Copper adsorption through chitosan immobilized on sand to demonstrate the feasibility for in situ soil decontamination

The contamination of soils and waters by metals all over the world continues to present a serious danger to the environment and human health. The development of innovative metal clean-up technologies remains a challenge as current procedures have many limitations, such as being expensive, disruptive, and only efficient for certain concentrations. With high molecular weight and repetitive functional groups, biopolymers provide excellent chelating material for metals. Chitosan is a well-known and efficient metal chelator, but its practical use is limited due to the relatively high costs of constructing clean-up devices (filters) from chitosan alone. In the current study we attempt to find a more cost-effective solution by investigating a new adsorbent material based on chitosan immobilized on sand, namely, chitosan-coated sand (5% chitosan content). This new material was studied for its copper adsorption capacity at contact times of 2, 4, and 6 h and the equilibrium result was compared with copper adsorption capacities of chitosan and sand alone. Hopefully this concept will lead to an application as a large-scale permeable reactive barrier. Copper recovery from an adsorbent with the possible reuse of the adsorbent material was also evaluated in leaching tests. The equilibrium isotherms for Cu adsorption on chitosan-coated sand were described by the Langmuir model. These preliminary results indicate the possibility of using chitosan-coated sand to build inexpensive large-scale barrier filters for metal removal from moving contaminated groundwater plumes. (C) 2003 Elsevier Ltd. All rights reserved.