As-prepared Materials Research Articles

Facile Solvothermal Synthesis of NiO/g-C3N4 Nanocomposite for Enhanced Supercapacitor Application

There is a desperate demand for efficient energy storage systems to fulfill future energy demands. Herein, we exemplify a facile solvothermal approach followed by heat treatment to synthesize NiO/g-C3N4 nanocomposites for enhanced supercapacitor applications. The molar ratio of g-C3N4 is varied to achieve numerous nanostructures like nanoparticles and nanorods with optimum specific capacitance. Further, all as-prepared electrode materials are examined for supercapacitor application. The electrochemical behavior of prepared NiO/g-C3N4 nanocomposites is carried out under cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in a three-electrode cell under different electrolytes such as aqueous sodium sulphate electrolyte (1.0 M Na2SO4) and potassium hydroxide electrolyte (3.0 M KOH). Among all the electrode materials, NO-4 (1 : 2) shows the highest specific capacitance of 338.68 F/g at a scan rate of 2 mV/s and 161.3 F/g at a current density of 1 A/g in 1.0 M Na2SO4 electrolyte. Also, this electrode material shows 95.22 F/g at a scan rate of 2 mV/s in 3.0 M KOH electrolyte. The excessive specific capacitance of this electrode material is due to retarded charge transfer resistance in the interface at the electrode and electrolyte and a increased number of active sites. The investigation of the electrokinetics of all the prepared electrodes was also carried out, and it revealed the charge storage contribution of capacitive and diffusive parts which levitates the higher specific capacitance. The two-electrode study for evaluating supercapacitor performance is studied. The NO-4//NO-4 SSD in 1.0 M Na2SO4 electrolyte shows 18.23 F/g at a specific capacitance of 1 A/g with a corresponding energy density of 10.13 Wh/kg and a power density of 1.01 kW/kg, respectively.

A new Milarite type KMLS:Eu3+ orange-red-emitting phosphor for pc-white LEDs and Forensic applications

In this article, we present the synthesis and characterization of Eu3+-activated KMLS:Eu3+ phosphor for pc-WLEDs, latent fingerprint detection, and security ink applications. The structural phase, luminescent property, and colour purity of the as-prepared phosphor were investigated. XRD profiles and Rietveld refinement analysis confirm the hexagonal crystal system of the as-prepared phosphor. Concentration quenching effect was not observed up to 17 mol% of Eu3+. The site occupancy preferences of Eu3+ were investigated using the bond-valence model. The CIE-coordinate of optimal Eu3+ is estimated to be close to the standard NTSC value, and color purity is found to be above 90% for all the Eu3+ concentrations. Both Judd-Ofelt (J-O) analysis and asymmetric ratios revealed that the local environment around Eu3+ is asymmetric in nature. The radiative properties, including the stimulated emission cross section and optical gain parameters, of the highest concentration of Eu3+ (17mol%) were determined. Further, the results of thermal quenching analysis show that 91% of the luminescence intensity can be maintained at 150 °C, demonstrating good thermal stability. The multilevel ridge characteristics of the latent fingerprint stained with as-prepared phosphor could be clearly visualized under 254 nm UV excitation. All of the above results indicate that as-prepared phosphor materials can be suitable for use in forensic applications as well as solid state lighting applications.

Facile Synthesis of Functionalized Porous Carbon by Direct Pyrolysis of Anacardium occidentale Nut-Skin Waste and Its Utilization towards Supercapacitors.

Preparing electrode materials plays an essential role in the fabrication of high-performance supercapacitors. In general, heteroatom doping in carbon-based electrode materials enhances the electrochemical properties. Herein, nitrogen, oxygen, and sulfur co-doped porous carbon (PC) materials were prepared by direct pyrolysis of Anacardium occidentale (AO) nut-skin waste for high-performance supercapacitor applications. The as-prepared AO-PC material possessed interconnected micropore/mesopore structures and exhibited a high specific surface area of 615 m2 g-1. The Raman spectrum revealed a moderate degree of graphitization of AO-PC materials. These superior properties of the as-prepared AO-PC material help to deliver high specific capacitance. After fabricating the working electrode, the electrochemical performances including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy measurements were conducted in 1 M H2SO4 aqueous solution using a three-electrode configuration for supercapacitor applications. The AO-PC material delivered a high specific capacitance of 193 F g-1 at a current density of 0.5 A g-1. The AO-PC material demonstrated <97% capacitance retention even after 10,000 cycles of charge-discharge at the current density of 5 A g-1. All the above outcomes confirmed that the as-prepared AO-PC from AO nut-skin waste via simple pyrolysis is an ideal electrode material for fabricating high-performance supercapacitors. Moreover, this work provides a cost-effective and environmentally friendly strategy for adding value to biomass waste by a simple pyrolysis route.

Rare earth ions doped Bi2MoO6 luminescent materials: Pechini sol-gel synthesis, down-conversion and up-conversion multicolor emissions, and potential applications

A series of rare earth ions (Eu3+, Sm3+, Yb3+/Er3+, Yb3+/Ho3+, Yb3+/Tm3+) doped bismuth molybdate (Bi2MoO6) phosphors with excellent multicolor luminescence have been synthesized by a facile Pechini sol-gel method. XRD, EDX, and XPS results confirm the highly crystalline orthorhombic phase of Bi2MoO6 and verify that the rare earth ions (RE3+) are effectively integrated into the Bi2MoO6 matrix. During the synthesis process, the calcination conditions play an important role in obtaining the luminescent host matrix, and the optimal calcination condition for the Bi2MoO6 products is determined of 800 °C for 2 h. The Eu3+ and Sm3+ doped Bi2MoO6 samples display intense red and orange-red light under UV/visible excitation whereas the Yb3+/Ln3+ (Ln = Er, Ho, and Tm) doped Bi2MoO6 materials emit green, green, and blue colors when excited by NIR light. Both down-conversion (DC) and up-conversion (UC) multicolor luminescence are obtained by doping the proper Ln3+ activators into the Bi2MoO6 host. The doping concentrations of various RE3+ ions are optimized to generate advantageous phosphors and the luminescence mechanisms of RE3+ ions are systematically studied. The LED devices fabricated by Bi2MoO6:Yb3+/Ln3+ UC phosphors exhibit dazzling multicolor emissions under an injection current, which directly discloses that the as-prepared materials may be of great potential in LEDs and optoelectronic devices. Interestingly, the Bi2MoO6:Yb3+/Er3+/Eu3+ phosphors can simultaneously exhibit red and yellow-green DC emissions and green UC light under excitation of 464, 488, and 980 nm. The multi-mode emission features illustrate that the as-synthesized phosphors may have application prospects in anti-counterfeiting applications.

Photocatalytic effects on Au@TiO2 confined in BMIm.NTf2 ionic liquid for hydrogen evolution reactions

We report a photocatalytic device based on gold nanoparticles (AuNPs/TiO2) coated with an ionic liquid (IL) as a very active, stable, and versatile system for hydrogen evolution reactions (HERs) via methanol photo reforming (MPR) and photocatalytic water-splitting (WSR) reaction. The devices prepared by magnetron sputtering yield hybrid materials with direct Au–TiO2 interactions that were subsequently coated with BMIm.NTf2 (IL@Au@TiO2). The IL presence critically enhances the photocatalytic performance given its interaction with the AuNPs and TiO2 surfaces by decreasing the flat band energy levels and the Schottky barrier thickness. The results show an increase in the number of charge carriers yielding a capacitor-like effect generated by interactions of IL and Au@TiO2 particles. Apparent quantum yield (AQY) up to 28.3% under UV irradiation (365 nm) and 22.9% at 405 nm irradiation were observed in the HER employing the as-prepared materials.

Defect-Healing Induced Monoclinic Iron-Based Prussian Blue Analogs as High-Performance Cathode Materials for Sodium-Ion Batteries.

Prussian blue analogs (PBAs) have attracted wide interest as a class of ideal cathodes for rechargeable sodium-ion batteries due to their low cost, high theoretical capacity, and facile synthesis. Herein, a series of highly crystalline Fe-based PBAs (FeHCF) cubes, where HCF stands for the hexacyanoferrate, is synthesized via a one-step pyrophosphate-assisted co-precipitation method. By applying this proposed facile crystallization-controlled method to slow down the crystallization process and suppress the defect content of the crystal framework of the PBAs, the as-prepared materials demonstrate high crystallization and a sodium-rich induced rhombohedral phase. As a result, the as prepared FeHCF can deliver a high specific capacity of up to 152.0mAhg-1 (achieving ≈90% of its theoretical value) and an excellent rate capability with a high-capacity retention ratio of 88% at 10C, which makes it one of the most competitive candidates among the cathodes reported regarding both capacity and rate performance. A highly reversible three-phase-transition sodium-ion storage mechanism has been revealed via multiple in situ techniques. Furthermore, the full cells fabricated with as-prepared cathode and commercial hard carbon anode exhibit excellent compatibility which shows great prospects for application in the large-scale energy storage systems.

Laser-induced graphene electrodes scribed onto novel carbon black-doped polyethersulfone membranes for flexible high-performance microsupercapacitors

A facile and expandable methodology was successfully developed to fabricate laser-induced graphene from novel pristine aminated polyethersulfone (amPES) membranes. The as-prepared materials were applied as flexible electrodes for microsupercapacitors. The doping of amPES membranes with various weight percentages of carbon black (CB) microparticles was then performed to improve their energy storage performance. The lasing process allowed the formation of sulfur- and nitrogen-codoped graphene electrodes. The effect of electrolyte on the electrochemical performance of as-prepared electrodes was investigated and the specific capacitance was significantly enhanced in 0.5 M HClO4. Remarkably, the highest areal capacitance of 47.3 mF·cm−2 was achieved at a current density of 0.25 mA·cm−2. This capacitance is approximately 12.3 times higher than the average value for commonly used polyimide membranes. Furthermore, the energy and power densities were as high as 9.46 µWh·cm−2 and 0.3 mW·cm−2 at 0.25 mA·cm−2, respectively. The galvanostatic charge–discharge experiments confirmed the excellent performance and stability of amPES membranes during 5,000 cycles, where more than 100% of capacitance retention was achieved and the coulombic efficiency was improved up to 96.67%. Consequently, the fabricated CB-doped PES membranes offer several advantages including low carbon fingerprint, cost-effectiveness, high electrochemical performance and potential applications in wearable electronic systems.

Application of Strontium-Doped Bismuth Ferrate in Lithium-Sulfur Battery Cathode

The modification of high-performance lithium-sulfur battery cathode have been extensively studied. Suppressing the shuttle effect of polysulfide, solving the volume expansion of sulfur and the poor electrical conductivity of sulfur are the main directions for scientists to modify the cathode. Here we prepared bismuth ferrate powder doped with different molecular percentages of strontium by sol-gel method. Compared with the unmodified cell, the capacity and cycle stability were improved by adding as-prepared material to the cathode, which indicates that bismuth ferrate doped with certain amount of strontium plays a positive role in the cathode material modification.

Ultra-sonic assisted synthesis of nitrogen rich-g-C3N5 @MoO3 Z-scheme system for efficient removal of acetaminophen in aqueous environment via photo- and electro-catalytically

Herein, a nitrogen-rich g-C3N5 @MoO3 hybrid material has been prepared via an ultrasonic method, and its photo- and electro-catalytic properties were confirmed through the degradation and determination of acetaminophen (AP) were reported. The as-prepared materials were confirmed using some analytical techniques including XRD, FT-IR, DRS, BET, XPS, SEM, TEM, EDX, and mapping analysis. In addition to that, the electron transfer properties as well as recombination were confirmed by photocurrent and impedance spectroscopy. The optimized g-C3N5 @MoO3 (10%) photocatalyst shows an excellent electron transfer and reduces the recombination rate of electron and hole pairs which was confirmed by the degradation of AP in the aqueous environment. The degradation rate and kinetic constant were calculated and presented. The radical scavengers test was investigated and proposed the degradation mechanism of g-C3N5 @MoO3 (10%) via Z-scheme. In addition, the g-C3N5 @MoO3 (10%) catalyst was fabricated on GCE and utilized for the detection of AP via electrochemically (CV, DPV, and impedance). The limit of detection and sensitivity of the prepared g-C3N5 @MoO3 were investigated thoroughly and presented. The electro-catalytic mechanism was also proposed and studied. These higher photo- and electro-catalytic properties of g-C3N5 @MoO3 (10%) are due to the higher surface area and synergistic effect between both g-C3N5 and MoO3. Hope this method and fabrication of materials could be an effective way to prepare new nanomaterials with high performance.

Bismuth oxychloride microcrystals decorated carbon foams based on waste polyurethane elastomer for enhanced removal of methylene blue

Multicomponent materials containing nanoscale structures, the so-called “nanocomposites” are one of the fastest-growing areas of photocatalytic research. In this study, the nanocomposites of bismuth oxychloride (BiOCl) with porous carbon foam (CF) derived from waste polyurethane (PU) elastomers were developed by a simple hydrothermal method, and the photocatalytic performance of the as-prepared materials was investigated. The structure, morphology and optical properties of the composites were characterized in detail. The photocatalytic activity of the samples was evaluated by studying the degradation of methylene blue (MB) under UV-A irradiation. Even at a high MB concentration (0.5 mmol/L), excellent photocatalytic activity was observed, with an overall removal efficiency of 99.0% in 100 min of irradiation. Kinetic studies were also carried out for the degradation of MB by pristine BiOCl and CF-BiOCl. The photodegradation rate constants were evaluated by fitting the kinetic data with a pseudo-first-order model, and the rate constants of CF-BiOCl composites were higher than that of pristine BiOCl. The enhanced activity of the composites was due to the well-connected heterojunction interface, improved hydrophilicity, more reactive sites, and effective separation of photo-generated charges. Thus, our work combines the valuable waste PU-derived CFs with BiOCl, which provides a strategy to achieve circular economy and environmental remediation objectives.

Spherical Co/Co9S8 as electrocatalyst for hydrogen production from alkaline solution and alkaline seawater

Cobalt-based sulfide catalysts are considered as potential materials for electrocatalytic hydrogen production from seawater. Here, we have successfully prepared a Co/Co9S8 electrocatalyst with hollow spherical structure. As-prepared material exhibited excellent electrocatalytic activity in hydrogen evolution reaction (HER) in alkaline seawater. The overpotentials for Co/Co9S8 in alkaline seawater were measured as low as 136.2 mV, when reached a current density of 10 mA cm− 2. It also had good stability and could be maintained for 24 h in 1.0 M KOH and alkaline seawater. The results of SEM and TEM confirmed that the catalyst had excellent reaction structure. Due to the hollow structure, Co/Co9S8 showed remarkable catalytic performance for HER. The construction method of Co/Co9S8 hollow structure is an effective strategy to improve the performance of HER for seawater splitting.

Doping molybdenum oxides with different non-metal atoms to promote bioelectrocatalysis in microbial fuel cells

The sluggish extracellular electron transfer has been known as one of the bottlenecks to limit the power density of microbial fuel cells (MFCs). Herein, molybdenum oxides (MoOx) are doped with various types of non-metal atoms (N, P, and S) by electrostatic adsorption, followed by high-temperature carbonization. The as-prepared material is further used as MFC anode. Results indicate that all different elements-doped anodes can accelerate the electron transfer rate, and the great enhancement mechanism is attributed to synergistic effect of dopped non-metal atoms and the unique MoOx nanostructure, which offers high proximity and a large reaction surface area to promote microbe colonization. This not only enables efficient direct electron transfer but also enriches the flavin-like mediators for fast extracellular electron transfer. This work renders new insights into doping non-metal atoms onto metal oxides toward the enhancement of electrode kinetics at the anode of MFC.

Efficient ion conductivity enhancement mechanism induced by metal ion diffusion of SOFCs based on Fe-doped Gd2O3 electrolyte

Considerable efforts have been made in the past several decades to search for electrolytes that can work at low temperatures for solid oxide fuel cells (SOFCs). The rare-earth oxide Gd2O3 is a thermodynamically stable semiconductor material, but it has not yet been thoroughly explored for use in SOFC devices. In this study, a series of Fe-doped Gd2O3 with varying compositions were successfully synthesized to function as electrolytes for SOFCs. The as-prepared material, 10% Fe-doped Gd2O3 (Fe0.1Gd1.9O3), exhibited an excellent peak power density of 1352 mW/cm2 at 550 ℃, while the ionic conductivity reached 0.25 S cm−1. Various spectroscopic measurements, such as X-ray photoelectron spectroscopy, ultraviolet-visible (UV–vis) spectroscopy, and density functional theory calculations, were employed to understand the enhanced ion transportation mechanism and the improved performance of Fe-doped Gd2O3. The results showed that the Fe-doped Gd2O3 and energy bandgap tuning of electrolytes can significantly improve fuel cell performance at low temperatures, which is of great significance for the future development of low-temperature ceramic fuel cells.

Cistanches herba residues derived nitrogen and oxygen self-doped porous carbon for high performance supercapacitor

Cistanches herba residues are successfully employed as starting materials to prepare porous carbon through pre-carbonization and KOH activation method. The effects of pre-carbonization, KOH activation, and pre-carbonization temperature are investigated. The optimal structure of as-prepared carbon has abundant micropores, high specific surface area (2767.2 m2 g−1), good affinity for electrolyte, and high content of self-doped O (29.09%) and N (1.37%). The supercapacitors constructed with the as-prepared carbon materials are able to exhibit good specific capacitance of 360.26 F g−1 at 1.0 A g–1 and 191.3 F g−1 at 100 A g–1 in 6.0 mol L−1 KOH electrolyte. Moreover, the as-prepared carbon-based supercapacitors also display good energy density of 21.72 Wh kg−1 (at 250 W kg −1) and achieve 100% specific capacitance retention after 13,000 cycles at 10 A g−1 in 1.0 mol L−1 H2SO4 electrolyte. Overall, this research presents a new avenue for high-value utilization of traditional Chinese medicine residues.

Choline chloride/urea etched carbon fiber to improve the elasticity of biomass-based carbon aerogel for efficient oil-water separation

Carbon aerogel prepared using waste biomass as the carbon source can be utilized as the ideal absorption material for the remediation of oil spill accidents. However, the brittleness of the fiber and agglomeration of precursor fiber chains due to hydrogen bonding leads to poor mechanical properties and low absorption capacity of the carbon aerogel. The doping treatment used to overcome such defects still shows some deficiencies, such as high cost, cumbersome process, and part of the process involving toxicity. To overcome the agglomeration between the cellulose chains, a chemically-etched biomass-based carbon aerogel (EBCA) was prepared using pineapple cellulose nanofiber (CNF) etched by the deep eutectic solvents (DES) of choline chloride/urea under a low carbonization temperature of 400 °C. The as-prepared material, designated as EBCA-400, possesses a 3D structure with a huge BET specific surface area of 501.56 m2 g−1, a density of only 0.032 g cm−3 and a porosity of 97.3% with excellent elasticity performance and self-recovery performance owing to the enhancement of the surface roughness of fibers through DES etching. Also, EBCA-400 shows a superhydrophobicity with a water contact angle (WCA) of 157.6° and has a strong and fast absorption capacity for various oils in various scenarios, the absorption capacity for CCl4 reaches 288 times its own weight, and the absorption efficiency to CCl4 can still reach more than 97% of the maximum value even after 15 oil absorption-removal cycles. With the characteristics of very low density, huge porosity, excellent elasticity and superhydrophobicity as well as better reusability, EBCA-400 has great potential in oil spill remediation. This study provides a convenient and environment-friendly way for surface modification to improve the elasticity of carbon aerogel, which is crucial to the recovery of carbon aerogel for its reusability.

Corchorus Olitorius-Mediated Green Synthesis and Characterization of Nickel and Manganese Ferrite Nanoparticles

Developing a method for preparing Ni and Mn ferrites was the main objective of this study due to the importance of these materials in high-frequency applications. These ferrites were made by assisting combustion with dried leaves of Corchorus olitorius and then heating them to 700 °C. Several methods, including FTIR, XRD, TEM, and SEM/EDX, were used to characterize these ferrites. The thermal behavior, surface and magnetic properties of the as-prepared materials were determined. The results revealed that the method used is cheap, economical, environmentally friendly and makes it easy to produce the studied ferrites. FTIR, XRD, TEM, and SEM/EDX analyses show the formation of nanocrystalline ferrites with brittle, spongy and spinel-type structures, having two main vibration bands located around 400 cm−1 and 600 cm−1. However, TG-DTG results display the thermal behavior of different materials which consisted of unreacted oxides, carbon and the corresponding ferrites in the range of 300 °C to 600 °C. Moreover, complete conversion of the unreacted oxides to the equivalent ferrite was achieved by increasing heat treatment from 600 °C to 1000 °C. Ferrites are heated at 700 °C, which reduces their surface area. The magnetic properties of different ferrites calcined at 700 °C were estimated using the VSM technique. The magnetism of Fe-based materials containing Ni and Mn is 12.189 emu/g and 25.988 emu/g, respectively. Moreover, the squareness and coercivity of Ni ferrite are greater than for Mn ferrite.

Fabrication of N-rich graphitic carbon nitride supported CeO2 for improved photocatalytic charge separation and electrochemical electron transfer properties

Environmental issues have become a worldwide problem due to the trace-level contamination of toxic pollutants in aqueous environments, which affects wildlife and human health. Hence, it's essential to need to remove toxic pollutants from wastewater systems. In this work, CeO2 nanoparticles with various weight percentages of nitrogen-rich carbon nitride (C3N5 or CN) heterostructure have been prepared by a simple ultrasonication method. The physical and chemical properties of as-prepared materials were identified by various techniques (XRD, FT-IR, UV-DRS, BET, TEM, and EDX). The optimized CeO2@CN (3) heterostructure showed the best degradation performance and low-level determination towards paracetamol (PC) compared to all other sole and binary heterostructures. The CeO2@CN (3) exhibits a remarkable conversion percentage (99.8 %), and rate constant (0.2361 min−1). The major active photodegradation species were investigated by radical scavenging experiments and improved electron transfer properties were confirmed via photoluminescence and photocurrent spectra. The photodegradation mechanism and kinetic rate were also investigated and discussed. The effective catalytic activity of optimized CeO2@CN (3) heterostructure is majorly ascribed to the stronger interfacial effects and faster electron transfer which reduced the recombination. Moreover, the CeO2@CN (3) modified electrode showed good selectivity and high reproducibility. The PC sensor exhibits a wide sensing linear range from 0.04 – 546 µM, the detection limit is found to be 0.0011 µM and the sensitivity is 0.467 μA μM−1cm−2. This method was useful for determining the PC in real samples.

A facile synthesis of WO3/g-C3N4 composite for chemical sensing of dopamine and hydrazine

The sensing of the bio-molecules and environmentally toxic compounds has been of interest for many years. However, the close reduction potential values, and the variety in chemical nature of compounds hinders the simultaneous and accurate determination of these potentially interesting analytes. Herein a successful fabrication of the transition metal oxide/ graphitic-carbon nitride composite having suitable band-gap formation resulting in ease in reduction of the dopamine and hydrazine at different potentials such as −0.1 V and 0.5 V vs Ag/AgCl is reported. Similarly, the composite material has been characterized by the SEM-EDX, XRD, FTIR and electrochemical analysis. The sensor response analysis revealed that the as-prepared material has superior LOD for hydrazine (1 nM with S/N = 3) as compared to the dopamine, due to the ease of reduction of hydrazine as compared to the dopamine.

Three-in-one LaNiO3 functionalized separator boosting electrochemical stability and redox kinetics for high-performance Li-S battery

The lithium-sulfur (Li-S) battery, as one of the energy storage devices, has been in the limelight due to its high theoretical energy density. However, the poor redox kinetics and the “shuttle effect” of polysulfides severely restrict the use of Li-S batteries in practical applications. Herein, a novel bimetallic LaNiO3 functional material with high electrical conductivity and catalytic property is prepared to act as a high-efficiency polysulfide shuttling stopper. The three LaNiO3 samples with different physical/chemical characteristics are obtained by controlling the calcination temperature. In conjunction with the high electrical conductivity and excellent catalytic properties of the as-prepared materials, the appropriate chemisorption toward polysulfides offers great potential to enhance electrochemical stability for high-performance Li-S batteries. Particularly, the Li-S cell with the separator modified by such functional material gives a specific capacity of 658 mA h g−1 after 500 cycles at a high current density of 2 C. Even with high sulfur loading of 6.05 mg cm−2, the Li-S battery still exhibits an areal specific capacity of 2.81 mA h cm−2 after 150 cycles. This work paves a new avenue for the rational design of materials for separator modification in high-performance Li-S batteries.

Effective Removal of Fe (III) from Strongly Acidic Wastewater by Pyridine-Modified Chitosan: Synthesis, Efficiency, and Mechanism.

A novel pyridine-modified chitosan (PYCS) adsorbent was prepared in a multistep procedure including the successive grafting of 2-(chloromethyl) pyridine hydrochloride and crosslinking with glutaraldehyde. Then, the as-prepared materials were used as adsorbents for the removal of metal ions from acidic wastewater. Batch adsorption experiments were carried out to study the impact of various factors such as solution pH value, contact time, temperature, and Fe (III) concentration. The results showed that the absorbent exhibited a high capacity of Fe (III) and the maximum adsorption capacity was up to 66.20 mg/g under optimal experimental conditions (the adsorption time = 12 h, pH = 2.5, and T = 303 K). Adsorption kinetics and isotherm data were accurately described by the pseudo-second-order kinetic model and Sips model, respectively. Thermodynamic studies confirmed that the adsorption was a spontaneous endothermic process. Moreover, the adsorption mechanism was investigated using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results revealed the pyridine group forms a stable chelate with iron (III) ions. Therefore, this acid-resistant adsorbent exhibited excellent adsorption performance for heavy metal ions from acidic wastewater compared to the conventional adsorbents, helping realize direct decontamination and secondary utilization.