Process for separating and recovering an anionic dye from an aqueous solution

A process for separating and recovering anionic dye molecules from an aqueous solution that comprises the steps of:

• (a) contacting separation particles with an aqueous solution containing (i) anionic dye molecules and (ii) a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt to form a solid/liquid phase admixture, said anionic dye molecules containing at least two 5- or 6-membered aromatic rings and at least one substituent group having a pK.sub.a value one unit below the pH value of said aqueous solution, said separation particles comprising reacted cross-linked poly(styrene-vinyl benzyl halide) particles having a plurality of covalently bonded --X--(CH.sub.2 CH.sub.2 O).sub.n --CH.sub.2 CH.sub.2 R groups wherein X is O, S, NH or N--(CH.sub.2 CH.sub.2 O).sub.m --R.sup.3 where m is a number having an average value of zero to about 225, n is a number having an average value of about 40 to about 130, R.sup.3 is hydrogen, C.sub.1 -C.sub.2 alkyl, 2-hydroxyethyl or CH.sub.2 CH.sub.2 R, and R is a C.sub.1 -C.sub.10 hydrocarbyl ether having a molecular weight up to about one-tenth that of the --(CH.sub.2 CH.sub.2 O).sub.n -- portion, said separation particles having a percent CH.sub.2 O/mm.sup.2 of particle surface area of greater than about 9000 and to about 20,000;
• (b) maintaining said contact for a time period sufficient to form anionic dye molecule-bound separation particles and an aqueous solution having a reduced concentration of anionic dye molecules;
• (c) separating said anionic dye molecule-bound separation particles from the aqueous solution of step (b) in the presence of an aqueous solution of a poly(ethylene glycol) liquid/liquid biphase-forming amount of a salt to form a second solid/liquid phase admixture containing anionic dye molecule-bound separation particles;
• (d) contacting said anionic dye molecule-bound separation particles of step (c) with second aqueous solution that does not contain a poly(ethylene glycol) liquid/liquid biphase-forming amount of dissolved salt to free the anionic dye molecules from the separation particles and form an aqueous solution containing free anionic dye molecules at a higher concentration than that of said first-named aqueous solution of step (a);
• and
• (e) recovering the anionic dye molecule-containing aqueous solution of step (d).

A process for recovering anionic dye molecules from an aqueous solution that comprises the steps of:

• (a) contacting separation particles with an aqueous solution containing (i) anionic dye molecules and (ii) a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt to form a solid/liquid phase admixture, said anionic dye molecules containing at least two 5- or 6-membered aromatic rings and at least one sulfonate substituent group, said separation particles comprising reacted cross-linked poly(styrene-vinyl benzyl halide) particles having a plurality of covalently bonded --O--(CH.sub.2 CH.sub.2 O).sub.n --CH.sub.2 CH.sub.2 R groups wherein n is a number having an average value of about 40 to about 130, and R is a C.sub.1 -C.sub.10 hydrocarbyl ether having a molecular weight up to about one-tenth that of the --(CH.sub.2 CH.sub.2 O).sub.n -- portion, said separation particles having a percent CH.sub.2 O/mm.sup.2 of particle surface area of greater than about 9000 and to about 20,000;
• (b) maintaining said contact for a time period sufficient to form anionic dye molecule-bound separation particles and an aqueous solution having a reduced concentration of anionic dye molecules;
• (c) separating said anionic dye molecule-bound separation particles from the aqueous solution of step (b) in the presence of an aqueous solution of a poly(ethylene glycol) liquid/liquid biphase-forming amount of a salt to form a second solid/liquid phase admixture containing anionic dye molecule-bound separation particles;
• (d) contacting said anionic dye molecule-bound separation particles of step (c) with second aqueous solution that does not contain a poly(ethylene glycol) liquid/liquid biphase-forming amount of dissolved salt to free the anionic dye molecules from the separation particles and form an aqueous solution containing free anionic dye molecules at a higher concentration than that of said first-named aqueous solution of step (a);
• and
• (e) recovering the anionic dye molecule-containing aqueous solution of step (d).