# US 2014/0154157 A1 · Process of Treating End-of-Life Cathode Ray Tubes for Lead and Soluble Silicates Recovery

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- Number: US 2014/0154157 A1
- Document ID: US20140154157A1
- Status: Published application
- Kind: A1
- Application number: 13/692,136
- Filed: 2012-12-03
- Published: 2014-06-05
- Earliest claimed: 2012-12-03
- Assignees: Costech International S.P.A.
- Applicants: Costech International S.P.A.
- Inventors: Giovanni Modica
- Web page: https://patentgrep.com/patent/US20140154157A1

## CPC

- C22B 13/045: {Recovery from waste materials}
- Y02P 10/20: Recycling
- C22B: PRODUCTION AND REFINING OF METALS (electrolytic C25); PRETREATMENT OF RAW MATERIALS
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

There is described a process of recycling screen glass resulting from the disposal of cathode tube televisions, with quantitative recovery of lead in the form of sulphide and of silicates of cations other than lead, and subsequently recycling all the materials so recovered.

## Claims

### Claim 1

A process of recovering lead and silicates from glasses resulting from cathode tube screen disposal, which comprises the following operations:
etching the glass by means of a strongly alkaline compound, thus obtaining an aqueous-based liquid phase;
adding a sulphide to the so obtained liquid phase, with the precipitation of lead sulphide;
separating the solid lead sulphide from the above liquid phase.

### Claim 2 (depends on 1)

The process according to claim 1, wherein said alkaline compound is an alkali metal hydroxide.

### Claim 3 (depends on 2)

The process according to claim 2, wherein said compound is chosen from sodium hydroxide and potassium hydroxide.

### Claim 4 (depends on 1)

The process according to claim 1, wherein said glass etching operation is conducted by means of an aqueous solution of the alkaline compound at a temperature not higher than 200° C.

### Claim 5 (depends on 4)

The process according to claim 4, wherein the process temperature is higher than 100° C.

### Claim 6 (depends on 5)

The process according to claim 5, wherein the process temperature is between 150° C. and 180° C.

### Claim 7 (depends on 1)

The process according to claim 1, wherein the alkaline compound is employed in the form of an aqueous solution with a weight concentration between 10 and 50%.

### Claim 8 (depends on 7)

The process according to claim 7, wherein said concentration is between 15 and 45%.

### Claim 9 (depends on 1)

The process according to claim 1, wherein said glass etching operation is conducted by blending the glass with the alkaline compound in solid form, heating the so obtained solid mixture at a temperature higher than the melting temperature of the alkaline compound employed, and taking again the resulting molten mass with water.

### Claim 10 (depends on 1)

The process according to claim 1, wherein in said glass etching operation, the lead glass/alkaline compound weight ratio is between 1/0.6 and 1/1.4.

### Claim 11 (depends on 10)

The process according to claim 10, wherein said weight ratio is between 1/0.8 and 1/1.2.

### Claim 12 (depends on 1)

The process according to claim 1, wherein the glass is ground before said etching operation by the alkaline compound.

### Claim 13 (depends on 1)

The process according to claim 1, wherein said operation of adding a sulphide to the liquid phase is conducted by adding a water-soluble sulphide to said liquid phase, or by bubbling hydrogen sulphide therein.

### Claim 14 (depends on 1)

The process according to claim 1, wherein said operation of separating solid lead sulphide from the liquid phase is conducted by filtration or centrifugation.

### Claim 15 (depends on 1)

The process according to claim 1 further comprising, after said operation of sulphide separation, a chemical analysis on said liquid phase, and:
if, in the analysis, the presence of lead ions in the liquid phase is detected, a sulphide is added thereto in the form of a water-soluble salt, or by bubbling hydrogen sulphide therein;
if, in the analysis, the presence of sulphide ions in the liquid phase is detected, an effective oxidant for the oxidation of sulphide ion to sulphate ion is added thereto.