Characterization and Sodium Sorption Capacity of Biochar and Activated Carbon Prepared from Rice Husk

Biochar and activated carbon, as carbon-rich porous materials, have wide environmental applications. In the present research, rice husk (RH) was used for preparation of biochar at 400, 600, and 800 °C under simple pyrolysis, physically-activated carbon with water steam, chemically-activated carbon with potassium hydroxide (KOH), and physiochemically-activated carbon with KOH and steam. Physical and chemical properties of biochar and activated carbons were characterized using nitrogen adsorption–desorption isotherm, Fourier transform, infra-red analysis, and Boehm method. The results showed that carbonization temperature and activation agents had significant effects on the characteristics of the samples. Activated carbon produced by KOH activation had the highest surface area (2201 m2 g-1) and total pore volume (0.96 cm3 g-1). High concentration of sodium (Na) is an important limiting factor to reuse poor quality water resources in arid and semiarid regions. The sorption capacity of biochars and activated carbons was investigated by performing batch sorption experiments using Na as adsorbate. Na sorption was increased with increasing surface area and pore volume. The highest Na sorption capacity of 134.2 mg g-1 was achieved by the KOH activated carbon, which has the highest surface area and pore volume. The kinetic data were well-fitted to pseudo-first order and intra-particle diffusion models.