Simultaneous Photocatalytic Tetracycline Oxidation and Cr(VI) Reduction by Z-Scheme Multiple Layer TiO2/SnIn4S8.

Wastewater pollutants are a major threat to natural resources, with antibiotics and heavy metals being common water contaminants. By harnessing clean, renewable solar energy, photocatalysis facilitates the synergistic removal of heavy metals and antibiotics. In this paper, MXene was both a template and raw material, and MXene-derived oxide (TiO2) and SnIn4S8 Z-scheme composite materials were synthesized and characterized. The synergistic mode of photocatalytic reduction and oxidation leads to the enhanced utilization of e-/h+ pairs. The TiO2/SnIn4S8 exhibited a higher photocatalytic capacity for the simultaneous removal of tetracycline (TC) (20 mg·L-1) and Cr(VI) (15 mg·L-1). The main active substances of TC degradation and Cr(VI) reduction were identified via free radical scavengers and electron paramagnetic resonance (EPR). Additionally, the potential photocatalytic degradation route of TC was thoroughly elucidated through liquid chromatography-mass spectrometry (LC-MS).

Back pressure generated by downwash and crosswind on spatial atomization characteristics during UAV spraying: CFD analysis and verification.

BACKGROUND: During unmanned aerial vehicles (UAVs) spraying, downwash and crosswind generate back pressure in comprehensive, which changes in spatial atomization characteristics of spraying droplets. However, the process of such atomization characteristics needs to be clarified. This study focuses on the effect of rotor speed and crosswind speed on spatial atomization characteristics. The computational fluid dynamics (CFD) models of the distributions of airflow, back pressure and atomization characteristics were established, and verification was conducted by developing a validation platform. RESULTS: The CFD results indicated that small droplets of 65-130 µm atomized by negative pressure would be coalesced near the nozzle, while large droplets of 390-520 µm atomized by positive pressure would be aggregated further away. Crosswind caused atomization stratification with droplet sizes of approximately 90 µm, 320 µm and 390 µm. When crosswind speed increased from 3 m/s to 6 m/s, the spraying drifted from 0.5 m to 1 m. When rotor speed increased from 2000 RPM to 3000 RPM, droplet distribution was expanded and droplet particle size was more uniform. Verification results demonstrated that the spraying distribution and the droplet size variation were consistent with the CFD. CONCLUSIONS: Spatial atomization characteristics were highly correlated with airflow and back pressure. Moreover, as crosswind generated droplet drift and atomization stratification and downwash could improve the uniformity of droplet distribution, spraying performance was superior by enhancing downwash to restrain the adverse effect of crosswind in real applications. © 2023 Society of Chemical Industry.

Interfacial architecting of organic-inorganic hybrid toward mechanically reinforced, fire-resistant and smoke-suppressed polyurethane composites.

Polyurethane (PU) composites integrated with outstanding fire retardancy, smoke suppression as well as ameliorated mechanical property is attractive, but remains a challenge. Here, we demonstrate the interfacial architecting of organic-inorganic hybrid (ACAPP) by reacting renewable chitooligosaccharide (COS) with ammonium polyphosphate (APP) and ammonium octamolybdate (AOM) via a one-pot, facile and eco-friendly approach. The ACAPP with multiple hydroxyl groups shows good compatibility and strong interfacial adhesion force with PU matrix due to the abundant covalent cross-linking points and hydrogen bonds networks. The incorporation of 15 wt% ACAPP enables the resultant PU composite to achieve a V-0 rating, a limiting oxygen index of 26.1%, 31.1% and 44.8% reduction in total heat release and total smoke production, respectively, far outdistancing conventional APP. The suppressed fire hazards mainly benefits from the synergy catalytic carbonization effect of ACAPP in condensed phase. Moreover, ACAPP reinforces the tensile strength of PU whilst retaining the decent ultimate elongation. This work may offer a referable exemplification for constructing green flame-retardant to balance high fire safety and mechanical properties.

Downwash characteristics and analysis from a six-rotor unmanned aerial vehicle configured for plant protection.

BACKGROUND: One theoretical advantage of using unmanned aerial vehicles (UAVs) to spray pesticides for maturing corn is that the strong downwash penetrates canopies. However, only few studies have been conducted to examine in-canopy downwash characteristics. This paper investigated the downwash by a six-rotor UAV in mature cornfields. 3D wind speeds in corn canopies and an open area were measured, and comparisons conducted. RESULTS: The downwash by the UAV resulted in in-canopy maximum wind speeds. Z-dimensional downwash was sensitive to all factors, whereas the X- and Y-dimensional downwashes were related to layers and crop positions. Meanwhile, when comparing with the downwash between a 2 m hovering position and the optimal flight parameters, the X-dimensional and Y-dimensional motion time of top-layer downwash generally advanced by 3.8 s and 1.6 s, whereas both motion time and the strength of the Z-dimensional downwash were impeded by ≈2.2-s hysteresis at middle layers and ≈4.5-s time reduction, respectively. Thus, combined with distributions, the corn on the left or right might not be sprayed sufficiently. Furthermore, under the convergence requirement error of 0.01, the overall correlation of the model was ≈0.846 in terms of the Z-dimensional downwash and ≈0.55 and 0.61 for the X- and Y-dimensions, respectively. CONCLUSION: The selection of operation parameters should mainly consider the Z-dimensional downwash. The optimal operation parameters were a height of 2 m with a speed of 4 m s-1 . Meanwhile, the canopy effect could influence the uniformity, motion and strength of downwash. Predictions could be achieved before operation. © 2022 Society of Chemical Industry.

Insights into efficient adsorption of the typical pharmaceutical pollutant with an amphiphilic cellulose aerogel.

An amphiphilic cellulose aerogel (HCNC-TPB/TMC) was fabricated by grafting 1,3,5-Tris (4-aminophenyl)benzene (TPB) and trimesoyl chloride (TMC) onto the aldehyde nanocellulose through Schiff alkali and substitution reaction. The obtained HCNC-TPB/TMC exhibited good morphology with cellulose fiber and owned abundant hydrophilic amino and carboxyl groups and hydrophobic aromatic groups. The batch adsorption experiments demonstrated that HCNC-TPB/TMC showed excellent adsorption performance (Qmax = 526.32 mg g-1) for sodium diclofenac (DCF), wide pH applicability (4-10) and outstanding stability and reusability. The DCF adsorption obeyed the pseudo-second-order kinetic model and the Langmuir isotherm, and underwent a spontaneous exothermic process. The main adsorption mechanisms involved electrostatic interaction, hydrogen bonds, π-π stacking interaction and hydrophobic effect. Importantly, the introduced carboxyl aromatic groups on TMC could effectively strengthen the hydrogen bonds and the π-π stacking between HCNC-TPB/TMC and DCF.

Surfactant-assisted hydrothermal synthesis of rGO/SnIn4S8 nanosheets and their application in complete removal of Cr(vi).

To solve the problem of contamination of hexavalent chromium (Cr(vi)), visible-light-driven graphene-based ternary metal chalcogenide nanosheets (rGO/SnIn4S8) were synthesized via a one-pot surfactant-assisted hydrothermal method for the photoreduction of Cr(vi). Characterizations demonstrated that SnIn4S8 nanosheets were uniformly distributed on the surface of rGO and the as-synthesized nanosheets exhibited excellent photocatalytic activity under visible light. In addition, the effects of pH, concentration of critic acid, holes and electron scavengers on the reduction of Cr(vi) were systematically investigated. It was found that 50 mg L-1 of Cr(vi) could be completely removed within 30 min at pH 2 when citric acid served as a hole scavenger. Kinetic studies showed that the photocatalytic reduction of Cr(vi) processes obeyed the pseudo first order model. Further study indicated that the Cr(iii) species was immediately adsorbed onto the surface of the rGO/SnIn4S8 nanosheets after photocatalytic reduction of Cr(vi). Additionally, recycling results suggested that rGO/SnIn4S8 nanosheets possessed high recycle ability and stability after repeated use (5 times). This effective and promising work might provide a new strategy for the photoreduction of Cr(vi) and complete removal of chromium from effluent through the novel photocatalyst rGO/SnIn4S8.