Enhanced and rapid adsorptive removal of toxic organic dyes from aqueous solution using a nanocomposite of saponified polymethyl acrylate grafted dextrin with embedded nanosilica

Abstract

A graft copolymer/nanosilica composite based on partially hydrolyzed dextrin-g-polymethyl acrylate and tetraethylorthosilicate was developed as an efficient adsorbent for the removal of toxic cationic and anionic dyes (methylene blue (MB), crystal violet (CV) and methyl orange (MO)) from their aqueous solutions. The biopolymer matrix acts as a novel template for nanosilica formation. The synthesized nanocomposite was characterized using FT-IR, 13C NMR, SEM, EDAX and XRD studies. The detail investigation of the adsorption dynamics, isotherms, kinetics and thermodynamics were studied for all the three dyes. The dye adsorption process onto the nanocomposite surface was controlled together by both pseudo-second-order and intraparticle diffusion model. Langmuir isotherm correlates well with adsorption equilibrium data. The adsorption capacity of cationic dyes onto the nanocomposite (qmax = 515.4 mg g−1 for MB and 383.1 mg g−1 for CV) was rationalized on the basis of strong electrostatic attraction and H-bonding. The spontaneous nature of adsorption was confirmed by the negative value of ΔGo. The preferential dye adsorption onto the nanocomposite was followed in the order MB > CV > MO. Further, desorption study affirmed that the synthesized nanocomposite has excellent regeneration capacity also.