Adsorption of methylene blue from aqueous solution using untreated and treated (Metroxylon spp.) waste adsorbent: equilibrium and kinetics studies

In this article, the use of low-cost adsorbents for the removal of methylene blue (MB) from solution has been reviewed. Adsorption techniques are widely used to remove certain classes of pollutants from waters, especially those which are not easily biodegradable. The removal of MB, as a pollutant, from waste waters of textile, paper, printing and other industries has been addressed by the researchers. Currently, a combination of biological treatment and adsorption on activated carbon is becoming more common for removal of dyes from wastewater. Although commercial activated carbon is a preferred adsorbent for color removal, its widespread use is restricted due to its relatively high cost which led to the researches on alternative non-conventional and low-cost adsorbents. The purpose of this review article is to organize the scattered available information on various aspects on a wide range of potentially low-cost adsorbents for MB removal. These include agricultural wastes, industrial solid wastes, biomass, clays minerals and zeolites. Agricultural waste materials being highly efficient, low cost and renewable source of biomass can be exploited for MB remediation. It is evident from a literature survey of about 185 recently published papers that low-cost adsorbents have demonstrated outstanding removal capabilities for MB. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Biosorption is a technique that can be used for the removal of pollutants from waters, especially those that are not easily biodegradable such as metals and dyes. A variety of biomaterials are known to bind these pollutants, including bacteria, fungi, algae, and industrial and agricultural wastes. In this review, the biosorption abilities of bacterial biomass towards dyes and metal ions are emphasized. The properties of the cell wall constituents, such as peptidoglycan, and the role of functional groups, such as carboxyl, amine and phosphonate, are discussed on the basis of their biosorption potentials. The binding mechanisms, as well as the parameters influencing the passive uptake of pollutants, are analyzed. A detailed description of isotherm and kinetic models and the importance of mechanistic modeling are presented. A systematic comparison of literature, based on the metal/dye binding capacity of bacterial biomass under different conditions, is also provided. To enhance biosorption capacity, biomass modifications through chemical methods and genetic engineering are discussed. The problems associated with microbial biosorption are analyzed, and suitable remedies discussed. For the continuous treatment of effluents, an up-flow packed column configuration is suggested and the factors influencing its performance are discussed. The present review also highlights the necessity for the examination of biosorbents within real situations, as competition between solutes and water quality may affect the biosorption performance. Thus, this article reviews the achievements and current status of biosorption technology, and hopes to provide insights into this research frontier.