Wojciech Kujawski

REMOVAL OF PHENOL FROM WASTEWATER BY DIFFERENT SEPARATION TECHNIQUES

Abstract Application of membrane techniques (pervaporation and membrane-based solvent extraction) and adsorption tothe removal of phenol from solutions modelling wastewater from phenol production by cumene oxidation processwas investigated. The transport and separation properties of composite membranes PEBA, PERVAP 1060 and PERVAP 1070 in pervaporation of water-phenol mixtures were determined. It was found that the best removal efficiency ofphenol was obtained using the PEBA membrane. MTBE, cumene and the mixture of hydrocarbons were applied in the membrane-based phenol extraction. Extra-Flow contactor with Celgard X-30 polypropylene hollow-fiber porousmembranes was used in the experiments. MTBE was found the most efficient extractant. Adsorption of phenol on the different Amberlite resins was also investigated. Among the Amberlite resins of various grades used, the Amberlite XAD-4 had the best properties in the phenol removal from the aqueous solutions. It was shown that regeneration of the adsorbent bed could be effectively performed with sodium hydroxide solution.

Irreversible thermodynamics of transport across charged membranes : Part I — Macroscopic resistance coefficients for a system with nafion 120 membrane

Summary The transport of aqueous NaCi solutions across the perfluorinated Nafion 120 membrane is studied on the base of irreversible thermodynamics. The straight resistance coefficients rii, partial frictions fiE and diffusion indices RT/cirii are presented and discussed. The results suggest that the main force, which impedes the flow of chloride ions across the membrane is not the friction of these ions with the negatively charged polymer network, but the friction with water. The diffusion indices RT~irii exceed self-diffusion coefficients found by some authors while using tracer technique. Following Meares’ suggestion such results point out to the convective ffow contribution to the transport of ions and water.

Ions and water transport across charged nafion membranes. Irreversible thermodynamics approach

Abstract The isothermal transport of ions and water across the perfluorinated Nafion 120 membrane in contact with sodium chloride solutions of concentration 0.05 up to 4 mol/l has been studied basing on irreversible thermodynamics of transport. The interactions of ions with water and polymer matrix on passing across the membrane have been discussed on the ground of the resistance coefficients rik, friction coefficients fik, coupling coefficients qik and mobility indexes uNa+ and uH2O. The variations of the coefficients with concentration of an external electrolyte made it possible to comment on the structure-selectivity problems and reflect sensitivity of a cluster-like morphology of the membrane to sorption and swelling.

Pervaporative Removal of Organics from Water Using Hydrophobic Membranes. Binary Mixtures

Results of pervaporation experiments are presented for the separation of several polar and nonpolar organic solvents from their aqueous solutions. Three membranes were evaluated: a polydimethylsiloxane (PERVAP-1060) membrane, a PDMS ZSM-5 zeolite filled (PERVAP-1070) membrane, and a poly(ether-block-amide) (PEBAX-4033) membrane. The effect of feed composition on flux and selectivity was also investigated. Performance parameters of a given membrane depended both on the kind of the organic solvent and the feed composition. The PERVAP-1070 membrane exhibited the highest selectivity with a separation factor over 900 in contact with a water–butyl acetate mixture. Polar solvents like methanol were also preferentially separated from aqueous solutions, but the separation factors were close to those obtained from liquid-vapor equilibria data. Permeate fluxes of organics increased with increasing feed concentration. Synergetic effects between water and organics fluxes were also observed.

Highly Efficient Hydrophobic Titania Ceramic Membranes for Water Desalination

Hydrophobic titania ceramic membranes (300 kD) were prepared by grafting of C6F13C2H4Si(OC2H5)3 and C12F25C2H4Si(OC2H5)3 molecules and thus applied in membrane distillation (MD) process of NaCl solutions. Grafting efficiency and hydrophobicity were evaluated by contact angle measurement, atomic force microscopy, scanning electron microscopy, nitrogen adsorption/desorption, and liquid entry pressure measurement of water. Desalination of NaCl solutions was performed using the modified hydrophobic membranes in air gap MD (AGMD) and direct contact MD (DCMD) processes in various operating conditions. High values of NaCl retention coefficient (>99%) were reached. The permeate fluxes were in the range 231-3692 g·h(-1)·m(-2), depending on applied experimental conditions. AGMD mode appeared to be more efficient showing higher fluxes and selectivity in desalination. Overall mass transfer coefficients (K) for membranes tested in AGMD were constant over the investigated temperature range. However, K values in DCMD increased at elevated temperature. The hydrophobic layer was also stable after 4 years of exposure to open air.

Irreversible thermodynamics of transport across charged membranes : Part II-ion-water interactions in permeation of alkali

Summary The detailed analysis of membrane phenomena in the system Nafion 120 membrane/NaOH, at 298,313 and 333 K has been performed, taking for discussion the phenomenological transport coefficients ri,, fib and diffusion indices n. Comparing the numerical values found here with the corresponding data determined for the system with NaCl solutions it is shown that cation-anion frictional force, which is usually assumed zero, cannot be neglected for the Na+-OH- pair of ions. These interactions influence diffusional and osmotic transport of a solute and water across the membrane. Another specific effect of OH- ions important for membrane permeation is the very low friction of OH- ions with water.

Ionic liquids as selective extractants and ion carriers of heavy metal ions from aqueous solutions utilized in extraction and membrane separation

Abstract This paper analyzes the applications of various ionic liquids (ILs) as metal ion carriers and extractants utilized for the separation of metal cations from aqueous solutions. Subsequently, an up-to-date review of the use of ILs in polymer inclusion membranes is presented. ILs represent a promising group of extractants and ion carriers of metal ions in extraction and membrane separation processes. The removal of heavy metals ions from aqueous solutions using ILs indicates an extensive and promising research area. It is expected that the role of ILs will gradually increase as the worldwide implementation of separation methods in recovery of metal ions from various aqueous solutions is growing quickly.

Membrane distillation properties of TiO2 ceramic membranes modified by perfluoroalkylsilanes

Abstract The tubular and planar TiO2 ceramic membranes were modified by grafting with perfluoroalkylsilanes (PFAS) molecules. Two types of PFAS were used for grafting process: 1H,1H,2H,2H-perfluorooctyltriethoxysilane (C6) and 1H,1H,2H,2H-perfluorotetradecyltriethoxysilane (C12). Studies showed that hydrophilic surface of titania ceramic membranes can be efficiently modified as a results of the proposed grafting method. Grafting efficiency of the tubular membranes was determined by measurement of liquid water entry pressure (LEPw), whereas grafting efficiency of planar membranes was verified by contact angle measurement. The contact angle values of the planar membranes are 130 and 140° for grafting with C6 and C12, respectively. The LEPw of the tubular membranes increased from 2 bar to 10 bar after modification by C12, whereas the LEPw values were constant at 2 bar when TiO2 membrane was modified by C6 molecules. It was found that water contact angle, LEPw, and water flux in the membrane distillation (MD)...

PERVAPORATIVE REMOVAL OF VOLATILE ORGANIC COMPOUNDS FROM MULTICOMPONENT AQUEOUS MIXTURES

The present study concerns with the separation of binary and ternary water–organics mixtures by pervaporation using different organophilic membranes (i.e., PERVAP-1060—polydimethylsiloxane, PERVAP-1070—zeolite filled polydimethylsiloxane, PEBAX-4033—polyether block amide). The following binary and ternary liquid mixtures were investigated: water–methyl acetate; water–ethyl acetate; water–butyl acetate, water–methyl t-butyl ether (MTBE), and water–methanol–MTBE. The organic components of these mixtures can be found in the wastewaters from textile, pharmaceutical, and petrochemical industries. The experiments were focused on the efficiency of investigated membranes used for the removal of organics from water. During the experiments, the following parameters characterizing system were determined: the separation factor (α), the permeate flux (J), and the degree of the removal of organics from water (D r) in the batch mode pervaporation. The influence of the feed temperature, the initial content of organics in the feed, and the feed volume to the membrane area (V/S) ratio were investigated. It was proved that all membranes were selective in the removal of volatile organic compounds from water. The selectivity and transport properties as well as the efficiency parameters were dependent strongly not only on the kind of the membrane and the kind of the separated feed mixture but also on the process parameters. The PERVAP-1060 membrane showed the best efficiency in the removal of organics from water, whereas the PERVAP-1070 membrane was the most selective one. Much lower efficiencies found for PEBAX-4033 membrane were caused by the fact that the selective layer of PEBAX-4033 membrane contained both the hydrophobic and hydrophilic blocks. Comparing the properties of a given membrane in contact with binary and ternary mixtures, it was stated that the selectivities and permeate fluxes were lower in contact with the latter ones.

A Fully Automated System for the Determination of Pore Size Distribution in Microfiltration and Ultrafiltration Membranes

Abstract An automated system controlled by a Amstrad CPC 6128 microcomputer was designed. The apparatus can be used for a fast characterization of MF and UF membranes by the bubble point method. The theory for a modified bubble-point method is reviewed. The system determines pore size, pore size distribution, and surface porosity for the membranes of pore radii not less than 45 nm. The whole experiment takes 3–5 h to complete. The apparatus was tested on various MF and UF membranes (Nuclepore, Synpor, PVC UF, PAN UF, CA UF).