Low-cost activated carbon preparation from Corn stigmata fibers chemically activated using H3PO4, ZnCl2 and KOH: Study of methylene blue adsorption, stochastic isotherm and fractal kinetic

The aim of this study was to produce a low-cost activated carbon (AC) from an inexpensive precursor material, corn stigmata (CS), by chemical activation at low temperatures using H3PO4, ZnCl2 and KOH. The results were showed that activation with phosphoric acid provides an adsorbent with a larger specific surface area (SBET) and high pore size. Textural and physicochemical properties of ACs activated with H3PO4 were then studied in different activation temperature. The increase of activation temperature from 200° to 500°C allows the development of many surface functions and the development of a mixture of meso and microporosity, so the SBET increase from 0.25 to 820 m2/g. The physicochemical and textural properties of ACs were analyzed by N2 adsorption–desorption, FTIR, Boehm’s titration, point of zero charge (pHPZC), SEM and EDX. The kinetics and isotherm of methylene blue (MB) adsorption were well described by BSf and GBS models indicating the stochastic and fractal adsorption process and a highly heterogeneous AC surface. The maximum adsorption capacity toward MB, 330.5 mg/g, was high compared to many other results found in literature.