In this research, a series of one-dimensional controllable crosslinked polymers with the different mass ratios of 4-vinylbenzychloride (VBC) and divinyl benzene (DVB) was prepared via cationic polymerization, and the polymers were grafted with the functional group N-methyl-D-glucamine (NMDG) for boron removal. The optimum polymeric mass ratio and a series of boron adsorption performances were studied. The maximum adsorption capacity was 18.15 mg g−1, of which 94% was retained after 4 cycles. Meanwhile, different pH values had negligible effect on the boron adsorption capacity, which was favorable for the removal of boron from its aqueous solution in a wide pH window. In addition, a magnetic adsorbent was prepared by the combination of Fe3O4 nanoparticles and the polymer, which provided an effective way to collect and recover adsorbents from their aqueous solutions.
Haixiang Sun,Xubing Luo,Jiahui Liu,Guoqing Li,Yanwei Zhang,Peng Li,Q. Jason Niu
Thin-film composite (TFC) pervaporation membranes is of widespread interest for the alcohol dehydration, since the thin selective layer allows a high permeation flux. However, how to obtain the desired flux and separation selectivity simultaneously is still the bottleneck of industrial application with pervaporation technology. In this study, a novel ultrathin multi-layer polyurea or polyamide pervaporation membrane was designed and assembled via layer-by-layer (LBL) interfacial polymerization (IP) method on the hydrolyzed polyacrylonitrile (HPAN) substrate membrane. During the LBL assembly process, the controllable crosslinking degree of the separation layer formed through changing the concentration of the oil phase monomer while remaining the concentration of the aqueous phase monomer constant based on the solution-diffusion mechanism of pervaporation separation process. The surface characterization revealed that the tris(2-aminoethyl) amine (TAEA) 1.5 -toluene 2,4-diisocyanate (TDI) 1-0.5-0 /HPAN composite membrane exhibited much rougher surface than that of the membranes with the same crosslinking degree. The optimized composite membrane exhibited a high separation factor of 844.6 with a desirable permeation flux of 1284.3 g·m −2 ·h −1 for the pervaporation dehydration 95 wt% ethanol aqueous solution at 80 °C, which was 10-fold increase of separation factor compared with the control membrane. Moreover, the excellent operation stability of the TFC membrane demonstrated the promising prospect for the alcohol dehydration separation. This preparation methodology has potential application in other membrane separation process on the basis of solution-diffusion mechanism, such as gas separation and reverse osmosis membrane.
Jiawen Fu,Haowei Pan,Mingzhe An,Zihao Li,Hong Wang,Xinping He,Chunhai Yi
Polyvinyl alcohol (PVA) is a promising membrane material for pervaporation (PV) desalination. However, the adjustment and control of the cross-linking structure is still a challenge for PVA membrane. In this study, a novel pH-resistant PVA-based composite membrane for efficient pervaporation desalination was developed by precisely adjusting the cross-linking behavior. Vinyl alcohol-vinylamine copolymer (VA-co-VAm) containing both hydroxyl and amino groups was synthesized. Cross-linking reaction was carried out based on the Schiff base reaction between amino groups (in VAm moiety) and glutaraldehyde (GA) under alkaline conditions. Cross-linking degree of PVA selective layer was carefully controlled by adjusting the amino group content in copolymer. Results showed that membrane prepared with VA-co-VAm that containing 5 wt% N-vinylformamide (NVF) displayed superior hydrophilicity and the largest free volume fraction. Pervaporation test indicated that the modified cross-linking membrane showed good stability under extreme pH conditions. Specifically, under strong acid conditions (pH ~ 1) and alkaline conditions (pH ~ 14), the membrane showed excellent desalination performance with water flux over 12 kg/(m 2 h), and the salt rejection higher than 99.95%. Based on the above results, the prepared membrane offers a promising platform for desalination under extreme pH conditions, which shows great potential in industrial wastewater treatment.
Guohao Miao,Hai Zhang,Yu Yang,Jin Qu,Xinru Ma,Junping Zheng,Xiaofei Liu
Zirconium is one of the most commonly used crosslinkers for guar gum-based fracturing fluid. Nevertheless, it is difficult for zirconium crosslinkers applied in fracturing to possess both high temperature resistance and adjustable crosslinking time. Meanwhile, few people did systematical research on the crosslinking process of fracturing fluid. In this study, an organic zirconium crosslinker with high temperature resistance and controllable crosslinking time was synthesized. The seawater-based fracturing fluid gel prepared with the crosslinker could perform well under 170°C. Oscillatory shear experiments were conducted to analyze the rheology of the gelation process. Moreover, steady-state shear and micro-rheological tests were conducted to analyze the dynamic and static crosslinking process of the fracturing fluid, respectively. Meanwhile, rheo-kinetic equation was used to fit the data and the effects that various factors had on the gelation process were illustrated thoroughly. This study not only prepared an organic zirconium crosslinker with good performances, but also explored the crosslinking process of fracturing fluid gel, which could improve its further application in oilfields.
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