Heavy metal ions such as copper, iron, nickel, lead, etc. in the environment are of major concern due to their toxicity to many life forms. Unlike organic pollutants, which are susceptible to biological degradation, metal ions do not degrade into any harmless end products (Mohammadiet al., 2010) and tend to accumulate causing several diseases and health disorders in humans, and other living organisms (Rosa et al., 2008). Several industrial activities are important sources ofenvironmental pollution due to their high content of several heavy metal ions(Dada et al., 2012).
Wide range of various treatment techniques available for the removal of heavy metal ions from aqueous solutions such as ion exchange, biodegradation, oxidation, solvent extraction, chemical precipitation, flotation, biosorption, electrolytic recovery, membrane separation and adsorption have been reported to be used for removal of heavy metal ions from industrialeffluents (Al-tameemi et al., 2012; Deosarkar,2012). However, adsorption has been universally accepted as one of the most effective pollutant removal process, with low cost, ease in handling, low consumption of reagents, as well as scope for recovery of value added components through desorption and regeneration of adsorbent(Dada et al., 2012).
Adsorption is collection of adsorbate on the surface of adsorbent due to force of attraction(Deosarkar,2012). The practical applications of adsorption can be at separation and purification of liquid and gas mixtures, bulk chemicals, drying gases and liquids before loading them into industrial systems, removal of impurities from liquid and gas media, recovery of chemicals from industrial and vent gases and water purification(Prabakaran&Arivoli,2012). Activated carbon is the most widely used adsorbent due to its excellent adsorption capability for heavy metals. However, the use of these methods is often limited due to the high cost, which makes them unfavorable for the needs of developing countries.
Many reports have been investigatedthe low-cost adsorbents for Adsorption of heavy metals from aqueous solutions(Souag et al., 2009)such as date pits(Belhachemi et al., 2009) bamboo(Kannan&Veemaraj, 2009) oil palm fibre(Hameedet al., 2011;Nwabanne&Igbokwe, 2012), coconut shell(Satya et al., 1997), apricot stones (Philip&Girgis, 1996), sugar beet bagasse (Jaguaribe et al., 2000), waste tires(Teng et al., 2000;Juan et al., 2005;Mui et al., 2010), coconut husk, seed shell (Gueu et al.,2006), dates stones (Alhamed&Bamufleh, 2008), sun flower (Surchi, 2011), asphaltic carbon(Ambursa et al., 2011), Henna Leaves (Shanthi&Selvarajan, 2012).The intrinsic properties of activated carbon are dependent on the raw material source. The source of raw material was based on the need for developing low cost absorbent for pollution control as well as reducing the effect of environmental degradation poised by agricultural waste(Itodo H. &Itodo A., 2010).
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(Author: Abbas Sabah Thajeel