Electro Membrane Processes

Electro Membrane Process

Discipline of Inorganic Materials and Catalysis

Discipline of Marine Biotechnology and Ecology

Salt & Marine Chemicals

Analytical Sciences

Phytosalnity

Reverse Osmosis Engineering

This division is indulged in three major areas such as

1. Solid polymer electrolyte membrane cells. Developed highly efficient electrochemical methods involving two-compartmental cells with ion-exchange membrane as solid polymer electrolytes for the preparation of (i) Citric acid from Maleic acid (ii) Dimethyl sulfone from dimethyl sulfoxide (iii) Potassium (alkali) iodate from iodine for salt iodisation, (iv) Ammonia from inorganic nitrites/nitrates (v) Bromine from bittern/bromide containing sources.
2. Decoloration of industrial azodye effluents. Studied the electrochemical decoloration of reactive azo-dye effluent belonging to one of the leading industry in Gujarat and achieved about 94-99% decolorization of various azo dye effluents of different plants under single pass conditions at a cost of around 0.02 - 0.04 per paise per liter.
3. Eco-friendly solid brominating reagents (Green bromine). Two solid brominating reagents were developed for bromination of a wide range of organic substrates through substitution and addition mechanisms. They are stable, easy to transport, non-hazardous and convenient to use in the bromine reactions in normal experimental conditions. The end liquor contains simple inorganic salts and hence are safe to discharge with nominal treatment.
4. Eco-friendly preparation of some industrially important bromo compounds. The procedures for the preparation of Tetrabromobisphenol-A (TBBPA-largely used flame retardant), 2,4,4,6-Tetrabromo-2,5-cyclohexadienone & N-bromo-succinimide(secondary brominating reagents for selective brominations), bromo benzene etc have been established with the solid brominating reagents.
5. Extraction of valuable metals in their reusable form. Methods have been developed for the recovery of chromium as sodium dichromate and manganese as MnO₂ from their respective acid effluents for reuse.

2. Development of polyethylene based interpolymer membranes and design of electrodialysis units

 

We are a pioneer-leading Institute working on ion exchange membranes and electrodialysis. Indigenously developed interpolymer ion exchange membranes are being used for various applications. It has also developed heterogeneous monopolar and Bipolar membranes. Development of these membranes enhances the scope of applications. Ion exchange membranes are now being used for various industrial applications to reduce the pollution, recover of water for reuse, separation and concentration of high value and toxic materials in addition to desalination of brackish and seawater. The domestic desalination unit developed by this Institute is marketed to the users to obtain potable water from brackish water. The properties of interpolymer ion-exchange membranes are equivalent to commercially available membranes. These membranes are being exported to China for R&D purpose. The Institute is also focusing for the use of non-conventional energy such as solar energy as a source of energy to be used in the ED technology. Efforts are being directed towards the development of improved membranes such as thermally stable membranes and the membranes for fuel cells etc. In addition to R&D activities this Institute is also engaged in installation and operation of various capacities of desalination plants in rural areas to provide safe drinking water to needy people.

The biggest ED unit fabricated and installed by us is of the size 100 cm x 50 cm with 150 cell pairs of ion exchange membranes which can produce 800 LPH of potable water of 500 ppm TDS from a feed water of around 3000 ppm brackishness. ED units of lower capacity can also be designed as per the requirement.

Development of Domestic ED unit. The Institute has also developed domestic ED unit to desalinate brackish water to obtain potable water required for domestic purpose. This newly developed unit treats about 3,000 ppm or less brackish water and gives potable water of 500 ppm total dissolved solids at an estimated rate of around 12 - 15 LPH. The power consumption would be of 2.0 - 2.5 KWH per cubic meter of product water.

The preparation of Organic-Inorganic based PVA-SiO₂ hybrid membranes has also been developed as described below on a laboratory scale by using sol-gel process under acidic and basic conditions.

Novel method for the preparation of thermally stable and highly charged membranes. The nano-structured organic-inorganic hybrid materials are currently the objects of intensive research, because they combine in a single solid both the attractive properties of a mechanically and thermally stable inorganic backbone and the specific chemical reactivity and flexibility of the organo-functional group. Organic-inorganic hybrid membrane based on PVA-SiO₂ hybrids, in which –SO₃H groups are introduced by oxidation of the existing –SH group in mercaptopropylmethyldimethoxysilane (MPDMS), were prepared using sol-gel process under acidic and basic conditions and their physicochemical and electrochemical properties were also studied. But proton-exchange membranes with sulphonic acid functional groups has a disadvantage regarding thermal degradation of sulphonic acid group at elevated temperature (around 200-250 ⁰C). Thus it was desirable to develop PVA/Si composite membrane with phosphonic acid functional group.

Organic-inorganic composite membranes based on PVA-SiO₂ (Aminopropyltri-ethoxysilane (APES)) hybrid were prepared using sol-gel process in aqueous medium with desired composition of silica. Obtained membranes were subjected to the phophorylation of aminopropylsilica monomer by refluxing it in 1 part (by weight) of formaldehyde and 1 part of phosphorous acid (by weight) for desired period in order to get different extent of phophorylation.

Characterization of these membranes by TGA, DMA and also boil water test revealed an adequate thermal and mechanical stability. Typical TGA curves and SEMs for these membranes with 50 and 70% silica content are also presented. These membranes with high water uptake, moderate ion-exchange capacity and good proton conductivity in comparison to commercial available Nafion 117 membrane, offers a new dimension for the development of proton-exchange membrane in aqueous medium. Methanol permeability of these membranes were also measured and found to be quite low in compare to Nafion 117. Although PVA-SiO₂ composite membranes with phosphonic acid functional groups exhibited comaparatively low proton conductivity but less methanol permeability extent their suitability for the direct methanol fuel cell (DMFC). From the result of proton conductivity and methanol permeability, we calculated the selectivity parameter (SP), which can be defined can be defined as (SP = ^m/P_MeOH) where ^m is the proton conductivity and P_MeOH is methanol permeability, to directly compare the applicability for DMFC between the membranes. Selectivity parameter for different membranes as well for Nafion 117 membrane is presented for the comparison purpose. Composite membrane with 50% Si content were exhibited about 20% more selectivity in comparison to Nafion 117 membrane.

Technology packages available with CSMCRI for ED

• Brackish or sea water desalination
• Domestic ED unit for the treatment of brackish water.
• ED Package for the desalination of brackish water of various capacities.
• ED technology package for the desalination of sea water to potable water.
• Desalting of industrial mixtures or effluents
• Technology package for treating industrial effluents to recover high value chemicals for the pollution reduction.
• Separation of inorganics and organics or bioactive molecules with very high purity by electrodialysis with conducting spacers.
• Ion-exchange membranes based on the interpolymer of polyvinyl chloride and styrene-divinyl benzene copolymer.
• ED package for the treatment of deacidification of fruit juices, deashing of sugarcane juice, demineralization of amino acids etc.
• Ion-exchange membranes based on the interpolymer of polyvinyl chloride and styrene-divinylbenzene copolymer.

Expertise availability in membrane designing and desalination applications

• Designing of membranes with desired charge density and porosity for different electro-membrane processes
• Separation/purification of bioactive molecules by electro-driven membrane separation techniques
• Consultancy work related to the electro-driven membrane separation technologies