Methylene blue removal using modified celery (Apium graveolens) as a low-cost biosorbent in batch mode: Kinetic, equilibrium, and thermodynamic studies

Celery residue modified with H2SO4 was utilized as a low-cost adsorbent for elimination of methylene blue cationic dye from aqueous solution in batch adsorption process. The adsorbent was characterized by Fourier transform infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM). The efficacy of dye removal of the modified celery residue (MCR) was verifying by changing adsorbent dose, contact time, pH, initial dye concentration, and temperature. The isotherm models analysis shows that the experimental data can be better demonstrated by Freundlich isotherm model. In order to evaluate the best fit isotherm, three error analysis methods (chi(2), ARE and MPSD) as well as correlation coefficient and non-linear regression were employed. The maximum monolayer adsorption capacity of MCR found out to be 476.19 mg/g at 303 K. The adsorption kinetic results were well explained by pseudo-second order model. Thermodynamic investigations revealed that this process is spontaneous and exothermic in nature. The values of Delta H degrees and Delta S degrees was negative which confirm that the adsorption procedure in more favourable in lower temperatures. Regeneration of adsorbent was evaluated and excellent results were obtained. The results of this research indicate that MCR is an executable low-cost adsorbent for elimination of methylene blue from aqueous solutions. (C) 2018 Elsevier B.V. All rights reserved.