Reagent neutralization of chromium-containing inhibitor solution
O. N. TSYBULSKAYA, T. V. KSENIK, D. A. VOLKOV, A. A. YUDAKOV, A. V. PERFILYEV, A. A. KISEL
Institute of Chemistry, Far Eastern Branch of the Russian Academy of Sciences, Vladivostok, Russia
Keywords: corrosion inhibitor, chromium, reagent treatment, barium chloride, neutralisation, precipitation
Abstract
The problem of neutralising liquid solutions containing hexavalent chromium compounds is considered. The advantages, disadvantages and features of the application of basic methods for neutralising chromium-containing waste, non-traditional approaches and combined technologies are analysed. A readily feasible reagent method is presented for purifying concentrated and dilute solutions from chromium by treatment in two stages: reduction of hexavalent to trivalent chromium using ferrous sulphate or sodium sulphite as reducing reagents, and precipitation of chromium hydroxide. An installation is described in which electrolytes, rinsing and waste water from galvanic production were neutralised. A practical approach to the problem of neutralising the inhibitor solution is proposed, which is similar to the methods used for processing chromium-containing waste from galvanic production. A technological process has been developed for the reagent treatment of an inhibitor with a high concentration of chromates in solution (up to 40 g/L) in one stage by the direct precipitation of poorly soluble chromates. Barium chloride was used as the precipitant. To implement the technology, a schematic diagram of the installation was developed, and appropriate equipment was selected. As a result of processing the inhibitor, waste water, heavy precipitate of barium chromates are formed, which can be used in the future as a raw material, and sludge, which is a non-recyclable waste. Experimental processing of the inhibitor solution shows that the proposed method is effective, economically feasible, readily implementable under industrial conditions, it allows for high purification degree with low consumption of reagents, and reduces the amount of precipitates formed, which confirms the practical significance of the results obtained.
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