A cotton-based adsorbent grafted with an EDTA analog and its metal ion-selective absorption properties in aqueous solution

Abstract

This paper reports the synthesis of a solid adsorbent derived from degreasing cotton, and its metal ion removal ability in low concentration aqueous solution. In the first section of this paper, a novel synthetic strategy was reported for the introduction of an EDTA analog (aminoacetic acid) onto the surface of cotton fibers, resulting in a modified cotton adsorbent N,N-(dicarboxymethylaminoethyl,carboxymethyl)aminoethylamine carboxymethyl cotton amide. This material was characterized using ¹³C NMR spectroscopy, elemental analysis and SEM/EDS/EBSD. In the second section, the adsorption behavior of this material for the removal of Cu²⁺, Pb²⁺ and Cd²⁺ from aqueous solution was assessed and analyzed using Langmuir and Freundlich models. Competitive ion adsorption and fixed-bed column adsorption experiments were carried out to evaluate its selective adsorption properties in mixed metal ion solutions using ICP spectroscopy. The results showed that this grafted cotton exhibited coordination properties similar to EDTA for the different metal ions, and that it exhibited selectivity and had good metal ion removal ability from low concentration solution. The maximum adsorption capacities for Cu²⁺, Cd²⁺, and Pb²⁺ were estimated to be 23.45 mg g⁻¹, 34.7 mg g⁻¹, and 66.93 mg g⁻¹, respectively. Regeneration and adsorption experiments illustrated that this material had good renewable properties and could be used for multiple metal ion removal adsorption–regeneration–adsorption cycles. This material has great potential for application in the adsorption of toxic elements such as Cu²⁺, Cd²⁺, Pb²⁺ and other metal ions from aqueous solution.