Pharos

University in

AlexandriaFaculty of

Engineering.

Petrochemical

Dep.PE.392

Pollution

ControlRemoval of Chromium

Objects:Introduction.

uses of Chromium

Chromium Removal Methods

Health Effects

Chromium Hazards in

Egypt

Introduction: Chromium is a metal that exists in several oxidation:

Chromium-3 Chromium-6

Chromium-3:

• Chromium (trivalent) is a basic food item helps the body use sugar, protein, and fat.

• Chrome III is an essential nutrient for maintaining blood glucose levels.

• Exist in food, fruit, fishes and underground water.

Chromium-6:

• A toxic form of chromium metal

• Used in many industrial applications primarily for its anti-corrosive properties.

• Used in electroplating (chrome plating), stainless steel and other high chromium Alloys and leather tanning.

uses of Chromium• Aircraft Painting

• Leather tanning

• Electroplating

• Textile manufacturing

• dyeing, cement industry

• metal finishing

Chromium Removal Methods•Chemical Precipitation

•Adsorption and Biosorption

•Reverse Osmosis

•Ion Exchange

•Electrodialysis

•Photo-catalysis etc.

•Chemical Precipitation

Formation of a separable solid substance from a solution, either by converting the substance into an insoluble form or by changing the composition of the solvent to diminish the solubility of the substance in it.

The removal of chromium can be accomplished by:1. the addition of ferrous sulphate and lime.

Ferrous ion 2. first reduces hexavalent chromium to

trivalent chromium by simultaneous oxidation of ferrous ion to ferric.

3. The resulting forms can be precipitated as hydroxides by lime.

Cr3++ (OH)-→ Cr (OH)3.

Chromium is precipitated as hydroxide:

• finally leads to the generation of a high water content sludge .

• its efficiency is affected by low pH and the presence of other salts (ions).

• and is ineffective in removal of the metal ions at low concentration.

Adsorption and Biosorption

• Defined as accumulation of liquid or gas phase on the surface of a solid phase.

• The material that adsorbs is called adsorbent and the substance getting adsorbed is called adsorbate.

• Adsorption may be physical adsorption or Chemical adsorption or a combination of both.

•If we have to remove soluble material from the solution phase, but the material is neither volatile nor biodegradable, we often employ adsorption processes.

•Biosorptions a property of certain types of inactive, dead, microbial biomass to bind and concentrate heavy metals from even very dilute aqueous solutions.

• The advantages of biosorption process are that these are cost effective, technically feasible and eco-friendly.

Health Effects• Ingestion Hazards–Erosive to stomach, Hemorrhaging and death • Eyes–Direct eye contact with chromic acid orchromate dusts can cause permanent eye damage. • Hexavalent chromium is considereda potential lung carcinogen. 1. Studies of workers in the chromate

production, plating, and pigment industries consistently show increase rates of lung cancer.

2. Insoluble forms such as zinc chromate are the most potent 20 year cancer latency

Chromium Hazards in Egypt

In a research that have done by AL-Watan news paper that took samples from the local stores and they’ve found that all of the samples contain chromuim-6 that is dangerous for the skin :1. About 60,000 employees work in 500 Tannery contact directly

with chromium-62. Most of the tannery use a cheap materials in the tanning process 3. The products of these tanneries (bag, shoes, jacket, leather) Standard Egyptian provide that the chromium ratio should be 0.00003% kgBut the products have a ratio of 13% kg which is very dangerous for the humans and effect on the health and cause a skin problems and in the long-term skin cancer.

Chromium-6 is used in Leather tanning

referenceshttp://water.epa.gov/drink/info/chromium/http://water.epa.gov/drink/contaminants/basicinformation/chromium.cfmhttp://www.slideshare.net/ArvindGupta9/methods-for-removal-of-chromiumhttp://www.elwatannews.com/news/details/585685http://digital.ahram.org.eg/articles.aspx?Serial=325739&eid=3041http://water.epa.gov/drink/contaminants/basicinformation/chromium.cfmhttp://gilgamish.org/printarticle.php?id=983.http://www.atsdr.cdc.gov/toxfaqs/index.aspAgency for Toxic Substances and Disease Registry Division of Toxicology and Human Health Sciences,47- 3رقم ™ToxFAQs الكروم - CAS 7440Health Effects of Hexavalent Chromium-OSHA Fact sheet