Concentration & Desalination of Dyes is being done all over the world for production of salt free concentrated high purity product. This has been possible through use of proprietary membranes developed after years of research.

Dyestuff producers require the salt content in the concentrated dye to be reduced to a certain level. The following is an illustration:

In the production of bulk drugs the main molecule is produced in the reactor/fermenter followed by multi-step separations and purifications involving various types of physical and/or chemical processes. At the penultimate stage often the drug is precipitated and separated by centrifugation or filtration. The centrifugate/filtrate, also known as Mother Liquor (ML), is normally sent to ETP for further treatment essentially to reduce BOD, COD, SS, TDS etc. to acceptable limits fixed by the respective pollution control boards.

Incorporation of suitable RO on the ML can recover the valuable drugs which otherwise causes pollution when drained to the ETP. Typically 0.2 to 3% of the valuable drugs, depending upon their solubility, are lost into the ML as the existing processes are incapable of further recovery. However, this small but significant quantity can be recovered if concentrated through RO. Therefore RO acts as a partial pollution control system besides being a source of additional revenue. Following Illustrations explain the general scheme recovery of specific drug/precursors.

General
6-Amino Penicillanic Acid (6 APA) is an intermediate, in the manufacturing of synthetic penicillus, with a molecular weight of 216. It is manufactured by enzymatic hydrolysis of Pen-G salt.

The typical mother liquor from a chemical reaction contains 0.3 to 0.4% of dissolved 6 APA, 15% Methanol, 2% Methylene Chloride and 3 - 4% salts. The membrane process concentrates the 6 APA to 3 - 4% using the solvent stable SelRO membranes. These membranes being solvent stable are not affected by organic solvents. The concentrated 6 APA solution thus obtained, can be added upstream before solvent extraction for additional recovery, the permeate stream obtained from the membrane system goes to the effluent with reduced pollution load to the extent of 6 APA recovery. Typically 70% recovery is possible, which makes the membrane process extremely attractive with pay back period of less than 6 months.

Recovery Of Spent Caustic In Dairies

Introduction:
To maintain high hygienic standards and to ensure proper functioning of the equipments, dairy evaporators, pipe line and other equipments are regularly cleaned after each production cycle. The cleaning solution typically contains 2 to 4% caustic and additional compounds such as antifoams and chelating agents. This solution removes caramelized organics, precipitated proteins, pectins and fats from the surface of tanks, pipes, heat exchangers and evaporators.

The contaminated solution, after cleaning, still contains high concentration of active caustic. This solution is generally reused in one of the following ways :

The solution is reused 7-10 times and then the CIP tank is completely discharged. Approximately 10% of the caustic solution is discharged daily while the remaining volume is recycled to the CIP tank.

In both the cases, discharged caustic solution is heavily loaded with dispersed and soluble organic contaminant which has to be neutralized. It is also difficult to discharge this effluent due to pollution control regulations and also from ecological point of view. As a solution to the above, the spent caustic solution can be passed through membranes for very effective reuse. Membrane system is very compact, energy saving, easy to operate and eco friendly.

Preparative HPLC is used in reverse phase (water/solvent) or normal phase (solvent/solvent) to separate the main product fraction from the contaminating molecules. The waste stream is spent solvent that must be discarded. While the main fraction contains the product that is to be concentrated.

A hydrophilic solvent stable membrane is used for reverse phase separations. In this example, the product stream from the HPLC contains a low molecular weight pharmaceutical compound dissolved in a methanol: water solution (90:10). The compound concentration is 0.5% leaving the HPLC. The product is concentration (0.025%) in the same solvent composition and is processed in the solvent recovery system. The overall solvent recovery is 96%.

Decolorisation of Heavy Metal Removal from Acidic Stream

Due to stability in acidic and basic conditions, NF membranes can be applied in the processing of inorganic acids and in the treatment of acid waste streams. The membranes can be used in the entire pH range (0 – 14) and at temperatures reaching 70^oC.

The mineral acid product quality is effectively enhanced by the use of the membrane system in the down stream processing. The membranes allow the product (acid) to pass with practically no retention (0-4%). The contaminants, such as dissolved organic molecules, which give the acid a characteristic coloration, are retained by the membrane with high retention values (>98% - 99%). In this manner a colourless acid stream, free of organic, is obtained. One popular example of this application is Decolourisation and Up-gradation of Green Phosphoric Acid.