Multifunctional biomolecular on P-biochar enhance the removal of total phosphorus from aquaculture wastewater: characterization, kinetics, and applications

Excess phosphorus in aquaculture wastewater is prone to pose a dual threat to ecological and economic benefits. This study is a simple and low-cost biomolecule-reinforced biochar composite based on three plant extracts with the ability to remove total phosphorus (TP) in real wastewater. Various analyses of the three plant extracts were conducted to understand the differences in TP removal efficiency and identify the differences in the functional groups on their surfaces. The results indicated that plant extracts derived from Excoecaria cochinchinensis Lour (Ec), Green tea (GT), and Pinus massoniana Lamb (PML), were rich in oxygen-containing functional groups, amino and carboxyl groups, and rich in organic acids, respectively. These results revealed differences in adsorption efficiency of the three materials. Among the three biochars obtained by plant modification, P -biochar 3, showed a superior TP removal capacity with a removal efficiency at 70.9 %. The kinetic analysis of its adsorption behavior followed a pseudo-second-order model (R 2  = 0.992), suggesting that the chemisorption mechanism was dominant. Advanced characterization also identified the enhancement of its oxygen-containing functional molecules, facilitating the interaction with phosphate species. Meanwhile, P -biochar 3 maintained a TP removal efficiency above 55.45 % in a real eel aquaculture wastewater column experiment, and it could remove multiple pollutants. This study demonstrates that functionalization of plant extracts is a viable strategy for the development of sustainable adsorbents capable of addressing nutrient pollution in various agricultural wastewater streams.