One step preparation of papyrus culm derived activated biochar using partial air oxidation and its use as a filter for water treatment in aquaponics culture

Papyrus culm derived activated biochars were prepared through carbonization and air oxidation at 400–600 °C. The activated biochars were analyzed by SEM-EDS, FT-IR, Raman, BET, and XRD techniques. The best product was collected for use as filter material in aquaponics. It was found that the activated biochars have diverse properties with high disorder of graphitic, oxygenated functional groups (OH, C=O, C-O, and Si-O), oxide compounds (CaO, MgO, Na₂O, K₂O, SiO₂), and relatively high specific surface area and micropore volume. These parameters increased with increasing carbonization temperature from 400 °C to 600 °C. For materials produced at 600 °C the pore size of the derived activated biochar falls in the range of micropores (<2 nm), with a small mesopore and macropore content. This product has BET specific surface area of 270.27 m²/g. Utilizing the derived activated biochar prepared with carbonization at 600 °C for aquaponics culture has shown that the values of total NH₃, NO₂^–, NO₃^–, PO₄^3-, and turbidity decreased, while the DO content increased in the water of the aquaponics culture with efficiency percentage values of 33.33–35.90 %, 4.93–13.43 %, 9.15–12.90 %, 34.97–43.04 %, 10.23–23.90 %, and 16.86–23.90 %, respectively, throughout the four weeks of the experiment. This was achieved via electrostatic attraction, exchangeable cation and anion attraction, and filtration. Furthermore, the activated biochar could also maintain the water pH in a relatively alkaline range for the duration of the experiment, which is suitable for cultivating tilapia and growing red oak lettuce. However, the activated biochar filter began to reach sorption saturation during the third week of the experiment. Therefore, the activated biochar filter should be replaced with a new one after four weeks of use. This research has shown that activated biochar from papyrus culm can be a candidate for an adsorbent material with a simple, cost-effective, and timesaving production.