Excess nutrients such as phosphorus (P) in watersheds jeopardize water quality and trigger harmful algal blooms. Capturing nutrients from wastewater and agricultural runoff is an essential step to develop a circular nutrient system, which can not only recover lost nutrients, but also prevent water pollution. In this study, a novel designer biochar was generated by pyrolyzing woody biomass pretreated with a flue gas desulfurization gypsum. The removal of dissolved P by the designer biochar was more efficient than the gypsum, suggesting the pretreatment of biomass with the gypsum results in a significantly synergic effect on enhancing dissolved P removal. The sorption kinetics study revealed that the designer biochar requires much less time to reach sorption equilibrium compared to the gypsum. The maximum adsorption capacity of dissolved P on the designer biochar was greater than 200 mg g-1 according to Langmuir or Langmuir-Freundlich model, which is significantly higher than that of the gypsum. These results clearly showed that designer biochar is a better phosphorus sorption material (PSM) to capture dissolved P from nutrient-containing water compared to the gypsum. Post-sorption characterization explored the mechanisms of enhancing dissolved P removal by the designer biochar. Although the sorption of dissolved P involves multiple mechanisms, the precipitation reactions of Ca ions and P anions to form CaHPO4and Ca3(PO4)2 precipitates on the highly alkaline surface of the designer biochar were identified as a main mechanism. By contrast, CaHPO42H2O is the only precipitated product for dissolved P sorption by the gypsum. In addition, the initial solution pH and the coexisting bicarbonate (HCO3-) had less effects on the dissolved P removal by the designer biochar in comparison with the gypsum, which further confirms the former is an excellent PSM to capture dissolved P from a variety of aquatic media. 2023, The Authors. All rights reserved.
- Gypsum-incorporated biochar
- Dissolved phosphorus