Influence of the alkyl chain length of surfactant on adsorption process: A case study

Abstract

To investigate the effect of alkyl chain length of surfactant on the adsorption process behavior, the present study was applied the adsorption of anionic methyl orange (MO) dye using mineral pumice (NP) as natural adsorbent, and Dodecyltrimethylammonium bromide (DTAB), Tetradecyltrimethylammonium bromide (TTAB), and Cetyltrimethylammonium bromide (CTAB) modified pumice as namely DMP, TMP, and CMP, respectively. Due to the differences in the alkyl chain length of the surfactants, the effect of chain length on the MO dye adsorption process can be evaluated. For an understanding of the physical and chemical structure of adsorbents, XRF, SEM, BET, and FTIR analyses were performed. The effect of contact time, initial MO concentration, adsorbent dosage, and solution pH was studied. Langmuir, Freundlich, Jovanovic and Temkin isotherm models were used for fitting of the experimental data. Based on the results of the isotherm models and also calculating the errors of each model, the highest match was obtained with Langmuir isotherm, and the maximum adsorption capacities for NP, DMP, TMP, and CMP were 6.43, 18.13, 28.60, and 31.73 mg/g, respectively. Also, the results of kinetic studies showed that the data are in maximum agreement with the pseudo-second-order kinetic model. Therefore, it can be concluded that an extended surfactant chain increases the adsorption capacity, and it can be found that one of the effective factors in the adsorption processes is the hydrophobic interactions of the modifiers.