Removal of lanthanum (La) from aqueous solution by crab shell, Portunus sanguinolentus, was investigated. Based on the experimental results obtained at different pH conditions and La speciation, it was identified that the micro-precipitation of lanthanum carbonate (La-2(CO3)(3)) on the surface of crab shell is the main mechanism responsible for La removal by crab shell. The SEM images together with EDX analysis confirmed the presence of La on the surface of crab shell. Isotherm experiments at pH 5 revealed that the maximum biosorption potential of crab shell was 140.1 (mg La)/g, according to the Langmuir model. The La biosorption kinetics was very fast, and the kinetic data were successfully modeled using non-linear pseudo-first order model. Experiments at different ionic strength revealed that La biosorption capacity of crab shell was least affected even at high ionic strength of 0.214 M. Thus, crab shell was identified as a low-cost and potent biosorbent for the removal of La from liquid waste. (C) 2009 Elsevier B.V. All rights reserved.