Pyridone Modified Cellulosic Adsorbent for Selective Segregation of Organic Dyes from Aqueous Solution

Abstract

Adsorption is recognised as an efficient method for the removal of contaminants from the water system. Cellulose is widely applied in the fabrication of new material because of its biodegradability, renewability, and abundance in nature. In particular, its adsorption performance to various adsorbates can be fine-tuned by chemical modification. A pyridone di-acid modified microcrystalline cellulose (PDA-MCC) adsorbent was synthesised by a simple two-step reaction, and its use as a highly selective adsorbent towards organic dyes was investigated. Parameters influencing adsorption, which include contact time, concentration of the adsorbate, and solution pH, were studied to determine the optimized adsorption conditions. Adsorption experiments revealed that the adsorbent preferentially adsorbs positively charged organic dyes over negatively charged dyes with an adsorption capacity for positively charged Methylene Blue of 135.46mg g−1 and for negatively charged Eosin Y of 3.80mg g−1. Competitive adsorption showed that the adsorbent was able to selectively adsorb the cationic dye from a binary solution of cationic and anionic dyes within 10min with a separation factor of up to 941.8. Ab initio modelling was performed to determine the mechanism of the selective dye binding and revealed that in addition to electrostatic interaction, non-covalent interactions, e.g. hydrogen bonding, and van der Waals interactions also play an important role in the selective dye adsorption based on the Independent Gradient Model analysis. Furthermore, the adsorbent was readily regenerated by a simple rinsing with dilute HCl without significant loss in performance, which indicates its potential to be used as a dye-selective adsorbent.