Jingke Song

Bioframe synthesis of NF–TiO2/straw charcoal composites for enhanced adsorption-visible light photocatalytic degradation of RhB

N–F codoped TiO2/straw charcoal composites (NF–TiO2/SC) were synthesized using a simple, bioframe-assisted sol–gel method and confirmed by XRD, SEM, EDX, TEM, N2 adsorption–desorption, Raman, FT-IR, XPS, and UV-vis DRS measurements. It has been found that the as-synthesized catalysts formed a 3D-hierarchical structure with carbon framework after calcination. The physicochemical properties, such as BET surface area, porosity, crystallite size and pore size distribution, could be effectively controlled by adjusting the calcination temperature. NF–TiO2/SC calcined at 450 °C exhibited higher surface area, smaller crystallite size and higher absorption in the visible light region. Under visible light irradiation, NF–TiO2/SC450 exhibited considerably high adsorption ability and photocatalytic activity, and there existed a significant synergistic effect between adsorption and photocatalytic degradation. Furthermore, the as-synthesized catalysts exhibited good mineralization ability, and could be used repeatedly, revealing their great potential for practical applications in environmental cleanup.

Floating photocatalysts based on loading Bi/N-doped TiO2 on expanded graphite C/C (EGC) composites for the visible light degradation of diesel

Floating Bi–N–TiO2 photocatalysts were synthesized using a novel sol–gel method grafted on expanded graphite C/C composites with high adsorption capacity and photocatalytic activity. The Bi–N–TiO2/EGC were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), the N2 adsorption/desorption method (BET), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), and X-ray photoelectron spectroscopy (XPS). The SEM and XRD results revealed that all the composites had with mesoporous structures; the crystalline phases were mainly influenced by calcination temperature and anatase transformed into rutile at 800 °C. The N2 adsorption/desorption method (BET) indicated that the specific surface area and pore size could be changed through adjusting the calcination temperature and Bi dosage. All Bi modified N–TiO2 composites exhibited higher photocatalytic activity for degradation of diesel (≥53.7%) than N–TiO2 under visible light irradiation. The composite Bi1.0–N–TiO2/EGC calcined at 550 °C with evenly distributed TiO2 exhibited the highest activity (83.8%), which was attributed to the high surface area, red shift of absorptive light to visible light as well as improved efficient charge separation. The results of influence experiments, under different conditions of pH, salinity, emulsifier and humic acid, also evidenced that Bi–N–TiO2/EGC composites are stable catalysts for the in situ remediation of diesel contaminated water.

Efficient visible light-driven in situ photocatalytic destruction of harmful alga by worm-like N,P co-doped TiO2/expanded graphite carbon layer (NPT-EGC) floating composites

The bloom of harmful algae in water has adversely affected water quality, local economies, and human health. Efficient visible light driven floating photocatalysts, namely N,P co-doped TiO2/expanded graphite carbon layer (NPT-EGC) composites, were successfully synthesized using a sol-carbonization method, and then applied as algaecides. The synthesized photocatalysts were characterized by means of XRD, FESEM/EDS, TEM, FTIR spectroscopy, XPS, UV-vis DRS, and PL spectroscopy. The results show that the NPT-EGC composites have a worm-like structure with the N,P co-doped TiO2 particles immobilized on the surface. Among the NPT-EGC photocatalysts with different calcination temperatures, NPT-EGC450 exhibits the highest photocatalytic activity. The removal rate of the algal cells is 98.15% for NPT-EGC450 following 9 h of visible light irradiation. The photocatalytic destruction process can be divided into a rapid adsorption phase and a repeat of the cell reduction phase-lag phase. During the photocatalytic process, the algal cells were damaged as a result of photocatalysis induced oxidation and inhibition. In addition, we simulated the release of MC-LR in the photocatalytic destruction process for the algal cells. The results show that the photocatalyst can remove both the algal cells and MC-LR simultaneously with high efficiency. After three consecutive cycles, the removal rate of the algal cells is still more than 90% for NPT-EGC450, which demonstrates that the NPT-EGC photocatalyst has good reusability and stability.

Surface modified TiO 2 floating photocatalyst with PDDA for efficient adsorption and photocatalytic inactivation of Microcystis aeruginosa

Microcystis aeruginosa, as the most common cyanobacteria, often grows uncontrollably in eutrophic lakes with the accumulation of microcystin-LR (MC-LR) in water, which heavily pollutes water and hence imposes tremendous threat to aquatic animals and human beings. To remediate the harmful algae polluted water, here we synthesize a series of poly dimethyl diallyl ammonium chloride (PDDA) modified TiO2 floating photocatalysts, PDDA@NPT-EGC, and apply them as a visible light driven multifunctional material. The fabricated PDDA@NPT-EGC composites have a worm-like structure with PDDA particles distributed on their surfaces, and the concentration of PDDA can affect the agglomerative condition and distribution of PDDA particles and the photoelectric properties of catalysts. Among these catalysts, the PDDA@NPT-EGC with 0.2 wt% PDDA (0.2PDDA@NPT-EGC) shows the highest adsorption and photocatalytic activity. Compared with the NPT-EGC, the dark adsorption efficiency for the 0.2PDDA@NPT-EGC after 3 h increases from 70.4% to 88.9%, and the total removal efficiency after visible light irradiation for 2 h increases from 77.8% to 92.6%. In addition, the 0.2PDDA@NPT-EGC exhibits a removal efficiency of 96.55% for photocatalytic degradation of MC-LR after irradiation for 3 h. The Adda side chain of MC-LR molecule is found to degradate gradually in the photocatalytic degradation process, indicative of the elimination of biotoxicity for MC-LR molecule in the reaction. We demonstrate that the 0.2PDDA@NPT-EGC is remarkably competitive in both algae inactivation and MC-LR removal, which shall hold substantial promise in remediation of algae pollution in eutrophic waters.