Synthesis Calcination Research Articles

Effective Activation of Peroxymonosulfate by Oxygen Vacancy Induced Musa Basjoo Biochar to Degrade Sulfamethoxazole: Efficiency and Mechanism.

Biochar materials have garnered attention as potential catalysts for peroxymonosulfate (PMS) activation due to their cost-effectiveness, notable specific surface area, and advantageous structural properties. In this study, a suite of plantain-derived biochar (MBB-400, MBB-600, and MBB-800), possessing a well-defined pore structure and a substantial number of uniformly distributed active sites (oxygen vacancy, OVs), was synthesized through a facile calcination process at varying temperatures (400, 600, and 800 °C). These materials were designed for the activation of PMS in the degradation of sulfamethoxazole (SMX). Experimental investigations revealed that OVs not only functioned as enriched sites for pollutants, enhancing the opportunities for free radicals (•OH/SO4•-) and surface-bound radicals (SBRs) to attack pollutants, but also served as channels for intramolecular charge transfer leaps. This role contributed to a reduction in interfacial charge transfer resistance, expediting electron transfer rates with PMS, thereby accelerating the decomposition of pollutants. Capitalizing on these merits, the MBB-800/PMS system displayed a 61-fold enhancement in the conversion rate for SMX degradation compared to inactivated MBB/PMS system. Furthermore, the MBB-800 exhibited less cytotoxicity towards rat pheochromocytoma (PC12) cells. Hence, the straightforward calcination synthesis of MBB-800 emerges as a promising biochar catalyst with vast potential for sustainable and efficient wastewater treatment and environmental remediation.

MWCNT@TiSiO4 nanocomposite for dispersive solid phase extraction of traces cadmium in food and environmental samples

Cadmium contamination presents substantial hazards to both human health and the environment due to its persistent presence in ecosystems and toxic characteristics. It accumulates in soil and water, causing chronic renal and respiratory issues, and carcinogenicity. Effective detection for monitoring the environmental and public health effects of Cd is required. This study addresses a new separation and enrichment method with a novel MWCNT@TiSiO4 nanocomposite synthesized via sol-gel and calcination synthesis techniques. A comprehensive characterization of the nanocomposite was conducted utilizing X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) Spectroscopy, and Field Emission-Scanning Electron Microscopy (FE-SEM) techniques. The nano-sorbent was utilized in conjunction with dispersive solid phase extraction (DSPE) to separate and preconcentrate trace amounts of Cd(II) prior to its determination by using flame atomic absorption spectrometry (FAAS). The optimization of analytical parameters, including pH, sample and eluent volumes, sorbent quantities, and eluent composition, was studied. The effect of matrix components was investigated. The method showed a low limit of detection (LOD), limit of quantification (LOQ), and relative standard deviation (%RSD) of 0.053 ng mL−1, 0.176 ng mL−1, and 4.6%, respectively. The method was validated by analyzing certified reference materials. The developed methodology was applied to determine Cd(II) levels in water, tobacco, and food samples. The recovery values were quantitative (90–101%). The maximum and minimum concentrations of Cd in food samples were in shrimp (47.87 ng g−1) and lentil (11.25 ng g−1), respectively.

One-step calcination synthesis of interface-coherent crystallized and surface-passivated LiNi0.5Mn1.5O4 for high-voltage lithium-ion battery

One-step calcination synthesis of interface-coherent crystallized and surface-passivated LiNi0.5Mn1.5O4 for high-voltage lithium-ion battery

Two-step calcination synthesis of 1T/2H mixed-phase MoS2/g-C3N4 with sulfur defects for efficient removal of Cr(VI) from water

In this paper, 1T/2H mixed-phase MoS2/g-C3N4 composites (1T/2H-MG) were successfully synthesized by a simple two-step calcination method and used for Cr(VI) removal from aqueous environment. A series of characterization methods were used to characterize the microstructure and surface morphology of the prepared materials. The experiment results showed that 1T/2H-MG (1:12) composite with good pH and temperature adaptability could completely remove Cr(VI) (100 mg∙L–1) within 50 min and showed an excellent adsorption capacity of 342.06 mg∙g–1. The presence of abundant sulfur defects in 1T/2H-MG composite could provide more adsorption and reduction active sites, which was the main reason for the enhanced removal efficiency of 1T/2H-MG in comparison with pure MoS2 and g-C3N4. This work not only contributes an excellent adsorbent for the wastewater treatment, but also provides evidences for the defects engineering.

Rational Construction ZnO@C3N4 Composite with Enhanced Photocorrosion‐Resistance for Simultaneous Removal of RhB‐MO Mixed Pollutants

AbstractA series of ZnO@C3N4 composites with excellent photocorrosion‐resistant and photocatalytic activity were prepared by using one‐pot calcination synthesis for the removal of organic pollutants from wastewater. Compared with ZnO and C3N4, ZnO@C3N4 presented the excellent photocatalytic performance for RhB, MO, DBP and RhB‐MO mixed systems under UV conditions. The degradation rate constants of 70ZnO@30 C3N4 for RhB and DBP were 7.66 and 4.71 times higher than those of ZnO, respectively. For RhB‐MO mixed systems, the rate constant was 4.65 times higher than that of RhB alone. XRD and FTIR analyses indicated a strong phase interaction between two components of ZnO@C3N4 composites. XPS results confirmed the formation of ZnO/C3N4 heterojunction. In addition, the mechanisms underlying the highly efficient catalytic performance of ZnO@C3N4 composites in the degradation of organic pollutants were also analyzed. It can be attributed to the fact that a tight contact at the interface and well‐matched band edge position between ZnO and C3N4 can effectively separate and transfer photoinduced carriers for organic pollutant degradation, rather than react with ZnO itself. This study clearly demonstrates a simple way to fabricate ZnO@C3N4 with photocorrosion‐resistant and to apply them for the removal of multi‐component organic pollutants from wastewater by photocatalysis.

Study on CuO/g–C3N4 S–Scheme heterojunction for enhanced visible-light-driven photocatalytic degradation of xanthate

Xanthate wastewater is a serious threat to the surrounding environment of mining sites, and it is important to use visible light photocatalytic technology to remove xanthatefrom wastewater. In this paper, a simple hydrothermal calcination synthesis route was used to grow submicron-sized CuO onto the surface of g-C3N4 for the degradation of xanthate in mineral processing wastewater. The results showed that the CuO/g–C3N4–0.4 composite catalyst degraded xanthate with an efficiency of 83.2% in 120 min, which was 6.2 times higher than that of pure g-C3N4. The catalyst materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. It was found that the excellent photocatalytic performance of the composite was attributed to the construction of S-scheme CuO/g–C3N4–Xheterojunction, which not only broadened the light absorption range but also retained the strong redox ability of holes and electrons to participate in the reaction while efficiently separating the photoinduced carriers. Based on the results of active substance capture, an S-scheme charge transfer model was proposed and the photodegradation mechanism of xanthate was reasonably elucidated.

Visible-Light-Driven Photocatalytic Dehydrogenation of Alcohols on TiO2 via Ligand-to-Metal Charge Transfer for Coproduction of H2 and Aldehydes.

Developing visible-light-driven photocatalysts for the catalytic dehydrogenation of organics is of great significance for sustainable solar energy utilization. Here, we first report that aromatic alcohols could be efficiently split into H2 and aldehydes over TiO2 under visible-light irradiation through a ligand-to-metal charge transfer (LMCT) mechanism. A series of TiO2 catalysts with different surface contents of the hydroxyl group (-OH) have been synthesized by controlling the hydrothermal and calcination synthesis methods. An optimal H2 production rate of 18.6 μmol h-1 is obtained on TiO2 synthesized from the hydrothermal method with a high content of surface -OH. Experimental characterizations and comparison studies reveal that the surface -OH markedly influences the formation of LMCT complexes and thus changes the visible-light-driven photocatalytic performance. This work is anticipated to inspire further research endeavors in the design and fabrication of visible-light-driven photocatalyst systems based on the LMCT mechanism to realize the simultaneous synthesis of clean fuel and fine chemicals.

One-step calcination synthesis of 2D/2D g-C3N4/WS2 van der Waals heterojunction for visible light-induced photocatalytic degradation of pharmaceutical pollutants.

It is well-documented that accumulation of pharmaceutically active compounds (PhACs), such as antibiotics, in aquatic ecosystems is a prominent environmental hazard. Herein, a series of 2D materials-based heterojunctions, conceptualized based on the integration of graphitic carbon nitride (g-C3N4) with tungsten disulfide (WS2), was fabricated through a facile one-step calcination process, and systematically evaluated for eliminating tetracycline (TC) and sulfamethoxazole (SMX) from aqueous matrices. The microstructure, optical properties, and surface chemistry of the as-prepared composites were examined with a range of microscopy and spectroscopy techniques. In comparison with pristine g-C3N4 or bare WS2, the g-C3N4/WS2 material, with optimal WS2 loading, showed significantly improved photocatalytic activity, towards degradation of TC (84%) and SMX (96%), under visible light. Free radical scavenging experiments revealed that superoxide anions and hydroxyl radicals were predominantly responsible for the rapid breakdown of the PhACs. In addition, the dissociation intermediates and residues were identified and the plausible photocatalytic degradation pathways of TC and SMX over the as-constructed 2D/2D heterojunction were discussed. Further, the photocatalysis end products were non-toxic, as inferred via the resazurin cell viability assay, employing Escherichia coli as a model organism. Most importantly, the 2D/2D g-C3N4/WS2 architecture was structurally resilient and exhibited a fairly stable cycling performance for persistent usage in wastewater treatment. The outcomes of this study testify that 2D/2D heterojunction of g-C3N4 fragments and WS2 nanosheets holds great promise for destroying antibiotics or their metabolites, usually present in wastewaters.

One-Step Calcination Synthesis of Bulk-Doped Surface-Modified Ni-Rich Cathodes with Superlattice for Long-Cycling Li-Ion Batteries.

Nickel-rich (Ni≥90 %) layered cathodes are critical materials for achieving higher-energy-density and lower-cost next-generation Li-ion batteries (LIBs). However, their bulk and interface structural instabilities significantly impair their electrochemical performance, thus hindering their widespread adoption in commercial LIBs. Exploiting Ti and Mo diffusion chemistry, we report one-step calcination to synthesize bulk-to-surface modified LiNi0.9 Co0.09 Mo0.01 O2 (NCMo90) featuring a 5 nm Li2 TiO3 coating on the surface, a Mo-rich Li+ /Ni2+ superlattice at the sub-surface, and Ti-doping in the bulk. Such a multi-functional structure effectively maintains its structural integrity upon cycling. As a result, such NCMo90 exhibits a high initial capacity of 221 mAh g-1 at 0.1 C, excellent rate performance (184 mAh g-1 at 5 C), and high capacity retention of 94.0 % after 500 cycles. This work opens a new avenue to developing industry-applicable Ni-rich cathodes for next-generation LIBs.

One‐Step Calcination Synthesis of Bulk‐Doped Surface‐Modified Ni‐Rich Cathodes with Superlattice for Long‐Cycling Li‐Ion Batteries

AbstractNickel‐rich (Ni≥90 %) layered cathodes are critical materials for achieving higher‐energy‐density and lower‐cost next‐generation Li‐ion batteries (LIBs). However, their bulk and interface structural instabilities significantly impair their electrochemical performance, thus hindering their widespread adoption in commercial LIBs. Exploiting Ti and Mo diffusion chemistry, we report one‐step calcination to synthesize bulk‐to‐surface modified LiNi0.9Co0.09Mo0.01O2 (NCMo90) featuring a 5 nm Li2TiO3 coating on the surface, a Mo‐rich Li+/Ni2+ superlattice at the sub‐surface, and Ti‐doping in the bulk. Such a multi‐functional structure effectively maintains its structural integrity upon cycling. As a result, such NCMo90 exhibits a high initial capacity of 221 mAh g−1 at 0.1 C, excellent rate performance (184 mAh g−1 at 5 C), and high capacity retention of 94.0 % after 500 cycles. This work opens a new avenue to developing industry‐applicable Ni‐rich cathodes for next‐generation LIBs.

MOFs-derived Mn/C composites activating peroxymonosulfate for efficient degradation of sulfamethazine: Kinetics, pathways, and mechanism

Both manganese oxides (MnOx) and carbon materials hold promise for persulfate activation to remediate polluted waterbodies. However, the aggregation of MnOx during the calcination synthesis and lower activity to persulfate of carbon materials seriously limit their industrial application. In this work, two Mn/C composites (MnOx-NA and MnOx-A) were synthesized from manganese-metal organic frameworks (MOFs) under nitrogen atmosphere and air atmosphere calcination respectively. The prepared MnOx-NA exhibited more excellent peroxymonosulfate (PMS) activation performance than MnOx-A, and almost 100% sulfamethazine (SMT) could be removed by the MnOx-NA/PMS system within 30 min. Moreover, the MnOx-NA/PMS system exhibited impressive stability even after 10 cycles and displayed high anti-interference ability to Cl−, ClO4−, CO32−, SO42−, NO3− and humic acid (HA). In addition, the oxidation system could efficiently remove SMT in different aqueous matrices. Three possible pathways of SMT degradation were proposed according to the LC-MS analysis. Electron paramagnetic resonance (EPR), quenching experiments, and cyclic voltammetry experiments revealed that SMT degradation predominantly occurred through a catalyst-mediated electron transfer pathway. Material characterization and electrochemical impedance spectroscopy (EIS) analysis showed that the derived carbon species strengthened the MnOx-NA's electron-transfer capability and promoted the uniform distribution of MnOx particles on the carbon materials surface, which significantly improved MnOx-NA's PMS activation performance. This study introduces a facile method for the design of Mn/C composites PMS activator and provides theoretical guidance for water pollution remediation.

Preparation of 2D/2D g-C3N4/Ti3C2 MXene composites by calcination synthesis method for visible light photocatalytic degradation of tetracycline

Preparation of 2D/2D g-C3N4/Ti3C2 MXene composites by calcination synthesis method for visible light photocatalytic degradation of tetracycline

One-step calcination synthesis of accordion-like MXene-derived TiO2@C coupled with g-C3N4: Z-scheme heterojunction for enhanced photocatalytic NO removal

This work explored an effective treatment method for removing NO from simulated flue gas at normal temperature. We synthesized accordion-like MXene-derived TiO2@C coupled with g-C3N4 (TiO2@C/g-C3N4) via one-step calcination utilizing Ti3AlC2, fluoride salts and melamine as raw materials in CO2 atmosphere. One-step calcination process simultaneously achieved the etch of Al layers of Ti3AlC2 by molten fluoride salts, the generation of g-C3N4 with melamine as precursor and the oxidation of Ti3C2 by CO2. TiO2@C/g-C3N4 for photocatalytic activation of hydrogen peroxide (H2O2) had as high as 94.0% removal rate of NO at parts per million level in a normal temperature environment. This efficiency was 5.3 times and 8.0 times that of TiO2@C/g-C3N4 and H2O2 individually, due to the synergy between photocatalysis and H2O2 oxidation. Meantime, TiO2@C/g-C3N4 exhibited an enhanced performance compared with g-C3N4 (40.3%) and TiO2@C (64.1%) for Z-type heterojunction accelerating the separation of electron-hole pairs. The mechanism was proposed that Z-type TiO2@C/g-C3N4 heterojunction activated H2O2 under visible light to generate hydroxyl radical and superoxide radical for oxidation of NO.

Calcination synthesis of tin niobate loaded porous carbon nitride S-scheme heterojunction for photocatalytic H2 production and tetracycline degradation

The fabrication of heterojunctions with large interfacial contact areas is an effective technique for the development of high-performance photocatalysts. Step-scheme (S-scheme) heterojunctions with enhanced charge separation and strong redox ability have been regarded as promising photocatalytic materials in recent years. Herein, an S-scheme heterojunction based on tin niobate nanosheets and porous carbon nitride was designed and constructed using a one-plot calcination method. The multifunctional photocatalyst showed greatly enhanced photocatalytic activity and outstanding chemical stability toward hydrogen evolution and tetracycline hydrochloride (TCH) degradation, with reaction rates 1.64 and 12.28 times higher for TCH degradation and H2 production, respectively, compared to those of pristine g-C3N4. Meanwhile, TCH degradation experiments at different pH, TCH concentrations, catalyst dosages, and anions were evaluated. The main reactive species, possible degradation intermediates, and pathways were determined. The heterojunction exhibited a high surface area and broad visible-light absorption, which are responsible for the improved photocatalytic performance and high apparent quantum yield (AQY). In addition, an S-scheme charge transfer mechanism under an internal electric field was proposed following the results of in-situ irradiation X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS), ESR, and Mott-Schottky measurements. This study offers a reasonable way to design another novel 2D/2D S-scheme heterojunction photocatalysts for energy and environmental applications.

Synthesis and characterization of analcime (ANA) zeolite using a kaolinitic rock

Analcime is nowadays an important component in dental porcelain systems, in heterogeneous catalysis, in the nanoelectronic field, in selective adsorption and in stomatology (dental filling and prosthesis). Analcime synthesis from an impure, silica-rich kaolinite rock coming from Romana (Sassari, Italy) is here presented. A synthesis protocol is proposed that aims to make an improvement of synthesis conditions compared to the past. The hydrothermal treatment is in fact here achieved without aging times and without the use of sodium silicate or other additional silica source reported in the literature. Lower calcination temperature, synthesis temperature and crystallization time are verified in this work. The kaolin is subjected to calcination at the temperature of 650 °C and then mixed with NaOH. The experiment is performed at ambient pressure and 170 ± 0.1 °C. The degree of purity of analcime is calculated in 97.57% at 10 h. Analcime is characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, inductively coupled plasma optical emission spectrometry and thermal analysis. Density is also calculated. Cell parameters and the amount of amorphous phase in the synthesis powders is estimated with quantitative phase analysis using the combined Rietveld and reference intensity ratio methods. The experimental conditions make the synthesis protocol particularly attractive from an economic point of view. Also this work does not use a commercial kaolin but silica-rich impure kaolinitic rock from a disused quarry. This further reduces the costs of the experimental protocol. It also gives the protocol an added value, as the synthesis of a useful mineral is obtained through the valorization of an otherwise unused georesource. Both chemical and physical characterization of analcime is satisfactory making the experimental protocol very promising for an industrial transfer.

Effect of phase type in the alumina precursor on the flash calcination synthesis

Economical alumina precursors, derived from bauxite or nepheline ores, were calcined through a very short time process. Results showed that phases of the precursor are a key parameter on the flash calcination process. The number of structural water molecules is the dominant phenomenon. A porous and fine structure of activated alumina was developed as the hydroxyl groups are explosively driven off and establish a hydrothermal condition. The presence of gibbsite phase with larger particle size and most structural water molecules has better product properties in comparison of other alumina precursors phase with small particle size because water vapor pressure achieves a critical value for splitting particles and developing nucleation desirable phases. The changes rate of properties reaches to its maximum value for gibbsite phase at lower calcination temperature. FESEM images showed the precursor phase forms different morphologies of products like, nanodimensional, a coral-like co-continuous or loose particles surrounded with macropores.

One-step calcination synthesis of WC–Mo2C heterojunction nanoparticles as novel H2-production cocatalysts for enhanced photocatalytic activity of TiO2

A WC–Mo2C@C modified-TiO2 (WC–Mo2C@C/TiO2) photocatalyst was prepared by loading WC–Mo2C@C heterojunction nanoparticles on TiO2 surface and its H2-production rate was 90.3, 3.6, and 2.5 times higher than that of TiO2, Mo2C@C/TiO2, and WC@C/TiO2, respectively.

An efficient strategy for the enhancement of adsorptivity of microporous carbons against gaseous formaldehyde: Surface modification with aminosilane adducts

In an effort to develop a cost-effective mitigation tool for volatile organic compounds, particularly formaldehyde (FA), microporous activated carbon (AC) was modified into three different forms of AC-1, AC-2, and AC-3 using a raw commercial AC product (AC-0). First, AC-1 and AC-2 were produced by the modification of AC-0 with N/S heteroatoms using identical mixture of dicyandiamide and thiourea precursors through either solvothermal (AC-1) or microwave-assisted calcination (AC-2) synthesis. Second, aminosilane-functionalized AC (AC-3) was prepared solvothermally using N-[3-(Trimethoxysilyl)propyl]ethylenediamine reagent. The relative adsorption performances for gaseous FA (1 ppm) in terms of 10% breakthrough volume (BTV10: L atm g−1) at near-ambient conditions (25 °C and 1 atm) were AC-3 (132) > AC-2 (66.5) > AC-1 (14.2) > AC-0 (10.4). In a comparison based on partition coefficients (mole kg−1 Pa−1) at BTV10, AC-3 outperformed AC-0 by a factor of 214, while the adsorption performance of AC-2 was 36-times higher than AC-1. The enhanced performance of AC-2 over AC-1 reflected the effect of the microwave synthesis protocol on the improvement of surface chemistry (e.g., N/S doping) and texture (e.g., surface area and pore volume) of AC-based adsorbents as compared to conventional solvothermal method. Further, the prominent role of surface chemistry (e.g., relative to textural properties), as observed with the increases in the amount of doped functional elements (including N:C and silicon:C ratios), is supported by the apparent dependence of performance on the selected modification procedures. Based on kinetic and X-ray photoelectron spectroscopy analyses, the superiority of aminosilylated AC-3 can be attributed to a synergistic effect between physisorption (e.g., pore diffusion) and chemical interactions of the FA carbonyl (C=O) group with amine and silica functionalities (via Mannich coupling [Schiff base] and cycloaddition reaction mechanisms, respectively). This confirms the significance of surface chemistry, relative to pore diffusion, in achieving maximum adsorption of gaseous FA molecules.

Two‐step calcination synthesis of Z‐scheme α‐Fe2O3/few‐layer g‐C3N4 composite with enhanced hydrogen production and photodegradation under visible light

AbstractSolar photocatalytic technology is of great significance for adjusting energy structure and environmental improvement. Developing an efficient and low‐cost photocatalyst is key to realizing the conversion of solar to chemical energy. In this study, α‐Fe2O3‐modified few‐layer g‐C3N4 hybrids (α‐Fe2O3/FL g‐C3N4) were successfully prepared by a two‐step calcination route with a mixture of α‐Fe2O3 and melamine. The samples were characterized by Thermogravimetric analysis, X‐ray diffraction, Fourier transform infrared, scanning electron microscope, transmission electron microscope, High‐resolution transmission electron microscopy, X‐ray photoelectron spectroscopy, Brunauer–Emmett–Teller, UV–Vis absorption spectrum, photoluminescence, and Time‐resolved photoluminescence spectroscopy; furthermore, their photoelectrochemical measurements and their photocatalytic performances were evaluated by visible light‐driven hydrogen evolution and degradation of RhB. The results showed that the hydrogen production activity and degradation ability of α‐Fe2O3/FL g‐C3N4 were significantly enhanced compared with those of α‐Fe2O3/multilayer g‐C3N4 (α‐Fe2O3/ML g‐C3N4) and FL g‐C3N4. The enhanced photoactivities were mainly attributed to the synergistic effect between the increased visible‐light absorption, enhanced surface area, and highly efficient electron transfer and separation on the Z‐type heterojunction interface. This work not only provides evidence for the formation of FL g‐C3N4 nanosheets using a thermal exfoliation method but also provides new insights into the interfacial charge carrier dynamics of Z‐scheme α‐Fe2O3/FL g‐C3N4 heterostructures for photocatalytic H2 generation and pollutant degradation.

One-pot calcination synthesis of Cd0.5Zn0.5S/g-C3N4 photocatalyst with a step-scheme heterojunction structure

Cd0.5Zn0.5S/g-C3N4 (CZS/CN) step-like heterojunction composites were facilely synthesized by annealing a sandwich of cadmium−zinc−thiourea precursors in one pot. The types of the used raw materials and the preparation procedure were simplified as much as possible in this work. The obtained hybrid exhibited enlarged specific surface area and higher separation/transfer efficiency of charge carriers compared to pure Cd0.5Zn0.5S and g-C3N4, thus exhibited much enhanced photocatalytic efficiency for dye degradation under visible-light irradiation. The interfacial charge-transfer mechanism of the formed step-scheme (S-scheme) heterojunction between Cd0.5Zn0.5S and g-C3N4 were carefully investigated and discussed. This work could widen the application prospect of the CdxZn1–xS/g-C3N4 composite and provide new ideas to the design and fabrication of novel heterojunctions with robust photocatalytic performance.