HEAVY METAL RECYCLING PROCESS AND MATERIAL USEFUL IN SUCH PROCESS

Abstract

The present invention relates to the field of water treatment/metal recovery and to materials/devices useful in such processes. Specifically the invention provides for composite materials comprising amyloid fibrils; activated carbon; optionally a support material; whereby said amyloid fibrils and said activated carbon are in intimate contact. The invention further provides for the treatment of water using such composite materials.

Claims

1. A composite material comprising (a) amyloid fibrils; (b) activated carbon; (c) optionally a support material; whereby said amyloid fibrils and said activated carbon are in intimate contact.

2. The composite material according to claim 1 where (a) the amyloid fibrils are selected from fibrils being 10 nm in diameter and 1 m in length and/or showing electrophoretic mobilities of the order 2 m.Math.cm/V.Math.s at pH 4; and/or (b) the activated carbon is selected from activated carbon obtained by chemical and/or physical activation; and/or (c) the support material, if present, is selected from porous support materials.

3. The composite material according to claim 1, selected from a filter membrane, comprising constituents (a), (b) and (c); or a particulate material, comprising constituents (a) and (b), but no supporting material (c).

4. The composite material according to claim 1, where the ratio (a)/(b) is in the range of 1/1 to 1/100 (w/w).

5. (canceled)

6. A method for manufacturing a composite material, said method comprising the steps of: (a) combining water, amyloid fibrils and activated carbon to obtain a suspension; and (b) filtering said suspension through a porous support material.

7. (canceled)

8. (canceled)

9. (canceled)

10. A method for the treatment of water, said method comprising the steps of: (a) providing a composite material according to claim 1-4 and waste water; (b) contacting said waste water with said composite material, thereby obtaining purified water and loaded composite material; (c) separating the purified water from the loaded composite material.

11. A method for recovering metals from an aqueous solution according to claim 10, said method further comprising the steps of: (d) oxidizing the loaded composite material in an high temperature environment to obtain elemental metals and ash; (e) separating the elemental metal from the ash.

12. The method according to claim 10, wherein in step (a) the composite material is provided in the form of a filter; and steps (b) and (c) are performed by filtering said waste water through said filter.

13. The method according to claim 10, wherein in step (a) the composite material is provided in the form of particulate material; and/or in step (b) said waste water and said composite material are contacted for a period of 20 sec-24 hrs., optionally with stirring, at a temperature range from 5-95 C.; and/or in step (c) the obtained materials are separated, by filtering, centrifuging or settling; and whereby steps (b) and (c) are optionally repeated.

14. The method according to claim 11, wherein in step (d) the oxidation takes place in a furnace, at temperatures in the range of 600-1200 C.; in step (e), separation is performed by floatation or air floating, optionally with the aid of ultrasound.

Description

EXAMPLE 1

Recovery of Au from Au(CN).SUB.4..SUP. Solution

[0041] 1.1 Preparation of Composite Material

[0042] 0.5 g act. carbon are mixed with 0.5 ml of 2 wt % beta-lactoglobulin pH2 protein fibrils solution (see PCT/CH2014/000014) at room temperature. This solution is vacuum filtered using 0.22 micrometre cellulose filter membrane. Protein fibrils remarkable adhesiveness and stiffness enable the assembly of act. carbon into the fibrils. The thus obtained coated cellulose filter is used in the next step.

[0043] 1.2 Contacting and Separating (Filtering Au(CN).sub.4.sup.)

[0044] 50 ml industrial waste water, containing 30 mg/l Au (present as Au(CN).sub.4.sup., determined by AAS) was filtered through the filter of step 1.1 using vacuum filtration. The purified water now contains, after a single passage through the filter, 0.105 mg/l Au (determined by the same AAS method). This corresponds to a reduction of 99.65% and shows the extremely high absorption rate of the inventive composite material.

[0045] 1.3 Oxidizing of Loaded Composite Material

[0046] The loaded composite material is placed in a furnace for 3 hrs. @ 750 C. After cooling to room temperature, the sample colour changed from black to red. This indicates formation of nanoparticulate material. Activated carbon converted to ash.

[0047] 1.4 Separating Elemental Gold

[0048] The material obtained from the previous step is mixed with distilled water and sonicated @ 100 Hz/15 min. Gold particles sediment on the bottom and the ash floated. The ash is removed and the sonicatonremoval cycle is repeated. The obtained particles contain elemental gold, as confirmed by AAS, and are virtually non-toxic and may be used for further applications.

[0049] 1.5 Preparation of Conductive Gold Crystals

[0050] The material obtained from the previous step is combined with 0.2 wt % beta-lactoglobulin fibril solution, FIG. 1 shows an AFM image thereof. This material is combined with 0.01M chloroauric acid and heated to 60 C./12 hrs. to produce conductive gold single crystals. The thus obtained gold crystals have hexagonal, triangle and polyhedral structures, see FIG. 2.

EXAMPLE 2

Recovery of Toxic Heavy Metal Pollutants

[0051] 2.1 Preparation of Composite Material

[0052] Hybrid composite filter membranes are prepared to absorb the toxic heavy metal pollutants. Initially, 5 ml of 10 wt % activated carbon solution mixed with the 0.5 ml of 2 wt % -lactoglobulin (pH 2) protein fibrils solution. 1 ml of above solution is vacuum filtered using 0.22 m cellulose filter. Protein fibril's extreme adhesiveness and stiffness behavior enable the assembly of activated carbon into homogeneous composite filtration membrane. These filtration membranes are very useful to absorb heavy metal ion pollutants as well as recovery of the expensive heavy metals from the environmental pollutants.

[0053] 2.2 Contacting and Separating

[0054] After preparing this composite filter membrane having the protein fibrils and activated carbon, the 50 ml of toxic heavy metal ion solution is passed through this composite membrane using vacuum filtration method.

[0055] The concentrations of the environmental pollutants were estimated before and after filtration to determine the absorption of toxic heavy metal ions inside the filter membrane.

[0056] The details of filtration and absorption efficiency of various toxic environmental pollutants within these hybrid filter membrane is discussed below

[0057] 2.3 Results:

[0058] Mercury chloride solution (pH 4) was filtered. The AAS measurements estimated that the mercury atom concentration is reduced from initial 84 ppm to <0.4 ppm after filtration.

[0059] Lead acetate solution (pH 3.7) was also filtered and the concentration of the lead is calculated by AAS, before and after the filtration process. Since the concentration of lead solution before filtration is above than our available AAS calibration curve, the initial unfiltered solution is diluted 20 times for the measurement. The concentrations of lead atoms are reduced from 65 ppm to <0.02 ppm after filtration. A change of the solution color before and after filtration is observed. The solution became completely colorless because of absorption of lead atoms inside the filter membrane.

[0060] Disodium tetrachloro palladate was also filtered to show the generality of this filtration approach to prove the filtration of the heavy metal pollutant. The concentrations of the solutions are measured by UV-Vis absorption spectroscopy. The concentrations reduced from the 12.2 ppm to <0.16 ppm after filtration process.

[0061] Based on the above data, it was realized that the inventive method is generally applicable. Particularly, different types of heavy metal pollutants are filtered using the inventive composite material. Accordingly, the inventive method is suitable to absorb several heavy metal toxic environmental pollutants. Especially, potassium gold cyanide [KAu(CN).sub.2], mercuric chloride [HgCl.sub.2], lead acetate [Pb(C.sub.2H.sub.3O.sub.2).sub.4], disodium tetrachloro palladate [Na.sub.2PdCl.sub.4] may be efficiently removed and recovered.