A mathematical model for metal ions uptake by aquatic plants for waste water treatment

A mathematical model is developed for metal ions uptake by aquatic plants. The model is based on a mechanism which assumes that the complex biological substances present in the plant react with the metal ions to form complexes of these ions at the solution–plant interface, and then the metal complexes diffuse through a membrane towards the bulk phase of the plant because of the concentration gradients present in the membrane. The model predicts the decreasing capacity of the plants for metal ions uptake as the contact time between the solution and the plant is increased. Experiments are conducted in the laboratory for the removal of chromium, copper, iron, nickel, lead and zinc by measuring metal ions uptake by two aquatic plants, Salvinia and Spirodela, in the solution of these metal ions of concentration ranging from 1 to 8 ppm. After estimating the parameters of the model, it is used for predicting the metal ions concentration in the solution as a function of time and the metal ions concentration inside the plants after 14 days of contact time. The comparison of the model predictions with the experimental results shows excellent agreement. The above model may be used for design and analysis of an aquatic‐plant‐based waste water treatment system. This revised version was published online in August 2006 with corrections to the Cover Date.