The role of oxidation on oil palm fiber biochar for ammoniacal nitrogen recovery from aquaculture wastewater

The existence of ammoniacal nitrogen (NH3−N) in water bodies has received much attention due to its toxicity and impact toward human health and the environment. The nitrogen element in NH3-N can be considered as nutrient and should be recovered for its circular economy. In this study, the feasibility of partial oxidation of oil palm fiber (OPF) on the removal of low concentration NH3-N from aquaculture wastewater was investigated. The OPF biochar preparation process was optimized via response surface methodology using design of experiments. Upon optimization, process study, thermodynamics, kinetics, and mechanism of the removal process was deduced using various parameters and models. The OPF biochar prepared at 300 °C, 150 min, and 100 ml air/min shows highest removal efficiency of NH3-N (71.6 %) in synthetic wastewater. The optimized OPF biochar was tested on actual aquaculture wastewater and the removal was almost similar (72.6 %), however the adsorption capacity was lower compared to the synthetic wastewater. The isotherm data of NH3-N agreed well with linear and non-liner Freundlich model and pseudo second order model for the kinetics. OPF biochar exhibits selective removal of NH3-N in actual aquaculture wastewater. In the removal process oxygen surface functional groups played an important role. It can be concluded that the partially oxidized OPF biochar has a good potential to recover nitrogen from low concentration NH3-N from aquaculture wastewater.