Facile synthesis, characterization and application of magnetic Fe3O4-coir pith composites for the removal of methyl violet from aqueous solution: Kinetics, isotherm, thermodynamics and parametric optimization

Abstract

Dyes are commonly used in coloring clothes; in fertilizers, as anti-freezers, as detergents and so on. The use of such dyes has carcinogenic and genotoxic effects. These dyes require proper removal from the environment. Subsequently, a green and low-cost approach promises to adhere to sustainability of the environment while maximum removal of these toxic dyes. The present study describes removal of methyl violet (MV) dye by adsorption process magnetically separable Fe3O4-coir pith composites. The study was evaluated in batch system taking the optimum conditions as: pH: 7, contact time: 12 h, stirring speed: 200 rpm, concentration of dye: 100 mg/L, adsorbent weight: 3 g/L, temp.: 308 K. The central composite design approach of response surface methodology in design-expert software showed maximum removal efficiency (> 98%) for optimal parameters. The experimental equilibrium data fitted reasonably well to Langmuir isotherm model. ANOVA analysis along with Fisher's statistical test was also performed to validate the model. The predicted model was at par with the experimental values with adjusted R-2 of 0.9914. A thorough investigation of kinetic (R-Pseudo second order(2) = 0.99; R-Pseudo second order(2) = 0.97; Rutra-particle diffusion = 0.98), thermodynamic, adsorption isotherm (R-Langmuir isotherm(2) = 0.997 R-Freundlich isotherm(2) = 0.99 and eco-toxicological characteristics were performed for proper evaluations of the properties as well as sustainability of the adsorbent material. The whole research indicated encouraging potential of the developed material for adsorption, reusability and sustainability in applications for industrial scale wastewater treatment.