Method for controlling microbial contamination, mineral suspensions obtained and uses thereof
The invention concerns a process for disinfection and/or conservation and/or reduction and/or control of microbial contamination of aqueous dispersions and/or aqueous suspensions of mineral matter, providing satisfactory stability in terms of Brookfield™ viscosity for the said aqueous dispersions and/or suspensions of mineral matter. It also concerns the said aqueous dispersions and/or suspensions thus obtained, together with their uses in the mineral, paper and paint industries. Finally it concerns the end products obtained.
1. A process for disinfecting or preserving an aqueous suspension of mineral matter comprising calcium carbonate of or from microbial contamination, said process comprising:
a) at least one stage to increase and maintain the OH − ion concentration of the aqueous suspension of the mineral matter comprising calcium carbonate, to a value greater than or equal to 1×10 −2 mole/l, by addition of an antimicrobial agent consisting of one or more OH − ion donors selected from alkali oxides and alkali hydroxides, for a sufficient time to disinfect or preserve the aqueous suspension of the mineral matter comprising calcium carbonate of or from microbial contamination, so that the aqueous suspension of the mineral matter comprising calcium carbonate has a microbe concentration of less than or equal to 100 microbes/gram,
b) at least one stage of dispersion and/or grinding of the aqueous suspension of the mineral matter comprising calcium carbonate, occurring before, during or after stage a), and
c) at least one stage to reduce the OH − ion concentration of the aqueous suspension of the mineral matter comprising calcium carbonate, occurring after stage a), to a value less than or equal to 1×10 −2 mole/l.
2. The process according to claim 1 , wherein the OH − ion concentration value in stage a) is higher than or equal to 2×10 −2 mole/l.
3. The process according to claim 1 , wherein the one or more OH − ion donors added in stage a) is NaOH.
4. The process according to claim 1 , wherein stage b) is conducted using at least one dispersing agent or at least one grinding aid agent.
5. The process according to claim 1 , wherein use of a physical process of microbial decontamination is introduced before, during or after stage a), and/or b), and/or c).
6. The process according to claim 1 , wherein the OH − ion concentration in stage c) is reduced to a value less than or equal to 1×10 −3 mole/l.
7. The process according to claim 1 , wherein the OH − ion concentration reduction in stage c) is undertaken using one or more weak, moderately strong or strong, monovalent or polyvalent H 3 O + ion donators.
8. The process according to claim 1 , wherein the OH − ion concentration reduction is undertaken using gaseous CO 2 dissociated in carbonic acid water.
9. The process according to claim 1 , wherein the microbial contamination comprises pseudomonas germs.
10. The process according to claim 1 , wherein the microbial contamination comprises pseudomonas aeruginosa germs.
11. The process according to claim 5 , wherein the physical process of microbial decontamination comprises at least one treatment process based on an increase of temperature.
12. The process according to claim 1 , wherein the OH − ion concentration reduction occurs between one week and one month after stage a).
13. The process according to claim 1 , which is used in a discontinuous, semi-continuous or continuous fashion.
14. The process according to claim 1 , which is for disinfecting an aqueous suspension of mineral matter comprising calcium carbonate that may comprise a microbial contamination.
15. The process according to claim 1 , wherein the mineral matter is natural and/or precipitated calcium carbonate.
16. The process according to claim 1 , wherein the mineral matter is natural calcium carbonate.
17. The process according to claim 1 , wherein the mineral matter is marble, calcite, chalk or their mixtures.
18. The process according to claim 1 , which is for disinfecting an aqueous suspension of mineral matter comprising calcium carbonate that comprises a microbial contamination.
19. The process according to claim 1 , which is for preserving an aqueous suspension of mineral matter comprising calcium carbonate.
20. The process according to claim 1 , wherein the one or more OH − ion donors added in stage a) is an alkali oxide.
21. The process according to claim 1 , wherein the one or more OH − ion donors added in stage a) is an alkali hydroxide.