Mechanism of supported liquid membrane degradation: emulsion formation

Treatment of Stainless Steel Rinse Waters Using Non-Dispersive Extraction and Strip Dispersion Membrane Technology

The extraction of Fe(III), Cr(III), and Ni(II) from stainless steel rinse water using non-dispersive extraction and strip dispersion membrane technology was carried out in a microporous hydrophobic hollow-fibre module contactor. The fibres were of polypropylene, whereas the organic extractant DP8R (bis(2-ethylhexyl) phosphoric acid) diluted in ExxsolD100 was used as the carrier phase. The rinse water containing the three elements was passed through the tube side, and the pseudo-emulsion formed by the organic phase of DP8R in Exxol D100 and an acidic strip solution were passed through the shell side in a counter-current operation; thus, a unique hollow fibre module was used for extraction and stripping. In non-dispersive extraction and strip dispersion technology, the stripping solution was dispersed into the organic membrane solution in a vessel with an adequate mixing device (impeller) designed to form strip dispersion. This pseudo-emulsion was circulated from the vessel to the membrane module to provide a constant supply of the organic phase to the membrane pores. Different hydrodynamic and chemical variables, such as variation in feed and pseudo-emulsion flow rates, strip phase composition, feed phase pH, and extractant concentration in the organic phase, were investigated. Mass transfer coefficients were estimated from the experimental data. It was possible to separate and concentrate the metals present in the rinse water using the non-dispersive extraction and strip dispersion technique.

Iron Control in Liquid Effluents: Pseudo-Emulsion Based Hollow Fiber Membrane with Strip Dispersion Technology with Pseudo-Protic Ionic Liquid (RNH3+HSO4-) as Mobile Carrier

The transport of iron(III) from aqueous solutions through pseudo-emulsion-based hollow fiber with strip dispersion (PEHFSD) was investigated using a microporous hydrophobic hollow fiber membrane module. The pseudo-protic ionic liquid RNH3HSO4- dissolved in Solvesso 100 was used as the carrier phase. This pseudo-protic ionic liquid was generated by the reaction of the primary amine Primene JMT (RNH2) with sulphuric acid. The aqueous feed phase (3000 cm3) containing iron(III) was passed through the tube side of the fiber, and the pseudo-emulsion phase of the carrier phase (400 cm3) and sulphuric acid (400 cm3) were circulated through the shell side in counter-current operational mode, using a single hollow fiber module for non-dispersive extraction and stripping. In the operation, the stripping solution (sulphuric acid) was dispersed into the organic membrane phase in a tank with a mixing arrangement (a four-blade impeller stirrer) designed to provide strip dispersion. This dispersed phase was continuously circulated from the tank to the membrane module in order to provide a constant supply of the organic solution to the fiber pores. Different hydrodynamic and chemical parameters, such as feed (75-400 cm3/min) and pseudo-emulsion phases (50-100 cm3/min) flows, sulphuric acid concentration in the feed and stripping phases (0.01-0.5 M and 0.5-3 M, respectively), metal concentration (0.01-1 g/L) in the feed phase, and PPILL concentration (0.027-0.81 M) in the carrier phase, were investigated. From the experimental data, different diffusional parameters were estimated, concluding that the resistance due to the feed phase was not the rate-controlling step of the overall iron(III) transport process. It was possible to concentrate iron(III) in the strip phase using this smart PEHFSD technology.

Earliest Results in the Use of Activated Composite Membranes for the Transport of Silver Ions from Aqueous Solutions

This paper presents the results concerning the first use of activated composite membranes (ACMs) for the facilitated transport of silver ions containing di-(2-ethylhexyl)-dithiophosphoric acid (DTPA) as the carrier. DTPA was immobilized by interfacial polymerization in a dense layer that was deposited in a porous layer, which was prepared on a nonwoven fabric support by phase inversion. The influence of fundamental parameters affecting the transport of silver ion as the carrier concentration in the membrane phase and stripping agent variation of the stripping solution have been studied. In the optimal conditions, the amount of silver transported across the ACMs was greater than 50%, whereas if the content of the carrier is modified, more than the 90% of the initial silver is removed from the feed phase.

Dye/water separation through supported liquid membrane extraction

The separation of synthetic dye Rhodamine 6G (R6G) and water was investigated using blended organic liquids in a supported liquid membrane (SLM) extraction system. Liquid membrane (LM) components include octyl alcohol (OcOH) as the dye extractant and a polysiloxane liquid as the stabilizing agent. Initial permeation results revealed the suitability of poly (phenyl methyl) siloxane (PPMS) over poly (octyl methyl) siloxane as the blending agent. The most acceptable condition for dye extraction was determined at feed solution pH congruent with 1, wherein highest distribution coefficient, K(D) (OcOH/H(2)O)=18, was attained. Though permeability decreased at optimal blending condition of 1:1 (w/w) OcOH/PPMS, SLM longevity was exhibited with>98% LM retention after 15 h operation in contrast to pure OcOH SLM system (>60% LM loss). Equilibrium experiments reveal that dye extraction followed Langmuir adsorption principle. The dye transport was elucidated using mass transfer analysis wherein it showed a decrease in overall coefficient (k(o)) at increasing feed concentrations. This was a direct consequence of K(D) decline, which becomes more apparent at higher concentrations when SLM saturation point is approached. At varied hydrodynamic conditions, improved k(o) values were observed up to Re(omega)=10,000 when minimal variation in film resistance is attained. Beyond this condition, k(o) becomes independent from stirring rate effect nonetheless SLM stability is compromised due to shear-induced LM losses.