praveen Kosaraju - Academia.edu (original) (raw)

Uploads

Papers by praveen Kosaraju

Research paper thumbnail of Hollow Fiber Membrane Contactor Based CO 2 Absorption−Stripping Using Novel Solvents and Membranes

Industrial & Engineering Chemistry Research, 2005

Nondispersive absorption of CO2 into an aqueous solution of a volatile amine and its subsequent r... more Nondispersive absorption of CO2 into an aqueous solution of a volatile amine and its subsequent regeneration by stripping in porous hydrophobic hollow fiber devices have encountered a number of issues: membrane pore wetting reducing CO2 transfer rates; ...

Research paper thumbnail of Interfacially polymerized thin film composite membranes on microporous polypropylene supports for solvent-resistant nanofiltration

Journal of Membrane Science, 2008

High-performance thin-film composite polyamide membranes for pervaporative dehydration processes ... more High-performance thin-film composite polyamide membranes for pervaporative dehydration processes were prepared by means of the interfacial polymerization of triethylenetetramine (TETA) and trimesoyl chloride (TMC) on the surface of a modified polyacrylonitrile (mPAN) membrane support. The effects of annealing processes applied during and after the composite membrane preparation on the pervaporation performance were investigated. Two annealing processes were applied. One was to the composite membrane formed after the interfacial polymerization by subjecting it to different annealing temperatures and the other to the aqueous amine (TETA) solution used during the interfacial polymerization process by varying its temperature. Positron annihilation spectroscopy experiments using a slow positron beam were carried out. One of the positron annihilation techniques, Doppler broadening energy spectroscopy (DBES), was used to study the effect of the annealing processes on the S parameter (corresponding to the free volume in the membrane). The first plateau (S 1 = 0.47798 ± 1.86E−4, L 1 = 182 ± 84 nm) in the curve obtained for the polyamide layer in the Type-B composite membrane was higher than that (S 1 = 0.47659 ± 2.74E−4, L 1 = 196 ± 52 nm) in the Type-A composite membrane. In other words, this corresponds to a higher S parameter and a thinner layer for the Type-B membrane than the Type-A membrane. This implies that the free-volume amount in the former membrane is higher than that in the latter. It was found that these two annealing processes greatly improved the pervaporation separation performances of the thin-film composite polyamide membranes prepared in this study in dehydrating aqueous alcohol solutions.

Research paper thumbnail of Pilot plant studies of novel membranes and devices for direct contact membrane distillation-based desalination

Journal of Membrane Science, 2008

A small pilot plant for direct contact membrane distillation (DCMD) based desalination was built ... more A small pilot plant for direct contact membrane distillation (DCMD) based desalination was built and operated successfully on a daily basis for 3 months. The operation employed hot brine at 64–93 °C and distillate at 20–54 °C. The hot brine was either city water, city water containing salt at the level of 3.5, 6 or 10%, or sea water trucked in from Long Island Sound, CT. One to ten horizontal crossflow hollow fiber membrane modules each having either 2448 or 2652 hollow fibers and 0.61 or 0.66 m2 surface area were combined in various configurations to study the plant performance. The highest water vapor flux of 55 kg/(m2 h) was achieved with two modules in series; the flux varied between 15 and 33 kg/(m2 h) for configurations employing 6–10 modules. The highest distillate production rate achieved was 0.62 gallons per minute (gpm). The membrane modules never showed any sign of distillate contamination by salt. The plant operated successfully with a very limited flux reduction at salt concentrations up to 19.5% from sea water. A mathematical model was successfully developed to describe the performance of the pilot plant with multiple crossflow modules in different test configurations.

Research paper thumbnail of Novel solvent-resistant hydrophilic hollow fiber membranes for efficient membrane solvent back extraction

Journal of Membrane Science, 2007

The advantages of employing hydrophilic hollow fiber membranes for efficient membrane solvent bac... more The advantages of employing hydrophilic hollow fiber membranes for efficient membrane solvent back extraction are explored via novel solvent-resistant hydrophilic hollow fiber membranes. The mass transfer rate of solute in membrane-based solvent extraction is controlled by boundary layer resistances and the membrane resistance. The membrane resistance can be reduced by preferentially filling the membrane pores with the phase preferred by

Research paper thumbnail of Interfacially polymerized hydrophilic microporous thin film composite membranes on porous polypropylene hollow fibers and flat films

Journal of Membrane Science, 2006

Solvent-stable ultrafiltration (UF) membranes are of significant interest especially if they are ... more Solvent-stable ultrafiltration (UF) membranes are of significant interest especially if they are also hydrophilic. Porous polypropylene flat films and hollow fibers can provide substantial chemical, pH, and solvent resistance and are therefore suitable as supports for forming appropriate coatings functioning as solvent-stable UF membranes. Flat Celgard 2400 films, Cegard X-10 and X-20 hollow fibers of polypropylene were used as a support for thin film composite (TFC) membranes prepared by interfacial polymerization (IP) technique. Monomer reactants for this reaction were diacyl chlorides such as sebacoyl chloride or iso-phthaloyl dichloride and diamines such as hexanediamine or polyethyleneimine (PEI). These TFC membranes have substantial solvent stability. Their IP layer and the membrane are also hydrophilic. The surface at the internal diameter of the hollow fibers was modified; plasma polymerization, UV techniques are generally not suitable for modification of this surface. The membranes obtained were characterized by the permeance of a gas (N2), permeability of water and ethanol, scanning electron microscopy (SEM), and ultrafiltration of a protein, zein, from an ethanolic solution. Amongst a number of factors which hold the key to a successful coating/membrane are hydrophilization of the different surfaces of the porous hydrophobic support via acetone and chromic acid oxidizing solution, order of introduction of the monomer-containing solutions, exposure of the nascent film to reduced shear conditions, and heat treatment of the IP layer formed. The hollow fibers membranes developed successfully were capable of 97% zein rejection from an ethanolic solution.

Research paper thumbnail of Hollow Fiber Membrane Contactor Based CO 2 Absorption−Stripping Using Novel Solvents and Membranes

Industrial & Engineering Chemistry Research, 2005

Nondispersive absorption of CO2 into an aqueous solution of a volatile amine and its subsequent r... more Nondispersive absorption of CO2 into an aqueous solution of a volatile amine and its subsequent regeneration by stripping in porous hydrophobic hollow fiber devices have encountered a number of issues: membrane pore wetting reducing CO2 transfer rates; ...

Research paper thumbnail of Interfacially polymerized thin film composite membranes on microporous polypropylene supports for solvent-resistant nanofiltration

Journal of Membrane Science, 2008

High-performance thin-film composite polyamide membranes for pervaporative dehydration processes ... more High-performance thin-film composite polyamide membranes for pervaporative dehydration processes were prepared by means of the interfacial polymerization of triethylenetetramine (TETA) and trimesoyl chloride (TMC) on the surface of a modified polyacrylonitrile (mPAN) membrane support. The effects of annealing processes applied during and after the composite membrane preparation on the pervaporation performance were investigated. Two annealing processes were applied. One was to the composite membrane formed after the interfacial polymerization by subjecting it to different annealing temperatures and the other to the aqueous amine (TETA) solution used during the interfacial polymerization process by varying its temperature. Positron annihilation spectroscopy experiments using a slow positron beam were carried out. One of the positron annihilation techniques, Doppler broadening energy spectroscopy (DBES), was used to study the effect of the annealing processes on the S parameter (corresponding to the free volume in the membrane). The first plateau (S 1 = 0.47798 ± 1.86E−4, L 1 = 182 ± 84 nm) in the curve obtained for the polyamide layer in the Type-B composite membrane was higher than that (S 1 = 0.47659 ± 2.74E−4, L 1 = 196 ± 52 nm) in the Type-A composite membrane. In other words, this corresponds to a higher S parameter and a thinner layer for the Type-B membrane than the Type-A membrane. This implies that the free-volume amount in the former membrane is higher than that in the latter. It was found that these two annealing processes greatly improved the pervaporation separation performances of the thin-film composite polyamide membranes prepared in this study in dehydrating aqueous alcohol solutions.

Research paper thumbnail of Pilot plant studies of novel membranes and devices for direct contact membrane distillation-based desalination

Journal of Membrane Science, 2008

A small pilot plant for direct contact membrane distillation (DCMD) based desalination was built ... more A small pilot plant for direct contact membrane distillation (DCMD) based desalination was built and operated successfully on a daily basis for 3 months. The operation employed hot brine at 64–93 °C and distillate at 20–54 °C. The hot brine was either city water, city water containing salt at the level of 3.5, 6 or 10%, or sea water trucked in from Long Island Sound, CT. One to ten horizontal crossflow hollow fiber membrane modules each having either 2448 or 2652 hollow fibers and 0.61 or 0.66 m2 surface area were combined in various configurations to study the plant performance. The highest water vapor flux of 55 kg/(m2 h) was achieved with two modules in series; the flux varied between 15 and 33 kg/(m2 h) for configurations employing 6–10 modules. The highest distillate production rate achieved was 0.62 gallons per minute (gpm). The membrane modules never showed any sign of distillate contamination by salt. The plant operated successfully with a very limited flux reduction at salt concentrations up to 19.5% from sea water. A mathematical model was successfully developed to describe the performance of the pilot plant with multiple crossflow modules in different test configurations.

Research paper thumbnail of Novel solvent-resistant hydrophilic hollow fiber membranes for efficient membrane solvent back extraction

Journal of Membrane Science, 2007

The advantages of employing hydrophilic hollow fiber membranes for efficient membrane solvent bac... more The advantages of employing hydrophilic hollow fiber membranes for efficient membrane solvent back extraction are explored via novel solvent-resistant hydrophilic hollow fiber membranes. The mass transfer rate of solute in membrane-based solvent extraction is controlled by boundary layer resistances and the membrane resistance. The membrane resistance can be reduced by preferentially filling the membrane pores with the phase preferred by

Research paper thumbnail of Interfacially polymerized hydrophilic microporous thin film composite membranes on porous polypropylene hollow fibers and flat films

Journal of Membrane Science, 2006

Solvent-stable ultrafiltration (UF) membranes are of significant interest especially if they are ... more Solvent-stable ultrafiltration (UF) membranes are of significant interest especially if they are also hydrophilic. Porous polypropylene flat films and hollow fibers can provide substantial chemical, pH, and solvent resistance and are therefore suitable as supports for forming appropriate coatings functioning as solvent-stable UF membranes. Flat Celgard 2400 films, Cegard X-10 and X-20 hollow fibers of polypropylene were used as a support for thin film composite (TFC) membranes prepared by interfacial polymerization (IP) technique. Monomer reactants for this reaction were diacyl chlorides such as sebacoyl chloride or iso-phthaloyl dichloride and diamines such as hexanediamine or polyethyleneimine (PEI). These TFC membranes have substantial solvent stability. Their IP layer and the membrane are also hydrophilic. The surface at the internal diameter of the hollow fibers was modified; plasma polymerization, UV techniques are generally not suitable for modification of this surface. The membranes obtained were characterized by the permeance of a gas (N2), permeability of water and ethanol, scanning electron microscopy (SEM), and ultrafiltration of a protein, zein, from an ethanolic solution. Amongst a number of factors which hold the key to a successful coating/membrane are hydrophilization of the different surfaces of the porous hydrophobic support via acetone and chromic acid oxidizing solution, order of introduction of the monomer-containing solutions, exposure of the nascent film to reduced shear conditions, and heat treatment of the IP layer formed. The hollow fibers membranes developed successfully were capable of 97% zein rejection from an ethanolic solution.