Adsorption of Indigo Carmine Dye onto Porous Adsorbent Derived from Banaba Peels Waste

Abstract

This study investigated the preparation method and adsorption efficiency of porous adsorbents prepared from banana peels (BP) waste. The BP waste was acquired from banana fried chip factories in Sukhothai province. Chemical activation by sulfuric acid was used to activate the raw material, followed by carbonization at 500 °C. The activated BP adsorbent has been characterized by energy dispersive X-ray spectrometer (EDXRF), N2 adsorption-desorption isotherms (BET), scanning electron microscopy (SEM), and zeta potential measurements. The analysis of chemical properties showed that it mainly contained 70.39 % K matter. The specific surface area of the BP sample reached 215.05 m2/g under acid activation and thermal treatment. The SEM images showed the morphologies of the BP adsorbent before and after activation. There was a significant change in the morphology and in the dried BP and activated BP. The pHPZC value of the activated BP obtained under optimal conditions was 4.13. Adsorption of indigo carmine (IC) onto porous activated BP at different initial IC concentrations (10 - 100 mg/L) and contact times (30 - 120 min) was investigated using batch experiments (0.1 g/50 mL). At an optimum contact time of 60 min, maximum adsorption capacity was determined at 56.18 mg/g. The Freundlich isotherm model with a high correlation coefficient was used to describe multilayer adsorption. The kinetic study fit well with a pseudo second-order kinetic model that represented chemisorption. The negative deltaG° value of –14.64 kJ/mol indicated that adsorption of IC onto the BP adsorbent was spontaneous in nature at 305.15 K. HIGHLIGHTS Increase the value of the biomass resources was produced form banana peels as high surface area adsorbent The qmaxfor indigo carmine (IC) adsorption was 56.18 mg/g under optimized conditions The adsorption of the IC follows the Freundlich model and pseudo-second order kinetic model Negative deltaG° value indicated the possibility of IC adsorption process GRAPHICAL ABSTRACT