Development of biochar from post-phytoremediation of Eichhornia crassipes

This study aimed to assess the chromium-removal capacity of Eichhornia crassipes and to characterize the biochar derived from its biomass after phytoremediation. E. crassipes plants were exposed for 14 days to FSSA lake water spiked with chromium at concentrations of 3 mg/L and 5 mg/L to simulate heavy-metal–contaminated wastewater. Plant health was monitored via visual symptoms (leaf chlorosis and wilting), while removal efficiency (%) and bioconcentration factor (BCF) were determined by measuring chromium concentrations in the water and in harvested tissues. Following phytoremediation, biomass was pyrolyzed at 300 °C for 30 minutes. The results showed that at 5 mg/L chromium, plants displayed toxicity, yellowing leaves and wilting whereas no adverse symptoms occurred at 3 mg/L. Under the lower concentration (3 mg/L), E. crassipes achieved 96.58% removal efficiency and a BCF of 338.54, confirming strong phytoaccumulation ability. Pyrolysis converted approximately 50% of biomass into biochar by mass. The chromium concentration in biochar (52.26 ug/g) exceeded that in residual plant tissue (37.24 ug/g), indicating effective immobilization of accumulated metal. Moreover, surface area, pore structure, and functional‐group analyses revealed that biochar derived from phytoremediated biomass closely matched the properties of control biochar, demonstrating that metal uptake did not adversely affect material quality. These findings highlight E. crassipes as a viable agent for chromium phytoremediation and demonstrate that its post-treatment biomass can be transformed into a stable, metal-rich biochar. Future work should optimize pyrolysis parameters to maximize metal retention, evaluate the biochar’s adsorption performance for other pollutants, investigate its long-term stability and leaching behavior under field conditions for sustainable wastewater management.