Application of eco-friendly material as an inexpensive adsorbent for methyl violet dye removal: experimental, response surface methodology and statistical physics

Methyl Violet (MV) removal from aqueous solutions is studied using an Algerian Bentonite sample as a low-cost adsorbent. SEM-EDX, X-ray diffraction, and chemical composition characterized the adsorbent material. The modeling and optimization study of MV adsorption using artificial neural network (ANN) and response surface methodology (RSM) were also examined. The effects of pH, contact time, dye concentration, and temperature are all considered. The adsorption kinetics results are adjusted to best fit the pseudo-second-order model. Langmuir-Freundlich and Langmuir models well describe the experimental data with an adsorption capacity of 472 mg g-1. The calculated thermodynamic data demonstrates that adsorption is spontaneous and endothermic. Desorption studies with methanol indicate that the adsorbent could successfully retain MV, even after five cycles. The statistical physics theory indicates the non-parallel orientation of the MV molecule's adsorption. The adsorption energies varied from 13.99 to 17.60 kJ mol-1, revealing the physical adsorption systems. From these results, it can be considered that the raw Algerian bentonite sample tested herein is effective in removing MV from aqueous solutions and may be used as an alternative to high-cost commercial adsorbents.