Abstract: The adsorption of Pb²⁺ by orange peel was studied,the orange peel was modified by H₃PO₄,NaOH,absolute ethanol-NaOH,CaCl₂-anhydrous ethanol-NaOH,etc.The effects of adsorption time,adsorbent amount,adsorption temperature and acidity of solution on the adsorption of Pb²⁺  were investigated.The morphology of the modified orange peel before and after the adsorption of Pb²⁺  was characterized by scanning electron microscopy and infrared spectroscopy.The results showed that in the four kinds of modified orange peel,the modified orange peel prepared with CaCl₂- anhydrous ethanol - NaOH had the best adsorption effect on Pb²⁺.When the adsorption time was 120 min,the adsorption of modified orange peel adsorbent to Pb²⁺  was saturated.The optimum adsorption temperature was 40 °C,and the best adsorption solution acidity was pH=5.0.When the initial concentration of Pb²⁺  was 200 mg/L,the optimum input of adsorbents was 0.15 g,the adsorption rate could reach 94.43 % and the adsorption capacity could reach 125.57 mg/g;and the adsorption mode of modified orange peel on Pb²⁺ conforms to the quasi two stage kinetic model,the maximum adsorption capacity of the modified orange peel was 156.98 mg/g by the simulation of Langmuir isothermal adsorption equation.Modified orange peel was a biosorbent with good performance,reusability,safety and environmental protection.

Key words: biosorbent, chemical modification, orange peel, lead ion