Concentrated Alkaline Media Research Articles

A Study of a Solvent Extraction Method for the Treatment of Spent Electrolyte Solutions Generated in Nickel-Cadmium (Ni-Cd) Battery Manufacturing

Spent electrolyte generated in the Ni-Cd rechargeable battery manufacturing process containing about 400 g l−1 KOH, 50 g l−1 K2CO3 and 20 mg l−1 Cd, has a high reuse value if the cadmium is removed. We performed a systematic investigation to apply the solvent extraction technique to remove cadmium from the spent electrolyte. Potential extractants for cadmium were carefully selected and the performances of the solvents containing these extractants were studied. Amongst the ten extractants that were tested, three acidic chelating extractants, viz., Cyanex 301 (Cytec Canada Inc., a dithiophosphinic acid), Cyanex 302 (Cytec Canada Inc., a monothiophosphinic acid) and Kelex 100 (Witco, 7-alkyl-8-hydroxyquinolines) showed favourable extraction characteristics for cadmium from the highly concentrated alkaline medium. Kelex 100 also showed excellent back-extraction (stripping) characteristics for the cadmium extracted; cadmium could be quantiatively stripped from the Kelex 100 solutions with a 0.1 M HCl or 0.1 M H2SO4 solution. A process employing Kelex 100 as the extractant was developed. The feasibility of this process was demonstrated with automated mixer-settler solvent extraction units using real spent electrolyte generated in a Ni-Cd battery manufacturing plant.

An improved method for the colorimetric assay of thiacetazone in pharmaceutical preparations.

An improved colorimetric procedure for the determination of thiacetazone (tibione) has been developed. It is based on the complete hydrolysis of tibione in a concentrated alkaline medium, after which the hydrolytic product is subjected to diazotisation and coupling with α-naphthylethylenediamine dihydrochloride. The procedure suggested in this paper eliminates some disadvantages of the original method and affords reproducible assay results for tibione in galenical preparations.

The nucleophilic substitution reactions in s-triazanic systems—I : Kinetics and mechanism of alkaline hydrolysis of the melamine

It was established through kinetic determinations that the alkaline hydrolysis of melamine is an S NAr2 mechanism scheme. The two process steps have near reaction rates, but as each depends upon the reaction conditions, the one or the other can determine the rate. In concentrated alkaline media (2–5M NaOH) the elimination step of the amide ion is slow, and in dilute alkali (0.01–1M NaOH) as well as in weak acids, the step involving a nucleophilic attack determines the rate.

Velocity of hydrolysis of sodium chloroacetate in alkaline medium and concentrated solutions)

AbstractThe reaction velocity of the hydrolysis of sodium monochloroacetate was determined in concentrated solutions and alkaline medium at 40° and 50°.It was found that the reaction follows the bimolecular equation. However, the reaction constant increases considerably with the normality of the hydroxide, which was explained by an effect of the total electrolyte concentration. The temperature coëfficient of the reaction was calculated to be 3.0 per 10°.