Process optimization, kinetics and equilibrium of orange G and acid orange 7 adsorptions onto chitosan/surfactant

We report an investigation of the title process. The corresponding process variables such as the concentration of surfactant, temperature, initial concentration of dye have been optimized by the response surface methodology (RSM). A 2 3 full factorial design was employed to analyze the individual and interaction effects of the process variables. The experimental data have been well-fitted to second order polynomial equations and the models were also examined using the analysis of variance and t test statistics. The obtained optimal conditions are as following: C s   =   30.92   μM, T   =   20   °C and C OG   =   320   mg/L for the orange G , and C s   =   34.10   μM, T   =   50   °C and C OA   =   500   mg/L for the acid orange 7. The measured experimental maximum adsorption capacities for the orange G and acid orange 7 systems under above optimization conditions were 1452.07 and 2352.99   mg/g, which were in good agreement with their corresponding predicted values (1427.13 and 2357.31   mg/g), with small relative errors of 1.72% and −   0.18%, respectively. Moreover, many aspects of the adsorption kinetics and isotherms for the two dyes are presented. The results indicated that the two adsorption equilibriums were achieved within 210 and 240   min for the acid orange 7 and orange G, the pseudo-second-order model was followed, and Langmuir isotherm model could be well described their adsorption data. In addition, the adsorption mechanism of two dyes onto chitosan/surfactant was discussed further by FTIR and X-ray diffraction (XRD) methods.