Adsorption Efficiency, Isotherms, and Kinetics for Cationic Dye Removal Using Biowaste Adsorbent

Dye pollutants in surface water can inflict serious damages for aquatic life and human health. In the present research, the efficacy of banana peel as biowaste adsorbent for the removal of cationic methyl green dye (MGD) and basic blue 41 dye (BB 41) from synthetic wastewater has been investigated. The banana peel adsorbent (BPA) was synthesized and characterized before and after the adsorption process by scanning electron microscope (SEM), and infrared spectroscopy (FTIR). According to SEM analysis images, the surface structure of BPA is of microrough texture and heterogeneous nature. The spectrum of FTIR analysis referred to the existence of different peaks belonging to various functional groups, such as hydroxyl, carboxylic, and amines. Adsorption experiments were conducted to investigate the effects of various parameters [i.e., contact time, pH, adsorbent (BPA) dose, and the initial concentration of dye] on the removal rate of each dye, and to obtain the optimum operating conditions. The maximum removal efficiency of MGD and BB 41 at optimal operating conditions, when adsorbed onto BPA, were found to be more than 99%. Three isotherm models (Langmuir, Freundlich, and Temkin) were utilized to exhibit the adsorption process. For both dyes, the Langmuir model was found to have greater suitability with adsorption experiment data. The kinetics of the MGD and BB 41 adsorption onto BPA were examined by utilizing pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetics models. Kinetic calculations revealed that the adsorption of MGD and BB 41 on BPA follow the pseudo-second-order kinetic. The thermodynamic parameters (free energy, enthalpy, and entropy) were determined. The regeneration and reusability study of BPA was carried out and revealed that it can be efficiently reused until the fifth cycle. The simplest method was used for the synthesis of an efficient adsorbent (BPA). For the first time, BPA proved to be an excellent bioadsorbent for the removal of aqueous MGB and BB 41 dyes, as it achieved nearly complete removal.