Papers by Keyword: Bipolar Membrane

Abstract: The porous nanostructured hydroxyapatite (HA) has the high specific surface area and loading capacity that is useful for enhancing bioactivity, sinterability, densification, and the capacity for loading the drug, protein, heavy metals, etc. For the first time, the bipolar membrane in electrochemical method was developed for the synthesis of hydroxyapatite nanosheet-assembled porous structures. The bipolar membrane was installed in the electrolysis cell to separate the cell into two chambers. The bipolar membrane prevented the OH^- ions to move away from the cathode chamber and the H+ ions to go to the cathode chamber. In this condition, HA was formed in the cathode chamber while the other calcium phosphate was formed in the anode chamber. The pH increase of solution rapidly leads to more effective the formation of the nanostructured HA. The higher the electrolysis time and the current density the greater the tendency of nanostructured HA formation. The mechanism of HA hydroxyapatite nanosheet-assembled porous structures formation includes the agglomeration formation of the spherical-like particles, the formation of agglomeration nanosheet structures, and the formation of HA hydroxyapatite nanosheet-assembled porous structures.

Abstract: The polyacrylonitrile (PAN)-iron octocarboxyphthalocyanine (FePc(COOH)₈) nanofibers were prepared using electrospinning technique and introduced into the interlayer of a carboxymethyl cellulose (CMC)-polyvinyl alcohol (PVA)/chitosan (CS)-polyvinyl alcohol bipolar membrane (BPM), which was characterized using SEM, contact angle measurement, current-voltage characteristics, AC impedance spectroscopy and so on. The experimental results showed that after modification by PAN-FePc(COOH)₈ nanofibers, the membrane impedance of the BPM and its cell voltage were decreased. That indicated that the water splitting efficiency in the interlayer of the BPM was increased. Then the prepared CMC-PVA/PAN-FePc(COOH)₈/CS-PVA BPM was used in the electro-oxidized preparation of dialdehydle starch (DAS). The experimental results indicated that a current density of 20mA·cm^-2 was suitable to obtain high current efficiency. When the electrolysis time was 3h at a current density of 20 mA·cm^-2 , the current efficiency of the CMC-PVA/PAN-FePc(COOH)₈/CS-PVA BPM-equipped cell was as high as 67%.

Abstract: Carboxymethyl cellulose (CMC)-polyvinyl alcohol (PVA) and chitosan (CS)-polyvinyl alcohol were cross-linked by Fe³⁺ and glutaraldehyde respectively to prepare cation exchange layer and anion exchange layer, and polyvinyl alcohol-sodium alginate (SA)-metal octocarboxyphthalocyanine (MePc (COOH)₈, a kind of water splitting catalyst, here, Me stands for Fe³⁺ or Co²⁺) nanofibers were prepared by electrospinning technique and introduced into the interlayer to obtain the CMC-PVA/PVA-SA-MePc (COOH)₈/CS-PVA bipolar membrane (BPM). The experimental results showed that compared with the BPM without the PVA-SA-MePc (COOH)₈ interlayer, the water splitting efficiency at the interlayer of the CMC-PVA/PVA-SA-MePc (COOH)₈/ CS-PVA BPM was obviously increased, and its membrane impedance decreased. When the concentration of FePc (COOH)₈ in the PVA-SA-FePc (COOH)₈ nanofibers was 3.0%, the trans-membrane voltage drop (IR drop) of the CMC-PVA/PVA-SA-FePc (COOH)8/CS-PVA BPM was as low as 0.6V at a high current density of 90 mA/cm².

Abstract: Polyvinyl Alcohol (PVA) was blent with sodium alginate (SA) and chitosan (CS) respectively in order to enhance flexibility and compatibility of bipolar membrane(BPM). The PVA-mSA/mCS BPM was prepared by a paste method. The PVA/ SA and the PVA / CS was cross-linked by inorganic nano-materials and glutaraldehyde(GA), respectively. The SEM photographs showed the PVA-ZnO-SA/mCS BPM was consists of anion layer and cation layer. The thickness of the BPM was 121μm, the interface of BPM was 5μm. The Electronic spectrum (EDS) indicated that ZnO well-distributed in cation layer. The J-V curve and the AC impedances of PVA-ZnO-SA/mCS BPM showed lower working voltage and smaller membrane impedance. The contact Angle of PVA-ZnO-SA/mCS dropped down from the original 101.01° to 32.65°. Compared of TG curves of the BPMs modified by nano-Fe3O4, nano-TiO2 and nano-ZnO, the surface of the PVA-ZnO-SA/mCS BPM exhibited stronger hydrophilic. The dopping nano-ZnO improved the hydrophilic property, thermal stability and mechanical properties of the PVA-ZnO-SA/mCS.

Abstract: A sandwich-type bipolar membrane (BPM) was prepared by a paste method, consisted of an anionic layer, a cationic layer and a catalytic intermediate layer. Carboxymethylcellulose (CMC) and chitosan (CS) were modified by Fe3+ and glutaraldehyde respectively to prepare the mCMC/mCS BPM. Semiconductor photocatalyst combined with photosensitizes was applied to improve the water dissociation at the intermediate layer of the bipolar membrane, using nanometer-sized titanium dioxide (TiO2) as a photocatalyst and anthraquinone (Anth) as a photosensitize. The impedance of bipolar membrane and the performance of hydrolysis influenced by the composite catalytic center were studied. The sandwich-type BPM exhibited several good properties, such as higher efficiency for the water splitting at the intermediate layer, protons and hydroxyl ions permeabilities, higher operational current density as well as lower impedance and potential drop. Under the UV illumination, the corresponding voltage reached as low as 5.0V when the operational current density was 125mA/cm2.

Abstract: P-ferrocene-SA/acetylferrocene-CS Bipolar Membrane (BPM) was prepared with phosphorylated agent as the cation exchange layer, and chitosan (CS) modified with acetylferrocene as the anion exchange layer. Zinc/Nickel alloy layer was placed on the surface of cation exchange layer to realize zero polar distance in the cathode chamber. The 2, 3, 5, 6-tetrachlopyridine (2,3,5,6-TCP) was electro-synthesized by reducing of pentachloropyridine(PCP). At the current density of 30mA·cm^-2, the current efficiency was 70.1% and the yield of 2, 3, 5, 6-TCP was up to 96%. Compared with the traditional method, the electro-generation technology greatly eliminated the environmental pollution.

Abstract: Based on the actual conditions during industrial production, this paper proposes an improvement method and solution to the typical grinding process model and derives a mathematical model of grinding process that’s suitable for industrial production. Sampling analysis and laboratory experiments of the production process were conducted, the derived model was tested, and the results show that particle size distribution curve obtained from the improved model is similar to the actual product, which means that the improved model can be applied to simulate industrial grinding process.

Abstract: Electrodeionization(EDI) is an electro-membrane process with high efficiency for deep desalinating, where water dissociation mechanism occurring on the surface of ion exchange membranes and resins typically exsits and acts. But when used to treat heavy metal-containing solutions such as effluents from the electronic industry, the EDI will suffer from metal-hydroxides precipitation which would destroy the separation process irreversible. With the primary aim to solve that problem, an electrodeionization process coupled with bipolar membrane (BMEDI) was developed together with a preacidification method. The effects of separating and concentrating heavy metal ions by the BMEDI were studied with NiSO₄ solution containing 24 mg×L^-1 Ni²⁺ ions. The results suggested that, the nickel-concentration in the dilute products were both below the analysis limit at constant current densities of 40 mA·cm^-2 and 10 mA·cm^-2, while a concentration factor of 31 was achieved at 40 mA·cm^-2. In addition, no Ni(OH)₂ precipitation was found in all the compartments throughout the experiments, which provide a guarantee of good stability for long-time operation.

Abstract: The mCMC/TiO₂-Oxine/mCS bipolar membrane (BPM) was prepared by carboxymethyl cellulose (CMC) as an anodic layer and chitosan (CS) as a cathodic layer modified by Cr³⁺ and glutaraldehyde as linking reagents, respectively. The Nano-TiO₂ modified with the photosensitizer oxine was taken as a photocatalytic interlayer to enhance the water splitting in the interlayer of the BPM. The mCMC/TiO₂-Oxine/mCS BPM shows a sandwich composition, and exhibited an excellent hydrophilic performance, lower impedance and working voltage. When the working current density is as high as 120 mA • cm^-2, the working voltage is as low as 5.0 V with UV irradiation.

Abstract: The hybrid SBS-g-(DMAEMA-SiO2)/SBS-g-(AA-StSO3Na-SiO2) bipolar membrane, SBS BPM was prepared by SBS (styrene-butadiene-styrene triblock copolymer) grafted with acrylic acid (AA), sodium sulfonic styene(StSO3Na) through free radical grafting reaction, then the grafting copolymer and γ-mercaptopropyltrimethoxysilane (KH-590) were exposed to UV illumination, and the SiO2 doped anode membrane was obtained through sol–gel reaction of trimethoxysilane group, as similar process the cathode membrane was prepared by SBS grafted with dimethyl amino ethyl methacrylate (DMAEMA) and KH-570. The SBS BPM exhibited good mechanical strength (tensile strength, TS is 1.55MPa) and high temperature tolerance (thermal degradation temperature in N2 is in the range of 230–250°C). The ion exchange capacities (IECs) of SBS-g-(DMAEMA-SiO2) and SBS-g-(AA-StSO3 Na-SiO2) were in the region of 1.42–2.82 mmol/g. The SEM images show that the membrane cross- sections are very smooth where no silica particles could be observed. SBS-g-(DMAEMA-SiO2)/ SBS- g-(AA-StSO3Na-SiO2) bipolar membrane was used as the separator in the electrolysis cell for electro- generation of 2,2-dimethyl-3- hydroxypropionic acid(HPAc) and succinic acid in pairs. The yield of HPAc and the corresponding average current efficiency in the anode chamber were 28.2% and 53.8％, respectively. The yield of succinic acid and the average current efficiency in the cathode chamber were 74.1% and 62.5%, respectively.