title: Removal of hexavalent chromium from contaminated waters by ultrasound-assisted aqueous solution ball milling.
abstract: Batch mode experiments were conducted to study the removal of hexavalent chromium (Cr(VI)) from aqueous solutions using ultrasound-assisted aqueous solution ball milling. The results show that the reduction rate of Cr(VI) by ultrasound-assisted aqueous solution ball milling was significantly faster than that by ball milling or ultrasound treatment alone, and an initial Cr(VI) concentration of 166mg/L could be decreased to 0.35mg/L at 120min. The decisive factors, including initial concentration of Cr(VI), pH value, ultrasonic frequency and filling gas, were studied. It was found that the optimal ultrasonic frequency for ultrasound-assisted aqueous solution ball milling device was 20kHz, and the rate of Cr(VI) reduction as a function of filling gas followed the order: Ar>air>N2>O2. Samples were characterized by X-ray diffraction, fluorescence measurements, atomic absorption and the diphenylcarbazide colorimetric method. The Cr(VI) transformed into a precipitate that could be removed from the contaminated water, after which the water could be reused.
authors.affiliation: College of Materials Science and Engineering, Hunan University, Changsha 410082, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Chen
authors.affiliation: College of Materials Science and Engineering, Hunan University, Changsha 410082, China.
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Chen
authors.affiliation: College of Materials Science and Engineering, Hunan University, Changsha 410082, China. Electronic address: ma97chen@hotmail.com.
authors.forename: Ding
authors.initials: D
authors.lastname: Chen
authors.affiliation: College of Materials Science and Engineering, Hunan University, Changsha 410082, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Xiong
mesh_terms: D002857:Chromium / Q000032:analysis / Q000737:chemistry*; D007700:Kinetics; D014465:Ultrasonics / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion
keywords: Ball milling; Cr(VI); Hydroxyl radicals; Ultrasound wave