*Article* **Valorization of Rice Husk for the Production of Porous Biochar Materials**

**Wen-Tien Tsai 1,\*, Yu-Quan Lin <sup>1</sup> and Hung-Ju Huang <sup>2</sup>**


**Abstract:** Rice husk (RH) is one of the most important crop residues around the world, making its valorization an urgent and important topic in recent years. This work focused on the production of RH-based biochars at different pyrolysis temperatures from 400 to 900 ◦C and holding times from 0 to 90 min. Furthermore, the variations in the yields and pore properties of the resulting biochars were related to these process conditions. The results showed that the pore properties (i.e., BET surface area and porosity) of the resulting RH-based biochar were positively correlated with the ranges of pyrolysis temperature and holding time studied. The maximal pore properties with a BET surface area of around 280 m2/g and porosity of 0.316 can be obtained from the conditions at 900 ◦C for a holding time of 90 min. According to the data on the nitrogen (N<sup>2</sup> ) adsorption–desorption isotherms and pore size distributions, both microporous and mesoporous structures exist in the resulting biochar. In addition, the EDS and FTIR analyses also supported the slight hydrophilicity on the surface of the RH-based biochar due to the oxygen/silica-containing functional groups. Based on the findings of this work, the RH-based biochar could be used as a material in environmental applications for water conservation, wastewater treatment and soil amendment.

**Keywords:** rice husk; pyrolysis; porous biochar; pore property; surface composition
