJ·mol~(-1). The overall reaction process was mainly controlled by pore diffusion.     

Preferential transport behaviors of ternary system ferric-cupric-nickel ions through cation ion exchange membrane with a complex agent by dialysis

Preferential transport behaviors of metal ions for ternary ions system through a cation exchange membrane were studied in a stirred batch dialyzer. Cu²⁺-Fe³⁺-Ni²⁺ was chosen for the experimental investigation. Oxalic acid, malonic acid, citric acid, and ethylenediaminetetraacetic acid were employed as a complex agent used in the investigated solution in order to increase the discrepancy between transport fluxes of metal ions. The experimental results show that the order of effective complex agents is malonic acid > citric acid > oxalic acid > ethylenediaminetetraacetic acid. The preferential transport behavior of metal ions depends on the stoichiometric ratio of the complex agent to metal ions and the pH value of the feed solution, but is independent of the concentration of counterion in the stripping phase. The optimal results of J_NiJ_Cu: J_Fe can be attained about 30 : 10 : 1.     

Synthesis and characterization of graft copolymers with poly(epichlorohydrin-co-ethylene oxide) as backbone by combination of ring-opening polymerization with living anionic polymerization

Series of graft copolymers with [Poly(epichlorohydrin-co-ethylene oxide)] [Poly(ECH-co-EO)] as backbone and polystyrene (PS), poly(isoprene) (PI) or their block copolymers as side chains were successfully synthesized by combination of ring-opening polymerization (ROP) with living anionic polymerization. The Poly(ECH-co-EO) with high molecular weight (M_n = 3.3 × 10⁴ g/mol) and low polydispersity index (PDI = 1.34) was firstly synthesized by ring-ROP using ethylene glycol potassium as initiator and triisobutylaluminium (i-Bu₃Al) as activator. Subsequently, by “grafting onto” strategy, the graft copolymers Poly(ECH-co-EO)-g-PI, Poly(ECH-co-EO)-g-PS and Poly(ECH-co-EO)-g-(PI-b-PS) were obtained using the coupling reaction between living PI⁻Li⁺, PS⁻Li⁺ or PS-b-PI⁻Li⁺ species capped with or without 1,1-diphenylethylene (DPE) agent and chloromethyl groups on poly(ECH-co-EO). By model experiment, the addition of DPE agent was confirmed to have an important effect on the grafting efficiency at room temperature. Finally, the target graft copolymers and intermediates were characterized by SEC, ¹H NMR, MALLS and FTIR in detail, and thermal behaviours of the graft copolymers were also investigated by DSC measurement.     

Preparation and characterization of a composite nanofiltration membrane from cyclen and trimesoyl chloride prepared by interfacial polymerization

A novel nanofiltration (NF) membrane was prepared with cyclen and trimesoyl chloride by interfacial polymerization on a poly(ether sulfone) ultrafiltration membrane with a molecular weight cutoff of 50,000 Da. The effects of the reaction time, monomer concentration, and heat‐treatment temperature are discussed. The physicochemical properties and morphology of the prepared NF membrane were characterized by Fourier transform infrared spectroscopy–attenuated total reflectance, scanning electron microscopy, energy‐dispersive spectrometry, and atomic force microscopy. The NF performances were evaluated with solutions of Na₂SO₄, MgSO₄, Mg(NO₃)₂, and NaCl. The salt‐rejection order of the prepared NF membrane was as follows: Na₂SO₄ > MgSO₄ > Mg(NO₃)₂ > NaCl. The resulting rejection of Na₂SO₄ and PEG600 (polyethylene glycol with the average molecular weight of 600) were more than 90%, whereas that of NaCl was approximately 10%. After the addition of silica sol in the aqueous phase (silica sol concentration = 0.1% w/v), the salt rejection of the membrane changed slightly. However, the water flux was from 24.2 L·m^?2·h^?1 (25°C, 0.6 MPa) up to 38.9 L·m^?2·h^?1 (25°C, 0.6 MPa), and the resulting membrane exhibited excellent hydrophilicity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42345.     

Performance enhancement of dye-sensitized solar cells using nanostructural TiO2 films prepared by a graft polymerization and sol–gel process

Nanostructural TiO₂ films with large surface areas were prepared by the combined process of graft polymerization and sol–gel for use in dye-sensitized solar cells (DSSCs). The surface of the TiO₂ nanoparticles was first graft polymerized with photodegradable poly(methyl methacrylate) (PMMA) via atom transfer radical polymerization (ATRP), after which the particles were deposited onto a conducting glass. The PMMA chains were removed from the TiO₂ films by UV irradiation to generate secondary pores, into which titanium isopropoxide (TTIP) was infiltrated. The TTIP was then converted into small TiO₂ particles by calcination at 450 °C, as characterized by energy-filtering transmission electron microscopy (EF-TEM) and field emission scanning electron microscopy (FE-SEM). The nanostructural TiO₂ films were used as a photoelectrode in solid-state DSSCs; the energy conversion efficiency was 5.1% at 100 mW/cm², which was higher than the values achieved by the pristine TiO₂ (3.8%) and nongrafted TiO₂/TTIP photoelectrodes (3.3%). This performance enhancement is primarily due to the increased surface area and pore volume of TiO₂ films, as revealed by the N₂ adsorption–desorption isotherm.     

Preparation and characterization of proton exchange membrane based on polyphosphoric acid modified by PVDF‐HFP

A polyphosphoric acid functionalized proton exchange membrane (PEM) was prepared by a ring opening reaction using the epoxycyclohexylethyltrimethoxysilane (EHTMS) and amino trimethylene phosphonic acid (ATMP) as raw materials and was modified by poly(vinylidene fluoride)–hexafluoro propylene (PVDF‐HFP). The structure of the membranes was characterized by Fourier transform infrared and scanning electron microscopy. The X‐ray photoelectron spectroscopy explores the content of the elements in the membrane related to the ion exchange capacity value. The membranes’ properties including water uptake, swelling ratio, proton conductivity, and hydrolysis stability were studied. Performance tests show that when ATMP/EHTMS = 1/5, conductivity of the PVDF‐HFP modified PEMs increased from 0.83 × 10^?4 S cm^?1 at 20 °C to 9.53 × 10^?3 S cm^?1 at 160 °C, the swelling ratio of membranes decreased from 2.71% to 2.13%. The results indicate that the introduction of F atoms is beneficial to increase the proton conductivity and the dimensional stability. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46737.     

Evaluation of compacted urea fertilizers prepared with acid and non-acid producing chemical additives in three soils varying in pH and cation exchange capacity; II. Yield and N use efficiency by rice

With a view to evaluate the effect of different chemical additives on the efficacy of urea, a green house study was conducted with wet season rice (Oryza sativa L.) as test crop. The results showed that compaction of phosphogypsum (PG), diammonium phosphate (DAP), ZnSO₄, NH₄Cl or KCl with urea increased the rice yield and N use efficiency as compared to that obtained with straight urea. A significant positive correlation between potential N loss (measured by soluble N in floodwater) and NH₃ volatilization (measured by forced air draft system) was observed. The results clearly indicate that N use efficiency can be increased through suitable modification of urea by compacting it with acid and non-acid producing fertilizers such as NH₄Cl, KCl, ZnSO₄ and DAP or industrial byproduct like phosphogypsum.