Method for processing a salt solution together with carbon dioxide

A method for processing a salt solution together with carbon dioxide, the method comprising:

• extracting lignin from biomass, wherein extracting the lignin comprises:
• deriving, by immersing the biomass in a basic solution of at least sodium hydroxide (NaOH), a lignin-containing solution from the biomass;
• and
• separating out a lignin residue from the lignin-containing solution;
• and
• treating the salt solution with the lignin residue and the carbon dioxide, wherein treating the salt solution comprises:
• combining the lignin residue with the salt solution to form a basic suspension having at least the lignin and the salt solution as constituents;
• passing carbon dioxide through the basic suspension so that at least a portion of the carbon dioxide reacts with the constituents to form bicarbonate ions (HCO3−) in the basic suspension and thereby cause ions to be adsorbed on the surface of the lignin present in the basic suspension to form precipitated salts;
• and
• separating the lignin and precipitated salts out from the treated basic suspension to produce a treated salt solution.