Amorphous High-Surface-Area Aluminum Hydroxide–Bicarbonates for Highly Efficient Methyl Orange Removal from Water

• DOI: 10.1021/acs.langmuir.0c00021
• Publication Date: 2020-05-19T00:53:35Z
• Authors: Yuki Kinoshita; Yuto Shimoyama; Yoichi Masui; Yoshiteru Kawahara; Kenji Arai; Teruki Motohashi; Yasuto Noda; Sayaka Uchida
• Keywords: Sodium hydroxide; Base (topology); Methyl orange; Langmuir adsorption model; Specific surface area

Amorphous high-surface-area aluminum hydroxide-bicarbonates were synthesized starting from AlCl3, base, and bicarbonate in water. Composites with a chemical formulas of [Al13O4(μ-OH)24(H2O)6.5(OH)5.5](HCO3)1.5 (I-NaOH) [Al13O4(μ-OH)24(H2O)6(OH)6](HCO3) (I-NH3) obtained by the use NaOH/NaHCO3 NH3/NH4HCO3 as base/bicarbonate, respectively. The surface area composites was highly dependent on pH level synthetic solution, high areas (ca. 200 m2 g-1) around 7-8. Pore-size distributions determined N2 adsorption isotherms showed that I-NH3 I-NaOH possess mainly large (pore radius rp > 3 nm) small (rp < pores, respectively, despite similar areas. While SEM images both aggregates nanoparticles, particles more fused I-NaOH, which is line existence pores stronger base (NaOH), would facilitate dehydration condensation reaction. applied adsorbents to remove methyl orange (MO) time course MO readily fitted pseudo-second-order model, over 90% removal attained within 10 min I-NH3, while much less (26%). isotherm reproduced Langmuir model an capacity 154 mg g-1. Notably, could not absorb methylene blue, cationic dye, anions (MO PO43-) absorbed. Solid-state 27Al MAS NMR spectra concentration 5-coordinated species, may serve guest binding sites, higher for I-NH3. These results show electrostatic interaction between anionic coordinatively unsaturated species external contribute efficient adsorption.