Evaluation of various preparation methods of oil palm fiber (OPF) biochar for ammonia-nitrogen (NH3-N) removal

The aim of this study is to develop a oil palm based biochar for the selective removal of NH₃-N in low concentration from aquaculture wastewater. In this study, three different preparation methods of biochar were evaluated for the adsorption of NH₃-N from synthetic aquaculture wastewater. The three methods are pyrolysis, activation with acid before pyrolysis and activation after pyrolysis with numerous oxidizing agents. In the 1^st method, various biochars have been prepared at different pyrolysis temperatures (300 – 500 °C) and holding time (0.5 – 2 hr). The maximum removal efficiency of 50 % was achieved at preparation condition of 300 °C and 2 hr. In the 2^nd method, the acid activated raw OPF was pyrolyze at 300 °C, 1 hr. The maximum removal was lower compared to the 1^st method without acid treatment. In the 3^rd Method, the optimized biochar from the 1^st method was activated with different activating agents such as, HNO₃, HCl, H₃PO₄, H₂SO₄, CH₃COOH and H₂O₂ at 100 °C for 2 hr. It was noticed that activation after pyrolysis did not show any improvement in the removal of NH3-N from synthetic aquaculture wastewater. Characterization of optimized samples were carried out to investigate the adsorption mechanism process of NH₃-N. The 1^st method (pyrolysis) was the best which reported the highest (50 %) removal of NH₃-N. Pyrolyzed OPF is a potential adsorbent for NH₃-N.