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

Patent metadata

Field	Value
Publication number	US-9604859-B2
Application number	US-201314421904-A
Country	US
Kind code	B2
Filing date	May 17, 2013
Priority date	Aug 17, 2012
Publication date	Mar 28, 2017
Grant date	Mar 28, 2017

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.

First claim

What is claimed is:

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 −1 ;
(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 −1 h −1 ;
(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 H 2 Ti 3 O 7 and anatase-TiO 2 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 H 2 O 2 and any other material containing the OH′ group except water.

5. The process as claimed in claim 1 , wherein H 2 O 2 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 −1 h −1 .

Assignees

• Council Scient Ind Res

Inventors

• Shukla Satyajit Vishnu
• Warrier Krishna Gopakumar
• Babu Babitha Kunnathuparambil

Classifications

• C02F2101/308

  Dyes; Colorants; Fluorescent agents · CPC title

• C02F1/725

  by catalytic oxidation · CPC title

• Y02W10/37

  using solar energy · CPC title

• C02F1/281 Primary

  using inorganic sorbents · CPC title

• C02F2303/18

  Removal of treatment agents after treatment · CPC title