The adsorption behavior and mechanism of Cr(VI) on facile synthesized mesoporous NH-SiO2

• Published in: Environmental science and pollution research international Vol. 27; no. 3; pp. 2455 - 2463
• Main Authors: Han, Caiyun, Yang, Liu, Yu, Hongli, Luo, Yongming, Shan, Xin
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 2020; Springer Nature B.V
• Subjects: Adsorbents; Adsorption; Anions; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Chromium; Earth and Environmental Science; Ecotoxicology; Electron transfer; Environment; Environmental Chemistry; Environmental Health; Environmental pollution and Restoration in Mining Area; Environmental science; pH effects; Selectivity; Silica; Silicon dioxide; Sodium hydroxide; Synthesis; Toxicity; Waste Water Technology; Water Management; Water Pollution Control; Amine group; One-step route; Cr(VI); Fast synthesis; Reduce
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-018-3599-1

An efficient Cr(VI) adsorbent, mesoporous amine-functionalized silica (NH-SiO
2
), was successfully synthesized within 2 h by a facile one-step route under room temperature and aqueous solution. The structure properties of the obtained materials were characterized by N
2
adsorption-desorption isotherm, XRD, TEM, and FT-IR. The Cr(VI) removal performance was investigated by batch experiment. It was found that Cr(VI) removal performance was dependent on solution pH, and the removal efficiency is above 90% for initial pH in the range of 1.0–4.0. The adsorption process was obeyed by pseudo-second-order model, and the equilibrium adsorption data were fitted well by Langmuir model. The maximum monolayer adsorption capacity was 205.76 mg/g at pH 2.0, which was larger than that of traditional two-step tri-amine-functionalized MCM-41. Additionally, high selectivity was exhibited in NH-SiO
2
for removal Cr(VI) from co-presence anions Cl
−
, NO
3
−
, PO
4
3−
, SO
4
2−
, and SiO
3
2−
. Furthermore, the spent NH-SiO
2
could be regenerated by 0.005 M NaOH, and Cr(VI) removal is above 92% after NH-SiO
2
recycled four. From the analyzed results of adsorption energy, FT-IR, and XPS, the electrostatic attraction between protonated amine group and HCrO
4
−
was the mainly adsorption mechanism. And then some adsorbed Cr(VI) was reduced to low toxicity Cr(III) on the adsorbent surface by electron transfer from nitrogen in –NBr group to Cr(VI).