No abstract

Separation and recovery of nickel from an actual waste solution of electroless nickel-phosphorous plating solution has been investigated, employing synergistic extraction with bis(2-ethylhexyl)phosphoric acid (D2EHPA) and nicotinic acid ester. The extractability of Ni with D2EHPA alone is low, due to suppression by phosphorous compounds coexisting in the waste solution. Effective extraction can be achieved with a synergistic extraction system, using both D2EHPA and nicotinic acid ester. By optimizing the operational conditions, satisfactory extraction and stripping of more than 95 % yield can be achieved. The present extraction -stripping processing can be successfully repeated, although a small amount of the nicotinic compound is dissolved into the aqueous solution.

A thermal-swing adsorption system for Eu(III) was developed using the thermosensitive polymer, poly(N-isopropylacrylamide) (PNIPAM), combined with the acidic extractants, acid phosphoxy ethyl methacrylate (Phosmer-M) or acrylic acid. The phase transition of the PNIPAM/acidic extractant copolymers was successfully achieved by changing the temperature around the lower critical solution temperature (LCST). The thermal-swing adsorption of Eu(III) was correspondingly achieved by changing the temperature of the aqueous solution. The adsorption ability of Eu(III) was increased when the temperature became higher than the LCST, due to the change in the hydrophobicity as well as in the volume of the copolymer. The difference in the adsorption at lower and higher temperatures against the LCST was increased with decreasing crosslinking agent during the preparation of the copolymer. The copolymer possessed sufficient loading and release capacity for Eu(III) even in repeated processes of the thermal-swing adsorption.