title: A study of the alumina-silica gel adsorbent for the removal of silicic acid from geothermal water: increase in adsorption capacity of the adsorbent due to formation of amorphous aluminosilicate by adsorption of silicic acid.
abstract: Two kinds of adsorbents (Si adsorbent and Al adsorbent) for the removal of silicic acid from geothermal water to retard the formation of silica scales were prepared using silicic acid contained in geothermal water. The Si adsorbent was prepared by evaporating geothermal water, and the Al adsorbent was prepared by evaporating geothermal water after the addition of aluminum chloride. The specific surface area of the Si adsorbent was small and it's adsorption capacity of silicic acid was low. Although the specific surface area of the Al adsorbent was also small, it was significantly increased by the adsorption of silicic acid and it's adsorption capacity was high. Based on the change in the local structure of aluminum ion by the adsorption of silicic acid, the Al adsorbent was considered to be silica particles covered with crystalline aluminum hydroxide. Moreover, it was concluded that the increase in the specific surface area of the Al adsorbent and the decrease in the zeta potential were due to the formation of an amorphous aluminosilicate with a large surface area and a negative charge (one 4-coordinated Al) by the reaction between aluminum ions and silicic acids.
authors.affiliation: Department of Chemistry, Faculty of Science, Kyushu University, Ropponmatsu, Chuo-ku, Fukuoka, 810-8560, Japan. yokotscc@mbox.nc.kyushu-u.ac.jp
authors.forename: Takushi
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Akira
authors.initials: A
authors.lastname: Ueda
authors.forename: Koichi
authors.initials: K
authors.lastname: Kato
authors.forename: Katsumi
authors.initials: K
authors.lastname: Mogi
authors.forename: Shorin
authors.initials: S
authors.lastname: Matsuo
mesh_terms: D000327:Adsorption; D000077410:Aluminum Chloride; D017607:Aluminum Compounds / Q000737:chemistry; D000536:Aluminum Hydroxide / Q000737:chemistry; D000537:Aluminum Oxide / Q000737:chemistry*; D000538:Aluminum Silicates / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry; D005782:Gels / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D036103:Nanotechnology / Q000191:economics / Q000379:methods*; D012824:Silicic Acid / Q000737:chemistry / Q000302:isolation & purification*; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D017607:Aluminum Compounds; D000538:Aluminum Silicates; D002712:Chlorides; D005782:Gels; D007477:Ions; D014867:Water; D012824:Silicic Acid; C049037:aluminosilicate; D000077410:Aluminum Chloride; D000536:Aluminum Hydroxide; D012822:Silicon Dioxide; D000537:Aluminum Oxide