| 摘要 |
Working-up of used photographic colour processing baths, namely the following baths with their predominant contents in brackets : bleach or blixing (ammonium-Fe-EDTA complex-former), fixing (thiosulphates, especially NH4- or optionally Na-thio-sulphate) and developing (especially Na sulphite): comprises the following steps subsequent to removing the Ag by conventional means: (i) setting the multi-component starting solution to pH 13.5-14 using NaOH and separating off the precipitated Fe(OH)3 derived from the decomposed Fe complex; (ii) setting the pH to 10 using acid and separating off the ammonia; (iii) setting the pH to 0.5 using concentrated HCl to decompose the thiosulphate into elemental S and sulphurous acid and separating off the S; (iv) raising the pH of the sulphurous acid solution to ca. 1.5 using an inorganic liquor and separating off the crystallised EDTA; and (v) setting the pH of the residual solution to 3 by addition of the developing bath and converting the sulphite to SO2 which is then separated off. |
