Indian Journal of Chemical Technology Vol. 13, May 2006, pp. 203-217 Conventional and non-conventional adsorbents for removal of pollutants from water – A review Amit Bhatnagar a,b* & A K Minocha b a Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247 667, India b Environmental Science & Technology Division, Central Building Research Institute, Roorkee 247 667, India Email: amit_b10@yahoo.co.in Received 7 September 2005; revised received 28 February 2006; accepted 10 March 2006 In the present article, the suitability of activated carbon and other alternative adsorbents for wastewater treatment has been reviewed. It is evident from literature survey of last 20-25 years that researchers have gained success to some extent in developing inexpensive adsorbents for water pollution control utilizing naturally available and waste materials. However, still there is a need to find out the practical utility of such developed adsorbents on large-scale and safe and eco-friendly disposal of spent adsorbents. Keywords: Water pollution, Wastewater treatment, Adsorption, Activated carbon, Low-cost adsorbents Among the various known forms of pollution, water pollution is of great concern since water is the prime necessity of life and extremely essential for the survival of all living organisms. Indeed, it is a part of life itself, since the protoplasm of most living cells contains about 80% of water. It is worthy noting that only 0.02% of the total available water on the earth is immediately available for use in the form of rivers, lakes and streams. However, years of increased industrial, agricultural and domestic activities have resulted in the generation of large amount of wastewater containing a number of toxic pollutants, which are polluting the available fresh water continuously. With the realization that pollutants present in water adversely affect human and animal life, domestic and industrial activities, pollution control and management is now a high priority area. The availability of clean water for various activities is becoming the most challenging task for researchers and practitioners worldwide. As a result of the serious efforts of researchers all over the world in the field of pollution control and management, a number of methodologies with varying degrees of success have been developed to manage water pollution. Some of them involve coagulation, foam flotation, filtration, ion exchange, sedimentation, solvent extraction, adsorption, electrolysis, chemical oxidation, disinfection, chemical precipitation and membrane process 1,2 . However, these methods have their own shortcomings and limitations. For example, the methods based on chemical/biological oxidation, ion exchange and solvent extraction have shown low efficiency for the removal of trace levels of pollutants 3 . Further, coagulation 4 requires pH control and causes further problems of sludge disposal, whereas, ozonation 5 while removing colour effectively does not minimize chemical oxygen demand (COD). Among various available technologies for water pollution control listed above, ‘adsorption’ process is considered better as compared to other methods because of convenience, easy operation and simplicity of design. Further, this process can remove/minimize different type of pollutants 6 and thus it has a wider applicability in water pollution control. Although certain phenomenon associated with adsorption were known in ancient times, the first quantitative studies were reported by C.W. Scheele 7 in 1773 on the uptake of gases by charcoal and clays. This was followed by Lowitz observations who used charcoal for decolorization of tartaric acid solutions. Larvitz 8 in 1792 and Kehl 8 in 1793 observed similar phenomenon with vegetable and animal charcoals, respectively. However, the term ‘adsorption’ was proposed by Bois-Reymond but introduced into the literature by Kayser 9 . Ever since then, the adsorption process has been widely used for the removal of solutes from solutions and gases from air atmosphere.