Combined molecular dynamics simulations and experimental studies of the removal of cationic dyes on the eco-friendly adsorbent of activated carbon decorated montmorillonite Mt@AC

In recent years, the combination of experimental and theoretical study to explain adsorbate/adsorbent interactions has attracted the attention of researchers. In this context, this work aims to study the adsorption of two cationic dyes, namely methylene blue (MB) and crystal violet (CV), on a green adsorbent Montmorillonite@activated carbon (Mt@AC) composite and to explain the adsorption behavior of each dye by the molecular dynamics (MD) simulation method. The eco-friendly nanocomposite Mt@AC is synthesized and characterized by the analysis methods: XRD, FTIR, BET, TGA/DTA, SEM-EDS, EDS-mapping and zeta potential. The experimental results of adsorption equilibrium show that the adsorption of the two dyes is well suited to the Langmuir adsorption model. The maximum adsorption capacity of the two dyes reaches 801.7 mg g(-1) for methylene blue and 1110.8 mg g(-1) for crystal violet. The experimental kinetics data fit well with a pseudo-first order kinetic model for the two dyes with coefficient of determination R-2 close to unity, non-linear chi-square chi(2) close to zero and lower Root Mean Square Error RMSE (R-2 -> 1 and chi(2) -> 0, RMSE lower). Molecular dynamic simulations are run to gain insights on the adsorption process. According to the RDF analysis and interaction energy calculations, the obtained results reveal a better affinity of the CV molecule with both the AC sheet and montmorillonite framework as compared with MB. This finding suggests that CV is adsorbed to a larger extent onto the nanocomposite material which is in good agreement with the adsorption isothermal experiment observations.

Automated summary

In recent years, researchers have been paying attention to the combination of experimental and theoretical study in order to understand adsorbate/adsorbent interactions. This study aims to investigate the adsorption behavior of two cationic dyes, methylene blue (MB) and crystal violet (CV), on a green adsorbent composite called Montmorillonite@activated carbon (Mt@AC), using molecular dynamics (MD) simulation. The results show that the adsorption of both dyes follows the Langmuir adsorption model, with maximum adsorption capacities of 801.7 mg g(-1) for methylene blue and 1110.8 mg g(-1) for crystal violet. Molecular dynamics simulations reveal that crystal violet has a better affinity with both the activated carbon sheet and montmorillonite framework compared to methylene blue.