Methods for stabilizing one or more peroxide compounds in solution comprising adding to the solution an effective amount of at least one compound selected from the group comprising (i) cyclic carbonates; (ii) poly-phosphonic acid chelating agents and salts thereof, and alkaline pH adjusting agents with a pKb value of up to 3.0, wherein the w/w ratio of the poly-phosphonic acid chelating agent or salt thereof to alkali or alkaline earth metal hydroxide is from about 1:1 to about 50:1; and (iii) mixtures thereof. Also disclosed are solutions comprising the above compounds, uses of the above compounds to stabilize peroxide compounds in solutions, and compounds recited above for use as novel stabilizers.

Processes for regenerating alkali process streams are disclosed herein, including streams containing sodium hydroxide, magnesium hydroxide, and combinations thereof. Systems for regenerating alkali process streams are disclosed herein, including streams containing sodium hydroxide, magnesium hydroxide, and combinations thereof.

A method for recovering alkali and aluminum during treatment of Bayer red mud using a calcification-carbonation method, including steps of mixing the Bayer red mud with calcium aluminate or with calcium aluminate and lime, performing calcification dealkalization conversion in a high-concentration alkaline liquor, and carbonizing the calcified residues produced during dealkalization to obtain carbonized residues; and then performing low-temperature aluminum dissolution, aluminum precipitation and the like to obtain calcium aluminate products, which is returned to the calcification dealkalization conversion of the red mud for recycling. Part of an alkali-containing and aluminum-containing liquid phase after calcification dealkalization conversion can be used as supplementary alkali in the Bayer production course for recycling. The method is energy-saving and environmentally-friendly, and allows recovering alkali and aluminum from the red mud and harmless treatment of the Bayer red mud.

A method for recovering alkali and aluminum during treatment of Bayer red mud using a calcification-carbonation method, including steps of mixing the Bayer red mud with calcium aluminate or with calcium aluminate and lime, performing calcification dealkalization conversion in a high-concentration alkaline liquor, and carbonizing the calcified residues produced during dealkalization to obtain carbonized residues; and then performing low-temperature aluminum dissolution, aluminum precipitation and the like to obtain calcium aluminate products, which is returned to the calcification dealkalization conversion of the red mud for recycling. Part of an alkali-containing and aluminum-containing liquid phase after calcification dealkalization conversion can be used as supplementary alkali in the Bayer production course for recycling. The method is energy-saving and environmentally-friendly, and allows recovering alkali and aluminum from the red mud and harmless treatment of the Bayer red mud.

Process for making a chelating agent according to the general formula (I), R.sup.1CH(COOX.sup.1)N(CH2COOX.sup.1).sub.2 wherein R.sup.1 is selected from hydrogen, C.sub.1-C.sub.4-alkyl, phenyl, benzyl, CH.sub.2OH, and CH.sub.2CH.sub.2COOX.sup.1, X.sup.1 is (M.sub.H.sub.1-), M being selected from alkali metal, x is in the range of from 0.6 to 1, said process comprising the following steps: (a) providing a solid, a slurry or a solution of a compound according to general formula (II a) R.sup.1CH(COOX.sup.2)N(CH.sub.2CN).sub.2 wherein X.sup.2 is (M.sub.yH.sub.1-y), M being selected from alkali metal, y is in the range of from zero to 1, (b) contacting said solid or slurry or solution with an aqueous solution of alkali metal hydroxide, wherein the molar ratio of alkali metal ions to nitrile groups is in the range of from 0.6:1 to 0.95:1, (c) reacting said compound according to general formula (II a) with said alkali metal hydroxide.

Process for making a chelating agent according to the general formula (I), R.sup.1CH(COOX.sup.1)N(CH2COOX.sup.1).sub.2 wherein R.sup.1 is selected from hydrogen, C.sub.1-C.sub.4-alkyl, phenyl, benzyl, CH.sub.2OH, and CH.sub.2CH.sub.2COOX.sup.1, X.sup.1 is (M.sub.H.sub.1-), M being selected from alkali metal, x is in the range of from 0.6 to 1, said process comprising the following steps: (a) providing a solid, a slurry or a solution of a compound according to general formula (II a) R.sup.1CH(COOX.sup.2)N(CH.sub.2CN).sub.2 wherein X.sup.2 is (M.sub.yH.sub.1-y), M being selected from alkali metal, y is in the range of from zero to 1, (b) contacting said solid or slurry or solution with an aqueous solution of alkali metal hydroxide, wherein the molar ratio of alkali metal ions to nitrile groups is in the range of from 0.6:1 to 0.95:1, (c) reacting said compound according to general formula (II a) with said alkali metal hydroxide.

Waste water is treated by contacting it with sodium to form hydrogen which is then contacted with air in a combustion chamber to produce clean water and heat.

A method for optimizing reduction and content of total titratable alkali of green liquor of a recovery boiler. The method comprises producing green liquor in a dissolving tank by conveying smelt and weak white liquor into the dissolving tank and measuring at least the contents of sodium sulphate, sodium hydroxide, sodium sulphide, and sodium carbonate of the green liquor. The method comprises controlling at least a process parameter of a recovery boiler to maximize the reduction of the recovery boiler and controlling the flow of the weak white liquor into the dissolving tank to optimize the content of total titratable alkali of the green liquor. In addition, a system for producing green liquor with optimized reduction and content of total titratable alkali. The system comprises a first sensor arrangement, a first and a second regulator, and a processing unit arrangement configured to perform the method.

A method for optimizing reduction and content of total titratable alkali of green liquor of a recovery boiler. The method comprises producing green liquor in a dissolving tank by conveying smelt and weak white liquor into the dissolving tank and measuring at least the contents of sodium sulphate, sodium hydroxide, sodium sulphide, and sodium carbonate of the green liquor. The method comprises controlling at least a process parameter of a recovery boiler to maximize the reduction of the recovery boiler and controlling the flow of the weak white liquor into the dissolving tank to optimize the content of total titratable alkali of the green liquor. In addition, a system for producing green liquor with optimized reduction and content of total titratable alkali. The system comprises a first sensor arrangement, a first and a second regulator, and a processing unit arrangement configured to perform the method.

This disclosure describes systems and methods for removing uranium hexafluoride (UF.sub.6) and/or other uranium fluoride (uranium fluorides identified herein generally as UF.sub.x) gases from a hydrogen fluoride (HF) gas stream.