Membrane assisted liquid extraction(MALE) technologies are gaining an important role as an extraction /separation technique for actinides and are being deployed as a promising tool for remediation of nuclear waste generated in the reprocessing plant and other radioactive wastes containing a trace level of radionuclides. The present contribution outlines the classification of membrane assisted liquid extractiontechniques, its operating principle, associatedtransport mechanism and merits and demerits with respect to industrial applications. Finally, selected applications of MALE techniques (BLM, SLM and ELM) are presented for extraction/separation of actinides and other radiotoxic nuclides from different streams of low level and high level radioactive wastes.
In this study, a mixed matrix polyethersulfone/iron-nickel oxide nanoparticle nanofiltration membrane was prepared by the solution casting technique. Polyvinylpyrrolidone was also used as a membrane pore former in membrane fabrication. The effect of iron-nickel oxide nanoparticles concentration in the casting solution on the membrane structure and performance was investigated. Scanning optical microscopy (SOM) and scanning electron microscopy analysis (SEM), water contact angle, NaCl/Na2SO4 salt rejection, water flux and tensile strength measurements were also carried out in membrane characterization. SOM images showed relatively uniform particle distribution and surface for the prepared membranes. Moreover, SEM images showed that the macro-voids’ size was enhanced in the membrane sub-layer with an increase of additive concentration. Results showed that increasing iron-nickel oxide nanoparticles from 0 to 0.1 wt.% in the membrane matrix caused a decrease in contact angle from 63 to 43° and again increased to 56° by increasing the particles concentration to 1 wt.%. The membrane water flux was enhanced sharply with an increase of nanoparticle concentration up to 0.01 wt.% in the membrane matrix and then decreased slightly at higher additive contents. Salt rejection was generally improved with an increase of nanoparticle concentration. Membrane mechanical strength was initially declined by using iron-nickel oxide nanoparticles up to 0.1 wt.% in the membrane matrix and then increased at higher additive contents. The nanocomposite membranes showed more appropriate antifouling capacity compared to a pristine PES membrane. The effect of feed concentration on membrane salt rejection and water flux was also studied.
This paper focuses on the effects of the addition of an ionic liquid, 1-Allyl-3-butylimidazilium bis(trifluoromethane sulfonyl)imide ([ABIM]TFSI), which has a high affinity for benzene, into the poly(vinyl chloride) (PVC) membrane on the pervaporation characteristics of the removal of benzene from aqueous solutions of dilute benzene. When aqueous solutions of 100~500 ppm benzene were permeated through the [ABIM]TFSI)/PVC membranes, they showed a high benzene/water selectivity and permeability of these membranes was enhanced with increasing [ABIM]TFSI content significantly. These pervaporation characteristics are discussed from the viewpoint of chemical and physical structure of [ABIM]TFSI)/PVC membranes in detail. The mechanism of permeation and separation was analyzed by the solution-diffusion model.
One of the barriers during whey filtration using UF membrane is the fouling phenomenon of the membrane, which is caused by whey proteins. In this work, the UF membranes were prepared using polysufone (PSf), dimethyl formamide (DMF), 1 wt.% poly vinyl pyrrolidone (PVP) and different concentrations of LiCl via phase inversion induced by immersion precipitation. The prepared membranes were characterized using SEM, AFM, porosity and mean pore size measurements, ultrafiltration performance and fouling analysis. The roughness of the membrane surface increased after the addition of LiCl in the casting solution. The SEM images and the measured data of porosity and pore size showed that the porosity was significantly enhanced after modification with LiCl but the pore sizes of the membrane were reduced. The performance analysis of these membranes demonstrated that the modified membranes had higher pure water and whey flux in comparison to the neat membrane and all of the prepared membranes exhibited protein rejection higher than 90%. In order to evaluate the membrane fouling, the experimental fouling analyses were carried out and the Zedney's pore blockage and cake filtration model was employed. The membranes fouling in terms of pore-blocking slightly decreased after the addition of LiCl.
A comprehensive study pertaining to the emulsion liquid membrane (ELM) extraction process to enrich dilute aqueous solutions of silver salt is presented. The study has highlighted the importance and influence of membrane composition for maximizing the extraction of Ag+ ions. The liquid membrane was made up of Cyanex-302 as an extractant and the industrial solvent mainly consists of paraffinic and naphthenic hydrocarbons (C10-C14) as a diluent, Montane®-80 (sorbitan monooleate) as the surfactant and nitric acid solution as the stripping solution. The selection of the extractant (Cyanex-302) and the stripper (HNO3) was based on conventional liquid–liquid extraction studies. The role of pH as an important parameter in the LEM process for extraction of Ag+ was studied. Extraction of Ag+ increased with an increase in strip phase and carrier concentration. The fundamental parameters (emulsion stability, pH of the feed aqueous solution, agitation speed, surfactant concentration, strip phase concentration, carrier concentration, surfactant concentrations and treatment ratio) affecting the separation of Ag+ through the ELM were investigated to select the best combination of process parameters. The maximum extraction of Ag+ (about 99%) was achieved at a Montane®-80 concentration of 5% (v/v), strip phase concentration of 0.4M nitric acid and a phase ratio of 1:1.