A process for recovering alkali from power boiler ash is provided. The power boiler ash is first contacted with Na.sub.2CO.sub.3 to produce a mixture containing settling and non-settling solid particles. A fraction of the settling particles is then separated from the mixture to produce a first clarified alkaline solution. The first clarified alkaline solution contains species such as NaOH and KOH depending upon the power boiler ash characteristics. The non-settling solid particles may optionally be further separated from the first clarified alkaline solution to obtain a second clarified alkaline solution. This process is also applicable for the extraction of alkali from other oxide/hydroxide containing materials.

One or more processes for producing lithium hydroxide monohydrate and related systems are described herein. One or more of the processes generally include feeding a slurry to one or more gravity separators, and separating the slurry using the one or more gravity separators into an underflow slurry and overflow slurry. The slurry comprises lithium hydroxide monohydrate and one or more insoluble impurities.

A process for preparing metal oxide comprising (i) at least one metal chosen from nickel and cobalt and optionally (ii) at least one metal chosen from manganese, lithium and aluminum. The process comprising: reacting a metal sulfate comprising (i) at least one metal chosen from nickel and cobalt and optionally (ii) at least one metal chosen from manganese, lithium and aluminum with lithium hydroxide and optionally a chelating agent to obtain a solid comprising a metal hydroxide comprising (i) at least one metal chosen from nickel and cobalt and optionally (ii) at least one metal chosen from manganese, lithium and aluminum, and a liquid comprising lithium sulfate, the metal sulfate comprising (i) at least one metal chosen from nickel and cobalt and optionally (ii) at least one metal chosen from manganese, lithium and aluminum; separating the liquid and the solid from one another to obtain the metal hydroxide; submitting the liquid comprising lithium sulfate to an electromembrane process for converting the lithium sulfate into lithium hydroxide; and reusing at least a first portion of said lithium hydroxide obtained by the electromembrane process for reacting with the metal sulfate; reacting at least a second portion of said lithium hydroxide obtained by the electromembrane process with the obtained metal hydroxide to obtain a mixture of metal hydroxides; and roasting said mixture of metal hydroxides to obtain the metal oxide.

A process for preparing metal oxide comprising (i) at least one metal chosen from nickel and cobalt and optionally (ii) at least one metal chosen from manganese, lithium and aluminum. The process comprising: reacting a metal sulfate comprising (i) at least one metal chosen from nickel and cobalt and optionally (ii) at least one metal chosen from manganese, lithium and aluminum with lithium hydroxide and optionally a chelating agent to obtain a solid comprising a metal hydroxide comprising (i) at least one metal chosen from nickel and cobalt and optionally (ii) at least one metal chosen from manganese, lithium and aluminum, and a liquid comprising lithium sulfate, the metal sulfate comprising (i) at least one metal chosen from nickel and cobalt and optionally (ii) at least one metal chosen from manganese, lithium and aluminum; separating the liquid and the solid from one another to obtain the metal hydroxide; submitting the liquid comprising lithium sulfate to an electromembrane process for converting the lithium sulfate into lithium hydroxide; and reusing at least a first portion of said lithium hydroxide obtained by the electromembrane process for reacting with the metal sulfate; reacting at least a second portion of said lithium hydroxide obtained by the electromembrane process with the obtained metal hydroxide to obtain a mixture of metal hydroxides; and roasting said mixture of metal hydroxides to obtain the metal oxide.