Rice husk was utilized into biochar by pyrolysis and used as adsorbent for ammonium removal. Rice husk biochar (RHB) was produced at temperature of 3500C, 4000C, 4500C, 5000C, and 5500C. Characteristics of biochar were analyzed by moisture content, ash content, pH Zero Charge and Fourier Transform Infrared (FTIR) Spectroscopy. As the temperature for the pyrolysis increases, the moisture content of RHB decreases while the ash content of RHB increases. From the pH zero charge analysis, the value obtained from analysis is pH 7. The FTIR spectra showed the organic part of RHB with different functional groups such as alkene, alcohol, phenol, ether, ester etc. Based on the result of the characterization test, RHB500 was chosen as the best biochar for the adsorption of ammonium. The equilibrium contact time was 180 minutes and the optimum adsorbent dosage was 0.1g and the optimum concentration of ammonium was 1.2 ppm. For the adsorption-desorption of ammonium, RHB can run up to 5 cycles for biochar regeneration. Adsorption kinetic, pseudo-second-order model is more preferable than pseudo-first-order model because R2 value is 0.9995 which closer to 1.
