Title of Invention

AN ELECTROLYSIS PROCESS FOR REMOVAL OF HEXAVALENT CHROMIUM FROM WASTE WATER OF CHROME ORE MINES

Abstract The present invention relates to an electrolysis process for removal of hexavalent chromium from waste water of chrome ore mines comprising the following steps of passing a DC current through electrodes in an electrolysis tank containing hexavalent chromium waste water and electrolysing water to produce bubbles of hydrogen and oxygen characterised in that during anodic oxidation reaction, the Fe2+ ions and large number of electrons are released which reduce the hexavalent dispersed chromium to Cr(III) at cathode, forming dispersed particles of chromite which collide and adhere with the upward moving hydrogen and oxygen gas bubbles and float them to the surface of the water in the form of foam and skimming off the top surface foam of waste water containing chromite in the electrolysis tank.
Full Text FIELD OF THE INVENTION
The present invention relates to an electrolysis process treatment to
minimize hexavalent chromium to trace levels from waste water of
chrome ore mines
BACKGROUND OF THE INVENTION
Chromlte ore mining operations involve the handling of the mines
waters which is termed as mines wastewater. This water contain
hexavalent chromium in the range of 0.3 ppm to less than 1 ppm
depending on natural weathering conditions and nature of deposit
and if It exceeds 0.05 ppm It could be environmental unfriendly as
per world health organization norm.
The conversion of this toxic hexavalent chromium, Cr(VI) to non-toxic
Cr(III) is useful way for the remediation of hexavalent chromium.
Conventionally chemical reduction of Cr(VI) to Cr(111) using
reductant like FeS04, has been a common method employed for


Cr(VI) remediation in mines wastewater. However, use of chemical
reluctance is undesirable in industrial practice due to their
unavoidable process and environmental unfriendly nature. This
method also adds other pollutant like sulphur to the wastewater
which Is not desirable. Hence there is need to address this issue
using alternative clean and environmental friendly process
technologies which does not add pollutants to the mine wastewater.
The present invention has proposed solution of the above mentioned
difficulties of the existing practice through employment of electrolysis
process.
DESCRIPTION OF THE INVENTION
One objective of the invention is to use electrolysis of water
containing the hexavalent chromium by passing Dc current through
iron electrodes in a tank.
Another objective of the invention is to produce hydrogen and
oxygen gas bubbles during electrolysis.


A yet another objective of the invention is to reduce hexavalent
chromium to Cr(III) at cathode by electrons released from anodic
oxidation reaction when Fe2+ions and large number of electrons are
released and forming dispersed solid particles of Chromite.
A further objective of the Invention Is to float the suspended particles
of Chromite at the top of the electrolysis tank through colliding those
particle with hydrogen and oxygen gas bubbles and floating those
particles at the surface adhered with the upwardly moving hydrogen
and oxygen gas bubbles.
A still another objective of the invention is to skimming off the
accumulated dispered particles in the form of foam at the surface of
the tank with a bladded transport system or skimmer.
The proposed Invention will be better understood from the following
description with reference to the accompanying drawings in which
Figure 1 shows, in photograph the experimental set up for
electrolysis of wastewater from chromite mines.


Figure 2 shows in graph plotted time Vs Cr(VI) [ppm]
Hexavalent chromium content in waste waters with time variation.
The electrolysis experimental setup is shown in Fig. 1. The Iron
electrodes (1) are arranged at the bottom of a tank ((2) filled with
the wastewater (3) containing hexavalent chromium. DC current is
passed through the electrodes, electrolyzing the water and producing
bubbles of hydrogen and oxygen gas. During the anodic oxidation
reaction, the Fe2+ ions and large number of electrons are released
which reduces the hexavalent chromium to Cr(III) at cathode, and
forms the dispersed solid particles of chromite. As the hydrogen and
oxygen bubbles float to the top of the tank, they collide with these
particles suspended in the water on the way up, adhere to them and
Moat them to the surface of the water. Dispersed particles
accumulate at the surface of the tank in the form of foam. The foam
is then skimmed off the surface of the tank with the bladed transport
system or skimmer. The electrolysis operation is carried out with a
stirring arrangement (4) to enhance homogenised generation in the

electrolytic tank. An AC to DC rectifier (5) supply DC current In the
tank through electrodes (1). The stirring assembly (4) is also
connected as the DC supply of the rectifier to provide stirring during
electrolysis. The reactions taking part in electrolysis process is stated
as below
Anodic oxidation reactions

Cathodic reduction reaction

The invention is exemplified with the equipment of Fig 1 as follows:-
The electrolysis experiments with wastewater for removing
hexayalent chromium were carried out at current density of 42 A/m2
and a sample size of 4 liters. The water samples collected at
different time Intervals were subjected to hexavalent chromium

analysis. The results of hexavalant chromium reduction with respect
to time are shown In Fig. 2. It can be seen from Fig. 2, that the
complete reduction of dissolvable Cr (VI) to trace levels (i.e. less than
0.01 ppm) have taken place in the initial 5 minutes Itself. Hence
even 5 minutes of time at current density of 42 A/m2 is sufficient to
remove hexavalent chromium from the mines wastewater.
The present invention for Cr +6 removal from waste water is faster,
easier to control, cost and space effective.
The invention as narrated herein above should not be read and
construed in a restrictive manner as varbus modifications, alterations
of sizes and parameters used in the process and adaptations are
possible within the scope and ambit of the invention as defined in the
encompassed appended claim.

WE CLAIM
1. An electrolysis process for removal of hexavalent chromium from waste water of
chrome ore mines comprising the following steps:
- passing a DC current through electrodes in an electrolysis tank containing
hexavalent chromium waste water;
- electrolysing water to produce bubbles of hydrogen and oxygen;
characterised in that during anodic oxidation reaction, the Fe2+ ions and large
number of electrons are released which reduce the hexavalent dispersed
chromium to Cr(III) at cathode, forming dispersed particles of chromite which
collide and adhere with the upward moving hydrogen and oxygen gas bubbles
and float them to the surface of the water in the form of foam and skimming off
the top surface foam of waste water containing chromite in the electrolysis tank.

2. An electrolysis process for removal of hexavalent chromium as claimed in claim
1, wherein the electrolysis tank is maintained with a current density of 42 A/m2
for 4 liters of waste water sample.
3. An electrolytic process as claimed in claim 1, wherein the Cr(VI) from waste
water is removed less than 0.01 ppm.

4. An electrolytic process as claimed in claim 3, wherein hexavalent chromium is
removed to trace levels of less than 0.01 ppm within 5 minutes on carrying out
the electrolysis at current density of 42 A/m2.
5. An electrolytic process as claimed in the preceding claims, wherein the foam
containing chromite is skimmed off the surface of the electrolytic tank with a
bladed transport system or a skimmer.
6. An electrolysing process as claimed in the preceding claims, wherein a stirring
arrangement is provided with the electrolysing cell to stir the waste water during
electrolysis when required.
7. An electrolysing device for removal of hexavalent chromium from waste water of
chrome ore mines comprising a electrolysing cell (2) with Cr(VI) containing waste
water (3) having iron electrodes (1), stirring assembly (4), and an AC to DC
rectifier to supply a DC current to the electrolysis tank (2) through the electrodes
(1) containing the waste water, wherein at anode oxidation reaction occur to
release Fe2+ ions and large number of electrons and at cathode reduction
reaction occur to release suspended solid particles of chromite, which are
collided with upward moving hydrogen and oxygen gas bubbles generated by

anodic reaction and the said upward moving gas bubbles being adhered with the
suspended chromite particles float the same to the top surface of waste water in
the electrolysis cell (2) in the form of foam and is removed by skimming.
8. The clean water being removed of hexavalent chromium from waste water of
chrome ore mines, produced according to the method of claim 1.


The present invention relates to an electrolysis process for removal of hexavalent
chromium from waste water of chrome ore mines comprising the following steps of
passing a DC current through electrodes in an electrolysis tank containing hexavalent
chromium waste water and electrolysing water to produce bubbles of hydrogen and
oxygen characterised in that during anodic oxidation reaction, the Fe2+ ions and large
number of electrons are released which reduce the hexavalent dispersed chromium to
Cr(III) at cathode, forming dispersed particles of chromite which collide and adhere
with the upward moving hydrogen and oxygen gas bubbles and float them to the
surface of the water in the form of foam and skimming off the top surface foam of
waste water containing chromite in the electrolysis tank.

Documents:

01049-kol-2007-abstract.pdf

01049-kol-2007-claims.pdf

01049-kol-2007-correspondence others 1.1.pdf

01049-kol-2007-correspondence others.pdf

01049-kol-2007-description complete.pdf

01049-kol-2007-drawings.pdf

01049-kol-2007-form 1.pdf

01049-kol-2007-form 18.pdf

01049-kol-2007-form 2.pdf

01049-kol-2007-form 3.pdf

01049-kol-2007-gpa.pdf

1049-KOL-2007-(05-12-2011)-FORM-27.pdf

1049-KOL-2007-ABSTRACT 1.1.pdf

1049-KOL-2007-AMANDED CLAIMS.pdf

1049-KOL-2007-CANCELLED PAGES 1.1.pdf

1049-KOL-2007-CORRESPONDENCE 1.2.pdf

1049-kol-2007-correspondence.pdf

1049-KOL-2007-DESCRIPTION (COMPLETE) 1.1.pdf

1049-KOL-2007-DRAWINGS 1.1.pdf

1049-kol-2007-examination report.pdf

1049-KOL-2007-FORM 1 1.1.pdf

1049-kol-2007-form 18.pdf

1049-KOL-2007-FORM 2 1.1.pdf

1049-kol-2007-form 3.pdf

1049-kol-2007-gpa.pdf

1049-kol-2007-granted-abstract.pdf

1049-kol-2007-granted-claims.pdf

1049-kol-2007-granted-description (complete).pdf

1049-kol-2007-granted-drawings.pdf

1049-kol-2007-granted-form 1.pdf

1049-kol-2007-granted-form 2.pdf

1049-kol-2007-granted-specification.pdf

1049-KOL-2007-PETITION UNDER RULE 137.pdf

1049-kol-2007-reply to examination report-1.1.pdf

1049-KOL-2007-REPLY TO EXAMINATION REPORT.pdf


Patent Number 247407
Indian Patent Application Number 1049/KOL/2007
PG Journal Number 14/2011
Publication Date 08-Apr-2011
Grant Date 05-Apr-2011
Date of Filing 27-Jul-2007
Name of Patentee TATA STEEL LIMITED
Applicant Address JAMSHEDPUR
Inventors:
# Inventor's Name Inventor's Address
1 GAJANAN U. KAPURE TATA STEEL LIMITED JAMSHEDPUR 831 001
2 SARIPALLI M. RAO TATA STEEL LIMITED JAMSHEDPUR 831 001
PCT International Classification Number C02F1/50
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA