en گروه سرامیک Ceramic Materials and Engineering Research Paper Research Paper Mesoporous SiO₂ nanopowder was synthesized under an acidic condition by a sol-gel method using various amounts of cetyltrimethyl ammonium bromide (CTAB) as structure directing agent. The samples were investigated with XRD, SEM, FTIR, TEM and N₂ absorption-desorption analysis. Also, the incremental effect of surfactant were examined. The results obtained from the analysis suggested that an increase in the amount of surfactant resulted in increasing specific surface area, pore size and pore volume, of the synthesized particles up to 549 m².g^-1, 17.3 nm, and 2 cm³.g^-1, respectively. Absorption behavior of the mesoporous silica was investigated for degradation of methylene blue pigments (MB) in aqueous solutions. The samples SC0, SC0.5 and SC1 showed the maximum absorption capacities of 333, 454 and 526 mg/g, respectively Mesoporous silica, Sol-gel, Absorption, Methylene blue. 48 56 http://ijmse.iust.ac.ir/browse.php?a_code=A-10-375-3&slc_lang=en&sid=1 F. Salehtash Salehtash_f@yahoo.com 1800319475328460010308 1800319475328460010308 No Nanotechnology Department, School of New Technologies, Iran University of Science & Technology (IUST), Narmak, Tehran 16846-13114, Iran. H. Banna Motejadded Emrooz banna@iust.ac.ir 1800319475328460010309 1800319475328460010309 No Nanotechnology Department, School of New Technologies, Iran University of Science & Technology (IUST), Narmak, Tehran 16846-13114, Iran. M. Jalaly maisam_jalaly@iust.ac.ir 1800319475328460010310 1800319475328460010310 Yes Nanotechnology Department, School of New Technologies, Iran University of Science & Technology (IUST), Narmak, Tehran 16846-13114, Iran.