Chelating Cellulose for Removal of Heavy Metals

Abstract

Cellulose is a renewable and promising material. However, native cellulose has to face the challenge of the removal of heavy metals with low efficiency which limits its application. In this work, a cellulose derivative with EDTA-like chelating groups (EDTA-CL) is designed and prepared by the chemical grafting of cellulose. Cellulose is partially oxidized to dialdehyde cellulose which is treated with 20% excess of diethylenetriamine through a Schiff base reaction for the preparation of the aminated cellulose. The amine groups of the aminated cellulose are carboxymethylated by reacting with 20% excess of bromoacetic acid through a substitution reaction. The high-efficient adsorption of the both ions by the EDTA-CL with high adsorptive amounts (Pb²⁺: 438.3 mg g⁻¹ and Cd²⁺: 287.2 mg g⁻¹) can be accomplished by controlled parameters (pH of 4–6, contact time of 30 min and the dosage of 1 g L⁻¹). The adsorptive processes of the both ions onto the EDTA-CL can be well fitted by pseudo-second-order and Langmuir equations. Thermodynamics data reveal that the adsorption of the both ions onto the EDTA-CL is a spontaneous and endothermic process. The loaded EDTA-CL can be regenerated five times with loss of adsorptive amounts (Cd²⁺: 14% and Pb²⁺: 17%).