title: Mechanism of boron uptake by hydrocalumite calcined at different temperatures.
abstract: Hydrocalumite (Ca-Al-layered double hydroxide (LDH)) was prepared and applied for the removal of borate. The properties of Ca-Al-LDH calcined at different temperatures were diverse, which affected the sorption density and mechanism of boron species. The sorption density increased with increase in calcined temperature and the sample calcined at 900°C (Ca-Al-LDH-900) showed the maximum sorption density in this work. The solid residues after sorption were characterized by (11)B NMR, (27)Al NMR, SEM, and XRD to investigate the sorption mechanism. Dissolution-reprecipitation was the main mechanism for sorption of borate in Ca-Al-LDH. For Ca-Al-LDH calcined at 300 and 500°C, regeneration occurred in a short time and the newly forming LDHs were decomposed to release Ca(2+) ions and formed ettringite with borate. Two stages occurred in the sorption of boron by Ca-Al-LDH calcined at 900°C. In the first stage, boron species adsorbed on the alumina gel resulting from the hydration of calcined products. In this stage, borate was included as an interlayer anion into the newly forming LDHs in the following stage, and then immobilized as HBO3(2-) into the interlayer, most the LDHs.
authors: Department of Earth Resources Engineering, Kyushu University,Fukuoka 819-0395, Japan. Electronic address: qxinhong@gmail.com.
authors: Xinhong
authors: X
authors: Qiu
authors: Department of Earth Resources Engineering, Kyushu University,Fukuoka 819-0395, Japan.
authors: Keiko
authors: K
authors: Sasaki
authors: Department of Earth Resources Engineering, Kyushu University,Fukuoka 819-0395, Japan.
authors: Yu
authors: Y
authors: Takaki
authors: Department of Earth Resources Engineering, Kyushu University,Fukuoka 819-0395, Japan.
authors: Tsuyoshi
authors: T
authors: Hirajima
authors: Institute for Materials Chemistry and Engineering, Kyushu University, Kasuga 816-8180, Japan.
authors: Keiko
authors: K
authors: Ideta
authors: Institute for Materials Chemistry and Engineering, Kyushu University, Kasuga 816-8180, Japan.
authors: Jin
authors: J
authors: Miyawaki
mesh_terms: D000327:Adsorption; D000535:Aluminum / Q000737:chemistry*; D001881:Borates / Q000737:chemistry; D001895:Boron / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D006878:Hydroxides / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D018508:Water Purification / Q000379:methods; D014961:X-Ray Diffraction
chemical_list: D001881:Borates; D006878:Hydroxides; D000535:Aluminum; D001895:Boron; D002118:Calcium
keywords: Boron; Calcination; Ettringite; Hydrocalumite; Mechanism