Assessment of the adsorption kinetics, equilibrium and thermodynamic for the potential removal of reactive red dye using eggshell biocomposite beads

Immobilized eggshell with a polymer mixture of alginate and polyvinyl alcohol was applied as a biocomposite adsorbent (ESC) for the adsorption of C.I. Remazol Reactive Red 198 from aqueous solution. ESC was characterized using XRD, TGA, FTIR and SEM. The Red dye adsorption onto the ESC was investigated in a batch system with respect to initial dye concentration, pH, contact time, agitation speed, solution temperature and biocomposite dosage. The prepared biocomposite exhibits high efficiency for red dye adsorption and the equilibrium states could be achieved in 3 h for the different studied initial dye concentrations. The equilibrium isotherm study indicated that sorption data were analyzed and fitted well by both Langmuir and Temkin models compared to Freundlich model. The maximum monolayer dye adsorption capacity (at the optimum pH 1.0) was estimated to be 46.9 mg/g at 22 °C. The kinetic study revealed that pseudo-second order model fitted well the kinetic data, while both the intraparticle diffusion and Boyd kinetic model indicated that intraparticle diffusion was the main rate determining step in the biosorption process. The negative values of both the enthalpy (ΔH°) and Gibbs free energy (ΔG°) changes indicate exothermic as well as feasible and spontaneous nature of the biosorption process respectively.

Research highlights
► Biocomposite eggshell was applied for the adsorption of Reactive dye.
► The sorption data were fitted well by both Langmuir and Temkin models.
► The kinetic data was fitted well with pseudo-second order model.
► Intraparticle diffusion was the main rate determining step.
► The negative values of ΔH° and ΔG° indicate exothermic and spontaneous nature.