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Oil-Water Separation: Emulsion Breakers

Oily wastewater occurs when oil enters a water body and becomes emulsified in the form of an oil water emulsion. Waste oil emulsions can also form where water becomes emulsified in oil. In either case, these emulsions require a customized oil water separation treatment program. ChemTreat’s treatment programs include chemical, electrolytic, and physical methods.

ChemTreat’s chemical treatments include a full portfolio of emulsion flocculants. Emulsion flocculants are suspensions of minute beads of high molecular weight polymer in water, with the beads having been emulsified in an oil carrier. The minute beads are approximately 1 micron in diameter and contain concentrated polymer dissolved in water. These concentrated polymer beads or “hydrogels” are dispersed in the carrier of high flashpoint mineral oil by means of a dispersing surfactant which keeps the hydrogels from coalescing into larger droplets. Because the hydrogels are denser than the oil carrier, they are prone to settle over time resulting in concentrated polymer solids on the bottom of a container and oil on the top. This separation will be faster if the droplets are large, so keeping the droplets small and well dispersed is important for stability of the product.

Emulsion flocculants are typically made as co-polymers of acrylamide, a nonionic building block, along with a charge bearing monomer. In the case of anionic flocculants, the anionic charge is provided by co-polymerizing acrylic acid along with the acrylamide monomer. The ratio of acrylic acid to acrylamide determines the degree of charge on the molecule.

In the case of anionic flocculants, the cationic charge is provided by co-polymerizing “AETAC”, a methyl acrylate derived cationic monomer along with the acrylamide monomer. The ratio of AETAC to acrylamide determines the degree of charge on the molecule.

Because the hydrogels are made up of very tightly coiled, concentrated polymer beads, mixing energy and time are required for full contact of the hydrogels with the water, and to enable the polymer chains to fully uncoil. The polymer chains may be cationic, anionic, or nonionic, and the amount of charge on the polymer chains varies. The charge on the chain helps to uncoil the chain, so a higher charged polymer will open faster than a low charged or uncharged polymer.