Abstract: A process for the production of a vanadium compound from carbonaceous residues containing vanadium, which includes the steps of: (a) combusting the carbonaceous residues at a temperature of 500-690° C. in an oxygen-containing gas to form vanadium-containing combustion residues; (b) heating the vanadium-containing combustion residues at a temperature T in ° C. under an oxygen partial pressure of at most T in kPa wherein T and P meet with the following conditions: log10(P)=−3.45×10−3×T+2.21 500≦T≦1300 to obtain a solid product containing less than 5% by weight of carbon and vanadium at least 80% of which is tetravalent vanadium oxide; (c) selectively leach tetravalent vanadium ion with sulfuring acid at pH in the range of 1.5-4; (d) separating a liquid phase from the leached mixture; (e) adding an alkaline substance to the liquid phase to adjust the pH thereof in the range of 4.5-7.

Abstract: A process for the production of a vanadium compound from carbonaceous residues containing vanadium, which includes the steps of:

Abstract: A redox battery electrolyte is prepared from a chromium and/or iron base raw material containing nickel as impurities by dissolving the raw material in a hydrochloric acid-containing aqueous liquid to form a solution containing chromium ions and/or iron ions and nickel ions, the resulting solution being subjected to a cathodic reduction in the presence of lead ions until the electric potential thereof becomes lower than -0.6 V vs. saturated calomel electrode, thereby to remove the nickel ions therefrom.

Abstract: A wet process for the desulfurization of exhaust gas comprising the following operation steps so as to eliminate and recover sulfur dioxide from exhaust gas containing it:(A) a step of absorbing sulfur dioxide by contacting exhaust gas with an absorbent mainly containing potassium salts of tartaric acid having a pH value of 4.5-6.5,(B) a step of recovering sulfur dioxide by drawing out a part of the absorbent in the step (A) and heating it to liberate and recover sulfur dioxide,(C) a step of circulating the absorbent by cooling the absorbent from the step (B) to a temperature suitable for the absorption of exhaust gas and recycling it to the step (A).