Chapter 7.2 - Modification of Cereal Straws as Natural Sorbents for Removing Metal Ions from Industrial Waste Water

Abstract

Environmental pollution caused by toxic heavy metals is one of the most pressing problems in many densely populated cities worldwide. The industrial and domestic wastes responsible for various damages to the environment adversely affect the health of the human population. The major toxic metal ions hazardous to humans as well as other forms of life are chromium (Cr), iron (Fe), selenium (Se), vanadium (V), copper (Cu), cobalt (Co), nickel (Ni), cadmium (Cd), mercury (Hg), arsenic (As), lead (Pb), zinc (Zn), etc. It is necessary to remove these metals from industrial effluents before discharging aqueous waste into the environment. Under the current regulations, industries are obligated to treat waste water and to reduce the concentration of toxic metals to less than certain designated values before the discharge of industrial and urban household waste water. Numerous methods exist for removing detrimental metal ions from aqueous solutions. The main techniques that have been utilized to reduce the concentration of the heavy metal ions in effluents include chemical precipitation, ion exchange, chemical oxidation, reverse osmosis, electrodialysis, and ultrafiltration. Most of these methods have their own inherent limitations such as less efficiency, sensitive operating conditions, production of secondary sludge, and expensive disposal of the secondary sludge. Another powerful technology is adsorption of heavy metals, such as activated carbon (AC). AC has been recognized as highly effective adsorbents for the removal of heavy metal ions from the concentrated and dilute metal-bearing effluents.