Facile chemically activation process of kapok husk as a low-cost biosorbent for removal methylene blue dye in aqueous solution

This study discusses kapok husk (KH) activated by HNO3 as a biosorbent for methylene blue dye and analyzes its adsorption ability. The adsorption capacity of KH is 330.161 mg g-1 with optimum conditions at pH 9, concentration 5500 mg L-1, contact time 15 minutes, and biosorbent temperature 25 ?C. The isotherm study followed the Langmuir isotherm model, as seen from the R2 value of 0.9993 and maximum adsorption capacity of 312.5 mg g-1, which indicated a monolayer layer in the adsorption process. The kinetic data show that KH followed the pseudo-second-order model. The results of the TGA analysis show that thermal stability affects the performance of biosorbents in the adsorption process. FTIR and SEM-EDS characterization results showed that electrostatic interactions, cation exchange, and pore filling regulate the methylene blue dye adsorption mechanism on the surface of the KH. The reusability of KH through adsorption-desorption cycle analysis was achieved five times. This indicates that the biosorbent can be economically feasible for real wastewater treatment based on its good reusability and simple preparation and activation.