Abstract: <SPAN lang=EN-US style="FONT-SIZE: 10.5pt; FONT-FAMILY: "Times New Roman"; mso-bidi-font-size: 12.0pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-fareast-font-family: 宋体">Desorption of acidic gases on surface of fumed silica is one of the key links in its production process,which is directly related to quality and surface performances of nano-sized silica products.Nano-sized silica prepared by gas phase method was treated in fluidized bed with dry heat and wet heat nitrogen desorption processes respectively.Acidic gas desorption mechanism and its influencing law on powder performances were systematically studied.In addition,difference of parameters,such as acidic gas desorption time,temperature,and number of surface hydroxyl.as well as diversity of powder aggregation of fumed silica powder in two dry heat and wet heat processes was also investigated in detail.Specific surface area tester,laser particle size analyzer,and TEM etc.were used to characterize the powders after deacidification.Results showed that wet heat nitrogen desorption process was more suitable for surface deacidification of fumed silica and desorption mechanism was discussed theoretically.</SPAN><SPAN style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 12.0pt; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman"; mso-bidi-font-family: "Times New Roman"; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"></SPAN>