Investigation of hydrochar derived from male oil palm flower: Characteristics and application for dye removal

Abstract

Male oil palm flower (MOPF) is an abundant and otherwise useless waste from oil palm cultivation. This work aimed to transform MOPF to hydrochar and use it as an adsorbent for the removal of methylene blue (MB) dye in water systems, thus dealing with two existing environmental issues simultaneously. The raw biomass was converted to hydrochar at 180ºC for 8 h in an air atmosphere. Characterization of the hydrochar using FTIR resulted in a change of functional groups after hydrothermal carbonization (HTC) as well as after adsorption, which might involve in MB adsorption. The small increase of pores in hydrochar detected in the BET isotherm analysis might also facilitate MB adsorption. SEM images confirmed the existence of pores on the hydrochar in comparison with the raw biomass. The equilibrium MB adsorption followed a pseudo second-order and a Langmuir isotherm model with the maximum adsorption capacity of 42.92 mg·g-1at 30ºC. These findings suggest that MOPF could be a low-cost value-added material and an alternative eco-friendlyhydrochar-based adsorbent for MB removal from aqueous solution.