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

Abstract

This study discusses kapok husk (KH) activated by HNO₃ as a bio­sorbent for methylene blue dye and analyses 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 min, 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 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 characterisation 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.