V. Ramachandhran

Preparation, characterization and performance of polyethersulfone ultrafiltration membranes

Abstract Asymmetric ultrafiltration (UF) membranes were prepared from locally made wholly aromatic polyethersulfone (PES) polymer, similar to Vitrex type, using aprotic solvents and organic additives by phase inversion method. The effect of nature of additive, solvent, ambient humidity during membrane casting and gelling medium on membrane performance were studied. The membranes were characterized in terms of separation behaviour for polyethylene glycol—5000 solute, molecular weight cut off (MWCO) profile and direct electron microscopic observations. The performance of UF membranes for sodium sulfate, rhodamine-B dye and oligomers of starch hydrolyzate are reported as a function of pressure.

Polyhydroxamic Acid Sorbents for Uranium Recovery

Crosslinked polyacrylamides were synthesized by solution polymerization using benzoyl peroxide as the radical initiator. The water–insoluble polymer obtained was functionalized by reacting with hydroxylamine to convert the amide group into hydroxamic acid group. The resultant functionalized polymer was characterized in terms of moisture uptake, elemental composition, IR spectra, thermal stability, exchange capacity and heavy metal sorption. The sorbent, obtained in particulate form, was investigated for its sorption properties with respect to uranium from uranyl nitrate solutions under unstirred batch conditions. This paper will concentrate on preparation, characterization and performance evaluation with respect to uranium sorption as a function of concentration, time, solution pH and temperature. The potential of this sorbent for uranium and other heavy metal ion recovery from sea water is ascertained.

Synthesis and characterization of low molecular weight cut off ultrafiltration membranes from cellulose propionate polymer

This paper describes the synthesis and characterization of low molecular weight cut-off ultrafiltration (UF) membranes from cellulose propionate (CP) polymer using dimethyl acetamide solvent. The casting conditions are studied with reference to changes in the nature of additive and additive to solvent ratio. The membranes are characterized in terms of product permeation rate, solute retention for different electrolytes, as a function of feed concentration and pressure. The retention of different dyes are also included. Molecular weight cut off profiles using polyethylene glycol solutes of different molecular weights are presented. The separation behaviour of oil-water and milk protein systems are presented in order to highlight the fouling resistance of CP membranes.

Separation Behavior of Composite Polyamide Membranes from Mixed Amines: Effects of Interfacial Reaction Condition and Chemical Post-Treatment

Abstract Composite polyamide membranes are prepared using in-situ interfacial polymerization using mixed amine system comprising 1,4-phenylene diamine and pipperazine. Separation performance of the membranes are studied as a function of the concentration of amine and acid chloride, the concentration ratio of the amines, nature of the acid chloride, and the presence of surfactant and acid acceptor in the aqueous reagent. The effect of esterification and hydrazide reactions involving residual carboxylic acid groups in the polymeric membranes on the co-polymeric composite membrane performance is also studied. The membrane performance can be tailored easily by conversion of the residual reactive functional groups in post-treatment.

SYNTHESIS, CHARACTERIZATION, AND PERFORMANCE OF SULFONATED POLYETHERSULFONE NANOFILTRATION MEMBRANES

ABSTRACT TGA/DTA data. Membranes were prepared from sulfonated polymer and performance characteristics in terms of permeate flux and solute separation are reported. The effects of the casting solution composition on performance of both PES & SPES membranes, effect of feed concentration and separation of different inorganic salts are also included. Separation of multivalent cation (Ca2+) was studied in presence of PAA of different concentration and as a function of pH.

Trace Level Separation of Zinc Sulfate and Lead Nitrate from Toxic Effluent Streams by Reverse Osmosis Modular Systems

Abstract Separation of trace toxic metallic constituents from effluent streams by membrane processes has been under investigation in our laboratory. Removal of zinc sulfate and lead nitrate in low concentration, especially in the millimolar range, using cellulose acetate and TFC-polyamide membranes assembled in plate-n-frame modules is reported in this paper. Separation data are presented as a function of concentration and pressure in single and mixed solute systems at low feed flow rates. Under the experimental conditions for dilute feed solutions, a decline in solute separation at very low concentrations as well as at high pressures are noticed. The solute and solvent transport across the membranes are analyzed in terms of pure water permeability constant (A) and solute transport parameter using Kimura-Sourirajans transport equations as applied to very dilute feed systems. Solute separation is predicted for various product permeation velocities and compared with experimental data.

Aromatic Polyamide Hydrazide Membranes for Reverse Osmosis Separations

Abstract Wholly aromatic polyamide hydrazide (PAH) polymers were synthesized by low temperature polycondensation from freshly prepared m-amino benzhydrazide, p-amino benzhydrazide, isophthaloyl chloride, and terephthaloyl chlorides in dimethyl acetamide solvent. A series of film-forming polymers prepared by altering the molar ratios of the reacting monomers was characterized in terms of % moisture regain, ηinh, and x-rays. Asymmetric membranes prepared from selected polymer samples were tested in reverse osmosis test cells, and the pure water permeability and the membrane constant were determined. An optimum meta: para molar ratio of the reacting monomers has been identified for the best performance under reverse osmosis which gave solute separation close to 98% for a feed concentration in the range of seawater. The PAH membranes appear to be potential barrier candidates for treatment of effluents containing ammonium, nitrates, etc. and radioisotopes. Separation data for a few other solute systems were al...

SYNTHESIS, CHARACTERIZATION, AND PERFORMANCE OF NITRATED POLYSULFONE MEMBRANES

Wholly aromatic polysulfone was modified by nitration and was investigated as a possible membrane material for separation of inorganic solutes, low molecular weight organic solutes and dyes from aqueous solutions. The nitrated polysulfones were characterized in terms of extent of nitration, percent moisture regain, inherent iscosity, IR spectra, TGA/DTA and DSC data. Membranes were prepared from nitrate polymer and performance characteristics in terms of permeate flux and solute separation are reported. The effects of the casting solution composition and casting condition, effect of feed concentration and separation of different inorganic salts are also included. Separation data for low molecular weight polyethylene glycol (PEG) solutes and dyes are studied. Nitrated polysulfone membranes have been found to give higher separation for polyvalent anionic electrolytes. The stability of membranes in acid and alkaline medium and chlorine tolerance of the membranes are also investigated.

HIGH SOLUTE REJECTING MEMBRANES FOR REVERSE OSMOSIS : POLYETHERAMIDE HYDRAZIDE

Abstract Synthesis of benzhydrazide polymers and determination of reverse osmosis properties of their membranes were reported earlier. Although high solute rejections could be achieved, their performance was not adequate for seawater desalination or for high radioactive decontamination factors (DF). In the process of investigation of polymers with improved performance, the same hydrazide polymers modified by incorporation of additional monomers with ether linkages were synthesized by low temperature polycondensation of freshly prepared m−amino benzhydrazide, p−amino benzhydrazide, and 4,4′-diamino diphenyl ether, with isophthaloyl chloride and terephthaloyl chloride in dimethyl acetamide solvent. A series of film-forming polymers prepared by altering the molar ratios of the reacting monomers were characterized in terms of percent moisture regain, inherent viscosity, solubility parameters, and interfacial sorption characteristics. Asymmetric membranes prepared from these polymer samples were characterized ...

PREPARATION AND CHARACTERIZATION OF POLYSULFONE AND POLYETHERSULFONE MEMBRANES FOR CALCIUM (Ca2+) AND MAGNESIUM (Mg2+) SEPARATION BY COMPLEXATION ULTRAFILTRATION

ABSTRACT Asymmetric ultrafiltration membranes were synthesized from locally available polysulfone and polyethersulfone polymers using aprotic solvents and organic additives by the phase inversion method. The membranes were characterized in terms of pure water permeability, separation behavior with respect to polyethylene glycols of various molecular weights and electrolytes. The suitability of using polyethyleneimine (PEI) for selective removal of calcium and magnesium salts by an ultrafiltration process was studied in terms of optimum polymer loading at reasonable permeate flux, irreversible adsorptive fouling of the macromolecular ligand on the polymer as functions of solution pH and ionic strength, and metal ion separation as a function of concentration and pressure. Direct electron microscopic observation of fresh, as well as fouled, membranes are presented.