Study of the adsorption isotherm of 2-mercaptobenzothiazole by activated carbon based on grape marc: linear and non-linear method

Abstract

The adsorption performance of 2-mercaptobenzothiazole from an aqueous solution on activated carbon synthesized through grape marc was explored. In this research, the agricultural waste was chemically treated with phosphoric acid (40% H₃PO₄, 170 °C, 3 h), then pyrolyzed at 650 °C for 2 h, to obtain the GMAC-650 to be used as an adsorbent. The resulting material was characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, and Brunauer–Emmett–Teller (BET). Maximum uptake (∼99%) is obtained under ideal conditions: an adsorbent dose of 0.8 g L⁻¹ and pH = 8 for an initial concentration of 10 mg L⁻¹ at 45 °C. The adsorption equilibrium data were fitted to the following isotherm models: Langmuir and Freundlich. For optimal equilibrium isotherm selection, a comparison of linear and non-linear methods for the adsorption of MBT. It was based on four error functions: the coefficient of determination R², the sum of squared errors, the Chi-square (χ²), and the root mean square error. The current work has shown that the non-linear method is a more adequate method for estimating the parameters of the isotherm compared with the linear method. The comparative analysis of the models shows that the Freundlich model is more appropriate for describing equilibrium data.

Graphical Abstract

Keywords:

• Adsorption
• activated carbon
• H₃PO₄
• 2-mercaptobenzothiazole
• isotherms
• Langmuir
• Freundlich
• linear and non-linear regression

Disclosure statement

No potential conflict of interest was reported by the authors.