The present application pertains to processes for making calcium oxide and/or sulfuric acid from calcium sulfate. In some embodiments the processes comprise reacting a component comprising calcium sulfate with a second component comprising magnesium sulfite under conditions to form a solid comprising calcium sulfite and a solution comprising magnesium sulfate. Next, at least a portion of the solid comprising calcium sulfite is decomposed to form a second solid comprising calcium oxide, or calcium hydroxide, or cement, or clinker, or any combination thereof.

In some embodiments the application pertains to processes comprising reacting a component comprising an alkaline earth weak acid with a component comprising an acid to form a component comprising an alkaline earth acid anion and a component comprising a weak acid derivative. At least a portion of the component comprising the alkaline earth acid anion is reacted with a component comprising an alkali sulfate to form a component comprising alkaline earth sulfate and a component comprising an alkali acid anion. At least a portion of the component comprising alkaline earth sulfate is decomposed to form a component comprising alkaline earth oxide, or alkaline earth hydroxide, or alkaline earth carbonate, or alkaline earth sulfide, or a derivative thereof, or any combination thereof, and a component comprising sulfur dioxide, or oxygen, or sulfur trioxide, or a derivative thereof, or any combination thereof.

In some embodiments the application pertains to processes comprising reacting a component comprising an alkaline earth weak acid with a component comprising an acid to form a component comprising an alkaline earth acid anion and a component comprising a weak acid derivative. At least a portion of the component comprising the alkaline earth acid anion is reacted with a component comprising an alkali sulfate to form a component comprising alkaline earth sulfate and a component comprising an alkali acid anion. At least a portion of the component comprising alkaline earth sulfate is decomposed to form a component comprising alkaline earth oxide, or alkaline earth hydroxide, or alkaline earth carbonate, or alkaline earth sulfide, or a derivative thereof, or any combination thereof, and a component comprising sulfur dioxide, or oxygen, or sulfur trioxide, or a derivative thereof, or any combination thereof.

In some embodiments the application pertains to processes comprising reacting a component comprising an alkaline earth weak acid with a component comprising an acid to form a component comprising an alkaline earth acid anion and a component comprising a weak acid derivative. At least a portion of the component comprising the alkaline earth acid anion is reacted with a component comprising an alkali sulfate to form a component comprising alkaline earth sulfate and a component comprising an alkali acid anion. At least a portion of the component comprising alkaline earth sulfate is decomposed to form a component comprising alkaline earth oxide, or alkaline earth hydroxide, or alkaline earth carbonate, or alkaline earth sulfide, or a derivative thereof, or any combination thereof, and a component comprising sulfur dioxide, or oxygen, or sulfur trioxide, or a derivative thereof, or any combination thereof.

In some embodiments the application pertains to processes comprising reacting a component comprising an alkaline earth weak acid with a component comprising an acid to form a component comprising an alkaline earth acid anion and a component comprising a weak acid derivative. At least a portion of the component comprising the alkaline earth acid anion is reacted with a component comprising an alkali sulfate to form a component comprising alkaline earth sulfate and a component comprising an alkali acid anion. At least a portion of the component comprising alkaline earth sulfate is decomposed to form a component comprising alkaline earth oxide, or alkaline earth hydroxide, or alkaline earth carbonate, or alkaline earth sulfide, or a derivative thereof, or any combination thereof, and a component comprising sulfur dioxide, or oxygen, or sulfur trioxide, or a derivative thereof, or any combination thereof.

A method can include coupling sulfur dioxide depolarized electrolysis (e.g., electrochemical oxidation of sulfur dioxide to sulfuric acid with electrochemical reduction of water to hydrogen) with the contact process to facilitate formation of high concentration sulfuric acid with concurrent hydrogen production. The sulfuric acid and hydrogen can optionally be used cooperatively for downstream processes (e.g., metal extraction from ore, fertilizer production, hydrocarbon processing, etc.).

A method can include coupling sulfur dioxide depolarized electrolysis (e.g., electrochemical oxidation of sulfur dioxide to sulfuric acid with electrochemical reduction of water to hydrogen) with the contact process to facilitate formation of high concentration sulfuric acid with concurrent hydrogen production. The sulfuric acid and hydrogen can optionally be used cooperatively for downstream processes (e.g., metal extraction from ore, fertilizer production, hydrocarbon processing, etc.).

A method of separating oxygen from a body of water includes providing a colony of denitrifying bacteria submerged in the body of water. The colony of denitrifying bacteria can be used to convert at least a portion of nitrogen oxides present in the body of water to nitrogen gas. The method can also include collecting the nitrogen gas and bubbling the nitrogen gas through a portion of water from the body of water to remove dissolved oxygen from the portion of water. This can form a mixture of the nitrogen gas and oxygen gas.

A method of separating oxygen from a body of water includes providing a colony of denitrifying bacteria submerged in the body of water. The colony of denitrifying bacteria can be used to convert at least a portion of nitrogen oxides present in the body of water to nitrogen gas. The method can also include collecting the nitrogen gas and bubbling the nitrogen gas through a portion of water from the body of water to remove dissolved oxygen from the portion of water. This can form a mixture of the nitrogen gas and oxygen gas.

Improved systems and methods are disclosed for treating tail gas in a sulfuric acid production plant. A tail gas treatment system is employed which comprises a product stripper and a purge gas scrubber. The inventive arrangement provides an advantageous economical way to remove high levels of SO.sub.2 from the tail gas stream.