Silicon comprising polymer coated particles

A process for separating at least one first material from a mixture comprising said at least one first material and at least one second material, wherein the process comprises the following steps:

• (A) contacting the mixture comprising the at least one first material and the at least one second material with at least one surface-modifying substance, optionally in the presence of at least one dispersant,
• (B) optionally, adding at least one other dispersant to the mixture obtained in step (A),
• treating the dispersion mixture from step (A) or (B) with at least one core-shell-particle wherein the core comprises:
• (i) at least one metal or a compound thereof, or
• (ii) a mixture of at least one metal or a compound thereof and at least one semimetal or a compound thereof,
• and the shell comprises at least one silicon comprising polymer comprising repeat units of the general formula (I)
• —[SiR1(OR2)—O]—(I)
• wherein
• R1 is the same or different and is selected from hydrogen, linear or branched C1-C18-alkyl, unsubstituted or alkylsubstituted C5-C12-aryl, and
• R2 is the same or different and is selected from hydrogen, linear or branched C1-C18-alkyl, unsubstituted or alkylsubstituted C5-C12-aryl, or —SiR1x(OR2)3-x, wherein x is 1 or 2 and R1 and R2 are the same or different and have the meanings as mentioned above,
• wherein the at least one metal or a compound thereof, or a mixture of at least one metal or a compound thereof and at least one semimetal or a compound thereof is magnetic, and the at least one first material to which the at least one surface-modifying substance is attached and the at least one core-shell-particle form an agglomerate, and
• (C)separating the agglomerate from step (C) from the mixture by application of a magnetic field.