Development of a kinetic model for the removal of zinc using the aquatic macrophyte, Lemna gibba L.

This work was conducted to develop a suitable kinetic model for the removal of zinc (Zn) using the duckweed Lemna gibba L. as a phytoremediation agent at laboratory scale. The 7-day treatments of 6.0–18.0 mg Zn/L were performed under controlled conditions: 12 h photoperiod, temperature of 21±1 °C, pH of 6.0±0.1 and a quarter Coïc and Lesaint solution as a culture medium. The results revealed a Zn removal efficiency of 60–70% and an accumulation capacity of plants ranging from 4.23 to 25.88 mg/g DM. Two simplified kinetic models namely pseudo-first-order and pseudo-second-order were used to study the mechanism that controls the biological process. The kinetic study proved that the removal rate of Zn by L. gibba was proportional to the Zn concentration present in water. Therefore, the pseudo-first-order model was considered to be more suitable to describe the disappearance of Zn from water in the presence of fronds of L. gibba L. These results may serve as a basis in mathematical modelling for large-scale application.