Process for sequestration of carbon dioxide

A process for sequestration of carbon dioxide comprising the following steps:

• (a) dispersing solid waste material comprising calcium oxide and a calcium-comprising mixed oxide in water to dissolve at least part of the calcium oxide and to form calcium oxide-depleted solid waste material in a calcium hydroxide solution;
• (b) separating the calcium hydroxide solution from the calcium oxide-depleted solid waste material;
• (c) converting the calcium hydroxide in the separated calcium hydroxide solution into precipitated calcium carbonate;
• (d) contacting an aqueous slurry comprising water and from 10 to 50 wt % of the calcium oxide-depleted solid waste material with carbon dioxide to form an aqueous solution of calcium bicarbonate for mineral carbonation of the carbon dioxide to form carbonated solid waste material;
• (e) separating part or all of the aqueous solution of calcium bicarbonate from the carbonated solid waste material;
• (f) precipitating calcium carbonate from the separated aqueous solution of calcium bicarbonate;
• and
• (g) recovering the precipitated calcium carbonate as product;
• in which process the calcium carbonate is precipitated from the separated aqueous solution of calcium bicarbonate in step (f):
• (i) by adding calcium hydroxide from the solution obtained in step (b) to the separated aqueous solution of calcium bicarbonate;
• and/or
• (ii) by removal of carbon dioxide from the solution of calcium bicarbonate and wherein the carbon dioxide removed in step (f) is added to the calcium hydroxide solution in step (c).