One-step vapor-phase assisted hydrothermal synthesis of functionalized carbons: Effects of surface groups on their physicochemical properties and adsorption performance for Cr(Ⅵ)

摘要

Amino-, carboxyl- and thiol-functionalized carbons (denoted as HT-N, HT-AA and HT-SCY, respectively) were successfully prepared via a facile one-step vapor-phase assisted hydrothermal carbonization process from glucose in the presence of ethylenediamine, acrylic acid and thioglycolic acid, respectively. Their physiochemical properties and static adsorption performance for Cr(VI) were comparatively studied by the Raman, FT-IR, XPS, Elemental analysis, SEM, N-2 adsorption/desorption, Zeta potential and UV-vis spectrophotometer. Their adsorption data fitted the pseudo-second order kinetic and the Langmuir model models well suggesting their chemical and single-layer adsorption processes. The maximum adsorption capacities obtained by the Langmuir model are as follows: HT-N (171.23 mg/g) HT-AA (94.25 mg/g) HT-SCY (15.41 mg/g) HT without functionalization (13.00 mg/g). The XPS and FT-IR results showed that Cr(VI) was enriched on the surfaces of the HT-N and HT-AA indicating that type of the functional group is a key factor to affect their adsorption performance. Their main adsorption mechanism involved electrostatic interaction and complexation between the functionalized groups and Cr(VI), and then the adsorbed Cr(VI) was partly reduced to Cr (III) with the help of electron donors. This simple vapor-phase assisted hydrothermal carbonization method could be extended to prepare diverse functionalized carbons for efficient treatment of heavy metal wastewater.