Differential Scanning Calorimetry Thermogravimetric Analysis Research Articles

Synthesis and characterization of magnesium doped titania for photocatalytic degradation of methyl red

Magnesium doped titania (MDT) composites with varying magnesium weight percentages (1–5 wt. %) were synthesized through a very simple and economical route of sol-gel method. The reactants used for making alkoxide precursor were titanium tetrachloride whereas magnesium nitrate was used for doping magnesium into titania in a mixture of solvents i.e. ethyl alcohol and water. The optimum conditions maintained for preparing sol were pH 3 and 60°C temperature with constant stirring for 2 hours. The gel obtained after drying the sol for each sample was calcined at 500°C for two hours. The powdered composite samples thus prepared were characterized by X-ray diffraction analysis (XRD), differential scanning calorimetry-thermogravimetric analysis (DSC-TGA), infrared spectroscopy (IR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The samples were evaluated for their photocatalytic activity against methyl red dye under UV light irradiation and the dye degradation was examined by UV-Vis spectrophotometer. The results confirmed the excellent photocatalytic activity of synthesized magnesium doped TiO2 for the degradation of methyl red dye where MDT-3 having 3% magnesium doping exhibited the maximum degradation i.e. 96.8%.

Relationships between the Decomposition Behaviour of Renewable Fibres and Their Reinforcing Effect in Composites Processed at High Temperatures.

Engineering polymers reinforced with renewable fibres (RF) are an attractive class of materials, due to their excellent mechanical performance and low environmental impact. However, the successful preparation of such composites has proven to be challenging due to the low thermal stability of RF. The aim of the present study was to investigate how different RF behaves under increased processing temperatures and correlate the thermal properties of the fibres to the mechanical properties of composites. For this purpose, hemp, flax and Lyocell fibres were compounded into polypropylene (PP) using a co-rotating twin screw extruder and test specimens were injection moulded at temperatures ranging from 180 °C to 260 °C, with 20 K steps. The decomposition behaviour of fibres was characterised using non-isothermal and isothermal simultaneous thermogravimetric analysis/differential scanning calorimetry (TGA/DSC). The prepared composites were investigated using optical microscopy (OM), colorimetry, tensile test, Charpy impact test, dynamic mechanical analysis (DMA) and melt flow rate (MFR). Composites exhibited a decrease in mechanical performance at processing temperatures above 200 °C, with a steep decrease observed at 240 °C. Lyocell fibres exhibited the best reinforcement effect, especially at elevated processing temperatures, followed by flax and hemp fibres. It was found that the retention of the fibre reinforcement effect at elevated temperatures can be well predicted using isothermal TGA measurements.

Effect of microwave pretreatment on chalcopyrite dissolution in acid solution

Microwave-roasting as an efficient method for extracting copper form chalcopyrite has attracted increasing attention. In this work, the microwave roasted chalcopyrite was pressure leached in 1.0 mol/L sulfuric acid solution at the temperature range of 110–150 °C, and the reasons why microwave-roasting improved the leaching kinetics were further studied by the electrochemical characterizations. Results show that microwave-roasting had a positive effect on better mineral leachability. Under the optimal conditions, the final copper extraction was 90.1% and the iron extraction was 87.5%. The leaching process of the microwave roasted chalcopyrite was controlled by chemical reaction, and the calculated activation energy was 41.7 kJ/mol. The electrochemical study results indicated that microwave-roasting had a significant effect on both the anodic dissolution kinetics and the cathodic reactions kinetics, and the charge transfer resistance of chalcopyrite oxidation and the resistance of the passive film were both lower than that of the un-roasted sample. X-ray diffraction (XRD), and scanning electron microscope (SEM) results suggested that microwave-roasting effectively activate chalcopyrite through modifying the surface structure. Besides the enlargement of the effective reaction surface, the differential scanning calorimetry-thermogravimetric analysis (DSC-TGA) results revealed that the increasing of active sites and/or the internal stress can increase the strain energy and instability of chalcopyrite, which plays an important role in improving chalcopyrite leaching kinetics. The main product of pressure leaching was elemental sulfur that mixed with the copper-rich sulfide, causing the passivation of chalcopyrite.

A case study of wood thermoplastic composite filament for 3D printing

The 3D printing technology is a method of converting proposed complex geometric shapes into solid models. One of these methods is the FDM (fused deposition modeling) printing technology as a considerably affordable and the most commonly used method in the world. The purpose of this study is to obtain FDM 3D printer filaments that are as natural as possible, resembling wood and evoking the sensation of wood upon touching through deployment of bio-based plastics and additives. Polylactic acid (PLA) and bio thermoplastic polyurethane (TPU) were used as matrices, and lignin and Arboform, a lignin-based biomaterial, were used as additives. The characteristics of composites achieved through addition of 10% lignin and Arboform to matrices were identified by differential scanning calorimetry (DSC) thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and the tensile test. The effects of some printing parameters on the mechanical characteristics were also determined. Lignin induced a decrease in mechanical characteristics for both PLA and TPU. Arboform, on the other hand, demonstrated good bonding with TPU and increased tensile strength. Production of flexible and sufficiently durable parts by means of 10% Arboform-containing TPU filaments was demonstrated.

Influence of Fe-doping on the structural and photoluminescence properties and on the band-gap narrowing of SnO2 nanoparticles

In this study the structural and optical properties of Fe-doped SnO2 (Sn1-xFexO2, for x = 0, 0.03, 0.05, 0.07) nanoparticles synthesized by co-precipitation technique and using short durations of sample sintering is reported. The prepared samples are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Thermogravimetric analysis – differential scanning calorimetry (TG-DSC), UV–Visible spectroscopy (UV-VIS) and Photoluminescence (PL) measurements. The Rietveld refined XRD data shows that all the samples are in tetragonal rutile crystalline phase. Fe doping in the samples hinder grain growth as the average crystallite size (ranging in between 13 and 29 nm) reduces with doping concentration. Information on the phase purity of the samples is obtained via the FTIR and Raman measurements while the Thermogravimetric–Differential Scanning Calorimetric (TG-DSC) studies give an idea on the crystallization process of and the presence of oxygen vacancies in the samples. The finger print wave number region of rutile phase of SnO2 corresponds to the A1g mode, which shows a red shift in the Raman studies undertaken. This is indicative of the effect of the defects arising due to the dopant introduced, which affects the crystallite size and leads to phonon confinement, observed as the red shift of the Raman peaks. The addition of Fe leads to a band-gap narrowing process due to the d – d transition and a feeble absorption occurs in the near infrared region. The Photoluminescence (PL) curve shows a broad and intense emission in the UV region, near ~ 375 nm (3.31 eV), owing to the presence of oxygen vacancies. Apart from this, two additional feeble emission peaks for the 5% and 7% Fe-doped samples also evolve. The substitution of Fe, existing in the Fe2+/Fe3+ state, in place of Sn, existing in the Sn4+ state, gives rise to a charge/oxidation state imbalance. This creates a vacancy in the crystal, which acts as the emission center in the doped semiconductor type SnO2. The PL studies confirm the existence of Fe induced inter bands in the energy band-gap of these samples. The CIE chromaticity diagram shows that the prepared materials are suitable and tunable for blue light LED applications.

High-Temperature microwave properties and phase transitions of ultramafic nickel ores

The mining of ultramafic ores is required to meet society’s continued demand for nickel. These deposits, however, are difficult to process due to their high serpentine content. Serpentine, a gangue mineral, increases slurry viscosity, slime-coats the valuable Ni-bearing mineral pentlandite, and reports to and dilutes the froth during flotation via the formation of bubble-fibre aggregates. Microwave pre-treatment can be used to convert the serpentine gangue to olivine, which should improve ore processing. However, the fundamental microwave properties and heating behaviour of ultramafic ores must be understood to develop a robust process. Microwave heating curves were developed for, and high temperature permittivity analysis was conducted on, two ultramafic nickel ores (Pipe and OK ore). Subsequently, TGA/DSC (thermogravimetric analysis/differential scanning calorimetry) and HTXRD (high-temperature x-ray diffraction) tests, along with a thermodynamic analysis using FactSage 7.3, were done to explain the heating behaviours and permittivity data. An unusual peak in the permittivity data was detected at 950 °C for the Pipe ore with both increasing and decreasing temperature; however, no phase transitions were detected in the TGA/DSC analysis. HTXRD of the Pipe ore revealed the presence of heazlewoodite at higher temperatures (950 to 1100 °C). Thermodynamic modeling of the Pipe ore system suggests that melting at higher temperatures is responsible for the decrease in the permittivities of this ore. To mitigate the melting and clumping of the ore particles, it is necessary to ensure that the processing temperature does not exceed 800 °C during microwave treatment. The OK ore, which contained less microwave response minerals than the Pipe ore, reached a maximum temperature of 500 °C after only 5 min of heating time, and therefore overheating was not an issue.

Synergetic Effect of Dual Functional Monomers in Molecularly Imprinted Polymer Preparation for Selective Solid Phase Extraction of Ciprofloxacin.

Background: Ciprofloxacin (CIP), an important broad-spectrum fluoroquinolone antibiotic, was often used as a template molecule for the preparation of imprinted materials. In this study, methacrylic acid and 2-vinylpyridine were employed for the first time as dual functional monomers for synthesizing ciprofloxacin imprinted polymers. Methods: The chemical and physicochemical properties of synthesized polymers were characterized using Fourier transform-infrared spectroscopy, thermogravimetric analysis-differential scanning calorimetry, scanning electron microscopy, and nitrogen adsorption-desorption isotherm. The adsorption properties of ciprofloxacin onto synthesized polymers were determined by batch experiments. The extraction performances were studied using the solid phase extraction and HPLC-UV method. Results: The molecularly imprinted polymer synthesized with dual functional monomers showed a higher adsorption capacity and selectivity toward the template molecule. The adsorbed amounts of ciprofloxacin onto the imprinted and non-imprinted polymer were 2.40 and 1.45 mg g−1, respectively. Furthermore, the imprinted polymers were employed as a selective adsorbent for the solid phase extraction of ciprofloxacin in aqueous solutions with the recovery of 105% and relative standard deviation of 7.9%. This work provides an alternative approach for designing a new adsorbent with high adsorption capacity and good extraction performance for highly polar template molecules.

Thermal Conversion Characteristics of Molasses

Agroindustrial biomass residues are considered potential feedstocks for renewable fuels and chemical production through processes such as thermal conversion. In this regard, thermal conversion characteristics of molasses, a byproduct from sugar production, have not been investigated. In this study, thermal conversion properties of molasses at temperatures of 700–900 °C have been studied using a single-particle reactor. Fuel swelling, combustion times, CO gas yields and gasification reactivities, and NO emissions and release of K and Cl during combustion and gasification were the thermal conversion characteristics of the molasses studied. In addition, the melting behavior of molasses ash produced at 500 °C was assessed using FactSage thermodynamic modeling and differential scanning calorimetry–thermogravimetric analysis measurements. Results of the molasses thermal conversion properties were compared with those of vinasse and black liquor samples from the integrated sugar–ethanol mill and soda pulping of hardwood, respectively. The results show that the molasses droplets had the least swelling tendency and the longest combustion time in the temperature range used, suggesting a lower conversion rate of molasses in an industrial boiler than the vinasse and black liquor. Moreover, at temperatures relevant for industrial gasification processes, that is, ≥800 °C, the gasification rates of molasses were lower than those of the vinasse and black liquor, probably owing to the lower total concentration of catalytic alkali and alkaline earth metals in the molasses. The release of K and Cl to a high degree from molasses during combustion and gasification and the low melting temperature of molasses ash make it a challenging fuel to utilize using the current thermal conversion technologies. Nevertheless, a black liquor recovery boiler type with a simpler (or an oxidizing) lower furnace than that of a black liquor recovery boiler and an entrained flow gasifier of the type demonstrated for black liquor may be potential options for the production of energy and recovery of inorganic chemicals from molasses.

Synthesis, characterization, and antibacterial activity of dibenzildithiocarbamate derivates and Ni(II)–Cu(II) coordination compounds

In this work, the study of the synthesis methodology to obtain dibenzylamine derivates as intermediates for the formation of dithicarbamate ligands (DTC) and its coordination compounds was conducted. Four molecules derived from dibenzylamine were synthesized by two methodologies: classical (reflux) and microwave. From these amines, Four dithiocarbamate ligands (DTC): dibenzyldithiocarbamate, N-benzyl-1-(4-methoxyphenyl)dithiocarbamate, N-benzyl-1-(4-chlorophenyl)dithiocarbamate, and N-benzyl-1-(3-nitrophenyl)dithiocarbamate, and eight coordination complexes with general formula [M(DTC)2]nH2O (M= Cu(II) and Ni(II)) were obtained. All the compounds were characterized using different spectroscopic and thermal techniques such as Fourier-transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–VIS), proton and carbon-13 nuclear magnetic resonance (1H and 13C NMR), thermogravimetric analysis–differential scanning calorimetry (TGA-DSC). Additionally, it was possible to characterize two new crystalline phases of salts through single-crystal X-ray diffraction: dibenzyl ammonium nitrate and N-benzyl-1-(3-nitrophenyl)ammonium chloride. Additionally, microbial inhibition tests were conducted using the dibenzildithiocarbamate derivates. All DTC compounds showed important activity against Pseudomonas aeruginosa and Staphylococcus aureus but less sensitivity against Escherichia coli and Mycobacterium smegmatis. Among the coordination compounds, only [Cu(N-benzyl-1-(3-nitrophenyl)dithiocarbamate)2] presented a moderate activity against M. smegmatis mc2 155.

Thermally Stable and Low‐Sensitive Aluminized Explosives with Improved Detonation Performance

AbstractTwo new types of aluminized explosives TATB/HMX/Al and LLM‐105/Al were formulated and compared with the formerly reported TATB/Al explosives in terms of thermal stability, mechanical sensitivity, and detonation performance. Firstly, the heat of the explosion was measured and two formulations were selected as the investigated samples. Next the thermal stability was studied by simultaneous thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) and thermal cook‐off tests. Then the impact and friction sensitivity were measured, and finally the detonation performance was characterized by cylinder tests and particle velocity measurements of the detonation reaction zone. From the calorimetric data, the new types of explosives increase the heat of the explosion significantly. In terms of thermal stability, LLM‐105/Al=65/30 is more stable than TATB/HMX/Al=50/15/30, but both of them are inferior to TATB/Al=70/25. The impact sensitivity of the two new explosives is higher than that of TATB/Al=70/25, and all of the samples are insensitive to friction. For detonation performance, both of the two new samples are superior to TATB/Al=70/25, and LLM‐105/Al=65/30 exhibits the best performance that it has the highest Gurney energy, detonation velocity, and detonation pressure. Conclusions about how to use those aluminized explosives to generate optimal effects are drawn.

Multi-distribution activation energy model on slow pyrolysis of cellulose and lignin in TGA/DSC

Developing a kinetic model to analyze the multi-step reaction of biomass pyrolysis is pivotal to elucidate the mechanism of the pyrolysis. For this purpose, a model-fitting method such as multi-distribution the Distributed Activation Energy Model (DAEM) is one of the most reliable methods. DAEM with 4 different distribution functions of Gaussian, Logarithmic, Gumbel, and Cauchy was utilized to characterize the pyrolysis of cellulose and lignin during Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC) instrumentation. By comparing Derivative Thermogravimetry (DTG) and DSC profiles, determination of pseudo-components can be done more accurately. A kinetics analysis on the pyrolysis of cellulose with a single Gaussian distribution DAEM yielded a single activation energy of 178 kJ mol−1 with a narrow standard deviation. This result was justified by a single and dominant endothermic peak followed by minor exothermic peaks in the DSC result. For lignin pyrolysis, the presence of multiple peaks is characterized by four pseudo-components in DAEM with activation energies of 157, 174, 194, and 200 kJ mol−1. These pseudo-components were confirmed by the DSC result which indicated the occurrences of two exothermic peaks with two lesser exothermic or possibly endothermic peaks at the same temperature range. These findings imply the importance of DSC to support a kinetics study of thermogravimetric pyrolysis.

The impact of atmospheric pollution on outdoor cultural heritage: an analytic methodology for the characterization of the carbonaceous fraction in black crusts present on stone surfaces

COVID-19 has reduced tourism in both museums and historical sites with negative economic effect. The wellbeing and good preservation of monuments is a key factor to encourage again tourism. Historical monuments exposed to outdoor pollution are subjected to well known degradation phenomenon including the formation on their surface of black crusts (BCs) causing blackening and deterioration of the monuments and, as a consequence, a worst fruition by the visitors. The aim of this research is the development and validation of a novel method to characterize and quantify the various components present in the black crusts. SO2 together with the carbonaceous fraction (i.e. OC, organic carbon, and EC, elemental carbon) represent the main atmospheric pollutants involved in the process of BCs formation which consists in the partial transformation of the carbonate substrate into gypsum where black particles are embedded.A new methodology based on the use of TGA/DSC (Thermogravimetric Analysis/Differential scanning calorimetry) and CHN (Carbon, Hydrogen, Nitrogen) analysis was set up allowing to determine organic carbon and elemental carbon together with other components such as gypsum. Four standard mixtures simulating BCs composition were prepared and analysed by the set-up methodology. The new procedure was subsequently applied to study real BCs samples taken from monuments and historical buildings placed in cities heavily affected by atmospheric pollution and by PCA (principal component analysis) their main features, from the point of view of carbonaceous fraction, were highlighted.

Investigation on hot melt extrusion and prediction on 3D printability of pharmaceutical grade polymers

The development of printable filaments has been identified as a critical aspect for the processing of pharmaceutical grade polymers and the fabrication of oral solid dosage forms. In this study a range of plain and drug loaded polymers were investigated and assessed for their printability in comparison to commercial filaments. Physicochemical characterizations of the polymers included differential scanning calorimetry (DSC) thermogravimetric analysis (TGA) and rheology were studied prior to Hot Melt Extrusion processing for the filament fabrication. A texture analyser was used to study the filament mechanical properties in order to derive the maximum tensile strength, Young’s Modulus and elongation at break. Principal component analysis was used to compare the printability of the polymer and to identify the contribution of each mechanical property. The analysis showed that maximum tensile strength with a threshold between 15 and 20 MPa is the most critical property for the prediction of the printability. Furthermore, printable filaments were processed using Fusion Deposition Modelling technology and optimal printing parameters were identified. The study demonstrated that the prediction of filament printability is feasible by evaluating the mechanical properties.

Improved Ionic Conductivity of MgM4P6O24 (M = Hf, Zr) Ceramic Solid-State Electrolytes by Sol-Gel Synthesis

Data from electrochemical impedance measurement of MgHf4P6O24 and MgZr4P6O24 solid-state electrolytes show significant improvement in the ionic conductivity of the ceramic electrolytes. The electrical behaviour of MgHf4P6O24 and MgZr4P6O24 solid-state electrolytes were measured using two-probe analysis at a temperature range of 182-764°C, and at a frequency range within 100 mHz to 32 MHz. In this analysis, promising bulk ionic conductivity of 4.52 x 10-4 Scm-1 and 7.23 x 10-3 Scm-1 were achieved for MgHf4P6O24 and MgZr4P6O24 electrolytes, respectively, at impedance maximum temperatures of 747°C and 725°C, respectively. The sol-gel method was deployed in the synthesis of MgHf4P6O24 and MgZr4P6O24 nanoparticles. The thermogravimetric analysis-differential scanning calorimetry analysis (TGA-DSC), and X-ray diffraction (XRD) characterisation techniques were deployed in this study to determine and evaluate the phase composition structure of the nanoparticles calcined at 900°C and the sample pellets sintered at 1300°C.

Eco-friendly immobilization of dithizone on coal bottom ash for the adsorption of lead(II) ion from water

Coal bottom ash is one of coal combustion wastes which mainly contains metal oxides of alumina and silica, thus it can be potentially used as adsorbent for heavy metal removal in aquatic environment. We have developed a new approach of eco-friendy immobilization of dithizone on activated coal bottom ash (CBA-Act) in water medium to yield dithizone-immobilized coal bottom ash (CBA-Dtz). The immobilization process in water medium is intended to replace previous method that uses more toxic organic solvents of toluene or carbon tetrachloride. Dithizone immobilization on CBA-Act is aimed to increase the selectivity and capacity of the adsorbent towards heavy metal ions. Characterization of the materials by FTIR (Fourier Transform Infra-Red), SEM-EDX (Scanning Electron Microscopy-Energy Dispersive X-Ray), TEM (Transmission Electron Microscope), XRD (X-Ray Diffraction) and DSC/TGA (Differential Scanning Calorimetry/Thermogravimetric Analysis) confirms that dithizone immobilization on CBA-Act in water medium has successfully accomplished and the new approach has proved to be twice more effective than that done in toxic organic media. Application of the original and modified CBA-Act in the adsorption of lead(II) ion from water suggests that the adsorption capacity of CBA-Dtz increases approximately three times as much as that of CBA-Act. The adsorption on both adsorbents follows pseudo-2nd order kinetic and can be best described by either Langmuir or BET isotherm adsorption models. Sequential desorption experiments reveal that lead(II) adsorption on CBA-Act is mostly governed by electrostatic and hydrogen bond interactions. However, upon immobilization of dithizone as found in CBA-Dtz, electrostatic interaction decreases while hydrogen bond interaction increases significantly.

Assembly of porous graphitic carbon nitride nanosheets into electrospun polycaprolactone nanofibers for bone tissue engineering

Polycaprolactone (PCL) is a widely used synthetic biopolymer in the field of biomedical applications. However, poor hydrophilicity, slow degradation rate, and weak cellular responses have been made to limit its use. Hence, improving these properties is essential to recognize as a broadly acceptable biomaterial with enhanced cellular activities. For this purpose, porous g-C3N4 nanosheets incorporated PCL nanofibrous scaffolds were synthesized via the electrospinning method. The effect of g-C3N4 nanosheets into the PCL/g-C3N4 composite scaffolds was characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis/differential scanning calorimetry (TGA/DSC). Moreover, mechanical behaviors, contact angle, biodegradability, and biocompatibility were also evaluated. Our findings showed that porous g-C3N4 nanosheets decreased the overall fiber diameter of composite scaffolds while increasing mechanical properties, wettability, biodegradability, and improved bioactivity on MC3T3-E1 cells in in vitro test. Based on the obtained results, we suggest that PCL/g-C3N4 composite could potentially provide a new platform for bone tissue engineering application.

Mesoporous acidic functional N-containing ZrNxOy material for polyoxymethylene diethyl ethers synthesis under mild conditions

Polyoxymethylene dialkyl ethers, which can be blended into diesel fuels, have attracted increasing attentions due to their advantages for fuel additives. It can utilize bioethanol and biomass syngas, helping to achieve the carbon neutral target earlier. Polyoxymethylene diethyl ethers (PODEEn) synthesis requires efficient catalysts with high performance. In this work, the mesoporous acidic functional N-containing ZrNxOy catalysts were prepared with a Sol-Gel assisted solvothermal method. The acid nature and strength, morphology, crystalline structure and pore distribution of catalysts were characterized by fourier transform infrared (FT-IR) spectroscopy, pyridine-adsorption infrared spectra (Py-IR), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), N2 adsorption-desorption isotherm, X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of ammonia (NH3-TPD) etc, showing catalyst possessing crystalline-amorphous mixed domains with smaller defective tetragonal nanoparticles and mesopores. The catalysts were applied in PODEEn synthesis, showing excellent activity and selectivity under mild conditions. And the high trioxane (TOX) conversion of 93 % and excellent PODEE2−8 selectivity of 98 % can be achieved at 80 °C under atmospheric pressure owning to the superior properties.

Adsorptive removal of P(V) and Cr(VI) by calcined Zn-Al-Fe ternary LDHs.

The present study deals with the preparation and structural and adsorbent characterization of the ternary layered double hydroxides (LDHs; ZFA-HT) with molar ratio Zn2+/Al3+/Fe3+ = 2/0.5/0.5 and its product calcined (ZFA-350) at 350 °C, which is examined for the removal of phosphate P(V) and chromate Cr(VI) from aqueous media. The as-obtained materials are characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), scanning electron microscopy-X-ray energy dispersion (SEM-EDX) and Brunauer-Emmett-Teller (BET). Structural characterizations show that the LDHs is successfully synthesized and its calcined product is a mixed oxide. Batch sorption studies are conducted to investigate the effects of various experimental parameters such as contact time, solution pH, adsorbent amount, initial P(V) or Cr(VI) concentration and temperature. The isotherms, kinetics and thermodynamic parameters of adsorption of phosphate and chromium are studied. The adsorption processes are well described by the pseudo-second-order kinetic model than the other models examined. The adsorption isotherms data fit best to the Langmuir isotherm model instead of Freundlich and Dubinin-Radushkevich models. The maximum monolayer adsorption capacity of ZFA-350 was found to be 140.85 mg/g for P(V) and 52.63 mg/g for Cr(VI). The positive ΔH and ΔS and negative ΔG values reveal that the P(V) and Cr(VI) sorption onto ZFA-350 is endothermic, irreversible and spontaneous in nature.

Effect of Mechanical Activation on Leaching Behavior and Mechanism of Chalcopyrite

ABSTRACT The leaching kinetics of chalcopyrite is sluggish due to the refractory nature of chalcopyrite and the formation of passive layers. In this study, the effect of mechanical activation on the leaching behavior and mechanism was studied by leaching tests, electrochemical measurements, particle size distribution analysis, scanning electron microscope (SEM), X-ray diffraction (XRD), differential scanning calorimetry-thermogravimetric analysis (DSC-TGA), X-ray photoelectron spectroscopy (XPS) and electron microprobe. The results show that mechanical activation can greatly promote the chalcopyrite leaching kinetics, and the copper extraction was increased from 14.1% to 55.7% and 91.8% after primary and secondary mechanical activation, respectively. The electrochemical study results indicated that mechanical activation did not change the cathodic reactions kinetics, however, the anodic dissolution kinetics was significantly promoted. XRD and DSC-TGA results show that mechanical activation treatment can effectively activate chalcopyrite due to the grain size reduction, formation of crystal defects and lattice deformation. The main solid product of chalcopyrite leaching is elemental sulfur. Besides particle size reduction, the reduction of grain size, formation of crystal defects and lattice deformation can increase the strain energy and instability of chalcopyrite, which plays an important role in improving chalcopyrite leaching kinetics.

In-situ investigation of melting characteristics of waste selective catalytic reduction catalysts during harmless melting treatment

Selective catalytic reduction (SCR) catalyst waste is a hazardous solid waste that seriously threatens the environment and public health. In this study, a thermal melting technology is proposed for the treatment of waste SCR catalysts. The melting characteristics and mineral phase transformation of waste SCR catalysts blended with three different groups of additives were explored by heating stage microscopy, thermogravimetric analysis/differential scanning calorimetry (TG/DSC) analysis, thermodynamic simulation, and X-ray diffraction (XRD) analysis; heavy metal leaching toxicity was tested by inductively coupled plasma-atomic emission spectrometry (ICP-AES) analysis. The results indicated that the melting point of waste SCR catalysts can be effectively reduced with proper additives. The additive formula of 39.00% Fe2O3 (in weight), 6.50% CaO, 3.30% SiO2, and 1.20% Al2O3 achieves the optimal fluxing behavior, significantly decreasing the initial melting temperature from 1223 °C to 1169 °C. Furthermore, the whole heating process of waste SCR catalysts can be divided into three stages: the solid reaction stage, the sintering stage, and the primary melting stage. The leaching concentrations of V, As, Pb, and Se are significantly reduced, from 10.64, 1.054, 0.195, and 0.347 mg/L to 0.178, 0.025, 0.048, and 0.003 mg/L, respectively, much lower than the standard limits after melting treatment, showing the strong immobilization capacity of optimal additives for heavy metals in waste SCR catalysts. The results demonstrate the feasibility of harmless melting treatments for waste SCR catalysts with relatively low energy consumption, providing theoretical support for a novel method of disposing of hazardous waste SCR catalysts.