Introduction
The hazardous effects of heavy metals in nature have considerably
limited use in industry. As the population increased
and the industry growed rapidly, metal discharge from various
industries caused environmental pollution. Dissolving chromium
ions are the most important pollutants for the environment
since they accumulate in living tissues, causing many harmful
effects. Many industries are responsible for the environment
pollution as they contained heavy metal ions in their wastewaters.
Chromium usually exists in the (III) or (VI) oxidation states.
Hexavalent chromium compounds are more soluble, mobile and
bioavailable compared to sparingly soluble trivalent chromium
species. In contrast to Cr(III), which is essential to mammalian
systems, Cr(VI) is dangerous for humans due to its toxicity and
carcinogenic properties. Since the compounds of chromium, especially
Cr(VI) species, are known to be detrimental to human
health, the maximum level permitted in wastewater are 5ppm
for trivalent chromium and 0.05ppm for hexavalent chromium