Ozone-functionalized acacia wood sawdust biochar for total nitrogen adsorption from pig wastewater
, Lương Thị Quỳnh Nga, , , , , , , Dec-2025, In: Mater. Research Express, 12, 125502, p. 1-26
Overview
Abstract:
The growing environmental problem of nitrogen-rich pig wastewater, with total nitrogen (TN)
concentrations ranging from 500 to 1,500 mg l-1 and ammonia (NH4 +-N) concentrations between
50 and 70 mg l-1, requires innovative treatment solutions. This study examines the effectiveness of
ozone-modified biochar (SPO) derived from acacia wood sawdust in removing nitrogen, with an
oxygen uptake rate increased from 17.11 wt% to 22.28 wt% at 5 l min-1. Under conditions (pH 7,
0.2g dosage/50 ml, 270 min contact time), SPO achieves a maximum adsorption rate of 32.38 mg g-1
and a removal rate of 46.39 mg l-1 at an initial TN of 279 mg l-1. Characterisation by SEM, EDS and
FTIR revealed a porous, oxygen-rich surface with functional groups (e.g., -OH, -COOH) that
facilitate both chemisorption and multilayer adsorption. The kinetic studies favoured the pseudosecond-order model (R2=0.9310) and the Elovich model (R2=0.9484), while heterogeneous
adsorption was indicated by the Freundlich isotherm (R2=0.9612). Machine learning models,
including the extreme gradient boosting (XGB) model with an R2 of 0.998, predicted the removal
efficiency and identified adsorption dose (average SHAP=7.736) and nitrogen concentration
(average SHAP=3.607) as the main drivers. The study shows the potential of SPO as a sustainable
adsorbent, confirmed by experimental data and predictive modelling, to mitigate the harmful effects
of pig wastewater. SPO demonstrated moderate reusability over five adsorption–desorption cycles,
retaining 53.27% of its initial capacity (17.35 mg g-1 from 32.57 mg g-1) at an estimated production
cost of 0.15–0.25 USD/kg, outperforming commercial zeolite (0.5–1.0 USD/kg) and activated
carbon (1–2 USD/kg) in cost-effectiveness for scalable swine wastewater treatment.
concentrations ranging from 500 to 1,500 mg l-1 and ammonia (NH4 +-N) concentrations between
50 and 70 mg l-1, requires innovative treatment solutions. This study examines the effectiveness of
ozone-modified biochar (SPO) derived from acacia wood sawdust in removing nitrogen, with an
oxygen uptake rate increased from 17.11 wt% to 22.28 wt% at 5 l min-1. Under conditions (pH 7,
0.2g dosage/50 ml, 270 min contact time), SPO achieves a maximum adsorption rate of 32.38 mg g-1
and a removal rate of 46.39 mg l-1 at an initial TN of 279 mg l-1. Characterisation by SEM, EDS and
FTIR revealed a porous, oxygen-rich surface with functional groups (e.g., -OH, -COOH) that
facilitate both chemisorption and multilayer adsorption. The kinetic studies favoured the pseudosecond-order model (R2=0.9310) and the Elovich model (R2=0.9484), while heterogeneous
adsorption was indicated by the Freundlich isotherm (R2=0.9612). Machine learning models,
including the extreme gradient boosting (XGB) model with an R2 of 0.998, predicted the removal
efficiency and identified adsorption dose (average SHAP=7.736) and nitrogen concentration
(average SHAP=3.607) as the main drivers. The study shows the potential of SPO as a sustainable
adsorbent, confirmed by experimental data and predictive modelling, to mitigate the harmful effects
of pig wastewater. SPO demonstrated moderate reusability over five adsorption–desorption cycles,
retaining 53.27% of its initial capacity (17.35 mg g-1 from 32.57 mg g-1) at an estimated production
cost of 0.15–0.25 USD/kg, outperforming commercial zeolite (0.5–1.0 USD/kg) and activated
carbon (1–2 USD/kg) in cost-effectiveness for scalable swine wastewater treatment.
Keyword(s): ozone-modified biochar, nitrogen adsorption, pig wastewater, optimization, sustainable remediation
| Pages (from-to) | 1-26 |
| Journal | Mater. Research Express |
| Volume | 12 |
| Issue number | 125502 |
| Publication status | Published - Dec-2025 |
| ISBN | 2053-1591 |