Tailoring activated carbons based cocoa pods lignocellulosic materials for Reactive blue 19 adsorption: optimization, adsorption isotherm and kinetic investigation
Anita Zemfack Mekuiko, Donald Raoul Tchuifon Tchuifon, Paul Alain Nanssou Kouteu, Cyrille Ghislain Fotsop, Christian Sadeu Ngakou, Hermann-Idriss Tiotsop Kuete, Aurelien Bopda, Arnaud Kamdem Tamo, Solomon Gabche Anagho
Abstract
ABSTRACT The present study reports on the performance of activated carbons derived from cocoa pods impregnated with H 3 PO 4 (CCCP) and ZnCl 2 (CCCZn) on the removal of Reactive blue 19 from a simulated wastewater. Central composite design, including three factors namely temperature ( X 1 ), concentration of the activating agent ( X 2 ) and time ( X 3 ) of calcination were used to optimize the production conditions. From the analysis of variance, the most significant variable was the calcination temperature. For CCCP activated carbon, optimum conditions were found as follows: X 1 : 600°C, X 2 : 0.3 M and X 3 : 88 min and for CCCZn, they were 600°C, 0.5 M, and 120 min. The experimental values of iodine number for the both activated carbons were 476.25 and 495.53 mg/g for CCCZn and CCCP, respectively. It was observed that the experimental values obtained were much closer to those predicted by the model. The functional groups on the prepared activated carbons were determined from Fourier-transform infrared spectroscopy and confirmed using Boehm’s titration. X-ray diffraction analysis showed the presence of amorphous phases in both activated carbons. The scanning electron microscopy images of both activated carbons showed that the activation stage produced extensive external surfaces with quite irregular cavities and pores. CCCP and CCCZn showed a Brunauer–Emmett–Teller surface area of 435.32 and 430.66 m 2 /g, respectively. Non-linear regression analysis showed that, equilibrium data were best described by the Freundlich model for CCCP and Dubinin–Radushkevich for CCCZn. Kinetic studies showed that the adsorption of Reactive blue 19 was better described by the pseudo-second-order model for CCCP, and the Elovich models CCCZn.