Gaseous Arsenic Capture in Flue Gas by CuCl₂-Modified Halloysite Nanotube Composites with High-Temperature NO_x and SO_x Resistance

Abstract

Gaseous arsenic emitted from coal combustion flue gas (CCFG) causes not only severe contamination of the environment but also the failure of selective catalytic reduction (SCR) catalysts in power plants. Development of inexpensive and effective adsorbents or techniques for the removal of arsenic from high-temperature CCFG is crucial. In this study, halloysite nanotubes (HNTs) at low price were modified with CuCl2 (CuCl2–HNTs) through ultrasound assistance and applied for capturing As2O3(g) in simulated flue gas (SFG). Experiments on arsenic adsorption performance, adsorption mechanism, and adsorption energy based on density functional theory were performed. Modification with CuCl2 clearly enhanced the arsenic uptake capacity (approximately 12.3 mg/g) at 600 °C for SFG. The adsorbent exhibited favorable tolerance to high concentrations of NO x and SO x . The As2O3(III) was oxidized and transformed into As2O5(V) on the CuCl2–HNTs. The Al–O bridge had the highest adsorption energy for the O end of the As–O group (−2.986 eV), and the combination formed between arsenic-containing groups and aluminum was stable. In addition, the captured arsenic could be stabilized in the sorbent at high temperature, making it possible to use the sorbent before the SCR system. This demonstrates that CuCl2–HNTs is a promising sorbent for arsenic oxidation and removal from CCFG.

Removal efficiency of arsenic in water using desulfurization slag

“…Similar to the Cl − analysis (Table 8), the effect of SO 4 2− concentration on As removal was insignificant. Regarding adsorption mechanism of SO 4 2− , some researchers believe that ligand displacement plays a vital role, whereas others hold that it is similar to minor electrostatic adsorption mechanisms involving Cl − and NO 3 − 32–34 . The experimental results are consistent with Section 3.5.…”

“…− . [32][33][34] The experimental results are consistent with Section 3.5. In this study, SO 4 2ions were possibly attached to the surface of desulfurization slag samples by minor electrostatic force, which could not compete with arsenate ions during coordinate covalent bonding.…”

Effective Capture and Immobilization of Hg0 from Flue Gas Using a Novel Selenium-Functionalized SrFeO3-δ/HNTs Half-Metal Composite: Adsorption, Photocatalytic Oxidation, and Mechanism

“…Figure a shows the FTIR spectra of HNTs and SrFeO 3‑δ . The peaks at 540, 922, 1640, and 3458 cm –1 resulted from the Al–OH bending bands, deformation vibration of Al–O–Si, and O–H stretching of H 2 O and HNTs, respectively. , The presence of peaks at 3642 and 3711 cm –1 was attributed to the vibration of the inner hydroxyl groups of halloysite. , The adsorption bands at 616 and 707 cm –1 ascribed to stretching and bending vibrations of Fe–O from SrFeO 3‑δ . Li et al thought that SrO was not stable, resulting in no peak of Sr–O at ∼400 cm –1 .…”

“…18 Our team-prepared Fe 3 O 4 @SiO 2 @Cu-MHNTs and CuCl 2 -HNTs were used to deal with elemental mercury and gaseous arsenic, respectively, showing super adsorption performance. 15,19 Besides, the surface chemical structures of alumina octahedral layers and rolling silica tetrahedral layers in HNTs can stimulate interfacial electron dynamics transmission, declining the electron−hole recombinations. 16 This further confirmed that HNTs as carriers were feasible for the photocatalytic performance of SrFeO 3-δ .…”

Phosphorus adsorption efficiency and characteristic analysis of basic oxygen furnace slag

“…3− is generally considered to be carried out by the mechanism of ligand substitution, 39,40 and a strong covalent bond is formed on the surface of the adsorbate. The Cl − and Mg 2+ selected in this study are all adsorbed on the surface of BOFS by relatively weak electrostatic force.…”