Chitosan-loaded coconut fiber for highly-enhanced heavy metal adsorption from wastewater

Abstract

Heavy metal adsorbents are critical for wastewater treatment, but they commonly have relatively low-efficient adsorption, high cost and short using-time. Herein, a new adsorbent has been explored for high-enhanced heavy metal adsorption through loading chitosan onto surface of carboxylated coconut fiber. This chitosan-loaded coconut fiber (CLCF) can be achieved by simply surface-modifying the carboxylated coconut fiber within acid chitosan aqueous solution based on the supramolecular interaction mainly including the hydrogen bond between the carboxyl group (–COOH) on coconut fiber and the amino group (–NH₂) of chitosan. First of all, thanks to super-hydrophilicity and high specific surface area of the coconut fiber, the chitosan on the CLCF can expose more coordination sites for highly-enhanced adsorption. Furthermore, owing to high-strength of the CLCF (100 ± 10 MPa of tensile strength), this adsorbent can be repeatedly utilized for many times during a relatively long term. Last but not least, because both of chitosan and coconut fiber are renewably and biodegradable natural bio-materials, this work can also maximumly protect environment and reduce cost. Consequently, this CLCF can efficiently adsorb various heavy metal ions including Cu²⁺, Pb²⁺, Cr³⁺, Ni²⁺ and Cd²⁺ reaching 19.1 ± 0.41, 9.9 ± 0.27, 8.1 ± 0.31, 11.3 ± 0.29, 15.8 ± 0.37 mg/g of equilibrium-adsorption-capacity within 2 ppm of each heavy metal solution respectively. This work provides a promising high-efficient adsorbent with degradability and renewability for wastewater treatment, which can also inspire new strategy for exploring eco-friendly heavy metal adsorbents.