Surface Chemical Behavior Research Articles

The biochar derived from Spirulina platensis for the adsorption of Pb and Zn and enhancing the soil physicochemical properties

Microalgae can be collected in large quantities and hold significant potential for environmental remediation, offering a cost-effective solution. This study explores the use of Spirulina platensis (SP) as feedstock for biochar production. SP contains abundant nitrogen-rich components, such as proteins, which can serve as nitrogen sources. We prepared SP-derived biochar through pyrolysis for the adsorption of Pb and Zn from aqueous solutions and used it as an amending agent to remediate heavy metal-contaminated agricultural soil. Pyrolysis of proteins in SP introduces nitrogen-functional groups, resulting in nitrogen-doped biochar. We investigated the surface chemical behavior of thermally treated SP using X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Surface analysis revealed the presence of pyridine-N and pyrrole-N from protein pyrolysis products. The study also demonstrated that these functional groups affect interactions with heavy metals. Batch experiments examined the effects of pH and initial concentration on the adsorption of Pb and Zn using SP400 and SP600. Both types of biochar showed satisfactory performance in adsorbing Pb and Zn. The effect of SP400 and SP600 on the removal of Pb and Zn through the physicochemical properties and surface functional groups was investigated. Analysis of SP400 and SP600 highlighted that electrostatic interactions, cation exchange, complexation, and mineral precipitation contributed to Pb and Zn adsorption. The study concludes that SP-derived biochar, particularly SP600, is effective for immobilizing Pb and Zn in contaminated agricultural soil, with SP600 showing superior performance.

Atomic reconstruction and oxygen adsorption behavior of the pyrite (100) surface: a DFT study.

The analysis of the surface chemical behavior of pyrite is highly crucial in the fields of environmental conservation, metal extraction, and flotation separation. In this paper, the mechanism of atomic reconstruction on the pyrite surface and the adsorption behavior of O2 on a reconstructed surface are calculated by density functional theory (DFT). Different reconstruction surfaces were constructed by deleting S and Fe atoms on the (100) surface of pyrite. In addition, the geometric configuration, formation energy, binding energy, cohesion energy, and surface electronic properties of the reconstruction surface were calculated. The adsorption energies and geometric configurations of O2 on different reconstructed surfaces were also determined. The results show that under Fe-poor conditions, the charge of Fe atoms increases, and S atoms form Sn on the reconstructed surface. The binding energy between the Sn and the substrate (ideal surface) is lower, which is similar to the Sn adsorption on the substrate surface with the Fe atom as the site. Sn has high cohesive energy and is resistant to being attacked by oxidants, which leads to structural collapse, and a low affinity for O2. Under S-poor conditions, the -[Fe-S]n- plane structure formed on the reconstructed surface. The -[Fe-S]n- structure stably bonds to the substrate by an Fe-S bond, and exhibits strong binding energy. However, the -[Fe-S]n- structure has low cohesive energy and exhibits thermodynamic instability. In contrast, O2 shows a strong affinity for the -[Fe-S]n- structure, indicating that the deficiency of the S atom promotes the surface oxidation reaction. The mechanism of atomic reconstruction on the surface of pyrite is of utmost importance for understanding its surface chemical behavior.

What Differentiates Dielectric Oxides and Solid Electrolytes on the Pathway toward More Efficient Energy Storage?

Taking advantage of electrode thicknesses well beyond conventional dimensions allowed us to follow the surface plasmonic THz frequency phenomenon with vacuum wavelengths of 100 μm to 1 mm, only to scrutinize them within millimeters-thicknesses insulators. Here, we analyze an Al/insulator/Cu cell in which the metal electrodes-collectors were separated by a gap that was alternatively filled by SiO2, MgO, Li2O, Na3Zr2Si2PO12–NASICON, Li1.5Al0.5Ge1.5(PO4)3–LAGP, and Li2.99Ba0.005ClO–Li+ glass. A comparison was drawn using experimental surface chemical potentials, cyclic voltammetry (I-V plots), impedance spectroscopy, and theoretical approaches such as structure optimization, simulation of the electronic band structures, and work functions. The analysis reveals an unexpected common emergency from the cell’s materials to align their surface chemical potential, even in operando when set to discharge under an external resistor of 1842 Ω.cminsulator. A very high capability of the metal electrodes to vary their surface chemical potentials and specific behavior among dielectric oxides and solid electrolytes was identified. Whereas LAGP and Li2O behaved as p-type semiconductors below 40 °C at OCV and while set to discharge with a resistor in agreement with the Li+ diffusion direction, NASICON behaved as a quasi n-type semiconductor at OCV, as MgO, and as a quasi p-type semiconductor while set to discharge. The capacity to behave as a p-type semiconductor may be related to the ionic conductivity of the mobile ion. The ferroelectric behavior of Li2.99Ba0.005ClO has shown surface plasmon polariton (SPP) waves in the form of surface propagating solitons, as in complex phenomena, as well as electrodes’ surface chemical potentials inversion capabilities (i.e., χ (Al) − χ (Cu) > 0 to χ (Al) − χ (Cu) < 0 vs. Evacuum = 0 eV) and self-charge (ΔVcell ≥ +0.04 V under a 1842 Ω.cminsulator resistor). The multivalent 5.5 mm thick layer cell filled with Li2.99Ba0.005ClO was the only one to display a potential bulk difference of 1.1 V. The lessons learned in this work may pave the way to understanding and designing more efficient energy harvesting and storage devices.

Metal Sulfides for Photocatalytic Hydrogen Production: Current Development and Future Challenges

Photocatalytic hydrogen production using semiconductor photocatalysts provides a promising strategy for solving the energy crisis. Metal sulfide photocatalysts have received extensive attention due to its visible‐light response, adjustable band structures, and relatively mild preparation conditions. In this review, the emerging strategies to improve photocatalytic performance and stability of metal sulfides are summarized, including engineering of heterojunction, defect engineering, loading single‐atom cocatalyst, photothermal effect, loading dual cocatalysts, and coating stable shell. Special attention is paid to the influence mechanism of latest strategies on the photocatalytic process, with a focus on charge transfer, separation, and participation in surface chemical reaction behavior. Finally, with the goal of promoting the rapid progress of metal sulfides for solar hydrogen production, the key challenges of the latest research frontiers and the prospects on future development of metal sulfides are discussed.

Ni foam conductive substrate supported interwoven ZnCo2S4 nanowires with highly enhanced performances for supercapacitors

In this work, ZnCo2S4 nanowires (ZnCo2S4 NWs) were synthesized by an easy hydrothermal route. The fabrication procedure approach involved a hydrothermal route fabrication of Zn-Co precursor in isopropanol and glycerol and then sulfidation to gain nanowires-like ZnCo2S4 architecture. The sulfidation content of ZnCo2S4 in Ni foam construction strongly affects the morphological structures and surface chemical behavior of the material, and could significantly enhance electrochemical properties. The ZnCo2S4 NWs exhibited superior a specific capacity of 324 mA h g−1 at 2.0 A g−1 and extraordinary longer-basic cycle stability capabilities (around 9.5% less-loss after continuous cycles of 4000). This literature not only illustrates ZnCo2S4 NWs utilizes as a favoring applicant for SCs but also gives a simplistic and lesser-cost approach for constructing and fabricating other higher performances well-architecture metal-sulfides-basic for electrochemical energy storage.

A facile approach to develop multifunctional cotton fabrics with hydrophobic, self-cleaning and UV protection properties using ZnO particles and fluorocarbon

The presented work reported a facile and low-cost approach for creating multifunctional cotton fabrics with hydrophobic, self-cleaning and UV protection properties. The facile dip-pad-dry-cure coating technique was employed to modify the cotton fabric surfaces with 1–3 wt% concentration of ZnO nanoparticles. The characterizations of surface morphology, UV protection and chemical self-cleaning behavior of the ZnO coated fabrics have been carried out. Then, fluorocarbon (FC) was applied on the ZnO coated fabrics to fabricate the hydrophobic surfaces. The physical self-cleaning properties were assessed through hydrophobicity and contact angle measurements. For fabrics surface coated with 1, 2 and 3 wt % ZnO particles, static water contact angles of 139.5°, 143.1°, and 145.7° were detected, respectively. According to Cassie-Baxter model, the wetted solid fraction was estimated to be 52%, 60% and 72% for the samples coated with the 1%, 2% and 3% wt % ZnO particles, respectively. Further, the chemical self-cleaning performance has been examined by photocatalytic degradation of dye stains on ZnO coated fabrics under UV exposure.

Interfacial engineering of reduced graphene oxide for high-performance supercapacitor materials

To solve the problems related to the re-stacking of reduced graphene oxides (rGO) and further improve their surface chemical behaviors to satisfy supercapacitor demands. The rGO decorated with graphene quantum dots has been successfully prepared via a facile low-power ultrasonic method. It is demonstrated the graphene quantum dots/reduced graphene oxide electrode has a high specific capacitance of 312 F g −1 , which is nearly three times higher than that of the reduced graphene oxide (132 F g −1 ). The enhanced super-capacitive performances of graphene quantum dots/reduced graphene oxide have been attributed to the introduction of graphene quantum dots, which effectively prevent the aggregation and restacking of reduced graphene oxide sheets, promoting its surface exposed to the electrolyte for sufficient mass transfer. Meanwhile, these features provide more pathways for the transportation of electrons between the interlayer of reduced graphene oxide sheets. Afterward, a detailed energy storage mechanism was analyzed. • Graphene quantum dots reduced the agglomeration of reduced graphene oxide. • More channels for the electrolyte transport into the interlayer of RGO sheets. • The electrode and device exhibit excellent electrochemical performance.

Surface area of ferrihydrite consistently related to primary surface charge, ion pair formation, and specific ion adsorption

The specific surface area (SSA) of metal oxides is pivotal for scaling of surface phenomena. For ferrihydrite (Fh), the SSA can be assessed by probing the surface with ions that specifically adsorb (e.g. protons or phosphate). In the approach, an appropriate material with a known surface chemical behavior is used as reference, accounting for differences in e.g. surface sites and structure. As Fh is a nanomaterial, the size-dependency of many of its properties requires a consistent implementation for data analysis and modeling. In the present study, the proton adsorption of Fh was measured in NaNO3, NaCl, and NaClO4 solutions using a potentiometric titration methodology that leads to an internally consistent primary data set (H/Fe). For data interpretation, we employed a size-dependent molar mass, mass density, and chemical composition (FeO1.4(OH)0.2·nH2O), as well as a size-dependent surface curvature since the latter increases the value of the Stern layer capacitance. Using well-crystallized goethite as reference, state-of-the-art multisite complexation modeling discloses the underlying SSA of Fh. Similar to goethite, a significant variation in electrolyte affinity constants (logK) is found for Fh. This largely explains the differences in pHPZC reported in literature when using e.g. KNO3 or NaCl rather than NaNO3 as electrolyte solution. Our data collection was done for Fh materials with a known aging history. The same Fh samples were also probed with phosphate ions and the collected primary data (PO4/Fe) were interpreted with the CD model. This methodology yields SSA values that are consistent with those found by probing the surface of Fh with protons. As ion probing with phosphate is rapid and sensitive, it is recommended as a tool to determine the SSA of Fh materials. This enables the development of a consistent thermodynamic database for application of surface complexation modeling in natural systems.

Sub-nanoscale polishing of single crystal diamond(100) and the chemical behavior of nanoparticles during the polishing process

Single crystal diamond is widely utilized in various high-tech fields due to its many excellent properties, but poor surface quality will affect its applications. Therefore, increased ability to process high-quality diamond will dramatically expand its applications in high-tech fields. A combination of mechanical grinding and chemical mechanical polishing was utilized to propose a new room-temperature polishing method, by means of abrasive particles and transition metal ions. This process activated the diamond surface and resulted in an ultra-smooth surface of Ra 0.452 nm and rms 0.572 nm (measurement area: 283 μm × 212 μm), as well as a monoatomic surface layer of Ra 0.115 nm and rms 0.145 nm in a local region (measurement area: 500 nm × 500 nm). The chemical behavior of nanoparticles during the polishing process was studies via reactive force field molecular dynamics simulation. The surface chemical behaviors of both abrasive particles and diamond substrate during the polishing process were elucidated by combining experiments with simulations and the diamond removal mechanism and activated mechanism of Fe2+ were explored. This work provides a theoretical basis and technical support for the ultra-precision machining of single crystal diamond.

Correction to: Effects of Heat Input on Weld-Bead Geometry, Surface Chemical Composition, Corrosion Behavior and Thermal Properties of Fiber Laser-Welded Nitinol Shape Memory Alloy

Correction to: Effects of Heat Input on Weld-Bead Geometry, Surface Chemical Composition, Corrosion Behavior and Thermal Properties of Fiber Laser-Welded Nitinol Shape Memory Alloy

Effects of Heat Input on Weld-Bead Geometry, Surface Chemical Composition, Corrosion Behavior and Thermal Properties of Fiber Laser-Welded Nitinol Shape Memory Alloy

Bead-on-plate laser welding was carried out on 1-mm-thick Nitinol sheets at different heat input values. The variations in weld-bead geometry and variations in microstructures across the bead were studied. The effects of heat input on surface layer composition of the welded samples, corrosion properties and phase transformation temperature were examined. From x-ray photoelectron spectroscopy (XPS), it was clear that relative intensity of elemental Ni peak was higher in parent material and the oxidation state of Ti was Ti4+. It was further observed from Auger electron spectroscopy (AES) that the Ti to Ni ratio on the top surface of the welded samples was more than 1, and as a result of this the stability of TiO2 layer was enhanced, which eventually helped to improve the corrosion property of the welded samples. The polarization resistance of the welded samples was increased by more than ten times compared to that of the un-welded samples. From differential scanning calorimetry (DSC), it became evident that phase transformation temperatures got changed due to welding.

Surface broken bonds: An efficient way to assess the surface behaviour of fluorite

Crushing and grinding, the prerequisite processes in many industries, are employed in areas such as minerals processing and powder technology. During these processes, minerals will cleave or fracture along specific crystal directions, where there are weak inter-planar bonds, generating exposed surfaces. On an exposed mineral surface, different ions can possess different numbers of broken bonds. The total number of broken bonds of all ions on the exposed surface can be considered as the number of broken bonds of the exposed surface. The broken bonds on the exposed surface make the latter more active and determine its reactivity. The broken bond density on the exposed surfaces of fluorite was calculated, enabling the anisotropic surface reactivity of fluorite such as surface energy, surface relaxation, dissolution, wettability, surface charge and adsorbability to be revisited. The results show that the surface broken bond density, which is related to the specific surface energy, could be used to predict the cleavage nature, surface relaxation degree, dissolution rate and surface stability of fluorite crystal. The distribution feature and the number of broken bonds of exposed active ions (such as Ca2+ for fluorite) can be used to predict and explain the anisotropic surface wettability and surface charge, as well as the adsorption mode and strength of organic molecule binding to different exposed surfaces. The calculation of surface broken bonds can serve as useful method to assess mineral surface chemical behavior. This approach is helpful for mineral/material chemistry research in general.

Highly efficient adsorption of dyes by biochar derived from pigments-extracted macroalgae pyrolyzed at different temperature

Biochar is known to efficiently adsorb dyes from wastewater. In this study, biochar was derived from macroalgae residue by pyrolysis, and the influence of varying temperature (from 400 °C to 800 °C) on biochar characteristics was investigated. Among the biochar samples tested, macroalgae-derived biochar possessing highly porous structure, special surface chemical behavior and high thermal stability was found to be efficient in removing malachite green, crystal violet and Congo red. The biochar derived by pyrolysis at 800 °C showed the highest adsorption capacity for malachite green (5306.2 mg g−1). In this study, the transformation of microalgae residue into a highly efficient dye adsorbent is a promising procedure for economic and environmental protection.

Magnetic Nanoscale Zerovalent Iron Assisted Biochar: Interfacial Chemical Behaviors and Heavy Metals Remediation Performance

It has been reported that zerovalent iron can help biochar improve efficiency in heavy metal (HM) absorption, but the surface chemical behaviors and HM removal mechanisms remain unclear. We successfully synthesized the magnetic nanoscale zerovalent iron assisted biochar (nZVI-BC). The porosity, crystal structure, surface carbon/iron atom state, and element distribution were comprehensively investigated to understand nZVI-BC’s interfacial chemical behaviors and HM removal mechanisms. We clearly revealed the formation of a nanoscale Fe0 core–Fe3O4 shell on the surface/pores/channels of biochar. With the combination of iron nanoparticles and biochar, C–O/COOH groups were cracked with the formation of C═O/C═C, indicating the C–O–Fe acted as an electron acceptor during the reduction reaction. We also demonstrated that the stabilization was dramatically improved in the nZVI-BC, while more reduced iron and better homogeneity were observed. These results, showing the surface chemical behaviors of nZVI-BC, would h...

High-efficiency removal of lead from wastewater by biochar derived from anaerobic digestion sludge

The properties of biochar derived from waste activated sludge and anaerobic digestion sludge under pyrolysis temperature varying from 400°C to 800°C were investigated. The heavy metals adsorption efficiency of the sludge-derived biochar was also examined. Among the biochar samples tested, ADSBC600 possessing highly porous structure, special surface chemical behaviors and high thermal stability was found to remove Pb2+ from aqueous solutions efficiently with an adsorption capacity of 51.20mg/g. The Pb2+ adsorption kinetics and isotherm for ADSBC600 can be described using the pseudo second-order model and Langmuir isotherm, respectively. Analysis of the characteristics of biochar before and after metal treatment suggests that electrostatic attraction, precipitation, surface complexation and ion exchange are the possible Pb2+ removal mechanisms. This study demonstrates a successful example of waste refinery by converting anaerobic digestion sludge to feasible heavy metal adsorbents to implement the concept of circular economy.

Parameter extraction using global particle swarm optimization approach and the influence of polymer processing temperature on the solar cell parameters

The accurate estimation of the photovoltaic parameters is fundamental to gain an insight of the physical processes occurring inside a photovoltaic device and thereby to optimize its design, fabrication processes, and quality. A simulative approach of accurately determining the device parameters is crucial for cell array and module simulation when applied in practical on-field applications. In this work, we have developed a global particle swarm optimization (GPSO) approach to estimate the different solar cell parameters viz., ideality factor (η), short circuit current (Isc), open circuit voltage (Voc), shunt resistant (Rsh), and series resistance (Rs) with wide a search range of over ±100 % for each model parameter. After validating the accurateness and global search power of the proposed approach with synthetic and noisy data, we applied the technique to the extract the PV parameters of ZnO/PCDTBT based hybrid solar cells (HSCs) prepared under different annealing conditions. Further, we examine the variation of extracted model parameters to unveil the physical processes occurring when different annealing temperatures are employed during the device fabrication and establish the role of improved charge transport in polymer films from independent FET measurements. The evolution of surface morphology, optical absorption, and chemical compositional behaviour of PCDTBT co-polymer films as a function of processing temperature has also been captured in the study and correlated with the findings from the PV parameters extracted using GPSO approach.

Surface investigation and tribological mechanism of a sulfate-based lubricant deposited on zinc-coated steel sheets

Phosphatation is a well-known technique to improve friction and wear behaviour of zinc coated steel, but has a variety of economic and ecologic limitations. In this study an alternative coating based on ammonium sulfate ((NH4)2SO4) is applied on skin-passed hot-dip galvanized steel sheets in order to investigate its surface chemical and tribological behaviour in a Pin-on-Disk Tribometer. Raman- and X-ray photoelectron spectroscopic results revealed a formation of ammonium zinc sulfate ((NH4)2Zn(SO4)2 * xH2O) on the surface, which is primarily located in the skin-passed areas of the steel material. Sulfate coated samples exhibited a superior friction behaviour in Pin-on-Disk Tests using squalane as a model substance for oil-like lubricated conditions and a formation of a thin lubrication film is obtained in the wear track. Squalane acts as a carrier substance for ammonium zinc sulfate, leading to an effective lubrication film in the wear track.

Surface-Active Properties of a Trimeric Sulfate-type Surfactant Derived from Glycerol

AbstractA trimeric sulfate-type surfactant was synthesized and the surface chemical properties and micellar behavior of this surfactant were investigated by surface tension and fluorescence measurements. The critical micelle concentration (CMC) and the surface tension at CMC both decreased with the increase of NaCl concentration. The thermodynamic parameters indicate that the micelle formation is entropy-driven. The micelle aggregation number was determined and changed little between 303 K and 313 K. All the experimental results show that the surface-active properties of the surfactant are insensitive to the temperature compared with conventional surfactants.

Fillers for Papermaking: A Review of their Properties, Usage Practices, and their Mechanistic Role

Issues of cost and product quality have caused papermakers to place increased attention on the use of mineral additives, which are the subject of this review article. Technologists responsible for the production of paper can choose from a broad range of natural and synthetic mineral products, each of which has different characteristic shapes, size distributions, and surface chemical behavior. This article considers methods of characterization, and then discusses the distinguishing features of widely available filler products. The mechanisms by which fillers affect different paper properties is reviewed, as well as procedures for handling fillers in the paper mill and retaining them in the paper. Optical properties of paper and strategies to maintain paper strength at higher filler levels are considered. The goal of this review is to provide background both for engineers working to make their paper products more competitive and for researchers aiming to achieve effects beyond the current state of the art.

Global distribution and surface activity of macromolecules in offline simulations of marine organic chemistry

Organic macromolecules constitute a high percentage of remote sea spray. They enter the atmosphere through adsorption onto bubbles followed by bursting at the ocean surface, and go on to influence the chemistry of the fine mode aerosol. We present a global estimate of mixed-layer macromolecular distributions, driven by offline marine systems model output. The approach permits estimation of oceanic concentrations and bubble film surface coverages for several classes of organic compound. Mixed layer levels are computed from the output of a global ocean ecodynamics model by relating the macromolecules to standard biogeochemical tracers. Steady state is assumed for labile forms, and for longer-lived components we rely on ratios to existing transported variables. Adsorption is then represented through conventional Langmuir isotherms, with equilibria deduced from laboratory analogs. Open water concentrations locally exceed one micromolar carbon for the total of proteins, polysaccharides and refractory heteropolycondensates. The shorter-lived lipids remain confined to regions of strong biological activity. Results are evaluated against available measurements for all compound types, and agreement is generally well within an order of magnitude. Global distributions are further estimated for both fractional coverage of bubble films at the air–water interface and the two-dimensional concentration excess. Overall, we show that macromolecular mapping provides a novel tool for the comprehension of oceanic surfactant patterns. These results may prove useful in planning field experiments and assessing the potential response of surface chemical behaviors to global change.