Adsorption Reaction Research Articles

A Revised High‐Throughput Screening Model on Oxygen Reduction Reaction Over Dual Atom Catalysts Based on the Axial Pre‐Adsorption and O2 Adsorption

AbstractDual‐atom catalysts (DACs) often exhibit superior electrocatalytic activity, due to their versatile combinations and synergistic effects. However, the neglect of both dynamic axial adsorption of the active site upon working potential and the reactant adsorption as a rate‐determining step hinders the establishment of an accurate high‐throughput screening strategy. Here, the oxygen reduction reaction (ORR) of 42 kinds of 3d–3d metal DACs by density functional theory (DFT) calculations are systematiclly investigated and demonstrated that the ORR kinetics can be limited by O2* adsorption besides the proton–electron transfer step and the active center of DACs may be reconstructed by axial pre‐adsorption of intermediates under working potential. Therefore, the ORR volcano plot is proposed by using both the O2* and OH* adsorption as activity descriptors. Then, a high‐throughput screening method is constructed and 38 promising ORR DACs are screened out from 267 DACs containing 3d, 4d, or 5d metals. Importantly, the previously unexplored MnCoN6 DAC is also experimentally synthesized, and exhibits ultrahigh ORR activity outperforming Pt/C, perfectly matching with theoretical prediction. In short, this work not only proposes a volcano plot‐based high‐throughput screening method but also provides a proof‐of‐concept of experimental verification of theoretical prediction to heuristically design electrocatalysts for other reactions.

Fabrication and Characterization of Aluminum-Doped Nickel Oxide Thin Films for Optoelectronic Applications using the SILAR Method

Study’s Excerpt The effect of varying annealing times on 10% Aluminum-doped Nickel Oxide (ANO) thin films, deposited via the SILAR technique is presented. SEM and RBS analyses were used for detailed correlation between annealing time and the film's microstructural improvements. ANO thin films could be used for advanced technological applications. Full Abstract The effect of varying the annealing time of %10 aluminium-doped Nickel Oxide thin film was studied to understand the possible effect on the optical, structural, and electrical properties of %10 aluminium-doped Nickel Oxide (ANO) for possible application. The thin films were deposited on glass substrates using the successive ionic layer adsorption reaction (SILAR) deposition technique. The samples formed were annealed at 3000C, and the annealing time varied at 1.35 hrs., 1.45 hrs., 1.55 hrs., and 2 hrs, respectively. The deposited films were characterized to obtain the optical, electrical, and structural characteristics and the compositional constituent of the film using the double beam photo spectrometer, Four-Point Probe, Scanned electron Microscope, Energy Dispersion Spectroscopy, and X-ray Diffractometer. The films were observed to have low absorbance in the range of 0.1 to 0.01 and high % transmittance within the range of 80% - 98% in the visible region of the spectrum. The reflectance of the film was observed to decrease with an increase in annealing time in the range of 10% - 2.5%, all in the visible region of the spectrum. The crystallite size of the deposited films decreased with increased annealing time with the structural formation of simple cubic phase NiO thin film. SEM micrograph of the thin films reveals that an increase in annealing time improved the crystallinity of the films with the grain size evenly distributed. The EDS result of the deposited films revealed the presence of nickel, aluminum and Oxygen as the major constituent of the deposited films. The Ruther Ford Backscattering (RBS) analysis of the thickness of the films shows an increase in the thickness with an increase in annealing time. Clearer compositions of the films were also seen from the RBS analysis. Their electrical properties revealed that the films formed had low electrical resistivity and high conductivity, so they could be useful in making optoelectronics devices and corrosion resistance.

Triggering Asymmetric Layer Displacement Polarization and Redox Dual-Sites Activation by Inside-Out Anion Substitution for Efficient CO2 Photoreduction.

Sluggish bulk charge transfer and barren catalytic sites severely hinder the CO2 photoreduction process. Seeking strategies for accelerating charge dynamics and activating reduction and oxidation sites synchronously presents a huge challenge. Herein, an inside-out chlorine (Cl) ions substitution strategy on the layered polar Bi4O5Br2 is proposed for achieving layer structure-dependent polarization effect and redox dual-sites activation. Cl ions in the bulk phase shrink the halogen layer interspace by 8‰, triggering asymmetric [Bi4O5]2+ layer displacement polarization, prolonging the average photocharge lifetime to 201.8ps. Meanwhile, surface substituted Cl ions enhance the electron-donating capability of neighboring Bi atoms, activating the intrinsic Bi reduction sites, and increasing H2O molecule adsorption on nearby intrinsic O oxidation site (cal. by 0.105eV), also self-donating as an alien oxidation site. Besides, Cl upshifts the p-band center closer to the Fermi level, facilitating the reactant adsorption. Therefore, the energy barrier for CO2 activation and rate-limiting *COOH intermediate formation steps are significantly decreased. Without cocatalysts and sacrificial reagents, inside-out Cl-substituted Bi4O5Br2 delivers a remarkable CO2-to-CO photoreduction rate of 50.18µmol g-1 h-1, being one of the state-of-the-art catalysts. This finding offers insights into exploiting polarization at the molecular-level and enhances understanding of catalytic site activation.

Investigation on mechanism of mechanical activation and chemical reactions in CMP of diamond assisted by hydroxyl free radicals

Chemical mechanical polishing (CMP) is a crucial manufacturing process for diamond substrate applications. However, due to the extremely high hardness and chemical stability of diamond, its CMP efficiency is extremely low. This study aims to achieve microscopic simulation of atomic oxidation removal at the three-phase interface between diamond abrasive particle, diamond substrate, and hydroxyl free radicals (∙OH) aqueous solution. The mechanical activation behavior, microscopic mechanism, and feasibility of elementary reactions in the ∙OH aqueous solution environment was studied using various perspectives of radial distribution function, central atomic coordination state, atomic bonding and removal forms, energy, electron orbitals, and density functional theory (DFT). The simulation results indicate that during the process of diamond atomic oxidation removal, the atomic density at the first adjacent position centered on one atom decreases, and the stable covalent bond structure is disrupted, resulting in an amorphous phase transition. The chemical adsorption reaction generates C-O and C–H bonds. The C atoms mainly separate from the diamond substrate by the forming products such as carbon monoxide (CO), carbon dioxide (CO2), and carbon chains. The mechanical activation behavior indirectly reduces the activation energy of chemical reactions, while increasing the absolute value of adsorption energy and improving the ability of chemical adsorption solution atoms H and O, as well as ∙OH groups. Based on DFT, it has been verified that the intrusion process of ∙OH groups in the elementary reactions involving the typical product C*O2 is an exothermic reaction that can occur spontaneously, and the energy barrier needs to be overcome by the mechanical action of abrasive particles. At the same time, the energetics of the oxidation of diamond C atoms to generate C*O2 have successfully confirmed that the combined action of ∙OH and diamond abrasive particles is expected to achieve efficient oxidation removal and finishing polishing of diamond atoms.

Constructing 2D Porous ZnO Gas Sensors Based on Polyvinylpyrrolidone-Assisted Zn-MOF Nanosheets for NO2 Detection.

Two-dimensional (2D) ZnO nanomaterials are promising for gas sensing, because of their large surface area, abundant active sites, and rapid charge transfer. However, it is challenging to prepare 2D ZnO nanosheet gas sensors with high sensing performance, due to the tight interlayer stack and low adsorptive property of ZnO for NO2 molecules. Herein, we synthesized Zn-MOF nanosheets employing polyvinylpyrrolidone (PVP) as the structure-directing agent, further through pyrolysis of the Zn-MOF to obtain 2D ZnO nanosheet gas sensors. As anticipated, the 2D ZnO gas sensors exhibited high sensitivity and selectivity for NO2, and the optimal sample could achieve a response value of 162 at the working temperature of 160 °C, which is 10 times higher than that of pristine ZnO. Meanwhile, experimental and DFT results showed that PVP plays critical roles in the lateral lattice growth of 2D Zn-MOF nanosheets, while the existence of PVP makes the ZnO gas sensors with rich porous property and more oxygen vacancy after the pyrolysis process, which promoted the adsorption, activity, and surface reaction for NO2 molecules. It provides a new approach for the application of 2D ZnO nanosheets in the NO2 detection field.

Trace Cu-Induced Low C─N Coupling Barrier on Amorphous Co Metallene Boride for Boosting Electrochemical Urea Production.

The electrochemical C─N coupling of carbon dioxide (CO2)and nitrate(NO3 -)is an alternative strategy to the traditional high-energy industrial pathway for urea synthesis, which urgently requires the design of efficient catalysts to achieve high yield and Faraday efficiency (FE). Here, amorphous low-content copper-doped cobalt metallene boride (a-Cu0.1CoBx metallene) is designed for urea synthesis via electrochemical C─N coupling. The a-Cu0.1CoBx metallene can drive electrocatalytic C─N coupling of CO2 and NO3 - for urea synthesis in CO2-saturated 0.1m KNO3 electrolyte, with 27.7% of FE and 312µgh-1mg-1 cat. of yield at -0.5V, as well as superior cycling stability. The in situ Fourier transform infrared and theoretical calculations reveal that electronic effect between Cu, Co, and B causes Cu and Co as dual active sites to promote the adsorption of reactants. Furthermore, the introduced trace Cu reduces the reaction energy barrier of the C─N coupling to facilitate urea synthesis. This work provides a promising route for the optimization of Co-based metallene for the electrosynthesis of urea through C─N coupling.

Multiscale Defective Interfaces for Realizing Na-CO2 Batteries With Ultralong Lifespan.

Despite their favorable high energy density and potential for CO2 recycling, Na-CO2 batteries have been held back by limitations in cycling capability, stemming from the sluggish CO2 reduction/evolution reaction (CO2RR/CO2ER) kinetics at CO2 cathode and unmanageable deposition/stripping of metallic Na at the anode upon cycling. Herein, a "two-in-one" electrode with multiscale defective FeCu interfaces (CP@FeCu) is presented, which is capable of improving the CO2RR/CO2ER kinetics of CO2-breathing cathode, while modulating sodium deposition behavior. Experimental and theoretical investigations reveal multiscale defective FeCu interfaces are responsible for the enhancement of sodiophilicity and catalytic properties. The defect and valence oscillation effects originate in multiscale defective FeCu interfaces, effectively facilitating the adsorption of reactants and decomposition of Na2CO3 during CO2RR/CO2ER processes, along with exceptional cycling stability of 2400 cycles (4800h) at 5µAcm-2. Meanwhile, the CP@FeCu with sodium affinity creates a uniform electric field and robust adsorption for Na, making initial nucleation sites more conducive to Na deposition and achieving dendrite-resistant and durable anodes. This work offers a scientific insight into the functionalization design of "two-in-one" electrodes, which is essential for a unified solution to the challenges in sodium anodes and CO2 cathodes.

Unveiling the Brønsted acid mechanism for Meerwein–Ponndorf–Verley reduction in methanol conversion over ZSM-5

The conversion of methanol over zeolites offers a sustainable alternative for fuels and chemicals production. However, a complete understanding of the competing reaction pathways, particularly those leading to C-C bond formation, remains elusive. This work presents a novel mechanism for selective methanol conversion in ZSM-5 zeolites, involving a Brønsted acid site (BAS)-mediated Meerwein–Ponndorf–Verley (MPV) reduction pathway. Employing a multidimensional solid-state NMR spectroscopy combined with isotopic labeling and theoretical calculations, we identify this pathway for acetaldehyde reduction with methanol, directly contributing to ethene formation. This mechanism, involving carbenium ion intermediates like 1-hydroxyethane or 1-methoxyethane ions, contrasts with the well-established Lewis acid-catalyzed MPV process. Based on reactant adsorption modes, we propose two distinct reaction routes for BAS-MPV reduction, bridging the gap between direct and hydrocarbon pool mechanisms in methanol conversion. We further demonstrate the applicability of this pathway to acetone, highlighting its broader role in the early stages of the reaction.

Copper hexacyanoferrate cathode as a selective adsorbent for ammonium ions in sodium-rich solutions

Abstract Ammonium ion remediation has led to innovative methods, such as Faradaic redox reaction using Prussian blue. Our approach uses an adsorption reaction that is controlled by electric current instead of potential. By sweeping the potential through current control, selective adsorption of NH4+ was achieved in solutions with high concentrations of Na+ (ca. 1:50). The use of thick electrodes enabled ammonium levels to be reduced to environmentally acceptable levels in 3 steps, even from highly concentrated solutions of NH4+ (200 mmol/L).

Enhancing catalytic oxidation of benzene with Cu-Doped MnO2: Insights into structural defects and electronic modifications

The present research focuses on the role of copper (Cu) doping in enhancing the catalytic efficacy of manganese dioxide (α-MnO2) for benzene oxidation, a representative volatile organic compound (VOC). Despite the abundance and low cost of MnO2, its pristine form requires improvement for industrial VOC oxidation processes. Utilizing a range of characterization methods, the study reveals that Cu doping generates oxygen vacancies and increases the Mn3+ content within the catalyst structure, which are crucial for enhancing the adsorption and activation of reactants. The findings indicate that Cu-doped α-MnO2 exhibits superior catalytic activity and lower activation energy for benzene oxidation compared to the undoped counterpart. The electronic interactions induced by the doping of Cu and the effect on the catalytic process are demonstrated and discussed in depth. This work emphasizes the strategic importance of dopant optimization and contributes to the advancement of MnO2-based catalysts for environmental remediation, aligning with goals of environmental protection and human health safety.

Rational Design of Diatomic Active Sites for Elucidating Oxygen Evolution Reaction Performance Trends.

Diatomic catalysts, especially those with heteronuclear active sites, have recently attracted significant attention for their advantages over single-atom catalysts in reactions with relatively high energy barrier, e.g. oxygen evolution reaction. Rational design and synthesis of heteronuclear diatomic catalysts are of immense significance but have so far been plagued by the lack of a definitive correlation between structure and catalytic properties. Here, we report macrocyclic precursor constrained strategy to fabricate series of transition metal (MT, Ni, Co, Fe, Mn, or Cu)-noble (MN, Ir or Ru) centers in carbon material. One notableperformance trend is observed in the order of Cu-MN < Mn-MN < Fe-MN < MN < Co-MN < Ni-MN. However, thepathway has been not altered, still following the traditional adsorption reaction mechanism. The effect of the MT atoms on theperformances could possibly originate from the distinct adsorption/desorption behaviors of key intermediates (i.e. *OH, *O and/or *OOH), strongly implying that ΔG*OOH-ΔG*OH could be used as the performance descriptor. We believe that our work provides useful strategy for synthesis of diatomic active sites with sole coordination configuration and varied composition, and in-depth insight to their catalytic mechanism, which could be used for further optimization of diatomic catalysts towards oxygen electrocatalysis.

Exploring performance and mechanism of modified metal-organic frameworks in calcium alginate/polyvinyl alcohol double-network hydrogels for effective dye wastewater treatment

To address the growing problem of dye wastewater pollution, a novel MOFs adsorbent calcium alginate/polyvinyl alcohol@UiO-66 was developed using environmentally friendly polymers, sodium alginate and polyvinyl alcohol creating gel spheres with a double-network structure through cross-linking. UiO-66 metal-organic frameworks are then grown onto the gel spheres, resulting in the final CA/PVA@UiO-66 adsorbent. This adsorbent boasts a high surface area (17.4 m2/g) and a mesoporous-nested microporous structure. It effectively removes MB from water, the actual maximum adsorption capacity was measured at 275.8 mg/g, which surpasses most existing adsorbents. Remarkably, the adsorbent retains 93.9 % of its initial capacity even after 10 reuse cycles. The adsorption process adhered to the Redlich-Peterson model and the PFO model. The N2-Sorption isotherm, actual Methylene blue (MB) adsorption experiments, and model analysis further suggest that the adsorption process is a complex heterogeneous diffusion process involving simultaneous chemical and physical adsorption. Additionally, the adsorption process is endothermic, indicating that it can occur spontaneously at 298 K. Increasing the temperature promotes the forward progress of the adsorption reaction, thereby enhancing the adsorption capacity. The gel adsorbent exhibited excellent dye wastewater purification capabilities, coupled with commendable reusability.

Mechanism of CeO2 modified CO2 adsorbent with SO2 resistance: Experimental and DFT study

The flue gas emitted from coal-fired boilers contains a trace amount of SO2 after desulfurization, resulting in poor performance of CO2 adsorbent. In this paper, CO2 adsorption performance of potassium adsorbent modified by CeO2 doping and the effect of SO2 on CO2 adsorption were investigated by simulated flue gas. Theoretical research on the reaction between SO2 and CO2 with dopant was conducted by Density Functional Theory (DFT) method. The results showed that the cumulative CO2 adsorption capacity of the 4% Ce doped adsorbent without SO2 and with SO2 were 10.2% and 53.6% higher than that of the undoped adsorbent. The oxygen vacancy could cause the f orbital of Ce to exert greater influence, making the surface properties more unstable. The activation energy of the adsorption reaction between SO2 and H2O on Ce doped adsorbent was 266.5 kJ/mol, and there were three transition states in this reaction, with O vacancy formation as the rate-controlling step.

Insights into the mechanism of enhancing resistance of MnAlOx-Str NH3-SCR catalyst derived from streptomycin waste residue and LDHs

Streptomycin waste residue composited with Layered double hydroxides (LDHs) derived Mn1Al1Ox-Str-2 catalyst was proposed for NH3 selective catalytic reduction (NH3-SCR) denitration technology, which improved the overall catalytic performance. In the wide temperature range of 150-300℃, the preferred Mn1Al1Ox-Str-2 catalyst had Nitrogen oxides (NOx) conversion of exceeded 96%, which was higher than that of the control Mn1Al1Ox and Mn/Al2O3 catalysts. In addition, Mn1Al1Ox-Str-2 catalyst had better resistance to SO2 and/or H2O, as well as good regeneration ability. Various analytical techniques had confirmed that the Mn1Al1Ox-Str-2 catalyst derived from streptomycin residue composite LDHs precursor had better surface properties with more active species, abundant surface oxygen, higher reduction capacity and better adsorption of NOx and NH3. Analytical techniques revealed that the Lewis acid site on the surface of Mn1Al1Ox-Str-2 catalyst was involved in SCR reaction and both the Eley-Rideal mechanism and Langmuir-Hinshelwood mechanism existed simultaneously in the NH3-SCR reaction, and SO2 had a weak effect on the adsorption of reactants with fewer sulfate species formation. This work provided feasible strategies for efficient and stable SCR technology and efficient utilization of streptomycin residue waste resources, which was significant for the design and application of SCR technology in the future.

Insights into the Effect of Crystal Facets and Sulfur Defects on the Product Selectivity of Various CdS Configurations for CO2 Photoreduction: A DFT Study

CO2 photoreduction into valuable hydrocarbons, such as CO, CH4, and C2H4, delivers a promising approach to address both environmental and energy challenges. Transition metal chalcogenides, particularly cadmium sulfide (CdS), have emerged as prominent candidates due to their tunable electronic properties and availability. This study delves into a comprehensive investigation of how CdS crystalline facets and sulfur-deficient surfaces modulate the product selectivity. Through employing density functional theory (DFT), we unravel the catalytic performance of various CdS crystal orientations and sulfur vacancy configurations. The results have shown that different CdS facets exhibit unique electronic characteristics and surface energetics, which influence the adsorption dynamics and reaction pathways. The introduction of sulfur vacancies further modulates the nature of active sites, leading to substantial shifts in product selectivity. A detailed investigation on the reaction mechanisms unveils that specific facets preferentially facilitate the formation of CO, while others are more conducive to the generation of hydrocarbons such as CH4 and C2H4, due to the variations in activation barriers and intermediate stabilities. These findings underscore the importance of crystal facet engineering and defect manipulation in tailoring catalyst performance thus providing valuable insights for the rational design of efficient and selective CO2 reduction metal catalysts.

Heterogeneous precipitation behavior and mechanism during the adsorption of cationic heavy metals by biochar: Roles of inorganic components

Heavy metals are commonly adsorbed by biochar in contaminated water and soil. However, the behaviour and underlying mechanisms of heterogeneous precipitation between the inorganic components of biochar and cationic heavy metals remain poorly understood. In this study, we comprehensively investigated the nucleation, growth, and aggregation of precipitates, ion exchange-coupled precipitation behaviour, adsorption-precipitation correlation, and the influence of environmental factors (e.g., anion content, pH, initial concentration, type of heavy metals, and biochar size). The kinetic results indicated that the generation of precipitates was accompanied by an adsorption reaction with a gradual increase in crystal size and aggregation behaviour. Moreover, precipitation includes both surface and solution precipitation. The increasing local concentration of Pb(II) around the biochar at high initial concentrations increased the supersaturation of the nucleating substance, which decreased the potential for heterogeneous nucleation and facilitated heterogeneous precipitation. Correlation analysis revealed the presence of a coupling mechanism between precipitation and cation exchange. The enhanced electrostatic attraction at high pH could lower the heterogeneous nucleation potential barrier, thus promoting heterogeneous precipitation. The small biochar size extended the induction time, which was unfavourable for heterogeneous nucleation. This study provides a deeper understanding of the heterogeneous precipitation behaviour of the inorganic components of biochar and cationic heavy metals.

Construction of 0-dimensional silver quantum dot/MoSe2@MXene/3-dimensional porous copper foam composite electrodes with heterogeneous interfaces for synergistic electrocatalytic degradation of antibiotics

This study proposes a novel and efficient Ag quantum dots (QDs)/MoSe2@two-dimensional transition metal carbide/nitride (MXene)/copper foam (CF) composite electrode to address the challenge of electrocatalytic degradation of antibiotics in water. The electrode formed a unique electron donor–acceptor system by loading Ag QDs and heterostructured nanosheets on CF, significantly facilitating charge transfer and segregation at the interface. The catalytically active sites at the edges and defective locations of MoSe2 in conjunction with the two-dimensional MXene structure, which formed an efficient electron transfer channel, promoted the electron transfer from the interior to the surface and accelerated the hydrogen adsorption and reduction reactions. Moreover, the charge redistribution at the interface of Ag QDs and MoSe2@MXene formed interfacial dipoles, increasing the active sites on the catalyst surface and promoting the generation of cathodic atomic hydrogen (H*). Under optimal conditions, the degradation rate of tigecycline (TGC) reached as high as 90.1 % ± 2.4 % within 60 min. The anode-generated OH and HClO, along with the cathode-generated H, further promoted the degradation of TGC through co-catalysis. The degradation pathways were analyzed using density-functional theory (DFT) calculations and liquid chromatography-mass spectrometry (LC-MS) techniques. Moreover, toxicity analysis of the degradation products was carried out to ensure the safety of the treated wastewater discharge. A reflux continuous effluent reactor was also designed to achieve high degradation efficiency and low energy consumption after stable operation, laying the foundation for industrial applications. This technology provides new ideas for the design of green, efficient, stable, and low-consumption electrocatalytic reactors and contributes to a sustainable future environment.

Heterogeneous Fenton system driven by magnetic graphene-like biochar for degrading tetracycline

In this study, a novel catalyst with high efficiency and low cost was synthesized from farmland waste peanut shells by one-step pyrolysis modification method via K2FeO4, and employed for the catalytic degradation of tetracycline (TC). The magnetic potassium ferrate modified graphene-like biochar catalyst (PFGB) exhibited a high porosity, a highly graphitized structure, and a large specific surface area (857.09 m2·g-1) which was almost 30 times higher compared with peanut shell biochar, and were found to contain more functional groups. The formation and distribution of Fe3O4 and Fe0 nanoparticles on the surface/pores of PFGB provided more active sites for promoting adsorption and catalytic degradation reactions, and accelerated Fe(II)/Fe(III) recycle. Under the optimal conditions (pH=3.5, catalyst dosage = 0.5g·L-1, H2O2 concentration = 10mmol·L-1), about 98% of TC were degraded within 90min when the initial concentration of TC was 150mg·L-1, and PFGB could perform effectively over a wide pH range of 3-6. Furthermore, PFGB exhibited the advantages of convenient magnetic separation and strong reusability, maintaining a TC removal rate of ~90% after five cycles of experiments. The results of free radical quenching experiment and electron spin resonance analysis revealed that •OH and 1O2 were the main active species in the radical and non-radical pathways, respectively. This study indicated that PFGB, a catalyst developed for heterogeneous Fenton-like systems, possessed high efficiency, stability and reusability, and could be promising for the removal of TC in wastewater and other polluted waters.

Remediation of heavy metal contaminated soil in mining areas with vaterite-type biological calcium carbonate

In recent years, research on the remediation of heavy metal contaminated soil by microbially induced carbonate precipitation (MICP) technology has yielded significant findings. However, when utilizing MICP for remediation in situ, urea and calcium chloride may produce high concentrations of NH4+ and Cl-, which subsequently cause secondary pollution. If the biological calcium carbonate (Bio-CaCO3) produced by MICP is employed as a highly efficacious adsorbent, secondary pollution can be avoided while remediating heavy metal pollution. In this study, vaterite-type Bio-CaCO3 was prepared under the regulation of sophorolipids, and the remediation effect and mechanisms for heavy metal contaminated soil were investigated. The results demonstrated that sophorolipids facilitate the formation and stabilization of vaterite-type Bio-CaCO3. The addition of vaterite-type Bio-CaCO3 could notably increase the content of soil organic matter, enhance soil urease activity, and reduce soil catalase activity. On the 30th day of remediation with vaterite-type Bio-CaCO3, the active state content of Pb and Cd in the soil exhibited a decrease of 41.23% and 35.00%, respectively. Additionally, the exchangeable state content demonstrated a reduction of 6.61% and 8.48%, while the carbonate-bound state exhibited an increase of 12.05% and 13.89%, respectively. The principal mechanisms for the remediation of heavy metal contaminated soil by vaterite-type Bio-CaCO3 may be attributed to ion exchange, chemical precipitation, physical adsorption, and complexation reactions. The analysis of the microbial community structure demonstrated that vaterite-type Bio-CaCO3 could enhance the abundance of multiple genera with urease-producing genes, including Pseudomonas, Staphylococcus, and Bacillus while maintaining the soil biodiversity. This study provides a new idea for the remediation of heavy metal contaminated soil around the mining area and offers technical support for the construction of green mines.

Highly efficient selective hydrogenation of furfural to tetrahydrofurfuryl alcohol over MOF-derived Co-Ni bimetallic catalysts: The effects of Co-Ni alloy and adsorption configuration

The targeted conversion of furfural (FA) over inexpensive catalyst is a critical and challenging project. Herein, CoNi alloy catalysts (xCoyNi/C) were prepared through one-step pyrolysis of metal–organic frameworks and used in furfural (FA) hydrogenation to tetrahydrofurfuryl alcohol (TFOL). The formation of CoNi alloy leads to a reconfiguration of the electronic structure on the metal surface, which affects the adsorption of functional groups on FA and furfuryl alcohol (FOL). In situ FT-IR analysis and DFT calculations verify that bimetallic CoNi alloy catalyst exhibits more suitable reactants adsorption and hydrogenation rate in comparison with the monometallic Co and monometallic Ni catalysts. Meanwhile, CoNi alloy significantly reduces the activation barrier from FOL to TFOL. Hence, the 1Co1Ni/C catalyst gives the highest TFOL yield of > 99 %. This study provides a simple strategy for the preparation of alloy catalysts for tuning product selectivity and presents practical potential for upgrading biomass-derived platform molecules.