Turning black rice husk waste into activated biosorbent for methylene blue removal: adsorption behavior and process optimization

Abstract

This study aimed to utilize black rice husk, an agricultural waste with significant environmental impacts, to produce a biosorbent. In this way, black rice husk, which would otherwise be released into the environment as agricultural waste, was transformed into a useful material, and its use as a biosorbent for removing methylene blue, a cationic dye, was investigated. A biosorbent was prepared from black rice husk via thermal carbonization, with H ₃ PO ₄ (1:2 by mass) as the activation agent. Experimental data showed that the Langmuir isotherm, with a correlation of 0.9997, provided a better fit. Furthermore, the Brunauer–Emmett–Teller test result showed that the surface area of the biosorbent was 295.35 m ² g ⁻¹ . Additionally, response surface methodology was used to determine the interactive and individual effects of various parameters, including contact time, biosorbent dose, and solution pH, on methylene blue dye removal. The experimental results show that the biosorbent derived from black rice husk has strong potential as an environmentally friendly, cost‐effective adsorbent for dye removal. This study is the first to report the use of a biosorbent synthesized by treating black rice husk, an agricultural waste, with H ₃ PO ₄ as an activation agent to remove methylene blue dye.