Synthesis of Nanoporous Biochar from Rice Husk for Adsorption of Methylene Blue

In this study, rice husk charcoal prepared with KOH and KOH-NaOH as activators were investigated as adsorbents for the removal of methylene blue from aqueous solutions in order to improve the utilisation of rice husk. Firstly, the rice husk carbon was morphologically and chemically characterised using scanning electron microscopy, specific surface area analyser, and infrared spectroscopy. Secondly, the effects of the alkali-carbon ratio, pyrolysis temperature, and pyrolysis time on the activation of KOH alone and combined activation of KOH-NaOH were investigated. The results showed that the adsorption capacity of the activated biochar was 359.7 mg/g (higher than that of 315.4 mg/g when KOH alone was activated) under the same adsorption conditions when KOH-NaOH was coactivated. Finally, combined with the characterization results and data analysis, it can be seen that the rice husk carbon obtained by KOH-NaOH composite activation is predominantly microporous with a more uniform pore size distribution, making it an economical and efficient adsorbent for the removal of methylene blue from aqueous solutions.