posted on 2021-07-21, 13:35authored byChuan
Xi Yang, Qing Zhu, Wen Ping Dong, Yu Qi Fan, Wei Liang Wang
Phosphoric acid-modified
biochar (PMBC)
was prepared using biochar (BC) as the carbon source and phosphoric
acid as the activating agent. The PMBC exhibited an ordered vessel
structure after deashing treatment, but the sidewalls became much
rougher, the polarity (O/C atomic ratio of BC = 0.2320 and O/C atomic
ratio of PMBC = 0.1604) decreased, and the isoelectric points (PI
of BC = 5.22 and PI of PMBC = 5.51) and specific surface area (SSA
of BC = 55.322 m2/g and SSA of PMBC = 62.285 m2/g) increased. The adsorption characterization of the removal of
sulfadiazine (SDZ) from PMBC was studied. The adsorption of SDZ by
PMBC was in accordance with the Langmuir isotherm model and the pseudo-second-order
kinetics model, and the adsorption thermodynamics were shown as Gibbs
free energy < 0, an enthalpy change of 19.157 kJ/mol, and an entropy
change of 0.0718 kJ/(K·mol). The adsorption of SDZ by PMBC was
a complicated monolayer adsorption that was spontaneous, irreversible,
and endothermic, and physical adsorption and chemical adsorption occurred
simultaneously. The adsorption process was controlled by microporous
capture, electrostatic interactions, hydrogen-bond interactions, and
π–π
interactions. PMBC@TiO2 photocatalysts with different mass
ratios between TiO2 and PMBC were prepared via the in situ sol–gel method. PMBC@TiO2 exhibited both an ordered vessel structure (PMBC) and irregular
particles (TiO2), and it was linked via Ti–O–C bonds. The optimal mass ratio between TiO2 and PMBC was 3:1. The removal of SDZ via PMBC@TiO2 was dependent on the coupling of adsorption
and photocatalysis. The PMBC-enhanced photocatalytic performance of
PMBC@TiO2 resulted in a higher absorption of UV and visible
light, greater generation of reactive oxygen species, high levels
of adsorption of SDZ on PMBC, and the conjugated structure and oxygen-containing
functional groups that promoted the separation efficiency of the hole–electron
pairs.