chromium reduction presentation
Post on 31-Jan-2016
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REDUCTION OF
HEXAVALENT CHROMIUM
AT THE END OF THE PRESENTATION,
YOU WILL BE ABLE TO UNDERSTAND :
•WHAT IS CHROMIUM• HOW HEXAVALENT CHROMIUM IS FORMED•WHERE THIS SUBSTANCE CAN BE FOUND•WHY HEXAVALENT CHROMIUM IS DANGEROUS• HOW TO REDUCE THE HEXAVALENT CHROMIUM
INTRODUCTION TO CHROMIUM
TRIVALENT FORM
HEXAVALENT FORM
• ESSENTIAL NUTRIENT FOR HUMANS• NON-TOXIC
• Atomic number 24• A hard silver metal used in stainless steel and other alloys
- FOUND IN STEEL, CHEMICAL, LEATHER AND TEXTILE MANUFACTURING- WATER AND SOIL POLLUTION- DANGER TO HUMAN HEALTH• ALTER GENETIC MATERIAL• CARCINOGENIC• ORGAN DAMAGE• FATAL
WHERE HEXAVALENT CHROMIUM / Cr (IV) CAN BE FOUND?
WELDING FUMES
METAL COATING & PROTECTIVE PAINT
DYES AND PIGMENTS
Methods to detect Cr (III) and Cr(VI)
ATOMIC ABSORPTION (AA)
SPECTOMETRY
ION EXCHANGE CHROMATOGRAPHY
HEALTH EFFECTSINGESTION HAZARDS- Erosive to stomach
EYES- Permanent eye damage when direct contact with chromic
acid or chromate dusts
RESPIRATORY TRACT- Hexavalent chromium can irritate nose, throat and lungs
- Ulcers in nasal
SKIN- Dermatitis and skin ulcers
- Worker that sensitive to chromium will cause serious skin rash even in small amount
CANCER and FATAL
HEXAVALENT CHROMIUM WASTE TREATMENT
There are 2-stages of treatment:• STAGE 1 – Reduce Chromium (VI) to Chromium (III)• STAGE 2 - Neutralization
FIRST STAGE
Reduce chromium (VI) to chromium (III)
Using reducing agents:• Sulfur dioxide,• Sodium bisulphate,• Or sodium-meta-bisulfite
Acid : Sulphuric acid
SECOND STAGE(Neutralization)
• Adding Calcium hydroxide (lime) to the wastewater
• Increase and maintain pH of 8.0 or higher
• For the precipitation of chromium hydroxide to occur.
Then, the precipitate can be easily separated (flocculation, coagulation and sedimentation) and then dispose
Collected as sludge
Main disadvantages of this treatment method are:
• Need to reduce wastewater pH between 2 and 3 to assure rapid and complete reduction.
• The acidic wastewater need to be neutralized before discharge.
• These steps consume large amount of chemicals and tend to increase the volume of sludge with unreacted precipitants.
END OF TOPIC
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