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Process for recovering high boiling solvents from a photolithographic waste stream comprising at least 10 percent by weight of monomeric units

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A method of recovering benzyl alcohol gamma butyrolactone or propylene carbonate from an impure effluent stream of an industrial process is provided. The effluent waste stream contains greater than about 10 percent by weight of monomeric units that are reacted to form larger oligomers and polymers. The first step in the recovery process involves polymerizing the monomeric units present in the effluent waste stream under conditions effective to reduce the concentration of monomeric units in the waste stream to less than about 10 weight percent. The waste stream then is fed to a first separation stage where it is separated into (i) a gaseous stream of water soluble gases and volatile contaminants and (ii) a suspension comprising the high boiling solvent semi-volatile materials and non-volatile contaminants and materials. Then the dewatered low vapor pressure high boiling solvent-containing suspension is either distilled or evaporated to separate the high boiling solvent from non-volatile materials. In this second separation stage the solvent-containing suspension is separated into (i) a solvent-containing fraction and (ii) a sludge fraction. The sludge fraction contains non-volatile materials in the high boiling solvent.

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