Impurities removal from waste solids in the production of soda ash, sodium bicarbonate and/or other derivatives

A method for reducing the content of impurities in a waste solid thereby allowing it to be used as a feed to a process which produces crystalline sodium carbonate, sodium bicarbonate, sodium sulfite, or other derivatives, the method comprising the following steps:

• providing a mass of a waste solid comprising a pond solid recovered from at least one waste pond, said pond solid comprising impurities selected from the group consisting of silicates, sodium chloride, sodium sulfate, organic matter, and combinations of two or more thereof, said pond solid further comprising one sodium compound selected from the group consisting of sodium carbonate decahydrate, sodium carbonate monohydrate, sodium carbonate heptahydrate, sodium bicarbonate, sodium sesquicarbonate, and any combinations of two or more thereof;
• contacting said waste solid mass with a leach solution to selectively dissolve at least a portion of a first impurity from the contacted mass into the leach solution to form a leachate and a leached residue;
• collecting the leached residue;
• dissolving at least a portion of the leached residue in an aqueous medium to form a liquor;
• carrying out a second impurity removal step comprising performing a magnesium treatment to form a treated liquor, said treatment comprising adding a magnesium compound during dissolution of the leached residue or adding a magnesium compound to said liquor or a portion thereof after dissolution of the leached residue in order to form water-insoluble matter with at least a portion of a second impurity, and passing said treated liquor though at least one separation unit to remove water-insoluble matter and to obtain a purified solution;
• wherein at least a portion of said purified solution provides a feedstock to a process which produces a crystalline product comprising sodium carbonate, sodium bicarbonate, sodium sulfite, or other derivatives.