REMOVAL OF DISSOLVED COPPER FROM POLLUTED WATER USING PLANT LEAVES. II. EFFECTS OF COPPER CONCENTRATION, PLANT LEAVES, COMPETING IONS AND OTHER FACTORS

摘要

Factors affecting copper removal from polluted water by poplar ( Populus euphratica ) leaves were investigated and a mechanism for copper removal was suggested. Increasing the amount of leaves from 5 to 25 g/L increased the rate and hence the amount of copper removed. Increasing the concentration of copper in solution from 2 to 20 mg/L caused a corresponding increase in copper uptake per unit weight of leaves at a constant leaf concentration of 20 g/L. The uptake of copper ions by poplar leaves was found to be noticeably affected by the presence of other metal ions. The effect of these ions could be dependent on the relative affinity of leaves to these ions and copper as well as to pH. Depending on the initial concentration, the presence of the chelating agent EDTA in the solution considerably reduced the rate and amount of copper uptake. Fresh leaves were found to uptake much less copper thandry leaves. Rough-crushing or fme-grinding of leaves slightly affected copper uptake. Agitation slightly increased the rate of copper uptake and cleaning leaves did not affect its ability to uptake copper. The main mechanism for copper removal by poplar leaves is most probably adsorption. Other mechanisms, such as complexation, may play a minor role as well. Intrapore diffusion is thought to be the rate-limiting step for the interaction between poplar leaves and copper ions.