Methane storage in multi-walled carbon nanotubes (MWNTs) is studied at ambient temperature and pressures of 0-10.5 MPa, with a quantity of 80 g samples that were synthesized by nano-agglomerate fluidized-bed reactors (NAFBR). The volume of methane released by MWNTs was measured by volumetric method. We study the effects of purification and the pretreatments on methane storage. Results show that mixed acid treatment, alkali treatment, and mechanical shearing can obviously enhance gas uptake while high-temperature treatment can only slightly reduce it. For properly pretreated samples, an optimal 11.7% of mass storage capacity was achieved at room temperature and the pressure of 10.5 MPa, indicating that CNTs is a potential material for methane uptake. (C) 2007 Elsevier Ltd. All rights reserved.