الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Recently, the worldwide population growth has put a pressure on the available clean water resources. Therefore, water pollution has become a challenging environmental issue which has attracted the attention of the researchers and countries to address this problem [1,2]. Among toxic water pollutants, chromium (Cr) which is one of the severely harmful heavy metal and it is classified as class A carcinogen by the U.S. Environmental Protection Agency (US EPA) [3]. chromium has two stable states for oxidation, Cr (III) and Cr (VI). The hexavalent form Cr (VI) is considered to have high toxicity, whereas the trivalent form Cr (III) is less toxic and essential for mammals. The normally used methods for the Cr (VI) removal from wastewater are including chemical precipitation, biological method, membrane separation, electrocoagulation, reduction, Ion exchange, adsorption, and so on [4,5].
Among them, adsorption is recognized as a simple, high-efficient, low- cost and recyclable method, which is widely applied for Cr(VI) removal [6]. So far, many adsorbents have been reported for Cr(VI) removal, including activated carbon[7], Graphene[8], industry solid waste[9], clay minerals [10], agricultural by products[11], chitosan[12,13], and so on. The most critical factor for the industrial application of Cr(VI)-treated adsorbents is to reduce capital investment. Chitosan (CTS) is a linear biopolymer consists of 2-amino-2-deoxy-β-D-glucopyranose units [14]. CTS is considered the second most abundant polymer in nature which is a mainly produced from marine organisms such as shrimp and crabs [15]. CTS owns important and versatile properties such as non-toxicity, biodegradability, antimicrobial, and biocompatibility[16]. The structure of CTS is characterized in presence of reactive amino and Hydroxyl groups which are considered active adsorption sites in wastewater treatment technologies[17].