Lipase-facilitated separation of organic acids in a hollow fiber contained liquid membrane module

On-Line Separation and Determination of Trivalent and Hexavalent Chromium with a New Liquid Membrane Annular Contactor Coupled to Inductively Coupled Plasma Optical Emission Spectrometry

We describe a new on-line sensitive and selective procedure for the determination of trivalent and hexavalent chromium in liquid samples by a tailor-made contactor (TMC), specifically a liquid membrane annular TMC, coupled with inductively coupled plasma with optical detection. The TMC was designed and developed to integrate the extraction and stripping phases of the analyte in one module to minimize the membrane solvent’s consumption and maximize the speed of transport through the liquid membrane. Moreover, the particular geometry studied, which consists of two coaxial hollow fibers, allows the TMC to be used for both separating and preconcentrating purposes. Both (−)-N-dodecyl-N-methylephedrinium bromide (30 mM) in dichloroethane and HNO3 (0.75 M) were used as the liquid membrane and receiving solution, respectively. The proposed method’s performance was evaluated in terms of the hexavalent chromium extraction efficiency and the coefficient of variation percentages; these were higher than 85% and less than 5%, respectively. In addition, the proposed procedure was applied to two real samples: a tap water sample and an eluate from solid urban waste. In both cases, the analytical performances were good and comparable to those obtained using synthetic standard solutions.

Th(iv) recovery from aqueous waste via hollow fiber renewal liquid membrane (HFRLM) in recycling mode: modelling and experimental validation

A new mathematical model was developed for recycling mode of HFRLM process which is in agreement with experimental results.

Characterization of an anion-exchange porous polypropylene hollow fiber membrane for immobilization of ABL lipase

Hollow fiber membrane offers the advantage to integrate catalytic conversion, product separation and catalyst recovery into a single separation process compared to conventional systems. Polypropylene (PP) hollow fiber membrane is a chemically inert and stable membrane with high potential for enzyme immobilization. The surface properties of polypropylene have been modified by radiation induced graft polymerization. Samples were prepared by grafting of glycidylmethacrylate (GMA) using gamma radiation, at different monomer concentrations and irradiation dose. The resulting epoxy was converted into a diethylamino group as an anion-exchange medium to bind the lipase molecules. Surface properties of the grafted and amine treated samples were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM) and contact angle measurements. AFM revealed higher surface roughness for grafted samples than that of virgin polymer. SEM micrographs illustrated that the porous network was retained at high degree of grafting. Contact angle measurements showed excellent wetting properties with water for the grafted and amine treated membranes. Thermal properties were studied using differential scanning calorimeter (DSC) and thermogravimetic analysis (TGA). It was observed that grafting occurred mainly in the amorphous region of the membranes. Activity and operational stability of ABL lipase, isolated from Arthobacter sp. were assayed after immobilizing it to the modified PP hollow fiber. Immobilized lipase retained 20U/g activity after ten hydrolysis cycles and 68% residual activity after 12 weeks of storage.