Shichang Wang

High‐Performance Membranes with Multi‐permselectivity for CO2 Separation

Multi-permselective membranes with diffusivity-selectivity, solubility-selectivity, and reactivity-selectivity for CO(2) separation are prepared by interfacial polymerization. The membranes are able to efficiently separate CO(2) from various light gases (H(2) , CH(4) and N(2) ) due to the optimized membrane structure and the comprehensive utilization of distinctions between CO(2) and light gases in size, condensability, and reactivity.

Gas separation membrane with CO2-facilitated transport highway constructed from amino carrier containing nanorods and macromolecules

The CO2-facilitated transport highway in the membrane was designed through amino carrier containing polyaniline nanorods and polyvinylamine. CO2 molecules could transfer quickly owing to the reversible reaction with amino groups. This strategy may have great inspiration for constructing ideal membrane structure and offering the possibility to fabricate highly permeable and selective membrane.

A study of the electrodeionization process — high-purity water production with a RO/EDI system☆

Abstract An electrodeionization post-reverse osmosis (RO/EDI) system was developed for the continuous production of high-purity water without the use of chemicals. The study was carried out with a laboratory pilot. The ion-exchange membrane stack has eight cell-pairs of which four dilute compartments were filled with mixed-bed ion-exchange resins. The feed is tap water with a conductivity of about 400 μs/cm, and the RO permeate with a conductivity less than 20 μs/cm. The EDI was achieved with a productivity of 20 l/h and a resistivity of 12–18 MΩ-cm. In addition, the V-I and pH-I characteristics of the EDI process were studied. It indicates that there are differences between the ED and the EDI in the concentration polarization.

Fabrication of high-performance facilitated transport membranes for CO2 separation

At present, liquid membranes, ion-exchange membranes and fixed carrier membranes are the three popular facilitated transport membranes for CO2 separation. They possess their own advantages, as well as their respective deficiencies. In view of the characters of these three types of facilitated transport membrane, we report a method to combine their advantages and overcome their deficiencies. A new membrane was fabricated by establishing high-speed facilitated transport channels in the fixed carrier membrane. This membrane displays excellent CO2 separation performance and good stability. The results suggest that this is an effective way to fabricate high performance and high stability CO2 separation membranes. Furthermore, establishing high-speed facilitated transport channels in fixed carrier membranes will be a universal route to improve the performance of gas separation membranes.

Electrochemical synthesis of polypyrrole nanowires on composite electrode

Abstract Polypyrrole nanowires growing with two-dimensional instantaneous nucleation and one-dimensional growth pattern were realized on graphite/paraffin composite electrode in phosphate buffer solution.

A novel N, O-carboxymethyl amphoteric chitosan/poly(ethersulfone) composite MF membrane and its charged characteristics

Abstract An amphoteric chitosan derivative, containing carboxymethyl (-COOH) groups and amine (-NH2) groups, had been prepared. FT-IR spectra confirmed the presence of γsymCOO (1408 cm−1) and γasCOO (1584 cm−1) on the structural units of the chitosan derivative, and 13C NMR spectra revealed that carboxy methylation reactions took place not only on the -OH but also on the -NH2. N, O—carboxymethyl chitosan (CM—CS)/ poly(ethersulfone) (PES) composite microfiltration (MF) membranes were prepared by immersing PES MF membranes into CM—CS solutions and cross-linking with glutaraldehyde. Streaming potential measurements indicate that the CM—CS/PES composite MF membranes possess a weaker positively charged characteristic at low pHs but a stronger negative charged characteristic at high pHs than the chitosan composite membrane (CS/PES). It was further observed that the CM-CS/PES composite membranes have higher adsorption capacities of bovine serum albumin (BSA) than the CS/PES composite membranes and PES membrane at lower pH 3.0–4.7, and lower adsorption capacities at higher pH 6.0–8.0. Therefore, the CM-CS/PES composite membranes may be suitable for resistant to protein fouling at high pHs or protein adsorption separations at low pHs applications.

Pressure dependence of the volume phase-transition of temperature-sensitive gels

Abstract The effect of hydrostatic pressure on the swelling of temperature-sensitive gels was studied by measuring the volume change of the beads of poly(N-isopropylacrylamide) gel, poly(N-n-propylacrylamide) gel, and poly(N,N-diethylacrylamide) gel under pressure up to 120 atm. The excess enthalpy and the excess volume of the gel-water systems during the volume phase-transition of the gels were measured. These measurements are helpful in understanding that the pressure sensitivity of these gels originates from their temperature sensitivity and is the consequence of the increase of their LCST with pressure. An equation relating the LCST of the temperature-sensitive gel to the pressure was obtained through thermodynamical analysis. These efforts contribute to reveal the interdependence between the pressure sensitivity and the temperature sensitivity of hydrogel.

Selective permeation of CO2 through new facilitated transport membranes

Abstract A new membrane material containing facilitated transport groups for carbon dioxide has been synthesized through the hydrolysis of polyvinylpyrrolidone (PVP) obtained by radical polymerization. The composite membrane was prepared with the hydrolysate as the top layer and microporous membrane as the support. The permeation of pure CO2 and CH4 as well as a binary mixture of CO2/CH4 through the composite membrane was measured. The effects of feed gas pressure, heat treatment and support membranes on the composite membrane performance were studied. The results show that the composite membranes possess better CO2 permeance and selectivity of CO2 over CH4 than that of other fixed carrier membranes reported in literature.

High-Performance Multilayer Composite Membranes with Mussel-Inspired Polydopamine as a Versatile Molecular Bridge for CO2 Separation

It is desirable to develop high-performance composite membranes for efficient CO2 separation in CO2 capture process. Introduction of a highly permeable polydimethylsiloxane (PDMS) intermediate layer between a selective layer and a porous support has been considered as a simple but efficient way to enhance gas permeance while maintaining high gas selectivity, because the introduced intermediate layer could benefit the formation of an ultrathin defect-free selective layer owing to the circumvention of pore penetration phenomenon. However, the selection of selective layer materials is unfavorably restricted because of the low surface energy of PDMS. Various highly hydrophilic membrane materials such as amino group-rich polyvinylamine (PVAm), a representative facilitated transport membrane material for CO2 separation, could not be facilely coated over the surface of the hydrophobic PDMS intermediate layer uniformly. Inspired by the hydrophilic nature and strong adhesive ability of polydopamine (PDA), PDA was therefore selected as a versatile molecular bridge between hydrophobic PDMS and hydrophilic PVAm. The PDA coating endows a highly compatible interface between both components with a large surface energy difference via multiple-site cooperative interactions. The resulting multilayer composite membrane with a thin facilitated transport PVAm selective layer exhibits a notably enhanced CO2 permeance (1887 GPU) combined with a slightly improved CO2/N2 selectivity (83), as well as superior structural stability. Similarly, the multilayer composite membrane with a hydrophilic CO2-philic Pebax 1657 selective layer was also developed for enhanced CO2 separation performance.

Mixed pharmaceutical wastewater treatment by integrated membrane-aerated biofilm reactor (MABR) system--a pilot-scale study.

A pilot-scale integrated membrane-aerated biofilm reactor (MABR) system, consisted of hydrolysis/acidification pretreatment, MABR process and activated carbon adsorption post-processing, was designed to treat the high-loading mixed pharmaceutical wastewater. A study of MABR process was conducted to investigate the effect of aeration condition, circulation flow rate and water quality on performance over 260 days. The performances of these processes were evaluated by the removal efficiency of COD, BOD(5), turbidity, NH(4)(+)-N and TN. MABR process could effectively remove above 90% of COD and 98% of ammonia. The capacities per unit volume of MABR could reach up to 1311 gCOD/m(3)d and 48.2 gNH(4)(+)-N/m(3)d with single membrane aeration, and the oxygen utilization rate could be as high as 45%. After post-processing, the effluent of integrated treatment MABR system kept stable with COD below 200 mg/L and NH(4)(+)-N below 3 mg/L.