Abstract: In this study,lead adsorption by chemically modified orange peel adsorbent was investigated.Effects of various parameters,including solution pH,adsorption time and initial Pb²⁺ concentration were studied by batch experiments.Kinetics was found to be best-fit pseudo-second order equations.Equilibrium was well described by Langmuir isotherms rather than Freudlich isotherms.At pH4.5,30℃,the maximum adsorption capacity was 146.413mg/g.This biosorbent was suitable for repeated use for more than five cycles.