Bioremoval of rhodamine B dye from aqueous solution by using agricultural solid waste (almond shell): experimental and DFT modeling studies

The current study aimed to investigate the biosorption of rhodamine B from aqueous solution using an almond shell as an agricultural solid waste biosorbent. The almond shell biosorbent was characterized via Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) with energy dispersive X-ray (EDX), and point of zero charge (pH(PZC)) analyses. The parameters that influence the biosorption process such as contact time, initial dye concentration, biosorbent dose, temperature, and pH were investigated. According to the correlation coefficient, the data were best outlined by the Langmuir isotherm with adsorption capacity of 14.70 mg g(-1). The adsorption energy found from the D-R model showed that the adsorption process is chemical. The kinetic data were described by the pseudo-second-order kinetic and intraparticle diffusion kinetic models. Thermodynamic parameters were calculated; it was seen that the biosorption process is spontaneous and endothermic. The density functional theory (DFT) calculation results are well-matched with those discovered through experimentation. The results indicate that almond shells could be interesting alternative material used for dye removal from aqueous solutions.