METHOD FOR TREATING A LEAD-CONTAINING GLASS THAT MAKES IT POSSIBLE TO LIMIT THE MIGRATION IN SOLUTION OF THE LEAD CONTAINED IN THIS GLASS

Abstract

A method for treating a lead-containing glass that makes it possible to limit the migration of the lead contained in this glass, the method successively comprising the following distinct steps: a step of placing the lead-containing glass in contact with a solution comprising perchloric acid; a step of heat treatment of the glass at a temperature less than or equal to the glass transition temperature of the glass.

Claims

1.-9. (canceled)

10. Method for treating a lead-containing glass that makes it possible to limit the migration of the lead contained in this glass, said method successively comprising the following distinct steps: a step of placing the lead-containing glass in contact with a solution comprising perchloric acid; a step of heat treatment of the glass at a temperature less than or equal to the glass transition temperature of the glass.

11. Treatment method according to claim 10, wherein the solution comprising perchloric acid is an aqueous solution of perchloric acid.

12. Treatment method according to claim 10, wherein the perchloric acid is present in the solution at a concentration ranging from 10.sup.−3 M to 10.sup.−1 M.

13. Treatment method according to claim 10, wherein the step of placing in contact is carried out at ambient temperature.

14. Treatment method according to claim 10, wherein the step of heat treatment is carried out at a temperature going up to 150° C. below the glass transition temperature of the glass.

15. Treatment method according to claim 10, wherein the step of heat treatment is carried out at a temperature ranging from 200° C. to 700° C., advantageously, from 300 to 600° C.

16. Treatment method according to claim 10, wherein the step of heat treatment is carried out for a duration ranging from 12 hours to 36 hours.

17. Treatment method according to claim 10, wherein the lead-containing glass is a glass of the crystal type.

18. Treatment method according to claim 10, which is a method for treating an object made of lead-containing glass.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 is a graph illustrating the concentration of lead C.sub.Pb (in mg/L) for the various trials and for a reference for the first series of trials of example 1 below.

[0035] FIG. 2 is a graph illustrating the concentration of lead C.sub.Pb (in mg/L) for the various trials, for a reference and a cemented glass powder for the second series of trials of example 1 below.

DETAILED DISCLOSURE OF SPECIFIC EMBODIMENTS

Example 1

[0036] First, a first series of trials is carried out with a glass powder (more specifically, a Baccarat commercial glass comprising 24% by weight of PbO having a particle size of 63-125 μm, having a specific surface area of 535 cm.sup.2.Math.g.sup.−1 and having a glass transition temperature of 458° C.), said powder being subjected to the following conditions: [0037] 1.sup.st trial: Placed in contact with an aqueous solution of HClO.sub.4; T=22° C.; Concentration: 10.sup.−3M (curve b in FIG. 1) or 10.sup.−4M (curve c in FIG. 1); Duration of contact: 1 day; [0038] 2.sup.nd trial: Placed in contact with an aqueous solution of H.sub.3PO.sub.4; T=22° C.; Concentration: 10.sup.−3M (curve d in FIG. 1) or 10.sup.−4M (curve e in FIG. 1); Duration of contact: 1 day; [0039] 3.sup.rd trial: Placed in contact with an aqueous solution comprising HClO.sub.4/H.sub.3PO.sub.4; T=22° C.; Concentration: 4*10.sup.−3M (pH=2.4) (curve fin FIG. 1); Duration of contact: 1 day; [0040] 4.sup.th trial: Placed in contact with an aqueous solution comprising K.sub.2S.sub.2O.sub.5; T=22° C.; Concentration: 1M (pH=0) (curve g in FIG. 1) or 2M (curve h in FIG. 1); Duration of contact: 1 day; [0041] 5.sup.th trial: Placed in contact with an aqueous solution comprising H.sub.2SO.sub.4; T=22° C.; Concentration: 0.5M (curve i in FIG. 1), 4*10.sup.−3M (curve j in FIG. 1) or 10.sup.−4M (curve k in FIG. 1); Duration of contact: 1 day; [0042] 6.sup.th trial: Annealing at 450° C. for 1 day (curve l in FIG. 1); [0043] 7.sup.th trial: Annealing at 500° C. for 1 day (curve m in FIG. 1); [0044] 8.sup.th trial: Annealing at 550° C. for 1 day (curve n in FIG. 1); [0045] 9.sup.th trial: Annealing at 420° C. for 10 days (curve o in FIG. 1); [0046] 10.sup.th trial: Placed in contact with an aqueous solution comprising Zn.sup.2+ ions (400 mg.Math.L.sup.−1); T=22° C.; Duration of contact=1 day and pH=5.5 (curve p in FIG. 1); [0047] 11.sup.th trial: Placed in contact with an aqueous solution comprising Zn.sup.2+ ions (400 mg.Math.L.sup.−1); T=22° C.; Duration of contact=1 day and pH=2.4 (curve q in FIG. 1).

[0048] The effectiveness of these trials was measured on the basis of the concentrations of lead analysed during the ISO 7086 test by placing the powders coming from these various trials in contact with a solution of acetic acid (4% by volume) for 24 hours at 22° C. according to a ratio (surface area of glass/volume of solution, called S/V) of 1000 m.sup.−1 (or 187 mg of glass powder in 10 mL of solution of acetic acid) then by quantifying the lead concentration of the solution of acetic acid.

[0049] The concentrations of lead quantified in the solution of acetic acid with each of the aforementioned trials are reported in FIG. 1, which is a graph illustrating the concentration of lead C.sub.Pb (in mg/L) for the various trials (curves b to q as defined above) and for a reference (indicated as Ref., corresponding to the glass powder not having undergone any treatment and forming the reference concentration of lead released into solution, curve a in FIG. 1).

[0050] The most effective conditions with respect to the release of the lead are those obtained with HClO.sub.4 perchloric acid and, in particular, with a concentration of 10.sup.−3 mol.Math.L.sup.−1.

[0051] Starting from these effective conditions thus determined (namely, the use of perchloric acid), a second series of trials was carried out, still with the same type of glass powder (namely, a Baccarat commercial glass comprising 24% by weight of PbO having a particle size of 63-125 μm and having a specific surface area of 535 cm.sup.2.Math.g.sup.−1), said powder being subjected to the following conditions: [0052] 1.sup.st trial: Placed in contact with an aqueous solution of HClO.sub.4; T=22° C.; Concentration: 10.sup.−3M; Duration of contact: 1 day (curve b in FIG. 2); [0053] 2.sup.nd trial: Placed in contact with an aqueous solution of HClO.sub.4; T=22° C.; Concentration: 10.sup.−3M; Duration of contact: 1 day followed by annealing at 450° C. (for 24 hours) (curve c in FIG. 2); [0054] 3.sup.rd trial: Placed in contact with an aqueous solution of HClO.sub.4; T=22° C.; Concentration: 10.sup.−2M; Duration of contact: 1 day (curve d in FIG. 2); [0055] 4.sup.th trial: Placed in contact with an aqueous solution of HClO.sub.4; T=22° C.; Concentration: 10.sup.−2M; Duration of contact: 1 day followed by annealing at 450° C. (for 24 hours) (curve e in FIG. 2); [0056] 5.sup.th trial: Placed in contact with an aqueous solution of HClO.sub.4; T=22° C.; Concentration: 10.sup.−1M; Duration of contact: 1 day (curve fin FIG. 2); [0057] 6.sup.th trial: Placed in contact with an aqueous solution of HClO.sub.4; T=22° C.; Concentration: 10.sup.−1M; Duration of contact: 1 day followed by annealing at 450° C. (for 24 hours) (curve g in FIG. 2); [0058] 7.sup.th trial: Placed in contact with an aqueous solution of HClO.sub.4 (10.sup.−3M)+Zn.sup.2+ (100 mg.Math.L.sup.−1); T=22° C.; Duration of contact: 1 day (curve h in FIG. 2); [0059] 8.sup.th trial: Placed in contact with an aqueous solution of HClO.sub.4 (10.sup.−3M)+H.sub.2O.sub.2 (10% by volume); T=22° C.; Duration of contact: 1 day (curve i in FIG. 2).

[0060] The concentrations of lead quantified in the solution of acetic acid according to the standard ISO 7086 with each of the aforementioned trials and with a ratio (S/V)=1000 m.sup.−1 are reported in FIG. 2, which is a graph illustrating the concentration of lead C.sub.Pb (in mg/L) for the various aforementioned trials (curves b to i) and for a reference (indicated as Ref., corresponding to the glass powder not having undergone any treatment and forming the reference concentration of lead released into solution, curve a in FIG. 2) and, also, for a cemented glass powder (indicated as cemented BAC, that is to say a glass powder having undergone a cementation treatment applied to the carafes, curve j in FIG. 2), said cemented glass powder leading to a reduction in the concentration of lead by a factor of 45 with respect to the powder not having undergone any treatment.

[0061] It appears that a heat treatment at 450° C. makes it possible to divide by at least a factor of approximately 3 the release of lead with respect to the trials carried out with the perchloric acid at the same concentration but without this heat treatment, the best result being obtained by a solution of 10.sup.−2M perchloric acid with annealing of 450° C. (the release of lead being improved by a factor of 6 with respect to the equivalent trial without heat treatment and by a factor of 40 with respect to the reference).

[0062] It also appears that a heat treatment at 450° C. also makes it possible to obtain better results than those obtained with a solution of perchloric acid comprising Zn.sup.2+ ions or H.sub.2O.sub.2 oxygenated water.

[0063] It should be noted, also, that the treatment with a 10.sup.−2M solution of perchloric acid with annealing of 450° C. leads to performance of the same order of magnitude as the cemented glass powder but makes it possible to ensure better reproducibility, given that this treatment can be applied onto objects having a complex shape, insofar as this treatment being carried out via a liquid process makes it possible for all of the surface to be treated in a homogenous manner.

Example 2

[0064] In this example, trials are carried out with objects made of glass of the crystal type and, more specifically, with a Baccarat glass and a Saint-Louis flute (these two objects being made of a glass having a glass transition temperature of 458° C.).

[0065] These two objects were subjected to a treatment method comprising: [0066] a step of placing the latter in contact with an aqueous solution of perchloric acid at 10.sup.−2M at 22° C. for 1 day; [0067] a step of heat treatment at 450° C. for 24 hours.

[0068] A visual test carried out after this treatment method shows that there is no difference with respect to the same objects not having undergone this method. This demonstrates that the treatment method does not alter the appearance of the objects.

[0069] The objects thus treated are also subjected to an ISO 7086 test with a solution of acetic acid (4% by volume) for 24 hours at 22° C., the volume of the solution being 50 mL (the ratio S/V being 100 m.sup.−1 for the glass from Baccarat and 120 m.sup.−1 for the flute from Saint-Louis). It appears from this test that for both objects, the factor of reduction of the release of lead is 40 with respect to the same untreated object.