Dye-Mediated Interactions in Chitosan-Based Polyelectrolyte/Organoclay Hybrids for Enhanced Adsorption of Industrial Dyes

Abstract

Non-covalent, dye-mediated interactions between organo-montmorillonites (''organo-clays'') and a chitosan-based polyelectrolyte are exploited for highly effective and fast removal of different, industrially-important anionic dyes (singleazo, double-azo, anthraquinone) from aqueous solutions. The addition of only 10 wt% of polyelectrolyte to a conventional organo-clay results in a 100% increase in absolute dye uptake capacity, an acceleration of dye uptake kinetics by up to 500%, and the flocculation of large, easily-separable sorbent aggregates. These substantial improvements in adsorption performance are driven by the mediating effect of the anionic dyes (acting as electrostatic mediator between the positively-charged polyelectrolyte chains and organo-clays), enabling the formation of true hybrid sorbent structures without the need for covalent crosslinking chemistry. The dye-mediated sorption and hybrid formation mechanism is further evidenced by structural and chemical characterization of the hybrid sorbents (small angle XRD, IR mapping) as well as by analysis of dye sorption kinetics according to the intraparticle diffusion model. Importantly, the organo-clay/polyelectrolyte hybrid system provides a highly interesting adsorbent for the treatment of dye mixtures. Our study shows that structurally different anionic dyes localise at different sites within the hybrid structure (organo-clay intergallery spaces vs polyelectrolyte/organo-clay interface), enabling the simultaneous adsorption of different dyes with high efficiency. Consequently, the total uptake capacity for dye mixtures was 50% larger than that of individual dyes, demonstrating the enormous potential of the hybrids for industrial wastewater purification, where dye mixtures are ubiquitous.

Amino-Functionalized Fe3O4@SiO2 Core-Shell Magnetic Nanoparticles for Dye Adsorption

“…These results prove that the adsorption process of these dyes on Fe 3 O 4 @SiO 2 -NH 2 NPs completely followed a the pseudo-second order kinetic model, suggesting that adsorption is dependent on the amount of the solute adsorbed on the surface of the adsorbent and the amount of active sites. It should be noted that the dye adsorption kinetics on magnetic nanoparticles is most often described in terms of the pseudo-second order model [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ].…”

Capacitive Organic Dye Removal by Block Copolymer Based Porous Carbon Fibers

“…Compared with other methods for high‐capacity dye removal, electrosorption provides recyclability and produces no secondary waste. [ 14,65 ]…”

“…Over the years a number of methods have been developed to treat organic dye‐containing wastewater. The methods include coagulation, [ 13 ] physisorption, [ 14 ] photocatalysis, [ 15 ] and electrocatalysis. [ 16 ] The high cost, low regeneration capacity, and slow processing of these methods, however, disfavor their wide use in wastewater treatment.…”

TiO2-Doped Chitosan Microspheres Supported on Cellulose Acetate Fibers for Adsorption and Photocatalytic Degradation of Methyl Orange

“…Multifarious materials have been developed for photocatalytic degradation carrier materials, comprising silica, ceramic, polymers, activated carbon, zeolite, and glass. As an environmentally friendly, nontoxic, biodegradable, biocompatible natural macromolecule [30,31,32,33,34], CS with functional groups of hydroxyl and amino groups derived from deacetylation of polysaccharide chitin, is a promising carrier material [35,36,37,38]. Li et al produced pure CS membranes by electrospinning, exhibiting high adsorption capacity for acid blue-113 [37].…”

“…Li et al produced pure CS membranes by electrospinning, exhibiting high adsorption capacity for acid blue-113 [37]. Huang et al produced an organoclay/CS hybrid system, allowing efficient and concurrent adsorption of different dyes [38]. However, CS is easily soluble in water when amino groups are protonated, making it difficult to maintain integrity of the whole materials.…”