Dongsheng Xia

Enhanced ozonation degradation of atrazine in the presence of nano-ZnO: Performance, kinetics and effects

Enhanced ozonation degradation of atrazine (ATZ) with nano-ZnO (nZnO) as catalyst and the influences of the operational parameters have been investigated through semi-continuous experiments in this study. The results demonstrated that the combination of ozone (O3) and nZnO showed an obvious synergetic effect and the ATZ degradation conformed to pseudo-first-order kinetics. An improvement of ATZ degradation efficiency by 41.8% and pseudo-first-order rate constant by more than a factor of four was obtained in the O3/nZnO process after 5min of reaction compared to O3 alone. Meanwhile, the degradation efficiency of ATZ was gradually enhanced with increasing nZnO dosage and initial pH in the range from 3.0 to 8.0, and a higher amount of ATZ was degraded when the initial concentration of ATZ rose from 0.5 to 5mg/L. Additionally, sulfate ion, chloride ion, nitrate ion and low concentrations of humic acid substances led to enhancement of the ATZ degradation. The notable decrease of ATZ removal efficiency observed in the presence of radical scavengers and the results of free radical tests indicated that OH is the dominant active radical species. The mechanism investigation demonstrated that the enhancement effect could be attributed to the introduction of nZnO, which could promote the utilization of O3, enhance the formation of superoxide radical, and further accelerate the production of hydrogen peroxide and the generation of OH/O2-.

Enhanced Adsorption of Bisphenol A from Aqueous Solution with 2-Vinylpyridine Functionalized Magnetic Nanoparticles

In this study, a novel 2-vinylpyridine functionalized magnetic nanoparticle (Mag-PVP) was successfully prepared. The prepared Mag-PVP was characterized by transmission electronic microscopy (TEM), Fourier transform infrared spectrophotometry (FT-IR), vibrating sample magnetometry (VSM) and thermogravimetric analysis (TGA), and was used for the adsorption of bisphenol A (BPA) from aqueous solutions. Mag-PVP, which is composed of Fe3O4 nanoparticles and poly divinylbenzene-2-vinylpyridine (with a thickness of 10 nm), exhibited magnetic properties (Ms = 44.6 emu/g) and thermal stability. The maximum adsorption capacity (Qm) of Mag-PVP for BPA obtained from the Langmuir isotherm was 115.87 mg/g at 20 °C, which was more than that of Fe3O4 nanospheres. In the presence of NaCl, the improved adsorption capacity of Mag-PVP was probably attributed to the screening effect of Mag-PVP surface charge and salting-out effect. In the presence of CaCl2 and humic acid (HA), the adsorption capacity of BPA decreased due to competitive adsorption. The adsorption of BPA by Mag-PVP increased slightly with the increase in pH from 3.0 to 5.0 and obtained the largest adsorption amount at pH 5.0, which was probably attributed to hydrogen bonding interactions. Moreover, in actual water, Mag-PVP still showed excellent adsorption performance in removing BPA. The high adsorption capacity and excellent reusability performance in this work indicated that Mag-PVP was an effective adsorbent for removing BPA from aqueous solutions.

Synthesis of a g-C3N4-Cu2O heterojunction with enhanced visible light photocatalytic activity by PEG

A g-C3N4-Cu2O was successfully synthesized in the presence of PEG-400 surfactant via a hydrothermal method and high-temperature calcination method. Based on the results of TEM, XPS, EPR, and other techniques, it was verified that a heterojunction was formed. The synthesized g-C3N4-Cu2O show excellent photocatalytic activity and stability was confirmed through cycling experiments, XRD and XPS. At a suitable addition amount, the value of band gap of g-C3N4-Cu2O is reduced to 1.87 eV, the PL intensity decreases effectively, the specific surface area is increased to 12.8114 m2/g, and the photocatalytic degradation rate is increased to 94%. Adding the surfactant PEG-400 in the precursor solutions leads to a reduction in the crystallite size, which can improve the morphology and specific surface area to form abundant heterojunction interfaces as channels for photo-generated carrier separation, and improve its light utilization and quantum efficiency.

Efficient enhancement of ozonation performance via ZVZ immobilized g-C 3 N 4 towards superior oxidation of micropollutants

A functional organic-metal composite material zero-valent zinc immobilized graphitic carbon nitride (ZVZ-g-C3N4) was prepared by a fast and facile two-step synthetic approach with an optimal ZVZ content of 5.4 wt%. The structure, surface morphology and chemical composition of the as-synthesized ZVZ-g-C3N4 were characterized by BET surface area, XRD, FT-IR, SEM, TEM, and XPS, respectively. ZVZ-g-C3N4 composite exhibited superior catalytic ozonation activity with an improvement of 61.2% on atrazine (ATZ) degradation efficiency in 1.5 min reaction, more than 12 times of the pseudo-first-order rate constant, and almost 16-fold of the Rct value obtained in O3/ZVZ-g-C3N4 process compared to O3 alone. Meanwhile, the ATZ degradation efficiency was gradually enhanced with increasing ZVZ-g-C3N4 dosage and initial solution pH in the range from 3.0 to 9.0, and a higher amount of ATZ was degraded when the initial concentration of ATZ rose from 1 to 10 mg L-1. The enhanced catalytic ozonation activity of ZVZ-g-C3N4 is attributed to the synergistic effects among ZVZ, ZnO and g-C3N4, as well as the improved dispersibility, increased surface area, and intensive electron-transfer ascribed to the electronic and surface properties modification. The radical scavengers experiments demonstrated that O2-, OH, and 1O2 were the dominant reactive radical species in the multifunctional processes. Moreover, an empirical kinetic model was proposed to predict ATZ degradation. The results indicated that the ZVZ-g-C3N4 composite was a highly efficient, recoverable, and durable catalyst, which would provide a promising alternative in catalytic ozonation.