PROCESS FOR DECOMPOSITION OF ORGANIC SYNTHETIC-DYES USING SEMICONDUCTOR-OXIDES NANOTUBES VIA DARK-CATALYSIS

• US 20150203365A1
• Filed: 05/17/2013
• Published: 07/23/2015
• Est. Priority Date: 08/17/2012
• Status: Active Grant

• Current Assignee: Council of Scientific & Industrial Research
• Original Assignee: Council of Scientific & Industrial Research
• Inventors: Shukla, Satyajit Vishnu, Warrier, Krishna Gopakumar, Babu, Babitha Kunnathuparambil
• Granted Patent: US 9,604,859 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: C02F 1/281 using inorganic sorbents
• CPC Class Codes: C02F 1/385 by centrifuging suspensions centrifuges B04B
• CPC Class Codes: C02F 1/722 Oxidation by peroxides
• CPC Class Codes: C02F 1/725 by catalytic oxidation
• CPC Class Codes: C02F 2101/308 Dyes; Colorants; Fluorescent agents
• CPC Class Codes: C02F 2303/18 Removal of treatment agents after treatment
• CPC Class Codes: C02F 2305/08 Nanoparticles or nanotubes
• CPC Class Codes: Y02W 10/37 using solar energy

Abstract

In the present invention nanotubes-based dye-adsorbent powder is used for adsorption and decomposition of synthetic dye under dark-condition without the use of any external power-source such as the applied potential-difference, microwave, ultrasonicator, and others to save the energy consumption, which results in a complete dye-decomposition on the powder-surface. The surface-cleaned dye-adsorbent powder has very high specific surface-area and dye-adsorption capacity comparable with those of the original dye-adsorbent powder and can be recycled for the next cycles of dye-adsorption and dye-decomposition under the dark-condition. In the present method, the nanotubes-based dye-adsorbent powder is stirred under the dark-condition in an aqueous dye solution containing a strong oxidizer to get simultaneous dye-adsorption and dye-decomposition on the powder-surface, or getting dye adsorption in one solution and dye decomposition in a separate solution by said adsorbent powder under dark condition.

Claims

1. A process for decomposition of organic synthetic-dyes using semiconductor-oxides nanotubes via dark-catalysis which comprises the steps of:

(i) suspending nanotubes-based dye-adsorbent powder in an aqueous solution of organic synthetic-dye,

(ii) adding a strong oxidizer in the above solution of step (i), stirring the suspension, under the dark-condition, using a magnetic or overhead stirrer for 10-3600 min for simultaneous dye-adsorption and dye-decomposition on the powder-surface;

(iii) optionally transferring the dye adsorbent powder treated with solution of organic synthetic dye in step (i) to another aqueous solution containing a strong oxidizer and stirring the suspension, under the dark-condition, using a magnetic or overhead stirrer for 10-3600 min for the complete dye-decomposition on the powder-surface,

(iii) separating the powder from the solution of step (ii) or step (iii) using a centrifuge operated at 2000-4000 rpm;

(iv) drying the powder in an oven at 70-90°

C. for 15-20 h;

(v) recycling the dried-powder to repeat step-(i) to step-(iv) for the next cycle of dye-decomposition under the dark-condition

2. The process as claimed in claim 1, wherein the nanotubes-based dye-adsorbent powder consists of high surface-area nanotubes selected from the group of H₂Ti₃O₇ and anatase-TiO₂ processed via hydrothermal.

3. The process as claimed in claim 1, wherein the organic synthetic-dye is selected from the group consisting basic (cationic), acidic (anionic), and reactive-dyes in an aqueous solution.

4. The process as claimed in claim 1 wherein the simultaneous dye adsorption and dye decomposition of step (ii) is designated as “

one-step”

method of dye decomposition under dark condition.

5. The process as claimed in claim 1 wherein the decomposition of dye carried out using a separate solution of step (iii) is designated as “

two-step”

method of dye decomposition under dark condition.

6. The process as claimed in claim 1, wherein the strong oxidizer is selected from a group consisting of H₂O₂ and any other material containing the OH′

group.

7. The process as claimed in claim 1, wherein H₂O₂ is used as a strong oxidizer is in the range of 0.5-15 M (3-50 wt. %).

8. The process as claimed in claim 1, wherein the concentration of nanotubes-based dye-adsorbent powder varies in between 0.1-3.0 g·

L<sup>−

1</sup> taken in 50-250 ml aqueous solution with the net dye-removal rate, involving the simultaneous dye-adsorption and dye-decomposition (one step method) under the dark-condition, varying in the range of 1-100 mg·

g<sup>−

1</sup>·

h<sup>−

1</sup>.

9. The process as claimed in claim 8, wherein the concentration of nanotubes-based dye-adsorbent powder with the surface-adsorbed organic synthetic-dye varies in between 0.1-3.0 g·

L<sup>−

1</sup> taken in 50-250 ml aqueous solution with the net dye-removal rate, involving the dye-adsorption and dye-decomposition occurring in separate aqueous solutions (two-step method) under the dark-condition, varying in the range of 0.1-10 mg·

g<sup>−

1</sup>·

h<sup>−

1</sup>.

10. The process as claimed in claim 1 wherein the dried nanotube powder obtained at step (iv) retain adsorbent capacity in both one-step and two-step method of dye decomposition.

11. The process as claimed in claim 1, the recycled dye-adsorbent powder is being pale-yellow color having the same capacity for the maximum dye-adsorption, under the dark-condition, as that of the original dye-adsorbent powder (white-color).

12. A process for decomposition of organic synthetic-dyes using semiconductor-oxides nanotubes via dark-catalysis as herein described with reference to examples and figures of this specification.