ADSORPTION OF HEAVY METALS: A REVIEW
S. Malathi* and N. Krishnaveni
Environmental pollution particularly from heavy metals and minerals in the wastewater is the most serious problem in India. Due to extensive anthropogenic activities such as industrial operations particularly mining, agricultural processes and disposal of industrial waste materials; their concentration has increased to dangerous levels. Heavy metals in industrial effluent include nickel, chromium, lead, zinc, arsenic, cadmium, selenium and uranium. So far, a number of efficient methods have been reviewed for the removal of heavy metals such as chemical precipitation, ion exchange, reverse osmosis, electrodialysis, ultrafiltration, nanofiltration, coagulation, flocculation, floatation, etc. However these methods have several disadvantages Such as high reagent requirement, unpredictable metal ion removal, generation of toxic sludge etc. Adsorption process being very simple, economical, effective and versatile has become the most preferred methods for removal of toxic contaminants from wastewater. This paper reviews the use of various readily available natural materials as adsorbents of heavy metals from industrial wastewater. Various low cost adsorbents reviewed includes sand, waste tea leaves eggshell, rice husk, activated carbon, zeolites, olive stones, wood sawdust etc.
Keywords: Heavy metals, adsorption, activated carbon, low cost adsorbents.
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