Removal of lead and cadmium ions from aqueous solution by adsorption onto micro-particles of dry plants

In the present work, Pb(II) and Cd(II) ion adsorption onto inert organic matter (IOM) obtained from ground dried plants: Euphorbia echinus, Launea arborescens, Senecio anthophorbium growing in semi-arid zones of Morocco and Carpobrotus edulis as the Mediterranean plant has been studied. A suspension of plant deroed micro-particles adsorbs lead and cadmium present as ionic species, with a higher affinity for Pb(II). The kinetics and the maximum capacity adsorption depend on the type of plant as well as on the metal ions (atomic weight, ionic radius and electronegativity). The adsorption process is affected by various parameters such as contact time, solution volume to mass of plant particles ratio (m/V), particle size, solution pH and metal concentration. A dose of 25 g/l of adsorbent was optimal to obtain maximum adsorption of both metal ions. The maximum metal uptake was obtained with particles of organic matter of <50 microm. As to classical ionic adsorption phenomena, the adsorption of both metal ions increases with the increase of the initial concentration in the solution. For the two metal cations, the uptake efficiency of the studied plants ranged from: C. edulis>E. echinus>S. anthophorbium>L. arborescens, however, the differences are rather small. Two different waste water types (domestic and industrial) were tested and good results were obtained for removal of Pb(II) and Cd(II) at more than 90%. The removal of the metal and mineral ions waste water was observed for PO(4)(3-) at 88%, for NO(3)(-) at 96.5% and for metal ions (Pb(II), Cd(II), Cu(II) and Zn(II)) at about 100%, using IOM as absorbent.