Rice straw was utilized into biochar by pyrolysis and used as adsorbent for ammonium removal. Rice straw biochar was found as one of the adsorbents for wastewater treatment. This study was conducted to analyses the capability of rice straw biochar on ammonium adsorption-desorption. Rice straw biochar was characterized by ash content, moisture content analysis, Fourier Transform Infrared (FTIR) analysis and pH of Zero Point Charge. Ash content increased meanwhile moisture content decreased as pyrolysis temperature increased. pH of Zero Point Charge for rice straw biochar was at pH 7.5. The rice straw produced at 550 °C was selected as best adsorbent for the adsorption of ammonium. The effect of process parameters such as adsorbent dosage, adsorption contact time, initial concentration and pH of ammonium were studied on the performance of ammonium adsorption. The results showed that maximum ammonium adsorption capacity was occurred at pH 7.5 by using 0.05 g of rice straw biochar in 3.0 ppm of ammonium solution for 130 minutes of contact time. Kinetic adsorption showed pseudo-second order is the best kinetic adsorption because involving a chemical adsorption as the value of R2 which was 0.9163 closer to 1. The adsorption-desorption of ammonium shown that rice straw biochar can run up to 5 cycles.
