1. Effect of pH on Adsorption of Lead from Water onto Tree Fern Hao-Ming Hu a, Chih-Chien Tu a, Yuh-Shan Ho b# * and Wen-Ta Chiu a a Taipei Medical University – Wan Fang Hospital, b School of Public Health, Taipei Medical University Introduction Tree fern, low-cost and easily available in tropical and subtropical areas, has currently been studied for its ability of removing heavy metals from water. It is a complex material containing lignin and cellulose as major constituents. [1] Chemical sorption can occur by the polar functional groups of lignin, which include alcohols, aldehydes, ketones, acids, phenolic hydroxides and others as chemical bonding. [2] Because of the fairly polar character of tree fern, the specific sorption for dissolved solids such as transition metals and polar organic molecules could be high. Its character of removing metals from water has been currently investigated [3]. Materials and Methods A range of initial pH values of solution from 2.49 to 6.81 were used and agitation was carried out for 2 h. All investigations were carried out using a baffled, agitated 2 dm 3 sorber vessel. Samples (3 ml) were withdrawn at suitable time intervals, filtered through a 0.45  m membrane filter and then analysed. A 6.8 g sample of tree fern (53-61 µm) was added to each 1.7 dm 3 volume of lead solution with an initial concentration 200 mg/dm 3 and an agitation speed of 300 rpm was used for all experiments. The temperature was controlled with a water bath at the temperature of 20 °C for all studies. Conclusion The agricultural by-product, tree fern, is a suitable sorbent for the removal of lead from water. The lead binding capacity of the tree fern was shown as a function of initial pH value of solution and the optimum pH for lead removal was 4.9. The kinetics of sorption of the lead on tree fern followed Boyd et al. (1947) ion exchange rate model, which considered rates of ion exchange sorption during the first 10 min. The ion exchange may be occurred in the beginning period of the reaction. The order of reaction for the sorption of lead on the tree fern followed the pseudo-second order rate expression. Results and Discussion Table 2. Pseudo-second order and ion exchange model parameters for effect of pH Table 1. The change of the solution hydrogen ion concentration for different initial pH value of lead solution.References [1] Newman RH. Cellulose, 1997;4:269. [2] Adler E, Lundquist K. Acta Chem. Scand., 1963;17:13. [3] Ho YS, Huang CT, Huang HW. Process Biochem., 2002;37:1421. Fig. 6. Plot of equilibrium capacity against the change of the solution hydrogen ion concentration Fig. 5. Plot of q e against initial pH value Fig. 4. Plot of pH of solution against time for lead sorption on the tree fern at various initial pH values Fig. 2. Ion exchange sorption kinetics of lead on the tree fern at various initial pH values Fig. 1. Pseudo-second order sorption kinetics of lead on the tree fern at various initial pH values Fig. 3. Plot of sorbed amount versus time for lead at various initial pH values