Xiaoting Hong

Transition force measurement between two negligibly charged surfaces: a new perspective on nanoparticle halos.

Since 2001, silica microspheres have been reported to be stabilized by highly charged hydrous ZrO(2) nanoparticles which form halos around the microspheres at pH 1.5. However, the exact mechanisms behind this novel stabilization method in terms of the relevant interaction forces remain unclear. In order to gain a greater insight into this mechanism, the interaction between a silica flat and a silica sphere in different ZrO(2) nanoparticle suspensions was investigated by the colloid probe technique. The interaction force between a silica flat and a 600 nm silica sphere was first investigated in a ZrO(2) nanoparticle (D approximately 8 nm) suspension with volume fractions of 10(-3), 10(-4), 10(-5), and 10(-6). When the volume fraction of ZrO(2) is 10(-6), only a purely attractive van der Waals force was observed between the silica surfaces. With an increase in the ZrO(2) nanoparticle volume fraction, a peak was detected on the transition force curve at a ZrO(2) volume fraction of 10(-5) while a purely repulsion force was observed for ZrO(2) volume fractions of 10(-4) and 10(-3). The average distance difference between the peak and the zero distance point on the transition force curve which should define the distance between the halo on the microsphere is approximately 2.3 nm. Additionally, the repulsion increases with the effective zeta potential of the binary composite sphere (BCS, the entity of the silica sphere and the surrounding zirconia particles) on an increase of the nanoparticle volume fraction while the adhesion force decreases, which indicates a denser nanoparticle halo.

Effect of pure oxygen fine bubbles on the organic matter removal and bacterial community evolution treating coal gasification wastewater by membrane bioreactor

A lab-scale study was investigated to evaluate the effect of pure oxygen fine bubbles on membrane bioreactor (O2-MBR) performance of treating coal gasification wastewater. Compared with conventional MBR using aeration source of air (CMBR), the removal efficiencies of COD and total phenols increased by 28% and 36%, and the organic compositions of treated effluent represented significant difference that was mainly attributed to the controlled the foam expansion and enhanced the enzymatic activities in O2-MBR. Moreover, membrane fouling mitigation was observed in O2-MBR, probably owing to the less EPS amount and larger PSD. It was notable that the pure oxygen with fine bubbles promoted marked evolution of bacterial community from CMBR to O2-MBR, particularly, the bacterial community richness and diversity in O2-MBR was lower than CMBR, and the genera Phycisphaera, Comamonas, Thauera and Ohtaekwangia composed the top four most relative abundance genera in O2-MBR, giving the total relative abundance of 26.7%.

CTAB-Assisted Hydrothermal Synthesis of Bi2Sn2O7 Photocatalyst and Its Highly Efficient Degradation of Organic Dye under Visible-Light Irradiation

Pyrochlore-type Bi2Sn2O7 (BSO) nanoparticles have been prepared by a hydrothermal method assisted with a cationic surfactant cetyltrimethylammonium bromide (CTAB). These BSO products were characterized by powder X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and UV-visible diffuse reflectance spectroscopy (DRS). The results indicated that CTAB alters the surface parameters and the morphology and enhances the photoinduced charge separation rate of BSO. The photocatalytic degradation test using rhodamine B as a model pollutant showed that the photocatalytic activity of the BSO assisted with CTAB was two times that of the reference BSO. Close investigation revealed that the size, the band gap, the structure, and the existence of impurity level played an important role in the photocatalytic activities.

Recycling rice straw derived, activated carbon supported, nanoscaled Fe3O4 as a highly efficient catalyst for Fenton oxidation of real coal gasification wastewater

Recycled rice straw was converted into an activated carbon support for nanoscaled Fe3O4. The resulting catalyst (Fe3O4MNPs/RSAC) was then evaluated for its effectiveness in the treatment of real coal gasification wastewater (CGW), which contained strong toxins and refractory pollutants that were poorly biodegradable. The results indicated that Fenton oxidation with the prepared catalyst was a highly efficient means of treatment for CGW over a wide pH range: the corresponding COD, cyanide and total phenols (TPh) removal efficiencies were 55.5, 46.5 and 85.5%, respectively. The treated wastewater was more biodegradable and less toxic, which aided in subsequent processing. The efficiency enhancement was attributed to the generation of more hydroxyl radicals and a possible reaction mechanism was proposed. Furthermore, Fe3O4MNPs/RSAC showed superior stability over ten successive runs. Moreover, heterogeneous Fenton oxidation by Fe3O4MNPs/RSAC also enhanced the aerobic biodegradation of CGW. Overall, 92.9% of COD and 98.5% of TPh were removed via the integration of Fenton oxidation and biological processing. Thus, the catalysis of Fenton oxidation by Fe3O4MNPs/RSAC was efficient, cost-effective and sustainable with a beneficial engineering application in the treatment of refractory wastewater, and a new and sustainable use for waste rice straw.

An Effective Zeta Potential Fitting Model for Sphere-Plate Interaction Force in Nanoparticle Suspensions

The silica sphere-plate interaction forces in zirconia nanoparticle suspensions have been successfully measured to explain how negligibly charged silica microspheres can be stabilized through the addition of highly charged zirconia nanoparticles. However, the influence of nanoparticle volume fraction on the stabilization as well as how various forces (the attractive van der Waals force, repulsive electrostatic force, and depletion force) contribute to the total interaction force still remains unclear. Therefore, an effective zeta potential fitting model is developed to explain the experimental interaction force curves based on a variable effective Debye length and a measured effective zeta potential using a continuum assumption.

Alginate Adsorbent Immobilization Technique Promotes Biobutanol Production by Clostridium acetobutylicum Under Extreme Condition of High Concentration of Organic Solvent

In Acetone-Butanol-Ethanol fermentation, bacteria should tolerate high concentrations of solvent products, which inhibit bacteria growth and limit further increase of solvents to more than 20 g/L. Moreover, this limited solvent concentration significantly increases the cost of solvent separation through traditional approaches. In this study, alginate adsorbent immobilization technique was successfully developed to assist in situ extraction using octanol which is effective in extracting butanol but presents strong toxic effect to bacteria. The adsorbent improved solvent tolerance of Clostridium acetobutylicum under extreme condition of high concentration of organic solvent. Using the developed technique, more than 42% of added bacteria can be adsorbed to the adsorbent. Surface area of the adsorbent was more than 10 times greater than sodium alginate. Scanning electron microscope image shows that an abundant amount of pore structure was successfully developed on adsorbents, promoting bacteria adsorption. In adsorbent assisted ABE fermentation, there was 21.64 g/L butanol in extracting layer compared to negligible butanol produced with only the extractant but without the adsorbent, for the reason that adsorbent can reduce damaging exposure of C. acetobutylicum to octanol. The strategy can improve total butanol production with respect to traditional culture approach by more than 2.5 fold and save energy for subsequent butanol recovery, which effects can potentially make the biobutanol production more economically practical.

Influence of interfering anions on Cu2+ and Zn2+ ions removal on chestnut outer shell-derived hydrochars in aqueous solution

Hydrothermal carbonization method was used to produce different hydrochars from chestnut outer shell at various temperatures while resolving the environmental issues of agricultural bio-waste. Hydrochars were adopted as adsorbents to remove heavy metal ions (copper and zinc ions) from aqueous solution. Hydrochar samples were characterized by Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), and Brunauer–Emmett–Teller (BET) nitrogen adsorption–desorption isotherm. An increase in the hydrothermal temperature from 160 °C to 220 °C results in higher BET surface area (18.81 m2 g−1) and the porosity of the samples. The resultant hydrochar at 220 °C exhibited a more excellent adsorption performance (8.13 mg g−1 for copper nitrate) than the other two hydrochars at low hydrothermal temperature. The current study addressed the influence of interfering anions of nitrates, sulfates and chlorides on the adsorption performance. The result shows that the hydrochar possesses larger removal efficiency for heavy metal nitrates that that of chlorides and sulfates.

Chloride ion-driven transformation from Ag3PO4 to AgCl on the hydroxyapatite support and its dual antibacterial effect against Escherichia coli under visible light irradiation

Visible light-driven photocatalytic inactivation of Escherichia coli was performed using hydroxyapatite-supported Ag3PO4 nanocomposites (Ag3PO4/HA). The antibacterial performance was evaluated by the methods of zone of inhibition plates and minimum inhibitory concentration test. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to investigate the instability and transformation of the nanocomposite by comparing the crystalline, phase, and the morphology before and after exposure to Luria-Bertani culture medium under visible light irradiation. Ag3PO4 nanoparticles on the support were found to be shortly transformed into AgCl due to high chloride concentration of Luria-Bertani culture medium. The AgCl/HA nanocomposite showed both excellent intrinsic antibacterial performance contributed by the released silver ions and visible light-induced photocatalytic disinfection toward E. coli cells. This dual antibacterial function mechanism was validated by trapping the hydroxyl free radical and detecting the silver ions during the photocatalytic antibacterial process. The morphological change of E. coli cells in different reaction intervals was obtained by scanning electron microscopy (SEM) to complementally verify photocatalytic inactivation of E. coli. This work suggests that an essential comparison study is required for the antibacterial materials before and after the photocatalytic inactivation of bacterial cells using Ag3PO4 nanoparticles or Ag3PO4-related nanocomposites in mediums containing high-concentration chloride ions.