Silicon comprising polymer coated particles

Abstract

The present invention relates to core-shell-particles, wherein the core comprises 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, and the shell comprises at least one silicon comprising polymer, to a process for the preparation of these core-shell-particles, to the use of these core-shell-particles in an agglomeration-deagglomeration process, in particular in chemical, physical or biological test methods or separation processes, decontamination processes, water purification, recycling of electrical/electronic scrap or gravity separation, and to a process for separating at least one first material from a mixture comprising this at least one first material and at least one second material.

Claims

1. 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)
[SiR.sup.1(OR.sup.2)O](I) wherein R.sup.1 is the same or different and is selected from hydrogen, linear or branched C.sub.1-C.sub.18-alkyl, unsubstituted or alkylsubstituted C.sub.5-C.sub.12-aryl, and R.sup.2 is the same or different and is selected from hydrogen, linear or branched C.sub.1-C.sub.18-alkyl, unsubstituted or alkylsubstituted C.sub.5-C.sub.12-aryl, or SiR.sup.1.sub.x(OR.sup.2).sub.3-x, wherein x is 1 or 2 and R.sup.1 and R.sup.2 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.

2. The process according to claim 1 wherein after process step (D), (C) the process further comprises the following process step (D)cleaving the agglomerate which has been separated from the mixture in step (C) to obtain the at least one first material and the at least one core-shell-particle separately.

3. The process according to claim 2, wherein after cleavage according to step (D) the at least one magnetic core-shell particle is separated from a dispersion comprising said at least one magnetic core-shell-particle and said at least one first material by means of a permanent magnet or an electromagnet.

4. The process according to claim 2, wherein after step (D) the following step (E) is conducted: (E) further processing of particles or of the agglomerate from step (D) via smelting, extracting and/or wet chemical refining.

5. The process according to claim 1, wherein in process steps (A) and/or (B) a dispersant is present or added and the dispersion comprises from about 5 to about 40% by weight solid content wherein the solid content is based on a total amount of solids present.

6. The process according to claim 1, wherein after completion of process step (D), (E), or (F) (C) at least about 70% of the core-shell-particles are recovered from the process mixture.

7. The process according to claim 1, wherein the silicon comprising polymer further comprises repeat units of general formula (II)
[SiR.sup.1.sub.2](II) wherein R.sup.1 is independently of another selected from hydrogen, linear or branched C.sub.1C.sub.18-alkyl, unsubstituted or alkylsubstituted C.sub.5-C.sub.12-aryl.

8. The process according to claim 1, wherein the sum of the number of repeat units according to general formula (I), of repeat units according to general formula (II), if present, and the number of groups R.sup.2 having the meaning SiR.sup.1.sub.x(OR.sup.2).sub.3-x, if present, is 10 to about 100,000.

9. The process according to claim 1, wherein the silicon comprising polymer comprising repeat unit of general formula (I) has a molecular weight Mw of about 500 to about 500000 g/mol (weight average).

10. The process according to claim 1, wherein the silicon comprising polymer is terminated with groups R.sup.1 and/or groups OR.sup.2, wherein R.sup.2 is independently of another selected from hydrogen, linear or branched C.sub.1-C.sub.18-alkyl or unsubstituted or alkylsubstituted C.sub.5-C.sub.12-aryl.

11. The process according to claim 1, wherein the at least metal or a compound thereof is selected from the group consisting of iron oxides, magnetic iron oxides and mixtures thereof.

Description

EXAMPLES

Example 1

According to the Present Invention

(1) As silicon comprising polymer, a solid methyl silicon resin (resin 1) of average composition [CH.sub.3SiO.sub.1.5].sub.100 having a molecular weight Mw of 6600 g/mol is used.

(2) 2.06 g of resin 1 are dissolved in 150 ml of toluene. 150.31 g magnetite having a BET surface of 3 m.sup.2/g, a d.sub.10 of 2 m, a d.sub.50 of 4 m and a d.sub.90 of 9 m, are added, and the black suspension is stirred at a temperature of about 70 C. for about one hour, Afterwards the pressure is decreased to 120 mbar at a temperature of 70 C. for 55 min, and then to 6 mbar at 70 C. and for 15 min. The solid that is obtained is dried, and a dry, grey solid is obtained. 152.35 g coated magnetite is obtained comprising 4.57 mg resin 1/m.sup.2 of the surface of the magnetite particle.

Example 2

Comparative

(3) As silicon comprising polymer, a solid (CH.sub.3).sub.3Si(OR)/Si(OR).sub.4 cohydrolysate with a ratio of 0.67 and an amount of hydroxygroups of less than 0.3% (resin 2) is used. This polymer is a SiO.sub.2-network that is terminated with (CH.sub.3).sub.3Si-groups. This silicon comprising polymer has a molecular weight (weight average) of 6000 to 10000 g/mol.

(4) 2.04 g of resin 2 are dissolved in 150 ml of toluene. 150.03 g magnetite having a BET surface of 3 m.sup.2/g, a d.sub.10 of 2 m, a d.sub.50 of 4 m and a d.sub.90 of 9 m, are added, and the black suspension is stirred at a temperature of about 70 C. for about one hour. Afterwards the pressure is decreased to 100 mbar at a temperature of 70 C. for 55 min, and then to 11 mbar at 70 C. and for 15 min. The solid that is obtained is dried, and a dry, grey solid is obtained. 152.14 g coated magnetite is obtained comprising 4.53 mg resin 1/m.sup.2of the surface of the magnetite particle.

Example 3

(5) Comparison of core-shell particle according to example 1 according to the present invention and comparative core-shell particle according to example 2.

(6) A naturally occurring sulfidic copper ore containing 0.62% by weight copper and 0.01% by weight molybdenum is treated with inventive core-shell-particles according to example 1 and comparative core-shell-particles according to example 2, separately.

(7) The valuable-containing particles in the ore are selectively hydrophobised by potassium n-octyl xanthate and contacted with the core-shell-particles and magnetic agglomerates of the valuables present in the ore are obtained, whereas the gangue does not agglomerate. The magnetic agglomerates are then separated magnetically. The amount of separated agglomerates is then acquired by weighting (cycle I). The agglomerates are then separated using an aqueous solution of surfactant yielding an enriched copper concentrate. After second magnetic separation to separate the magnetic particles from the values, the magnetic particles are reused in a second ore treatment and the amount of magnetic agglomerates is acquired again (cycle II).

(8) Results:

(9) Use of core-shell-particles according to the present invention of example 1:

(10) Cycle 1: 3.67 g concentrate

(11) Cycle 2: 3.25 g concentrate, being 89% of cycle 1

(12) Use of comparative core-shell-particles according to example 2:

(13) Cycle 1: 3.18 g concentrate

(14) Cycle 2: 1.04 g concentrate, being 33% of cycle 1

(15) Whereas with core-shell-particles according to the present invention in cycle 2 still 89% of the amount of cycle 1 can be separated, with comparative core-shell-particles only 33% of agglomerates are obtained in cycle 2. These results clearly show that the shell according to the present invention is more stable under mechanical and chemical conditions of magnetic separation than the shell of the comparative particles.