Photocatalytic Hydrogen Production from Pure Water Using a IEF-11/g-C3N4 S-Scheme Heterojunction.

Construction of S-scheme heterojunction offers a promising way to enhance the photocatalytic performance of photocatalysts for converting solar energy into chemical energy. However, the photocatalytic H2 production in pure water without sacrificial agents is still a challenge. Herein, the IEF-11 with the best photocatalytic H2 production performance in MOFs and suitable band structure was selected and firstly constructed with g-C3N4 to obtain a S-scheme heterojunction for photocatalytic H2 production from pure water. As a result, the novel IEF-11/g-C3N4 heterojunction photocatalysts exhibited significantly improved photocatalytic H2 production performance in pure water without any sacrificial agent, with a rate of 576 µmol/g/h, which is about 8 times than that of g-C3N4 and 23 times of IEF-11. The novel IEF-11/g-C3N4 photocatalysts also had a photocatalytic H2 production rate of up to 92 µmol/g/h under visible light and a good photocatalytic stability. The improved performance can be attributed to the efficient separation of photogenerated charge carriers, faster charge transfer efficiency and longer photogenerated carrier lifetimes, which comes from the forming of S-scheme heterojunction in the IEF-11/g-C3N4 photocatalyst. This work is a promising guideline for obtaining MOF-based or g-C3N4-based photocatalysts with great photocatalytic water splitting performance.

Transition-Metal Single Atom Anchored on MoS2 for Enhancing Photocatalytic Hydrogen Production of g-C3N4 Photocatalysts.

Single-atom catalyst technology with near-100% atomic utilization and a well-defined coordination structure has provided new ideas for designing high-performance photocatalysts, which is also beneficial for reducing the usage of noble metal cocatalysts. Herein, a series of single-atomic MoS2-based cocatalysts where monoatomic Ru, Co, or Ni modify MoS2 (SA-MoS2) for enhancing the photocatalytic hydrogen production performance of g-C3N4 nanosheets (NSs) are rationally designed and synthesized. The 2D SA-MoS2/g-C3N4 photocatalysts with Ru, Co, or Ni single atoms show similar enhanced photocatalytic activity, and the optimized Ru1-MoS2/g-C3N4 photocatalyst has the highest hydrogen production rate of 11115 µmol/h/g, which is about 37 and 5 times higher than that of pure g-C3N4 and MoS2/g-C3N4 photocatalysts, respectively. Experimental and density functional theory calculation results reveal that the enhanced photocatalytic performance is mainly attributed to the synergistic effect and intimate interface between SA-MoS2 with well-defined coordination single-atomic structures and g-C3N4 NSs, which is conducive to the rapid interfacial charge transport, and the unique single-atomic structure of SA-MoS2 with modified electronic structure and appropriate hydrogen adsorption performance offers abundant reactive sites for enhancing the photocatalytic hydrogen production performance. This work provides new insight into improving the cocatalytic hydrogen production performance of MoS2 by a single-atomic strategy.

Simulation Study on the Corrugated Plate Gas-Liquid Separator with the Assistance of the Drainage Hook.

Corrugated plate separators are widely used in the field of gas-liquid separation because of their excellent separation performance. The separation effect is very sensitive to the internal auxiliary structure of drainage hooks, so it is extremely important to study the action principle of drainage hooks to optimize the performance of corrugated plate separators. In this paper, Fluent is used as the solver and the realizable k-ε model is used to compare the separation performance of unhooked, single-hooked, and double-hooked corrugated plates. The results show that the separation efficiency of wave plates with hooks can reach 100%, the separation efficiency of wave plates without hooks is about 90%, and the superiority of the separation efficiency of single-hook and double-hook wave plates is related to the droplet partition diameter, which is positively correlated with Re. The pressure drop and separation efficiency increase with the increase of plate hook spacing, and the pressure drop and separation efficiency of single-hook and double-hook corrugated plates have different performance advantage zones influenced by Re and K a. When the Re is 9.64 × 103 and K a is 0.294, the separation effect of corrugated plates with the single hook and double hook is the same. Through the analysis of the gas-phase flow field and droplet motion trajectory, it is found that the drainage hook enhances the separation effect of the corrugated plate separator by increasing the local gas velocity and forming a vortex inside the drainage hook.

Rapid Construction of Green Nanopesticide Delivery Systems Using Sophorolipids as Surfactants by Flash Nanoprecipitation.

Green delivery carriers of nanopesticides, like sophorolipid biosurfactants, are of great significance to reduce environmental pollution and promote sustainable agricultural development. However, the molecular diversity of an unisolated sophorolipid mixture with almost unpredictable self-assembly properties has limited the in-depth study of its structure-activity relationship and hindered the development of green pesticide delivery systems. In this work, the acidic and lactonic sophorolipids were successfully separated from the sophorolipid mixture through silica gel column chromatography. A series of cost-effective green nanopesticides loaded with lambda-cyhalothrin (LC) were rapidly fabricated based on a combination of the acidic and lactonic sophorolipids as surfactants by flash nanoprecipitation. The effects of the acidic-to-lactonic ratio on particle size, drug loading capacity, and biological activity against Hyphantria cunea of LC-loaded nanoparticles were systematically investigated. The resultant nanopesticides exhibited a better insecticidal efficacy than a commercial emulsifiable concentrate formulation. This work opens up a novel strategy to construct scalable, cost-effective, and environmentally friendly nanopesticide systems.

Melting Characteristics of Coal Ash and Properties of Fly Ash to Understand the Slag Formation in the Shell Gasifier.

The flow temperature (FT) of the coal ash from the Liuqiao no. 2 mine in North Anhui Province (C00) is too high (∼1520 °C) to fit the Shell gasifier due to its relatively high content of SiO2 and Al2O3. To solve this problem, a series of coals were blended with C00 with different ratios, and the relations between FT and the ash composition were investigated. The coal ash was analyzed by X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy-EDX to elucidate the mechanism of the improved ash fusion performance and the slag formation in the waste heat boiler of the gasifier. It is shown that FT is relevant to the coal ash compositions as well as the structures formed at high temperatures. The existence of alkaline oxides (CaO, MgO, and Fe2O3) decreases the coal ash FT to a low level. The FT can decrease to <1350 °C to cater to the Shell gasifier by blending C00 and C03 with a mass ratio of 4:6 owing to the plentiful alkaline oxides in C03. The FTIR results indicate that the high flow temperature of C00 is attributed to the formation of mullite at high temperatures. The coal blending with various ratios changes the compositions of CaO, MgO, and Fe2O3, which can form some low-melting-point eutectic compounds with SiO2 and Al2O3 under high temperatures, inhibit the formation of mullite, and thus decrease the ash FT. The coal ash FT was found to have a good linear relation with the ash compositions, which can sever as a reference to the coal blending. According to the model parameters, it is shown that Mg has the most significant promoting effect on the decrease in FT of the coal ash. The caking tendency of fly ash increases with the rising Ca content and an excessive Ca-based fluxing agent used in the coal blending will lead to the aggregation of the Ca-rich clasts around the fly ash particle, resulting in the plugging of the waste heat boiler in the gasifier. Therefore, the Mg-based fluxing agent is more promising to improve the ash fusion performance and reduce the caking tendency of the coal fly ash.

Evaluation of renewable pH-responsive starch-based flocculant on treating and recycling of highly saline textile effluents.

Herein, we report a novel renewable pH-responsive starch-based flocculant (CIAT-ST) via etherifying 2-chloro-4,6-isopropylamino-[1,3,5]-triazine (CIAT) onto the starch backbones for decontamination and reuse of highly saline effluents. The obtained CIAT-ST shows a unique pH-sensibility and reversibility in response to a subtle pH change due to a pH-controllable surface charge density of polymer chains. The level of residual CIAT-ST in the solution can be facilely monitored by using UV-vis detection. The dye flocculation performance of CIAT-ST was evaluated by using a batch experiment. The results exhibited that the dye removal was highly dependent on the solution pH (optimal pH was 2), the flocculation equilibrium can be achieved within 5 min, and the maximum flocculation capacity of CIAT-ST for K-2BP and KN-B5 were calculated to be 2452.6 ± 23.9 and 792.7 ± 14.1 mg/g, respectively. The multiple flocculation mechanisms, including charge neutralization, bridging and charge patching, may participate in the flocculation process. Adjustment in pH-mediated hydrophilicity-hydrophobicity switch of flocculant facilitates readily recovery and then sequentially reused three times while retaining satisfying flocculation efficiency. A significant contribution was also confirmed that the highly saline effluents after flocculation and sedimentation were reused in three successive dyeing processes without sacrificing fabric quality (ΔE* < 1) due to relatively low polymer residuals, and the efficiency of salt reuse for consecutive regeneration processes could be achieved above 85%. The present work could provide alternative thoughts for the reutilization of spent flocculant and clarified saline wastewater, which is also an efficient and sustainable strategy for textile wastewater management.

Chemical Fixation of CO2 Using Highly Dispersed Cu on Hierarchically Porous N-Doped Carbon.

Chemical transformation of carbon dioxide (CO2) into fine chemicals such as oxazolidinones and carbamates is mainly reported using transition-metal complexes as homogeneous catalysts. Herein, we demonstrate that a heterogeneous catalyst of highly dispersed Cu (Cu/NHPC) supported on hierarchically porous N-doped carbon (NHPC) can efficiently promote CO2 fixations to oxazolidinones and ß-oxopropylcarbamates. The obtained NHPC, assembled by ultrathin nitrogen-doped carbon nanosheets with a three-dimensional (3D) structure, is readily prepared by pyrolysis of a nitrogen-containing polymer gel (NPG) in the presence of an activator of potassium bicarbonate (KHCO3). The resulting NHPC shows specific Brunauer-Emmet-Teller (BET) surface areas up to 2054 m2 g-1 with a mean micro/mesopore size of 0.55/3.2 nm and a broad macropore size distribution from 50 to 230 nm. The Cu/NHPC can efficiently promote three-component coupling of CO2, amines, and propargyl alcohols for syntheses of various oxazolidinones and ß-oxopropylcarbamates with yields up to 99% and a wide substrate scope. Moreover, the Cu/NHPC exhibits excellent recyclability in CO2-to-oxazolidinone transformation during nine-time recycling. The research thus develops an NHPC-based heterogeneous Cu catalyst for green transformation of CO2.

Methanol promoted naphtha catalytic pyrolysis to light olefins on Zn-modified high-silicon HZSM-5 zeolite catalysts.

The methanol promoted naphtha catalytic pyrolysis system to obtain light olefins (ethylene and propylene) was studied over Zn-modified high-silicon HZSM-5 (Zn/HZSM-5) catalysts. Compared with the individual naphtha catalytic pyrolysis to light olefins, the addition of methanol remarkably improved the naphtha conversion and the yield of the light olefins. All Zn/HZSM-5 samples were characterized by using a variety of techniques including inductively coupled plasma-optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption, NH3-temperature programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), pyridine adsorption infrared spectroscopy (Py-IR), and Fourier transform infrared spectroscopy (FT-IR). The performances of the catalysts for methanol promoted naphtha catalytic pyrolysis were evaluated in a fixed-bed reactor. In the methanol promoted naphtha catalytic pyrolysis reaction, the yield of the light olefins was strongly dependent on the reaction conditions and the degree of Zn ion-exchange. Due to the heterogeneous distribution of the protons of high silicon ZSM-5, two types of Lewis acid sites were formed by the interaction of Zn with hydroxyl groups (OH) adsorbed on HZSM-5. The 0.3-Zn/HZSM-5 (0.3 mol L-1 Zn ion-exchange HZSM-5) sample holds a comparatively high light olefin yield of 51.7 wt% possibly because of the moderate density and distribution of the acid sites on the catalyst.