WO2008139485A1 - A process for the determination of hexavalent chromium in organic reductant treated chromite materials - Google Patents

A process for the determination of hexavalent chromium in organic reductant treated chromite materials Download PDF

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Publication number
WO2008139485A1
WO2008139485A1 PCT/IN2007/000200 IN2007000200W WO2008139485A1 WO 2008139485 A1 WO2008139485 A1 WO 2008139485A1 IN 2007000200 W IN2007000200 W IN 2007000200W WO 2008139485 A1 WO2008139485 A1 WO 2008139485A1
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WIPO (PCT)
Prior art keywords
hexavalent chromium
solution
organic reductant
chromite
treated
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Application number
PCT/IN2007/000200
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French (fr)
Inventor
K. Gajanan
S. Mohan Rao
K. C. Das
Original Assignee
Tata Steel Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tata Steel Limited filed Critical Tata Steel Limited
Priority to PCT/IN2007/000200 priority Critical patent/WO2008139485A1/en
Priority to TR2009/02462T priority patent/TR200902462T1/en
Publication of WO2008139485A1 publication Critical patent/WO2008139485A1/en
Priority to ZA2008/09893A priority patent/ZA200809893B/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/40—Concentrating samples
    • G01N1/4044—Concentrating samples by chemical techniques; Digestion; Chemical decomposition
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/40—Concentrating samples
    • G01N1/4077—Concentrating samples by other techniques involving separation of suspended solids
    • G01N2001/4088—Concentrating samples by other techniques involving separation of suspended solids filtration
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated

Definitions

  • This invention relates to a process for analysis of hexavalent chromium in organic reductant (Myrobalam Powder) treated chromite materials.
  • Hexavalent chromium presence in chromite products beyond 0.05 ppm is environmental unfriendly.
  • the chromite ore materials will be preferred by the customers only if it is hexavalent chromium free which is the differential for future marketing of chromite ore materials.
  • the US EPA method 7196a and Japanese method as per JIS K0102-1993 are most relevant standard methods used for determination of dissolvable hexavalent chromium in soils, sediments and solid wastes using the UV-Spectrophotometer.
  • the present process has been developed to reduce the hexavalent chromium to trace levels in concentrates/fines by using the organic reductant. On using this, analyzing hexavalent chromium by using UV-Spectrophotometer method; which is commonly used to analyse hexavalent chromium in ppm levels, becoming impossible. To circumvent this situation a method has been developed.
  • An object of this invention is to propose a process for analyzing the hexavalent chromium in solid chromite materials.
  • Another object of this invention is to propose a process for removing colour and turbidity contributing colloidal particles.
  • Yet another object of this invention is to propose a process for determining hexavalent chromium using UV-Spectrophotometer with the suggested additional process step to current standard method.
  • a process for reducing the hexavalent chromium in solid chromite materials comprising the steps of: mixing the organic reductant with a fixed volume of water to obtain a solution, adding the said solution to the chromite material with continuous stirring to obtain the chromite material with reduced concentration of hexavalent chromium.
  • a process has been proposed for analyzing the hexavalent chromium in these chromite materials.
  • the organic reductant (Myrobalam powder) used for the reduction of hexavalent chromium from the chromite materials in the present process is commonly known as Myrobalam powder and obtained by grinding a naturally occurring forests plant nut known as Terminalia Chebula (Botanical Name).
  • Terminalia Chebula (Botanical Name).
  • the proximate analysis of the organic reductant is given in Table 1.
  • hexavalent chromium in chromite ore material On using this organic reductant for treating the chromite materials, the analysis of hexavalent chromium in chromite ore material is generally carried out using the Japanese industrial method JIS K0102-1993. The different process steps involved in this standard method for hexavalent chromium analysis are shown in Fig. 1a.
  • Fig. 1a & b Comparison of the standard method for hexavalent chromium analysis in chromite materials and the proposed method for organic reductant treated chromite materials.
  • the standard method of hexavalent chromium analysis (Fig. 1a) consists of broadly two steps. The first step is the digestion of the solid chromite samples and the second step consists of analysis of the digested samples.
  • Digestion Step Take chromite solid material in a glass bottle. Add distilled water to this bottle. The dilution ratio of solid chromite material: distilled water must be maintained as 1 :10. Adjust the PH of this solution from 5.8 to 6.3 with HCL/NaOH. Shake the bottom with the help of shaking machine. Allow it to stand for few minutes. Filter with 0.45 micro meter filter paper. Collect the filtrate.
  • the filtrate solution For analysis of hexavalent chromium in this filtrate using the spectrophotometer method the filtrate solution must be free from any iron interferences.
  • the solid chromite materials which are not treated with organic reductant, after digestion gives the filtrate which is colourless and free from any interfering colour or turbidity.
  • the solid chromite materials which are treated with organic reductant, after digestion gives the filtrate which will be a coldured solution with a turbidity of greater than 400 NTU (Shown in Fig. 1 b).
  • the digested solution cannot be analyzed using UV-spectrophotometer for hexavalent chromium because of the interfering colour and high turbidity of this solution.
  • the solution For the hexavalent chromium analysis of this solution by UV-spectrophotometric method the solution must be turbidity free ie. Turbidity ⁇ 1 NTU. The.PH of this solution is neutral.
  • the colour and the turbidity of this solution are due to the suspended colloidal gamma iron oxide particles as well as traces of unreacted organic reductant. These gamma iron oxide particles remains in the colloidal form in the solution at around neutral PH, in the present case and generally the zeta potential is more positive than +30 mV or more negative than -30 mV in stable colloidal system.
  • the collected filtrate will be invariably coloured and turbid.
  • a process step is developed in order to decolourize this filtrate so that the analysis can be carried out using UV- spectrophotometer. For this, take about 50 ml of this coloured and turbid solution and add about 0.25 ml of 1 :1 H 2 SO 4 acid to adjust the PH of the digested solution below 3.0. All the colloidal particles present in the solution will settle down. Filter the solution with 0.45 micro meter filter paper to separate the settled particles. The solution is now ready for the hexavalent chromium analysis as a colour and turbidity free solution for following the standard method.
  • the developed method will help in determining the hexavalent chromium in the colour and turbid solutions obtained after digestion of solid chromite materials treated with organic reductant (Myrobalam powder).

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

A process for analyzing the hexavalent chromium in solid chromite materials treated with organic reductant: by introducing additional process step of decolourization of the digested filtrate solution.

Description

TITLE .
A process for the determination of hexavalent chromium in organic reductant treated chromite materials.
FIELD QF INVENTION:
This invention relates to a process for analysis of hexavalent chromium in organic reductant (Myrobalam Powder) treated chromite materials.
BACKGROUND OF INVENTION:
Hexavalent chromium presence in chromite products beyond 0.05 ppm is environmental unfriendly. The chromite ore materials will be preferred by the customers only if it is hexavalent chromium free which is the differential for future marketing of chromite ore materials. The US EPA method 7196a and Japanese method as per JIS K0102-1993 are most relevant standard methods used for determination of dissolvable hexavalent chromium in soils, sediments and solid wastes using the UV-Spectrophotometer. These methods can not be used for analysing the hexavalent chromium in chromite materials treated with organic reductant (Myrobalam Powder) because of development of colour and turbidity in the solution obtained after digestion of organic reductant treated chromite materials.
The present process has been developed to reduce the hexavalent chromium to trace levels in concentrates/fines by using the organic reductant. On using this, analyzing hexavalent chromium by using UV-Spectrophotometer method; which is commonly used to analyse hexavalent chromium in ppm levels, becoming impossible. To circumvent this situation a method has been developed. OBJECTS OF THE INVENTION:
An object of this invention is to propose a process for analyzing the hexavalent chromium in solid chromite materials.
Another object of this invention is to propose a process for removing colour and turbidity contributing colloidal particles.
Yet another object of this invention is to propose a process for determining hexavalent chromium using UV-Spectrophotometer with the suggested additional process step to current standard method.
STATEMENT OF THE INVENTION:
According to this invention there is a process for reducing the hexavalent chromium in solid chromite materials comprising the steps of: mixing the organic reductant with a fixed volume of water to obtain a solution, adding the said solution to the chromite material with continuous stirring to obtain the chromite material with reduced concentration of hexavalent chromium. A process has been proposed for analyzing the hexavalent chromium in these chromite materials.
DETAILED DESCRIPTION OF THE INVENTION:
Developing newer reductants especially with solids which are environmental friendly, cost effective and no impurities addition in down the line metallurgical process is a challenging task and this mostly possible by using organic reductants or any other innovative methods where there is no inorganic salts are used. On using organic reductants, colour and turbidity development is eminent. This will make the application of generally used UV-Spectrophotometer method impossible.
The organic reductant (Myrobalam powder) used for the reduction of hexavalent chromium from the chromite materials in the present process is commonly known as Myrobalam powder and obtained by grinding a naturally occurring forests plant nut known as Terminalia Chebula (Botanical Name). The proximate analysis of the organic reductant is given in Table 1.
Table 1 : Proximate analysis of organic reductant
Figure imgf000004_0001
On using this organic reductant for treating the chromite materials, the analysis of hexavalent chromium in chromite ore material is generally carried out using the Japanese industrial method JIS K0102-1993. The different process steps involved in this standard method for hexavalent chromium analysis are shown in Fig. 1a.
Fig. 1a & b: Comparison of the standard method for hexavalent chromium analysis in chromite materials and the proposed method for organic reductant treated chromite materials.
The standard method of hexavalent chromium analysis (Fig. 1a) consists of broadly two steps. The first step is the digestion of the solid chromite samples and the second step consists of analysis of the digested samples. Digestion Step: Take chromite solid material in a glass bottle. Add distilled water to this bottle. The dilution ratio of solid chromite material: distilled water must be maintained as 1 :10. Adjust the PH of this solution from 5.8 to 6.3 with HCL/NaOH. Shake the bottom with the help of shaking machine. Allow it to stand for few minutes. Filter with 0.45 micro meter filter paper. Collect the filtrate. For analysis of hexavalent chromium in this filtrate using the spectrophotometer method the filtrate solution must be free from any iron interferences. The solid chromite materials which are not treated with organic reductant, after digestion gives the filtrate which is colourless and free from any interfering colour or turbidity. However the solid chromite materials which are treated with organic reductant, after digestion gives the filtrate which will be a coldured solution with a turbidity of greater than 400 NTU (Shown in Fig. 1 b). The digested solution cannot be analyzed using UV-spectrophotometer for hexavalent chromium because of the interfering colour and high turbidity of this solution. For the hexavalent chromium analysis of this solution by UV-spectrophotometric method the solution must be turbidity free ie. Turbidity < 1 NTU. The.PH of this solution is neutral.
The colour and the turbidity of this solution are due to the suspended colloidal gamma iron oxide particles as well as traces of unreacted organic reductant. These gamma iron oxide particles remains in the colloidal form in the solution at around neutral PH, in the present case and generally the zeta potential is more positive than +30 mV or more negative than -30 mV in stable colloidal system.
After following the digestion step of standard method for digesting the solid chromite materials treated with organic reductant, the collected filtrate will be invariably coloured and turbid. Hence a process step is developed in order to decolourize this filtrate so that the analysis can be carried out using UV- spectrophotometer. For this, take about 50 ml of this coloured and turbid solution and add about 0.25 ml of 1 :1 H2SO4 acid to adjust the PH of the digested solution below 3.0. All the colloidal particles present in the solution will settle down. Filter the solution with 0.45 micro meter filter paper to separate the settled particles. The solution is now ready for the hexavalent chromium analysis as a colour and turbidity free solution for following the standard method.
The developed method will help in determining the hexavalent chromium in the colour and turbid solutions obtained after digestion of solid chromite materials treated with organic reductant (Myrobalam powder).

Claims

WE CLAIM
1. A process for analyzing the hexavalent chromium in solid chromite materials treated with organic reductant: by introducing additional process step of decolourization of the digested filtrate solution.
2. The process as claimed in claim 1 , wherein said organic reductant is -> Myrobalam powder.
3. The process as claimed in claim 1 , wherein the chromite material is treated with the organic reductant for 2 to 2.5 hours.
4. The process as claimed in claim 1 , wherein the said organic reductant is obtained by grinding the nut of Terminalia Chebula.
10 5. The process as claimed in claim 1 , wherein the said additional process step is to take 50 ml of coloured and turbid filtrate solution obtained from digestion of chromite materials treated with organic reductant, and add about 0.25 ml of 1 :1 H2SO4 acid to adjust the pH of the digested solution below 3.0. All the colloidal particles present in the solution will settle down. Filter the solution with 0.45 micro meter filter paper to separate the settled particles.
PCT/IN2007/000200 2007-05-11 2007-05-11 A process for the determination of hexavalent chromium in organic reductant treated chromite materials WO2008139485A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
PCT/IN2007/000200 WO2008139485A1 (en) 2007-05-11 2007-05-11 A process for the determination of hexavalent chromium in organic reductant treated chromite materials
TR2009/02462T TR200902462T1 (en) 2007-05-11 2007-05-11 A process for determining hexavalent chromium in chromite materials treated with organic reducing agent.
ZA2008/09893A ZA200809893B (en) 2007-05-11 2008-11-24 A process for the determination of hexavalent chromium in organic reductant treated chromite materials

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105452841A (en) * 2013-05-24 2016-03-30 株式会社住化分析中心 Sample pre-treatment method for measuring the quantity of toxic elements in agricultural produce samples
CN111077090A (en) * 2019-12-10 2020-04-28 中国环境科学研究院 Cr in soil containing large amount of reducing agent6+Is detected by
CN111077091A (en) * 2019-12-16 2020-04-28 中国环境科学研究院 Method for detecting hexavalent chromium in soil

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS48102693A (en) * 1972-04-11 1973-12-24
SU1478113A1 (en) * 1987-01-23 1989-05-07 Курский Трикотажный Комбинат Method for chromium analysis

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS48102693A (en) * 1972-04-11 1973-12-24
SU1478113A1 (en) * 1987-01-23 1989-05-07 Курский Трикотажный Комбинат Method for chromium analysis

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105452841A (en) * 2013-05-24 2016-03-30 株式会社住化分析中心 Sample pre-treatment method for measuring the quantity of toxic elements in agricultural produce samples
CN111077090A (en) * 2019-12-10 2020-04-28 中国环境科学研究院 Cr in soil containing large amount of reducing agent6+Is detected by
CN111077091A (en) * 2019-12-16 2020-04-28 中国环境科学研究院 Method for detecting hexavalent chromium in soil

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ZA200809893B (en) 2010-02-24
TR200902462T1 (en) 2009-08-21

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