Surface Chemical Properties Research Articles

Influence of spin-coating speed on the morphology, surface chemistry and electrochemical performance stability of liquid precursor derived La0.6Ca0.4CoO3 electrode films

In this work, we investigate for the first time, effect of spin-rate on the microstructural and surface-chemical properties of (La,Ca)CoO3 electrode films. It was shown that fabricating films via different spin-coating rates influenced the types, sizes and amounts of cracks formed at the electrode films. This, in turn, was detrimental to the local oxygen partial pressures and the amounts of Co species transported to the surface via gas phase, and hence, to the as-fabricated surface chemistry. Initial surface chemistry of the films had a significant impact on the long-term electrochemical performance of the electrode films. Comparing films with similar thicknesses, those fabricated by spinning at 2000 rpm had a stable polarization resistance of 0.12 Ω.cm2 at 700 °C, while this value was ca. 0.43 Ω.cm2 in those that were fabricated by spinning at 1000 rpm, which increased by ca. 100 % when exposed to the same temperature for 100 h.

Band Engineering of Perovskite Quantum Dot Solids for High-Performance Solar Cells.

CsPbI3 perovskite quantum dot (PQD) shows high potential for next-generation photovoltaics due to their tunable surface chemistry, good solution-processability and unique photophysical properties. However, the remained long-chain ligand attached to the PQD surface significantly impedes the charge carrier transport within the PQD solids, thereby predominantly influencing the charge extraction of PQD solar cells (PQDSCs). Herein, a ligand-induced energy level modulation is reported for band engineering of PQD solids to improve the charge extraction of PQDSCs. Detailed theoretical calculations and systemic experimental studies are performed to comprehensively understand the photophysical properties of the PQD solids dominated by the surface ligands of PQDs. The results reveal that 4-nitrobenzenethiol and 4-methoxybenzenethiol molecules with different dipole moments can firmly anchor to the PQD surface through the thiol group to modulate the energy levels of PQDs, and a gradient band structure within the PQD solid is subsequently realized. Consequently, the band-engineered PQDSC delivers an efficiency of up to 16.44%, which is one of the highest efficiencies of CsPbI3 PQDSCs. This work provides a feasible avenue for the band engineering of PQD solids by tuning the surface chemistry of PQDs for high-performing solar cells or other optoelectronic devices.

Fenton-Based Treatment of Flax Biomass for Modification of Its Fiber Structure and Physicochemical Properties

The availability of a sustainable technique for degumming lignocellulose fibers is a challenge for the fiber processing industry. Removal of non-cellulosic content from lignocellulose fibers is essential for improving their mechanical and chemical properties, which makes the fibers more suitable for various applications. Herein, a catalytic Fenton-based oxidation process was employed to isolate microcellulose fibers from raw flax fibers. Various complementary methods such as FT-IR/NMR spectroscopy and TGA were used to obtain insight into the thermal behavior of the treated fibers. The morphology of the fibers was studied using Scanning Electron Microscopy (SEM), whereas the surface chemical properties of the fibers was evaluated by a dye-based adsorption method, along with a potentiometric point-of-zero-charge method. To obtain fibers with suitable properties, such as uniform fiber diameter, several Fenton reaction parameters were optimized: pH (7), reaction time (15 h), iron sulfate (2 wt.%), and hydrogen peroxide (10 wt.%). The results indicate that, under the specified conditions, the average diameter of the raw fibers (12.3 ± 0.5 µm) was reduced by 58%, resulting in an average diameter of 5.2 ± 0.3 µm for the treated fibers. We demonstrate that the treated fibers had a lower dye adsorption capacity for methylene blue, consistent with the smoother surface features of the treated fibers over the raw flax fibers. Overall, this study contributes to utilization of the Fenton reaction an efficient oxidation technique for the production of lignocellulose fibers with improved physicochemical properties, such as reduced fiber diameter distribution, in contrast with traditional alkali-based chemical treatment.

Insight into adsorption behaviors of shale oil in kerogen slit by molecular dynamics

Shale oil is predominantly stored in organic nanopores, with kerogen playing a pivotal role in its adsorption. This study utilizes molecular dynamics (MD) simulations to quantitatively investigate the adsorption behavior of multi-component shale oil within kerogen slits. Unlike previous studies that focused on single-component hydrocarbon fluids and simplified kerogen models to graphene, this research employs an authentic kerogen structure and a multi-component shale oil model, incorporating the effects of surface roughness. The research analyzes the interaction mechanisms and distribution patterns of light, medium, and heavy components within the pores. Additionally, it examines the effects of temperature, pore size, and wall surface physical and chemical properties on shale oil adsorption. Results indicate that strong adsorption between asphaltene and kerogen significantly reduces the width of the kerogen slits, inhibiting the adsorption of lighter components. The study introduces the concept of effective radius for kerogen slits and provides a quantitative analysis of the adsorption capacity of kerogen surfaces. Different kerogen surface roughness and chemical properties were compared to understand their influence on shale oil adsorption. Key findings show that with increasing temperature, the distribution of hydrocarbons becomes more uniform, with medium components showing the most significant response. Surface roughness of kerogen affects the adsorption capacity, although the component proportions remain consistent, while different chemical property surfaces influence selective adsorption and the overall adsorption amount of shale oil components. This research offers a deeper understanding of shale oil adsorption mechanisms and provides valuable insights for optimizing shale oil extraction and utilization.

A novel preparation strategy for an oil-soluble catalyst in slurry phase hydrocracking: Synergistic effect and electronic regulation of Fe on MoS2

The appropriate electronic structure of catalysts is vital for the slurry phase hydrocracking activity of inferior vacuum residue. Herein, a series of chemically bonded oil-soluble bimetallic FeMo catalysts with excellent performance were prepared by a novel strategy. Both experimental and density functional theory (DFT) calculations were conducted to investigate the regulatory effect of Fe on MoS2. It was found that the incorporation of Fe can reduce the average length and stacking layers of the MoS2 catalyst by 16.7% and 20.0%, respectively, thus exposing more active sites. Meanwhile, XPS, Raman and EXAFS results show that Fe transfers electrons to Mo to form electron-rich MoS2 and generate more defect sites on the surface of the FeMoS catalyst. For the VR hydrocracking activity test, it was demonstrated that the electron-rich MoS2 catalyst exhibits excellent performance, with the coke yield reduced by 32.0% and the total conversion rate of resin and asphaltene increased by 13.5%. Moreover, DFT results further reveal that the electrons transfer from Fe to Mo induces the change of chemical properties of the MoS2 surface and the adjustment of the d-band center, which promotes the migration of H and reduces the generation energy of coordinatively unsaturated sites. This study provides valuable insights into the design and upgrading of prominent oil-soluble bimetallic catalysts for slurry phase hydrocracking.

The impact of chemical functionalization of carbon nanotubes on the electrochemical performance of carbon fiber/pyrocarbon/carbon nanotube composites as potential materials for electrodes for nerve cell stimulation

In this work, we propose a new carbon–carbon (C–C) composites as a potential materials for electrodes for neural stimulation in neurodegenerative disorders. The C–C composites were made via chemical vapour deposition (CVD) synthesis of pyrocarbon on carbon fibers, with subsequent thermal spray deposition of carbon nanotubes (CNT). Different CNT types were tested to evaluate their impact on electrochemical and biological performance. Materials were analyzed for microstructure, surface chemistry, and electrochemical properties, then tested using SH-SY5Y neuroblastoma cells for biological assessment. TheC–C composites coated with a hydroxy-terminated CNT demonstrated significantly enhanced electrochemical properties, inparticular increased cathodal charge capacity upto12.51mCcm−2, a wide safe potential window of −1.53 to 1.26 V, and decreased impedance, and cut-off frequency (fcut-off = 0.16 kHz). No acute negative biological responses of the materials were detected after 48 h of exposition. Such properties significantly outperform the properties of platinum, which is the basic element of platinum electrodes, demonstrating the excellent performance of the obtained composites and showing it may constitute the basic element of carbon electrodes for nerve stimulation in the future. Our work presents the method for obtaining biologically inert carbon composite micro-electrodes which can potentially be adapted to neural stimulation.

Tailored Physicochemical Cues Direct Human Mesenchymal Stem Cell Differentiation through Epigenetic Regulation Using Colloidal Self-Assembled Patterns.

The extracellular matrix (ECM) shapes the stem cell fate during differentiation by exerting relevant biophysical cues. However, the mechanism of stem cell fate decisions in response to ECM-backed complex biophysical cues has not been fully understood due to the lack of versatile ECMs. Here, we designed two versatile ECMs using colloidal self-assembly technology to probe the mechanisms of their effects on mechanotransduction and stem cell fate regulation. Binary colloidal crystals (BCC) with a hexagonally close-packed structure, composed of silica (5 μm) and polystyrene (0.4 μm) particles as well as a polydimethylsiloxane-embedded BCC (BCCP), were fabricated. They have defined surface chemistry, roughness, stiffness, ion release, and protein adsorption properties, which can modulate the cell adhesion, proliferation, and differentiation of human adipose-derived stem cells (hASCs). On the BCC, hASCs preferred osteogenesis at an early stage but showed a higher tendency toward adipogenesis at later stages. In contrast, the results of BCCP diverged from those of BCC, suggesting a unique regulation of ECM-dependent mechanotransduction. The BCC-mediated cell adhesion reduced the size of the focal adhesion complex, accompanying an ordered spatial organization and cytoskeletal rearrangement. This morphological restriction led to the modulation of mechanosensitive transcription factors, such as c-FOS, the enrichment of transcripts in specific signaling pathways such as PI3K/AKT, and the activation of the Hippo signaling pathway. Epigenetic analyses showed changes in histone modifications across different substrates, suggesting that chromatin remodeling participated in BCC-mediated mechanotransduction. This study demonstrates that BCCs are versatile artificial ECMs that can regulate human stem cells' fate through unique biological signaling, which is beneficial in biomaterial design and stem cell engineering.

Role of regulating synthetic solvents in enhancing the catalytic performance of VPO catalysts for n-butane oxidation to maleic anhydride

Vanadium phosphorus oxide (VPO) catalysts have been successfully applied in the selective oxidation of n-butane to maleic anhydride (MA). However, there is still much work to be done to enhance the n-butane conversion while maintaining a relatively high MA selectivity. Regulating the solvents in preparing VPO catalysts is an effective way to improve the catalytic performance. In this work, the correlation between the physicochemical properties of VPO catalysts and the composition of solvents was investigated by combining various characterization techniques to reveal the role of regulating synthetic solvents in enhancing the catalytic performance. Varying synthetic solvents could regulate both the synthetic mechanism and crystal growth of VOHPO4·0.5H2O. The VOHPO4·0.5H2O tended to form a nice plate-like structure in isobutanol but possessed large crystallite sizes and a low specific surface area. The introduction of n-butanol prevented the continuous growth of VOHPO4·0.5H2O, reducing the crystallite sizes and thus increasing the specific surface area. Introducing the n-butanol also optimized the catalyst surface chemical properties. The best catalyst synthesized in a solvent containing 80 % n-butanol and 20 % isobutanol enhanced the n-butane conversion from 71 % to 87 % while maintaining the MA selectivity (64 %) almost unchanged compared to the catalyst synthesized in a conventional solvent.

Monitoring the Behavior of Na Ions and Solid Electrolyte Interphase Formation at an Aluminum/Ionic Liquid Electrode/Electrolyte Interface via Operando Electrochemical X-ray Photoelectron Spectroscopy.

In electrochemical energy storage devices, the interface between the electrode and the electrolyte plays a crucial role. A solid electrolyte interphase (SEI) is formed on the electrode surface due to spontaneous decomposition of the electrolyte, which in turn controls the dynamics of ion migration during charge and discharge cycles. However, the dynamic nature of the SEI means that its chemical structure evolves over time and as a function of the applied bias; thus, a true operando study is extremely valuable. X-ray photoelectron spectroscopy (XPS) is a widely used technique to understand the surface electronic and chemical properties, but the use of ultrahigh vacuum in standard instruments is a major hurdle for their utilization in measuring wet electrochemical processes. Herein, we introduce a 3-electrode electrochemical cell to probe the behavior of Na ions and the formation of SEI at the interface of an ionic liquid (IL) electrolyte and an aluminum electrode under operando conditions. A system containing 0.5 molar NaTFSI dissolved in the IL [BMIM][TFSI] was investigated using an Al working electrode and Pt counter and reference electrodes. By optimizing the scan rate of both XPS and cyclic voltammetry (CV) techniques, we captured the formation and evolution of SEI chemistry using real-time spectra acquisition techniques. A CV scan rate of 2 mVs-1 was coupled with XPS snapshot spectra collected at 10 s per core level. The technique demonstrated here provides a platform for the chemical analysis of materials beyond batteries.

Tuning the active plane and crystallinity of GaN microcrystals for high-performance supercapacitors through potassium nitrate-mediated synthesis

The surface atomic structure and crystallinity have an important effect on the electrochemical energy storage of electrode materials, in addition to the surface chemistry and textural properties. We report here for the first time that the surface atomic structure and crystallinity of GaN, a renowned electrode material for energy storage, can be tuned by controlling the annealing time via potassium nitrate-mediated synthesis. The underlying mechanism for GaN microcrystals with enhanced intensity ratios of I(002)/(100) and I(101)/(100) manifesting excellent rate performance has been revealed by theoretical computations. The energy storage mechanism and electrode kinetics of the GaN electrodes have been clarified. In addition, the GaN microcrystals-based symmetric supercapacitors empowered by 52 wt% H3PO4 can deliver an output voltage of 1.5 V and volumetric specific energy of 11.6 and 40.2 W h L−1 at a specific power of 392.2 W L−1 when operating at −60 and 60 °C, respectively, with electrode material on a commercial loading level.

Adjustable nanoarchitectonics of N-doping Yolk-Shell carbon spheres via “Pyrolysis-Capture” method for High-Performance supercapacitor

The energy storage capacity of porous carbon materials is closely tied to their surface structure and chemical properties. However, developing an innovative and straightforward approach to synthesize yolk-shell carbon spheres (YCs) remains a great challenge till date. Herein, we prepared a series of porous nitrogen-doped yolk-shell carbon spheres (NYCs) via a “pyrolysis-capture” method. This method involves coating the resorcinol–formaldehyde (RF) resin sphere with a layer of compact silica shell induced by 2-methylimidazole (ME) catalysis to produce a confined nano-space. Based on the confined effect of compact silica shell, volatile gases emitted from the RF resin and ME during pyrolysis can not only diffuse into the pores of the RF resin but can also be captured to form an outer carbon shell. This results in the tunable structures of NYCs materials. As the pyrolysis temperature rises, the shell thickness of NYCs reduces, the pore size expands, the roughness increases, and the N/O content of surface elements is enhanced. Notably, as an electrode material used forsupercapacitors,the optimized NYCs-800 exhibits excellent performance with a capacitance of 301.2F g−1 at the current density of 1 A/g and outstanding cycling life stability of 96.1% after 10,000 cycles. These results signify that controlling the surface structure and chemical properties of NYCs materials is an effective approach for constructing advanced energy storage materials.

Comparative study of machine learning based prediction of supercapacitance performance of activated carbon prepared from Bio-based Materials

The performance of electrochemical double-layer capacitors (EDLCs) is evaluated by the capacitance of activated carbon (AC) electrodes. The capacitance of AC electrodes is influenced by many factors such as precursor type, activation method, pore structure, surface chemistry and electrolytic properties. In this paper, we present a comparative study of machine learning based prediction of surface area, mesopore volume and total pore volume of activated carbon for energy storage applications. The ML models were trained on a dataset of synthetic data that were generated from the limited number of experimental data and which included the activation temperature, methylene blue number and iodine number of the activated carbon (AC). The best performing ML model was random forest model and XG boost model. The results of this study can be used to optimize the production of activated carbon and improve its performance in energy storage applications.

Hierarchical porous carbon nanofibrous membranes with elaborated chemical surfaces for efficient adsorptive removal of volatile organic compounds from air

Volatile organic compounds (VOCs) in the air pose great health risks to humans and the environment. Adsorptive separation technology has proven effective in mitigating VOC pollution, with the adsorbent being the critical component. Therefore, the development of highly efficient adsorbent materials is crucial. Carbon nanofibers, known for their physical–chemical stability and rapid adsorption kinetics, are promising candidates for removing VOCs from the air. However, the relatively simple porous structures and inert surface chemical properties of traditional carbon nanofibers present challenges in further enhancing their application performance further. Herein, a hierarchical porous carbon nanofibrous membrane was prepared using electrospinning technology and a one-step carbonization & activation method. Phenolic resin and polyacrylonitrile were used as co-precursors, with silica nanoparticles serving as the dopant. The resulting membrane exhibited a specific surface area of up to 1560.83 m2/g and surfaces rich in functional O-/N- groups. With a synergistic effect of developed micro- and meso-pores and active chemical surfaces, the carbon nanofibrous membrane demonstrated excellent adsorption separation performance for various VOCs, with comparable adsorption capacities and fast kinetics. Moreover, the membrane displayed remarkable reusability and dynamic adsorption performance for different VOCs, indicating its potential for practical applications.

Arthropods-mediated Green Synthesis of Zinc Oxide Nanoparticles using Cellar Spider Extract: A Biocompatible Remediation for Environmental Approach

This study presents an eco-friendly approach to synthesizing zinc oxide nanoparticles (ZnO NPs) using extracts from cellar spiders, addressing environmental and health concerns associated with conventional methods. The spider extract efficiently reduced zinc acetate dihydrate, and the synthesized ZnO NPs underwent comprehensive quantitative characterization, including size, shape, morphology, surface chemistry, thermal stability, and optical properties using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), zeta potential measurements, thermogravimetric analysis (TGA), and UV-vis spectroscopy. The nanoparticles exhibited intended characteristics, and their adsorption capability for methylene blue (MB) was quantitatively assessed using the Freundlich isotherm model and pseudo-second-order kinetic model, providing numerical insights into MB removal efficiency. The study demonstrates the potential of these green-synthesized ZnO NPs for applications in environmental remediation, wastewater treatment, and antibacterial therapies, contributing to both sustainable nanomaterial development and quantitative understanding of their functional properties.

Graphene Oxide as Novel Visible Light Active Photocatalyst: Synthesis, Modification by Nitrogen and Boron Doping, and Photocatalytic Application

Graphene oxide (GO) has become one of the emerging and important sole photocatalyst nanomaterials in recent years due to its exceptional/tunable optoelectronic properties, multifunctionality, and eco‐friendly nature. However, challenges remain in tuning surface chemistry, tailoring the band gap, developing doping strategies, and understanding the sole photocatalytic mechanism. This contribution investigated the synthesis of GO via the improved Hummers method by varying the ratio of the oxidizing agents (K2Cr2O7:KMnO4), as well as modifications by nitrogen (N) and boron (B) doping in view of its applications in photocatalytic degradation of organic dye pollutants. Furthermore, changes in surface chemistry, optical, compositional, morphological, and structural properties are investigated to understand the photocatalytic mechanism. The synthesized GO showed a broad spectrum of light absorption with a tunable band gap of 2.4–4.3 eV and exhibited more than 91% degradation of methylene blue dye under direct sunlight. However, the photocatalytic activity decreased after N and B doping attributed to reduced oxygen‐containing functional groups, low surface area, and dopants‐induced bonding configurations within the GO structure. This study provides a new insight into replacing metallic semiconductor photocatalysts with highly affordable, environmentally friendly, and potent metal‐free GO photocatalysts.

Customized heterostructure of transition metal carbides as high-efficiency and anti-corrosion electromagnetic absorbers

The ever-increasing presence of electronic devices and communication equipment imposes a critical demand for the development of highly efficient microwave absorption materials, as a means to combat the detrimental effects of electromagnetic (EM) wave pollution. The extraordinary advantages offered by heterointerface and defect engineering, coupled with their distinctive electromagnetic traits, infuse boundless energy into the development of MXene-based absorbers for EM attenuation. However, there is still a lack of understanding regarding the consequences of irreversible oxidation on the surface chemistry and dielectric properties of MXenes. Through the employment of heterointerface engineering strategy to promote interfacial charge accumulation and polarization, remarkable EM absorption properties coupled with corrosion resistance have been realized. The partially oxidized MXenes, particularly Ti3C2Tx and V2CTx, displayed remarkable reflection loss (RL) values of −56.83 dB and −52.13 dB, respectively. Additionally, the Nb2CTx composites showcased exceptional performance, offering a significantly broader bandwidth of 9.84 GHz. By conducting an extensive examination of the structural changes in MXenes, this work aims to elucidate the oxidation mechanisms and proposes a feasible method for producing MXenes with excellent absorption properties.

Aging effect on surface chemistry and sorption properties of atmospheric pressure plasma treated lignocellulosic jute fibers

Jute fibers are characterized by a heterogeneous chemical composition (cellulose and non-cellulosic components) and a complex layered structure with a hydrophobic surface outer layer responsible for their low wettability. In this work, after the removal of water-soluble components, raw jute fibers were subjected to atmospheric pressure dielectric barrier discharge (DBD) under different conditions (at 150 or 300 Hz) to tailor jute fiber surface structure and wettability. The research was focused on the aging effect during natural aging in a standard atmosphere investigated up to three weeks after DBD treatment. Alterations in the surface morphology of DBD-treated jute fibers were investigated by FE-SEM and AFM, while ATR-FTIR, XPS, and electrokinetic measurements were used to assess the changes in the jute fiber surface chemistry. Sorption properties were monitored through wetting time and capillary rise measurements. The sorption properties of DBD-treated jute fibers were improved (about 100 times lower wetting time and 15 % higher capillary rise height in comparison to untreated) due to the changes in surface chemistry (decreased lignin and hemicellulose content in parallel with cellulose oxidation) and morphology (about 4.6 times higher average roughness). The electrokinetic and sorption properties measurement confirmed the significance of aging effects in lignocellulosic fibers' functionalization using plasma.

VOCs (toluene) removal from iron ore sintering flue gas via LaBO3 (B = Cu, Fe, Cr, Mn, Co) perovskite catalysts: experiment and mechanism

Abstract The challenges posed by volatile organic compound (VOC) emissions in iron ore sintering flue gas are significant. La-based perovskite catalysts offer a promising solution for efficiently degrading VOCs. In this study, a series of LaBO3 (B = Cu, Fe, Cr, Mn, Co) perovskite catalysts were synthesized using the sol-gel method. The influence of various B-site elements on the catalyst’s structure and surface chemical properties was thoroughly examined. Simulations were conducted to assess the VOC reduction capabilities of these catalysts under conditions mimicking sintering flue gas composition. It was found that the crystallite size of the perovskite catalyst decreases as the ionic radius of the B-site elements increases, while the specific surface area, total pore volume, and average pore size increase correspondingly. Notably, LaCoO3 and LaMnO3 demonstrated exceptional activity, attributed primarily to their elevated surface oxygen concentration and oxygen migration capability, positioning them as highly promising materials for further development. Furthermore, a proposed mechanism elucidates the La-based perovskite catalytic reduction of toluene, wherein lattice oxygen and adsorbed oxygen undergo mutual conversion during the oxidation process. This mechanism aligns with the L-H and M-v-K models, providing a comprehensive understanding of the catalytic process.

Biofunctionalisation strategies of material surface and the inspired biological effects for bone repair

AbstractDue to trauma and disease, bone defects endanger the healthy life of human beings. At present, the gold standard for bone defect repair is still autologous bone transplantation and allogeneic bone transplantation. However, its insufficient source, potential disease transmission and immune rejection limit its clinical application. Therefore, the development of bone repair materials plays an important role in promoting bone repair. As the interface between material and tissue, the surface of the material plays an important role in the reaction after implantation, which determines the effectiveness of defect repair treatment. With the development of surface engineering and technology, bone repair materials have developed from biological inertia to biological activity by endowing various biological functions by controlling the composition, topological morphology and structure of the material surface etc. The inspired biofunctionalisation of material surface includes the capacities of inducing osteogenesis, promoting angiogenesis, antibacterial, immune regulation etc., as well as integration of postoperative repair and treatment. The authors review the biofunctionalisation of biomaterial surface and the inspired biological effects for bone repair, mainly including physical and chemical properties of material surface to regulate osteogenesis, and functional strategy of bone repair material surface.

Surface pretreatment of scheelite and cassiterite by gallic acid to achieve high efficiency flotation separation

Scheelite and cassiterite are common tungsten and tin oxide minerals that often coexist in nature. However, the similar oxidation degrees and solution and surface chemical properties of scheelite and cassiterite pose challenges to their flotation separation. Moreover, research in this area is currently limited. This study investigated the selective depression mechanism of gallic acid (GA) in the flotation separation of scheelite and cassiterite and successfully achieved the effective separation of the two minerals. Single mineral and artificially mixed mineral experiments were performed to analyze the flotation separation behavior of scheelite and cassiterite. The results revealed that in the absence of a depressant, scheelite and cassiterite exhibited recovery of 93.43 % and 89.72 %, respectively. After the addition of 5 × 10−4 mol/L GA to the mineral slurry, the grades of WO3 and Sn in the flotation concentrates were 48.93 % and 18.13 %, with recovery of 82.50 % and 31.62 %, respectively. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, zeta potential, adsorption amount, contact angle, and atomic force microscopy imaging analyses were conducted to examine the selective depression mechanism of GA in the flotation separation of scheelite and cassiterite. In the slurry, the cassiterite surface provided active Sn sites for the chemical adsorption of GA. Moreover, the phenolate O- donor atoms of the deprotonated polar groups of GA will undergo coordination with metal ions and then adsorb on the mineral surface. GA forms metal gallate through adsorption of its –COOH and –OH groups on mineral surface and produces textured oxide layer rich in OH groups, thus reducing the surface hydrophobicity of cassiterite and then depressing cassiterite. The selective adsorption of GA on the cassiterite surface hindered the further adsorption of NaOL, thereby reducing its surface hydrophobicity. Therefore, GA finally realized the flotation separation of the two minerals.