Process for decomposition of organic synthetic-dyes using semiconductor-oxides nanotubes via dark-catalysis

• US 9,604,859 B2
• Filed: 05/17/2013
• Issued: 03/28/2017
• 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
• Primary Examiner(s): BARRY, CHESTER T
• Application Number:
  US14/421,904
• Publication Number:
  US 20150203365A1
• Time in Patent Office: 1,411 Days
• Field of Search: None
• 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, wherein the concentration of nanotubes-based dye-adsorbent powder is in the range of 0.1-3.0 g L<sup>−

1</sup>;

(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, designated as “

one-step method”

, wherein the net dye-removal rate is in the range of 1-100 mg g<sup>−

1</sup> h<sup>−

1</sup>;

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

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

C. for 15-20 h; and

(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 of basic, acidic, and reactive-dyes in an aqueous solution.

4. 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 except water.

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

6. The process as claimed in claim 1, wherein the dried nanotubes powder obtained at step (iv) retains adsorbent capacity in the one-step method of dye decomposition.

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

8. The process as claimed in claim 1, wherein the step (ii) is replaced by the step of:

transferring the dye-adsorbent powder treated with the solution of organic synthetic dye in step (i) to another aqueous solution containing a strong oxidizer and stirring the suspension, under the dark-condition, designated as “

two-step method”

, using a magnetic or overhead stirrer for 10-3600 min for the complete dye-decomposition on the powder-surface.

9. The process as claimed in claim 8, wherein the dried nanotubes powder obtained at step (iv) retains adsorbent capacity in the two-step method of dye decomposition.

10. The process as claimed in claim 8, wherein the concentration of nanotubes-based dye-adsorbent powder with the surface-adsorbed organic synthetic-dye is in the range of 0.1-3.0 g L⁻

1 and the net dye-removal rate, involving the dye-adsorption and dye-decomposition occurring in separate aqueous solutions under the dark-condition, designated as “

two-step method”

, is in the range of 0.1-10 mg g<sup>−

1</sup> h<sup>−

1</sup>.