Guodong Kang

Development of antifouling reverse osmosis membranes for water treatment: A review.

With the rapidly increasing demands on water resources, fresh water shortage has become an important issue affecting the economic and social development in many countries. As one of the main technologies for producing fresh water from saline water and other wastewater sources, reverse osmosis (RO) has been widely used so far. However, a major challenge facing widespread application of RO technology is membrane fouling, which results in reduced production capacity and increased operation costs. Therefore, many researches have been focused on enhancing the RO membrane resistance to fouling. This paper presents a review of developing antifouling RO membranes in recent years, including the selection of new starting monomers, improvement of interfacial polymerization process, surface modification of conventional RO membrane by physical and chemical methods as well as the hybrid organic/inorganic RO membrane. The review of research progress in this article may provide an insight for the development of antifouling RO membranes and extend the applications of RO technology in water treatment in the future.

Enhancing antifouling property of commercial polyamide reverse osmosis membrane by surface coating using a brush-like polymer containing poly (ethylene glycol) chains

Abstract To enhance fouling resistance, the commercial polyamide reverse osmosis (RO) membrane was coated using a brush-like polymer containing poly (ethylene glycol) chains. The membrane properties, including hydrophilicity, charge and roughness, were improved after surface modification. The coated and uncoated RO membranes were characterized by attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), static contact angle (CA) and streaming potential. The pure water flux and salt rejection of RO membranes before and after surface coating were measured. Moreover, the fouling experiments were performed using simulated foulants including protein, cationic surfactant and colloidal solution. The results indicated that the coated RO membrane exhibited better resistance compared to that of uncoated membrane.

Effect of MIL-53 on phase inversion and gas separation performance of mixed matrix hollow fiber membranes

In this paper the θ-composition for the Ultem®1000/NMP/EtOH ternary phase system was determined firstly and based on this, membranes with different non-solvent ratios (lower, slightly lower, and larger than the θ-composition) were prepared. It was found that dopes with a non-solvent ratio slightly lower than the θ-composition gave membranes the most attractive gas separation performance. Then the metal–organic framework (MOF) of MIL-53 was incorporated into Ultem®1000 to fabricate asymmetric mixed matrix hollow fiber membranes (MMHFMs). MIL-53, which was grouped with EtOH as a non-solvent, turned out to influence the phase inversion more significantly than EtOH did. Similar to the pure Ultem®1000 membrane, MMHFMs formed with the dopant close to the θ-condition for the Ultem®1000/MIL-53/NMP/EtOH phase system possessed the best permeation performance: MMHFMs with 5 wt% MIL-53 loading exhibited an O2 and CO2 permeance of 8.1 GPU and 27.9 GPU, an increase of 138% and 129% respectively compared with the pure Ultem membrane. Meanwhile, the O2/N2 and CO2/CH4 selectivity was almost unchanged. Moreover, the rule was also embodied in MMHFMs with different filler loadings. This study quantitatively revealed the pseudo non-solvent effect of MOFs, which offers an effective method for the fabrication of MMHFMs with a low MOF loading but high performance.

Sintering process investigation during polytetrafluoroethylene hollow fibre membrane fabrication by extrusion method

In this study, the effect of sintering conditions including manner, temperature and duration on properties of polytetrafluoroethylene (PTFE) hollow fibre membrane fabricated by extrusion method was intensively investigated. Different from un-sintered and relaxed sintered, the fixed sintered PTFE hollow fibre membrane was observed to generate a uniform ‘fibril–node’ porous structure and a main crystal transformation to folded chain crystal with smaller size. Consequently, it was found that for fixed setting sintering, both temperature increase from 340°C to 400°C and duration prolongation obviously improved pore size, ethanol permeation performance and mechanical strength. Additionally, the test results revealed that the membrane sintered below virgin melting point (350°C) had a noticeable higher porosity but poorer ethanol permeation performance that could be primarily attributed to increased ratio of closed pore. The sintering condition exhibited evident influence on PTFE hollow fibre membrane thermal stability, though it showed no alteration to the thermal decomposition of PTFE. The obtained PTFE hollow fibre membrane was tested to evaluate their vacuum membrane distillation (VMD) performances. It was found that PTFE membrane from lower sintering temperature delivered a better salt rejection; on the other hand, the permeate flux was improved by increased vacuum pressure during VMD operation.