The sawdust of a tropical wood, Triplochyton Scleroxylon (Ayous), has been used as a lignocellulosic biosorbent for removing mercury(II) ions from water. In this study, it’s adsorption capacity can be increased by previous treatment with hydroxide sodium solution. The efficiency of elimination of mercury(II) ions from water using unmodified and modified sawdust depends on contact time, pH and biosorbent dose. Biosorption is maximum at pH 7, and more than 88% and 94% removal mercury(II) ions were achieved within 1 h from a 10 mg L-1 solution at neutral pH using unmodified and modified sawdust, respectively. Mercury adsorption kinetic was well fitted by a pseudo-second order model. Among the two isotherm models tested for the unmodified and modified sawdust, Langmuir model gave the best fit. The modified sawdust exhibited the best efficiency for mercury(II) ions removal from water. The alkaline treatment of sawdust improves the maximum adsorption capacity of mercury(II) from 5.32 to 6 mg g-1 at pH 7. Both ionic strength of solution and metal co-cations decrease mercury(II) uptake by modified sawdust, with Na+ showing a more pronounced effect than Ca2+ and K+. Mercury(II) ions adsorbed on modified sawdust were better desorbed by EDTA than HCl and HNO3. The maximum desorption ratio of 48% is achieved within 60 min using EDTA, and base treated sawdust reuse for two cycles operation showed a loss of 58%.