IITK - Indian Institute of Technology Kanpur

Applied Research

Membrane Contactor as Degasser

Removal of dissolved gases, particularly present in lower concentrations, from liquid streams is a serious requirement of many chemical industries. Membrane contactor was utilized to remove dissolved gases (NH₃ + CO₂) in water condensate emanating out of urea-plant using a membrane contactor having number of hydrophobic hollow fibres; utilizing both the modes of operations: liquid-liquid extraction (LLE) and sweep/vacuum (S/V). An experimental set-up has been designed and installed with Liqui-Cel^® contactor. For LLE mode, dilute sulphuric acid solution was used as extract phase. Results obtained from both the modes have demonstrated the feasibility of the removal of gases through membrane contactor. Excellent matching of experimental data with developed model as well as with empirical models validate the attempt to remove gases utilizing membrane contactor and help to design the process.

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Recovery of Lignosulfonates from Spent Sulphite Liquor

Separation and purification of Lignosulfonates, present in spent sulphite liquor, has been carried out through a Dia-filtration operation. Around 80-85% recovery is obtained. The technology development is complete and ready for pilot plant trial. Results of molecular mass distribution of lignosulphates have shown that variable size distribution may be obtained by using different cut-off size of membranes.

* P. K. Bhattacharya, R. K. Todi, M. Tiwari, C. Bhattacharjee, S. Bhattacharjee, S. Dutta, “Studies on UF of spent sulphite liquor (SSL) using various membranes for the recovery of lignosulphonates“, Desalination, 174, 287 – 297 (2005).

Micellar Enhanced Ultrafiltration (MEUF)

In MEUF process, the surfactant having charge opposite to target ions, is added to the effluent stream containing the metal ions at a concentration greater than the critical micellar concentration (CMC), so that they form aggregates of around 50–150 of monomer molecules, called micelles. Therefore, a large fraction of the metal ions get electrostatically attached to the micelle surface. Retention of such metal ions attached to the micelles is possible if the resulting solution is passed through an ultrafilter, having pore size smaller than the micelle diameter. The recovery and the reuse of surfactant are of utmost importance from economical point of view. Several studies were done for the removal of metal ion and organic solutes under aqueous medium through MEUF under both stirred and unstirred conditions using batch cells. Bonding or solubilizations of these solutes in surfactant micelles were also experimentally ascertained. Mathematical models were also developed.

* M. Syamal, S. De and P. K. Bhattacharya, “Phenol solubilization by cetyl pyridinium chloride micelles in micellar enhanced ultrafiltration“, J. Membrane Sci., 137, 99-107 (1997).

* S. Ralph Jadhav, N. Verma, A. Sharma and P. K. Bhattacharya, “Flux and retention analysis during micellar enhanced ultrafiltration for the removal of phenol and aniline“, Separ. Purif. Technol., 24, 541-557 (2001).

* Gargi Ghosh and Prashant K. Bhattacharya, "Hexavalent chromium ion removal through micellar enhanced ultrafiltration", Chem. Eng. J.: Environ. Chem. Eng., 119, 45 - 53 (2006).

Hydrazine Hydrate Separation through Pervaporation

Hydrazine is an important inorganic chemical that upon combustion produces nitrogen and water, unlike hydrocarbon fuels producing carbon dioxide and water. Hydrazine is less flammable and less volatile than hydrocarbon fuels and hence it is used as a component in jet fuels because it produces a large amount of heat when burned. It finds active applications in rocket propulsion; however, in anhydrous hydrazine form. By ordinary distillation, 64 wt.% of hydrazine is produced. Therefore, removal of water from hydrate state to produce anhydrous hydrazine is essential. Conventional separation technique, like distillation forms an azeotrope with water at 71.5 wt% of hydrazine. Further, hydrazine and water, being highly polar substances (surface tension values very close) impart strong hydrogen bonding between them. Therefore, pervaporation processes* is recommended to seek dehydration.

* S. V. Satyanarayana, P. K. Bhattacharya, “Pervaporation of Hydrazine Hydrate: Separation characteristics of membranes with hydrophilic to hydrophobic behaviour“, J. Membrane Sci., 238, 103 -115 (2004).

* Nazish Hoda, Satyanarayana V. Suggala and Prashant K. Bhattacharya, “Pervaporation of Hydrazine – Water through Hollow Fiber Module: Modeling and Simulation“, Computers Chem. Eng., 30 (2), 202-214 (2005).

* Mrinal Kanti Mandal, Sukalyan Dutta and P. K. Bhattacharya, “Characterization of Blended Polymeric Membranes for Pervaporation of Hydrazine Hydrate”, Chem. Eng. J., 138, 10-19 (2008).

Ultrafiltration of Sugar Cane Juice for recovery of Sugar

Sugar industry is one of the largest agro-based industries in India; however, suffer from many problems. There is need to investigate the energy saving and technically efficient alternative processes. Application of the integrated membrane technology is has been attempted (processes like RO, UF, MF and ED. Such processes may offer certain advantages in clarification and concentration of multi-component solutions and suspensions like sugar cane juice. However, the membrane systems pose problems like decline of flux over time which prevents widespread applicability of such processes commercially. Several studies* were made accordingly.

* A. D. Sarode, N. Verma and P. K. Bhattacharya, “Analysis of retention and flux decline during ultrafiltration of limed sugarcane (clarified) juice“, Chem. Eng. Commun., 188, 179-206 (2001).

* U. V. S. RamGopal, N. Verma and P. K. Bhattacharya, “Analysis of flux decline during ultrafiltration of sugarcane juice (limed) using cross-flow cell“, Can. J. Chem. Eng., 80(1), 105-115 (2002).

* P. K. Bhattacharya, Shilpi Agarwal, S. De and U.V.S. RamaGopal, “Ultrafiltration of sugar cane juice for recovery of sugar: analysis of flux and retention“, Separ. Purif. Technol., 21, 247-259 (2001).

Enzymatic (immobilized) Membrane reactor

Enzymatic hydrolysis of lactose mainly yields glucose and galactose. In addition galacto-oligosaccharides (GOS) are also formed by transgalactosylation activity of enzyme from the same biochemical reaction. GOS is a very beneficial functional component for human. GOS, also recognized as prebiotics consists of a number of oligosaccharides which are linked with different b-glycosidic bonds, depending on enzyme source. Work is going on in this direction.

Prehydrolysis Liquor Treatment to Disposal Level

Treatment of prehydrolysis liquor was done biologically using sacchromyces cerevisiae, zymomonus mobilis and torulla utilis as strains, which convert sugar into yeast. High percentages (75 to 90%) of reductions in sugars, COD, BOD and total dissolved solids were observed. Modeling was done to predict the rate equations for all the cases. Further to this biological treatment, ultra-centrifuging was done to separate out the formed yeast. The clarified biologically treated liquor was then subjected to UF/ RO to obtain the desired level of quality of permeate for disposal. The membrane operation becomes extremely simpler because of the depletion of micro-solutes (by bio means) as the osmotic pressure of the feed solution gets drastically reduced.

* R. L. Rath, C. Bhattacharjee, Shikha Jain, P. K. Bhattacharya, “Treatment of prehydrolysis liquor from pulp mill using biological route followed by Reverse Osmosis“, Chem. Eng. Technol., 28 (10), 1201-1211 (2005).

* R. Jayan, C. Bhattacharjee and P. K. Bhattacharya, “A combined biological and membrane based treatment of prehydrolysis liquor from pulp mill“, Separ. Purif. Technol., 45 (2), 119-130 (2005).

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