Optimization, equilibrium, kinetics and thermodynamic study of congo red dye adsorption from aqueous solutions using iraqi porcelanite rocks

Iraqi Porcelanite rocks were chosen to remove Congo Red dye from aqueous solutions. The experimental variables of initial dye concentration 50–250 (mg/l), adsorbent dosage 0.2–1.0 (g/50 ml) and contact time 20–120 min were optimized using full factorial design (FFD) approach. This technique was invested to develop mathematical model and to study the interactive effects of adsorption parameters. The obtained results at optimum adsorption conditions reveal that maximum adsorption capacity has been attained at 29.1558 (mg/g) for 250 (mg/l) initial concentration. The adsorbent based rock type was characterized with FTIR instrument. The equilibrium results were well fitted with Langmuir isotherm followed by the Sips model. However, the kinetic results followed the pseudo-second-order model. The thermodynamic constants of Enthalpy, Entropy, and Gibbs free energy were calculated at 50 (mg/l) initial concentration and equilibrium conditions. The findings show that the adsorption nature of CR dye was spontaneous and chemisorption exothermic process. The statistical analysis depicts that the second-order model has optimally described the Congo red removal with high accuracy. The gained computations illustrated that the Iraqi Porcelanite rock can be successfully employed as a promising cheap material alternative to the commercial and activated adsorbent for the removal of anionic dyes from wastewater treatment plants.