Andrzej Warszawski

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.

Diffusion Dialysis. Effect of Membrane Composition on Acid/Salt Separation

Diffusion dialysis is an energy-saving separation technique. In order to highlight the relationship between membrane composition and ability to separate acid/salt mixtures by diffusion dialysis, a few anion-exchange membranes were examined. Experiments on solubility/diffusivity phenomena were carried out in contact with hydrochloric acid and sodium chloride solutions (single- and two-solute experiments). Computations using Glueckauf and Tye models have indicated high nonuniformity in the distribution of fixed charged within the membranes and different accessibilities of the internal membrane volumes for the acid and salt. The Neosepta AFN-7 membrane (Tokuymam Soda Co.) has proved effective in differentiating the permeants by sorption (k{sub HCl}/k{sub NaCl} {approx} 2) and diffusivity ({bar D}{sub HCl}/{bar D}{sub NaCl} up to 10). This membrane is also the only one which, when in contact with two-solutes solutions, absorbs the acid preferentially to the salt. For this membrane the preferential sorption and transport of the acid depends not only on the physical structure of the membrane but also on the chemical nature of the polymer which contains pyridine moieties.

Diffusion dialysis Transport phenomena by irreversible thermodynamics

Abstract The transport phenomena in the permeation of acid and salt across anion-exchange membranes used to separate electrolytes by diffusion dialysis (DD) were studied. The experiments and computations were performed as imposed by irreversible thermodynamics. The phenomena are discussed in terms of the phenomenological (Lp, LD and LpD), reflection (σ) and permeability (υ) coefficients. The negative reflection coefficient indicated facilitated permeation of acid across the anion-exchange membranes. The negative osmotic flow was one of the phenomena increasing the permeation rate of acid. The data suggested that efficient separation by DD resulted from two effects: facilitated transport of one component (an acid) and restrictions in the sorption and permeation of the other one (a salt) by Donnan exclusion.

Siloxane-urethane membranes for removal of volatile organic solvents by pervaporation

Abstract Aqueous dispersions of siloxane-urethane copolymers (polysiloxaneurethanes) containing 0–49% of siloxane moieties were synthesized by the modified prepolymer-ionomer method. The properties of the dispersions were determined. Dense membranes were prepared from those dispersions by crosslinking with a multifunctional aziridine derivative. The structure of the obtained membranes was investigated by FTIR, solid state 13 C NMR, 29 Si NMR and DSC. Prepared membranes were tested in vacuum pervaporation of the following water-organic mixtures: water- tert -butyl methyl ether (1.8% wt. MTBE) and water-butyl acetate (0.25% wt. BuAc) at a temperature of 313 K. It was found that pervaporation properties of the polysiloxaneurethane membranes depended on the content of siloxane moieties. The best separation and transport properties were observed for the membrane containing 49% of siloxane groups. For this membrane separation factor a was equal to 750 and 1370 for water-MTBE and water-BuAc mixtures, respectively. The ratio of organic to water partial molar fluxes ( J org/ J water) was 2.8 and 0.5, respectively. This membrane was highly hydrophobic, thus the measured flux of pure water was about half of that for the membrane with a lower content of siloxane moieties.

Irreversible thermodynamics of transport across charged membranes. Part V. Isothermal transport through anion-exchange membranes and macroscopic resistance coefficients

Abstract Membrane properties: swelling, Donnan sorption, conductivity, transport numbers; and isothermal transports: diffusional, pressure driven, osmotic and electro-osmotic of the acid (HCl) and salt (NaCl) across two anion-exchange membranes Neosepta AM-1 and AFN-7 (Tokuyama Corp. Japan) are presented and discussed. Experiments have been performed aimed at the detailed analysis of transport phenomena applying irreversible thermodynamics. In this paper the ion-ion, ion-water and ion-polymer network interactions are discussed in terms of the molar straight, r ii , and cross, r ik , resistance coefficients. The effect of strong cation-anion and co-ion-membrane interactions have been discussed from the point of view of the composition and state of internal liquid phase. The results point out again that the permselectivity of operating membranes depends not only on the properties of the networks but not less on the mutual interactions of the species moving within. These interactions may oppose or accelerate permeations of individual ions.

Irreversible thermodynamics of transport across charged membranes. Part VI. Frictional interactions and coupling effects in transport of acid through anion exchange membranes

Abstract Having performed experiments described in [1–3] the friction coefficients,fik, coupling coefficients, qik, and diffusion indexes for ions and water, D i , have been computed in order to discuss the interactions on transport of acid (HCl) through anion exchange membranes. Two membranes were examined — diffusion dialysis Neosepta AFN-7 and standard grade Neosepta AM-1 (Tokuyama Corp.). The frictional interactions and coupling effects in AFN-7 membrane, the dual mode sorption, high diffusion coefficient, D HCl , and negative reflection coefficient, σ, can be explained postulating the dual mechanism of transport: a simple diffusion of acid dissolved in internal water combined with a kind of facilitated transport of the “absorbed” acid.

Studies on some properties of pristine and iodine-doped poly(phenylene sulphide)

Some properties of poly(phenylene sulphide) prepared by direct synthesis from benzene and sulphur are discussed in the light of thermal analysis, X-ray, SEM, and infrared data. Pristine poly(phenylene sulphide) is characterized by great thermal stability; it loses only 22.5% of its mass during dynamic heating to 873 K. Mass loss for iodine-doped samples increases to 41% depending on the iodine content. Doping with iodine also changes crystallinity, morphology and brings about a rise of electrical conductivity by several orders of magnitude. A conductivity of 1.45 × 10−2 S m−1 was obtained in air at room temperature for the poly(phenylene sulphide) sample containing 22.6% iodine.