Optimizing copper (Cu) ions dissolution from charred Chrysopogon zizanoides (L.) Roberty used in phytoremediation via...

The global issue of soil and water contamination by heavy metals such as copper has become more prevalent, and demand for sustainable remediation strategies. Phytoremediation offers an eco-friendly approach, yet the proper disposal of metal-laden biomass remains a critical gap. Hence, this study represents the first systematic optimization of copper (Cu) recovery directly from charred vetiver grass (Chrysopogon zianoides (L.) Roberty) phytoremediation biomass using citric acid leaching combined with face-centered central composite design (FCCD), integrating kinetic modelling through Shrinking Core Model (SCM) and the cementation on Fe filings for Cu metal recovery. Batch experiments evaluated four key parameters: temperature (30-70 °C), L/S ratio (10.0-23.3 mL/g), leaching time (130-170 min), and stirring speed (30-70 rev/min). Maximum Cu²⁺ ions dissolution of 97% was achieved at 70 °C, 19.32 mL/g L/S ratio, 130 min, and 38 rev/min. Statistical analysis (R2 = 0.89, p < 0.0001) confirmed that L/S ratio and temperature were the most significant factors. Shrinking core model analysis revealed mixed control by interfacial transfer and diffusion through the product layer, with an activation energy of 32.14 kJ/mol. The highest relative cemented fraction of 99.69% was attained at pH 1 after 50 min of contact time with Fe filings. The results of this study highlight the potential of sustainable phytoremediation practices and the advancement of heavy metal management from contaminated sites.