Adsorption studies of Orange II onto polyaniline/bentonite nanocomposite.

Modification of bentonite is essential for the adsorption of anionic dyes, as its negative surface charge. In this study, polyaniline/bentonite (PAni-Bent) nanocomposite was synthesized by in-situ intercalative polymerization technique and used to remove anionic dye Orange II (ORII) from synthetic wastewater. Its structure was confirmed by X-ray diffraction (XRD), scanning electron microscopy, Fourier-transform infrared spectra and Brunauer-Emmett-Teller specific surface area measurements. The adsorption behaviours of PAni-Bent towards ORII in the single anionic dye wastewater, the cationic/anionic mixture dye wastewater, with or without salt or surfactant, were investigated principally. The results show that cetyl trimethyl ammonium bromide have an obviously suppressing effect on dye removal in the MB/ORII mixture system. The Langmuir and Temkin isotherm models described the adsorption process better than Freundlich or Dubinin-Radushkevich (D-R) model, and the pseudo-second-order and Boyd kinetic models fit better with the experimental data. Considering all these unique characteristics, PAni-Bent can be considered as effective adsorbent material for potential removal of dye from aqueous solution in industry.

Synthesis of magnetic epichlorohydrin cross-linked carboxymethyl cellulose microspheres and their adsorption behavior for methylene blue.

Epichlorohydrin cross-linked carboxymethyl cellulose microspheres (ECH/CMC) obtained by inverse suspension method and magnetic Fe3O4 nanoparticles encasing the ECH/CMC microspheres (M-ECH/CMC) obtained by two different methods were successfully prepared and compared. Their structures and morphologies were analyzed using polarizing microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The adsorption behaviors of M1-ECH/CMC for methylene blue (MB) in the single cationic dye wastewater, the cationic/anionic dye mixture in the absence or presence of co-existed additives (salt and surfactant) wastewater, were also investigated with UV-vis spectrometer. The results showed that the magnetic Fe3O4 nanoparticles were loaded readily in situ into ECH/CMC by specific, chemical interactions between COO- groups of ECH/CMC and magnetic responsive Fe3O4. The Langmuir isotherm and pseudo-second-order kinetic model provide best correlation with the experimental data for the adsorption of MB onto ECH/CMC and M1-ECH/CMC microspheres, while the Langmuir isotherm and pseudo-first-order kinetic model for M2-ECH/CMC. These microspheres are easily recyclable and exhibit high desorption and adsorption, which suggests that they can be applied as potential environmental adsorbents.

Multiscale Characteristics and Drivers of the Bundles of Ecosystem Service Budgets in the Su-Xi-Chang Region, China.

Managing ecosystem services (ESs) to meet human needs is critical to achieving sustainable development in rapidly urbanizing regions. Identifying ES budget bundles and analyzing their drivers at a multiscale level can facilitate management decision-making; however, further research is required in areas undergoing rapid urbanization. This study quantified the supply, demand, and budgets of six typical ESs at the county, township, and village scales in the Su-Xi-Chang region in 2020. Additionally, the influence of natural environmental and socioeconomic factors on ES budget bundles was investigated based on K-means cluster analysis and the Geodetector model. The results showed that ESs on all three scales showed a mismatch between supply and demand. The similarity in the spatial pattern of supply, demand, and budgets of ESs at the township and village scales was higher than that at the township and county scales. The location and area of surplus, balance, and deficit varied with scale. We found that population density and the proportion of impervious surfaces are the main factors influencing the formation of the ES budget bundles at different scales. In addition, the diversity and degree of interpretation of drivers varied with scale. We believe that focusing on the overall situation on a large scale and implementing precise management on a small scale can make management decisions more effective. This study can provide a scientific basis for the sustainable utilization of ESs in the Su-Xi-Chang region, and the research results and methods can provide a reference for similar studies in other rapidly urbanizing areas in the world.

The Interaction Mechanism of Fiscal Pressure, Local Government Behavioral Preferences and Environmental Governance Efficiency: Evidence from the Yangtze River Delta Region of China.

In environmental governance, local governments are the main actors, and their behavioral preferences between economic growth competition (EGC) and environmental regulation (ER) affect the inputs and outputs of environmental governance. Most studies discuss the relationship between government behaviors and the environment from the fiscal decentralization perspective, with few studies from the fiscal pressure (FP) perspective. Importantly, the bidirectional interaction mechanism is easily ignored. This study measured local government FP, EGC, ER, and environmental governance efficiency (EGE) in China's Yangtze River Delta (YRD) region from 2000 to 2020. Moran's I index was used to identify the change characteristics of local government behavioral preferences. The interaction mechanism was analyzed by a panel vector autoregression (PVAR) model. The results show that (1) from 2000 to 2020, FP was generally strengthened. EGE generally showed fluctuating and rising change characteristics, with more obvious fluctuating and rising characteristics before 2012 and after 2012, respectively. Local governments shifted from a strong alternative preference to a weak synergistic preference. (2) FP had a self-reinforcing effect. EGC and ER had a self-weakening effect. EGE had not only a self-weakening effect but also a weak self-dependence. (3) There is a double negative interaction mechanism between FP and local government behavioral preferences. FP made local governments prefer to reduce EGC and relax ER, but in fact, EGC and ER were conducive to alleviating FP. (4) There is a negative transitive influence mechanism between FP, local government behavioral preferences and EGE. The negative effect of FP on EGE can be transmitted by reducing EGC and ER. This paper provides a scientific basis for improving EGE in the YRD region and understanding the behavioral logic of local governments' environmental governance and a reference for other rapidly industrializing and urbanizing regions.

Theoretical study of the influence of doped oxygen group elements on the properties of organic semiconductors.

Organic semiconductor materials are widely used in the field of organic electronic devices due to their wide variety, low price, and light weight. However, their developments are still restrained by their low stability and carrier mobility. Density functional theory (DFT) was used to study the influence of doped oxygen group elements (O, S, Se, and Te) on the properties of organic semiconductor materials (seven-membered benzothiophene, o-pentacene, thiophene derivatives, and pentacene) in this paper. Based on the calculation of E HOMO, E LUMO, ΔE, and total energy, the performances of organic semiconductor materials without and with doped elements were compared, and it was found that the doping of multi-element Te makes the material have high stability and potential high mobility. For these studied organic semiconductor materials, when the atoms of the doped site change in the order of O, S, Se, and Te, the carrier mobility gradually increases, and the molecules show a tendency of stability. In this paper, promising doping elements and doping methods for these studied molecules are determined through calculations and screening out suitable materials more efficiently and economically without a large amount of repetitive experimental work, which may provide a theoretical basis and guidance for preparing high-performance organic semiconductor materials.

Electrocatalytic Synthesis of Ammonia Using a 2D Ti3 C2 MXene Loaded with Copper Nanoparticles.

As an energy-saving and environmentally friendly ammonia synthesis method, electrocatalytic nitrogen reduction reaction (NRR) has received a great deal of attention. There is thus an urgent need to find high-efficiency electrocatalysts for the NRR. In this work, a Cu/Ti3 C2 composite catalyst was prepared and demonstrated excellent selectivity under environmental conditions, which could efficiently convert N2 into NH3 electrochemically. In 0.1 M KOH, Cu/Ti3 C2 can achieve a high Faradaic efficiency of 7.31 % and a high NH3 production rate of 3.04 µmol h-1 cm-2 at -0.5 V vs. RHE. Moreover, the material also exhibits superior electrochemical stability and durability. At the same time, density functional theory (DFT) shows that, compared with Ti3 C2 , Cu/Ti3 C2 exhibits a wider conduction and valence band and a larger Fermi level, thus indicating that Cu plays a vital role in the enhancement of the catalytic activity and conductivity of Ti3 C2 -based materials. This work provides a feasible strategy for designing high-efficiency MXene-based NRR electrocatalysts.

A two-dimensional MXene-supported metal-organic framework for highly selective ambient electrocatalytic nitrogen reduction.

The conversion of nitrogen into ammonia is crucial for human activities. The electrochemical synthesis of ammonia from nitrogen and water is a green process with great application prospects; to this end, much effort has been made to improve the catalytic activity and selectivity. Here, a Co-based metal-organic framework (MOF), that is, zeolitic imidazolate framework-67 (ZIF-67), supported on a Ti3C2 MXene (defined as ZIF-67@Ti3C2) was prepared via in situ growth. Due to the high porosity and large active surface area of the MOF and the superior conductivity of the Ti3C2 MXene, the composite could efficiently synthesize ammonia electrochemically. In particular, the prepared ZIF-67@Ti3C2 catalyst exhibited an excellent NH3 yield (6.52 µmol h-1 cm-2), significantly higher than those achieved by Ti3C2 and ZIF-67 (2.77 and 1.61 µmol h-1 cm-2, respectively) alone, and good Faraday efficiency (20.2%) at -0.4 V (vs. the reversible hydrogen electrode). This study not only expands the application of the MXene family in the electrochemical nitrogen reduction reaction but also provides ideas for the development of high-performance electrocatalysts for NRR.

A two-dimensional Ru@MXene catalyst for highly selective ambient electrocatalytic nitrogen reduction.

Compared with the traditional Haber-Bosch process, electrochemical ammonia synthesis has attracted much attention owing to its low energy consumption, low pollution potential, and sustainability. However, owing to the influence of high overpotential and low selectivity, the nitrogen reduction reaction (NRR) process was of limited applicability in industry. Here, we report a high-performance Ru@Ti3C2 MXene catalyst for an ambient electrocatalytic NRR. In a 0.1 M KOH electrolyte, the NH3 yield of the Ru@MXene catalyst reached 2.3 µmol h-1 cm-2, furthermore, at -0.4 V (vs. RHE) the Faraday efficiency was 13.13%.

Current Progress of Electrocatalysts for Ammonia Synthesis Through Electrochemical Nitrogen Reduction Under Ambient Conditions.

Ammonia, one of the most important chemicals and carbon-free energy carriers, is mainly produced by the traditional Haber-Bosch process operated at high pressure and temperature, which results in massive energy consumption and CO2 emissions. Alternatively, the electrocatalytic nitrogen reduction reaction to synthesize NH3 under ambient conditions using renewable energy has recently attracted significant attention. However, the competing hydrogen evolution reaction (HER) significantly reduces the faradaic efficiency and NH3 production rate. The design of high-performance electrocatalysts with the suppression of the HER for N2 reduction to NH3 under ambient conditions is a crucial consideration for the development of electrocatalytic NH3 synthesis with high FE and NH3 production rate. Five kinds of recently developed electrocatalysts classified by their chemical compositions are summarized, with particular emphasis on the relationship between their optimal electrocatalytic conditions and NH3 production performance. Conclusions and perspectives are provided for the future design of high-performance electrocatalysts for electrocatalytic NH3 production. The Review can give practical guidance for the design of effective electrocatalysts with high FE and NH3 production rates.

Adsorption properties of crosslinking carboxymethyl cellulose grafting dimethyldiallylammonium chloride for cationic and anionic dyes.

Novel and efficient microspheres adsorbent (MCA-E0.7/CMC-g- PDMDAAC), based on monochloroacetic acid (MCA) modified epichlorohydrin (ECH) cross-linked carboxymethyl cellulose (CMC), then grafting by dimethyldiallylammonium chloride (DMDAAC), was synthesized and its adsorption properties on cationic and anionic dyes were investigated. The results demonstrated that such MCA-E0.7/CMC-g-PDMDAAC microspheres showed pH-sensitive and could effectively adsorb cationic dye methylene blue (MB) or anionic dye orange II (OR II), at near neutral (pH>4) or acidic (pH<3) condition, respectively. Moreover, it could selectively adsorb the cationic dye MB from the cationic/anionic dye mixture at neutral pH condition. The desorption experiments were mainly performed under acidic (pH 3) or basic (pH 11) condition, over 98.54% of MB and 83.07% of OR II can be desorbed within 20min, respectively. The pseudo-second-order kinetic model and Langmuir isotherm provide better correlation with the experimental data for the adsorption of dyes onto MCA-E0.7/CMC-g-PDMDAAC microspheres.