Chitosan-based adsorbents for the removal of metal ions from aqueous solutions

Abstract

Wastewater containing heavy metal ions is one of the most serious environmental concerns. Exposure to elevated levels of heavy metals can adversely affect water resources, endangering the ecosystems and human health. Among the various treatment technologies, adsorption using biopolymer seems a promising alternative method. Chitosan is a natural polymer produced from chitin with excellent properties such as biocompatibility, biodegradability and non-toxicity. Moreover, chitosan is known as an effective sorbent due to the presence of amino and hydroxyl groups in its molecules which can serve as attachment sites towards metal ions. Recently, chitosan derivatives as metal ion sorbents have gained considerable attention. These derivatives are prepared by either physical or chemical modifications or both in order to improve chitosan properties in adsorption. This paper discusses recent developments in the modifications of chitosan and the application of the derived materials in the removal of metal ions from aqueous solutions. The mechanisms of adsorption, metal sorption capacities, effect of pH, isotherm and kinetic models are also described.