Patent ID: 8662311

Claim:
A process for separating silicates and alkaline earth metal carbonates, wherein the process comprises the following steps: a) providing at least one mineral material comprising at least one silicate and at least one alkaline earth metal carbonate, said mineral material having a weight median grain diameter in the range of from 5 to 1000 μm; b) providing at least one hydrophobically modified polyalkyleneimine, wherein: i) the polyalkyleneimine is hydrophobically modified by replacement of all or part of the hydrogens of their primary and/or secondary amino groups by functional group R, where R comprises a linear or branched or cyclic alkyl and/or aryl group and contains 1 to 32 carbon atoms; ii) prior to modification, the polyalkyleneimine has at least 3 alkyleneimine repeat units and a molecular weight of between 140 and 100,000 g/mol; iii) modification of the polyalkyleneimine results in an increase in the atomic C amount, relative to the unmodified polyalkyleneimine, of between 1 and 80%; c) contacting said mineral material(s) of step a) with said hydrophobically modified polyalkyleneimine(s) of step b), in one or more steps, in an aqueous environment to form an aqueous suspension having a pH of between 7 and 10; d) passing a gas through the suspension of step c); e) recovering an alkaline earth metal carbonate-containing product and a silicate-containing product from the suspension; f) raising the pH of the silicate of step e) in an aqueous environment by at least 0.5 pH units to desorb all or part of the hydrophobically modified polyalkyleneimine(s) from the silicate fraction and extracting the hydrophobically modified polyalkyeleneimine(s) into the washing liquid; and g) treating the liquid fraction of step f) with an acid to reduce the pH of this liquid fraction by at least 0.5 pH units.