Thermal Decomposition Of Precipitates Research Articles

Innovative strategies for ammonia nitrogen removal in rare earth tailings: An advanced element recycling process using leaching, chemical precipitation and adsorption

Residual ammonium salt in closed rare earth mining sites leads to elevated levels of ammonia nitrogen in the surrounding environment. To mitigate ammonia nitrogen pollution at its source, a cost-effective and environmentally friendly recycling process was proposed. This process involves leaching residual ammonia nitrogen using a magnesium sulfate solution, followed by chemical precipitation for ammonia nitrogen removal. Additionally, nitrogen can be recovered as ammonia gas through the thermal decomposition of precipitates, allowing for further ammonia nitrogen adsorption from the leachate. The residual ammonium salts leaching rate reached 96.38 % with a 0.1 mol/L magnesium sulfate solution at a flow rate of 0.6 mL/min. The chemical precipitation method achieved a maximum nitrogen removal rate of 86.87 %, with an activation energy of 2.6 kJ/mol, indicating a relatively rapid process. At 190 °C, the ammonia nitrogen release rate of precipitates was 82.5 % after 2 h of thermal decomposition. The adsorption process was consistent with pseudo-second-order kinetics models using thermal decomposition products. Overall, the comprehensive removal rate of residual ammonium salts from the closed rare earth mining site was approximately 83.3 % in recycling process, optimizing the utilization of phosphorus, magnesium, and nitrogen and achieving efficient and environmentally friendly nitrogen removal.

Au nanoparticles decorated β-Bi2O3 as highly-sensitive SERS substrate for detection of methylene blue and methyl orange.

In this work, Au/Bi2O3 was synthesized by loading Au nanoparticles (NPs) onto β-Bi2O3 by a simple solution reduction method. β-Bi2O3 was synthesized by a precipitation-thermal decomposition procedure, which results in significantly improved SERS detection limits down to 10-9 M for methylene blue (MB) and 10-7 M for methyl orange (MO) as probe molecules, comparable to those reported for the best semiconductor SERS substrates. In particular, further deposition of Au NPs (5.20% wt%) onto β-Bi2O3 results in a two-order-of-magnitude enhancement in detection sensitivity, achieving a detection limit of 10-11 M for MB and 10-9 M for MO. Under ultraviolet/visible irradiation, the Au/Bi2O3 hybrids substrate exhibits superior self-cleaning ability due to its photocatalytic degradation ability which can be applied repeatedly to the detection of pollutants. The advanced composite substrate simultaneously achieved ultra-low mass loading of Au NPs, outstanding detection performance, good reproducibility, high stability and self-cleaning ability. The development strategy of low load noble metal coupled high performance semiconductor β-Bi2O3 to obtain nano-hybrid materials provides a method to balance SERS sensitivity, cost effectiveness and operational stability, and can be synthesized in large quantities, which is a key step towards commercialization and has good reliability prospects.

Synthesis and application of V2O5-CeO2 nanocomposite catalyst for enhanced degradation of methylene blue under visible light illumination

Methylene blue dye is among the toxic, mutagenic, and carcinogenic pollutants. Hence, its treatment via photocatalytic degradation is an important remediation method for the sake of a healthy environment. Herein, the V2O5-CeO2 nanocomposite catalysts were synthesized via a simple precipitation-thermal decomposition approach and used for the photodegradation of methylene blue in the presence of H2O2 as an effective electron scavenger under visible light illumination. The nanocomposite catalysts were systematically characterized to investigate the effects of V2O5 with the aids of X-ray, morphology, light absorption, catalytic activity, and charge transfer properties of the nanocomposite catalysts. The VC-2 nanocomposite prepared with NH4VO3:CeO2 molar ratios at 0.15:1 was found to be the best efficient catalyst where ≥98% of methylene blue was degraded within 25 min irradiation time. From the kinetics analysis, its rate constant was found to be higher than those of the pure V2O5 and CeO2 catalysts by a factor of 12.0 and 13.5, respectively. The plausibly mechanistic elucidation of charge transfer and utilization of reactive species are conspicuous allegations of the combined effects of the nanocomposite catalyst, H2O2 sacrificial agent, and visible light for the photodegradation of the dye.

Effects of composition on the microwave absorbing properties of FexNi100−x (x = 0–25) submicro fibers

The morphology and composition of a material have important influences on its electromagnetic parameters and microwave absorbing property. In this paper, the FexNi100−x (x = 0–40) powders were prepared by an oxalate precipitation-thermal decomposition process. When x = 0–25, the powders show submicro fibrous morphologies, however, when x > 25, some granular particles appear due to the weak coordination ability of ethylenediamine with Fe2+ in the oxalate precipitation process. The electromagnetic parameters and microwave absorbing properties of the composites of the FexNi100−x (x = 0–25) submicro fibers with 80 wt% paraffin were studied in 2–18 GHz. Compared with the Ni/paraffin composite, enhanced electromagnetic losses and microwave absorbing properties are observed for the Fe10Ni90/paraffin and Fe25Ni75/paraffin composites. The Fe10Ni90/paraffin shows the best microwave absorbing property that at the composite thickness of 2.0 mm, the effective bandwidth and minimum RL reach 3.78 GHz (12.21–15.99 GHz) and −45.37 dB at 13.90 GHz, respectively. The excellent microwave absorbing property of the Fe10Ni90/paraffin composite is from its high loss factor and the quarter-wavelength cancellation mechanism.

Synthesis, Characterization and Recyclable Cerium Loaded CuO Nanocatalyst for the Synthesis of 1, 4- Disubstituted 1, 2, 3-Triazoles and Propargylamines

Cerium loaded CuO nanoparticles (Ce-CuO NPs) were successfully synthesized by a precipitation-thermal decomposition method. The synthesized Ce-CuO NPs were used as a nanocatalyst for the synthesis of 1, 4-disubstituted-1, 2, 3-triazoles by the click reaction of substituted benzyl azides and alkynes and synthesis of propargylamines via a three-component coupling reaction of aldehydes, alkynes and amines under ultrasonication. One-pot operation, atom-economical nature, regioselectivity and good yields are the significant features of this protocol. The reusability of the prepared nanocatalyst was successfully examined six times without any appreciable loss in catalytic activity. Synthesized compounds were characterized by 1H NMR, 13C NMR and mass spectral studies.

Preparation of Fe20Ni80 submicron fibers by an oxalate precipitation-thermal decomposition process and their microwave absorbing properties

Fe20Ni80 submicron fibers were prepared by an oxalate precipitation-thermal decomposition process, and their morphologies, structures and microwave absorbing properties were systematically investigated. Firstly, an oxalate precursor with a one-dimensional growth mechanism was synthesized by using ethylenediamine as a coordination agent. Secondly, the Fe20Ni80 submicron fibers with a diameter of about 300 nm were obtained by a thermal decomposition of the precursors. The electromagnetic parameters of Fe20Ni80 submicron fibers (20 wt%)/paraffin composite were measured and the microwave absorbing properties were determined by the reflection loss (RL) values in the frequency range of 2–18 GHz. The results show that the composite exhibits excellent microwave absorption properties. When the composite thickness is 2.0 mm, the minimum RL reaches −36.97 dB at 11.89 GHz, and the bandwidth of RL < −10 dB reaches 3.22 GHz (10.36–13.58 GHz).

Investigation on UV-A light photocatalytic degradation of an azo dye in the presence of CdO/TiO2 coupled semiconductor

CdO/TiO2 composites were prepared by sonochemically assisted sol–gel method. Initially, CdO was prepared by precipitation-thermal decomposition method and used for composites preparation. The prepared catalysts were used for the degradation of an azo dye, Reactive Orange 4 (RO 4) under UV-A light. 5wt% CdO/TiO2 composite was found to be very efficient towards RO 4 degradation, this catalyst was characterized by different characterization techniques (XRD, SEM, EDS, TEM, PL and BET surface area measurements) besides bare TiO2 was also characterized for comparison. 5wt% CdO/TiO2 showed the best photocatalytic activity in the degradation of RO 4 compared with the bare TiO2, TiO2-P25 and CdO. The effects of operational parameters such as the amount of photocatalyst, initial pH and dye concentration have been analyzed. The mineralization of RO 4 has been confirmed by chemical oxygen demand (COD) measurements. A mechanism has been proposed for the degradation of RO 4 under UV-A light. This catalyst is found to be more stable and reusable.

Influence of thermal-decomposition temperatures on structures and properties of V2O5 as cathode materials for lithium ion battery

Submicron spherical V2O5 particles with a uniform size and a lower crystallinity were successfully synthesized by a chemical precipitation-thermal decomposition technique using the commercial V2O5 powders as starting material. The crystal structure and grain morphology of samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Electrochemical testing such as discharge–charge cycling (CD) and cyclic voltammetry (CV) were employed in evaluating their electrochemical properties as cathode materials for lithium ion battery. Results reveal that the crystallinity and crystalline size of V2O5 particles increased when the thermal-decomposition temperature increased from 400°C to 500°C, and their adhesiveness was also synchronously increased. This indicate that the thermal-decomposition temperature palyed a significant influence on electrochemical properties of V2O5 cathodes. The V2O5 sample obtained at 400°C delivered not only a high initial discharge capacity of 330mAhg−1 and also the good cycle stability during 50 cycles due to its higher values of α in crystal structure and better dispersity in grain morphology.

Ethanol Catalytic Oxidation on Yb Promoted Pd/C in Alkaline Medium

To promote the alcohol catalytic oxidation of Pd/C catalysts, it was implemented that the lanthanide Yb was introduced to the catalyst via the precipitation thermal decomposition and chemical reduction methods. The structure analysis and surface morphology of Pd-Yb/C catalysts were investigated by XRD and SEM. The ethanol electrocatalytic oxidation activity of in alkaline media was studied by cyclic voltammetry. The results show that the performance of ethanol catalytic oxidation on Pd-Yb/C electrode is better than that on the Pd/C electrode. The introduction of Yb can promote Pd/C catalytic oxidation alcohol and its poisoning tolerance ability.

Mineralization of Basalts in the CO2–H2O–SO2–O2System

Sequestering carbon dioxide (CO2) containing minor amounts of co-contaminants in geologic formations was investigated in the laboratory through the use of high pressure static experiments. Five different basalt samples were immersed in water equilibrated with supercritical CO2 containing 1 wt % sulfur dioxide (SO2) and 1 wt % oxygen (O2) at reservoir conditions (∼ 100 bar, 90 °C) for 48 and 98 days. Gypsum (CaSO4) was a common precipitate, occurred early as elongated blades with striations, and served as substrates for other mineral products. In addition to gypsum, bimodal pulses of water released during dehydroxylation were key indicators, along with X-ray diffraction, for verifying the presence of jarosite-alunite group minerals. Well-developed pseudocubic jarosite crystals formed surface coatings, and in some instances, mixtures of natrojarosite and natroalunite aggregated into spherically shaped structures measuring 100 μm in diameter. Reaction products were also characterized using infrared spectroscopy, which indicated OH and Fe-O stretching modes. The presences of jarosite-alunite group minerals were found in the lower wavenumber region from 700 to 400 cm(-1). A strong preferential incorporation of Fe(III) into natrojarosite was attributed to the oxidation potential of O2. Evidence of CO2 was detected during thermal decomposition of precipitates, suggesting the onset of mineral carbonation.

Synthesis and microwave absorbing properties of quasione-dimensional mesoporous NiCo2O4 nanostructure

• A quasione-dimensional mesoporous NiCo 2 O 4 nanostructure was synthesized. • The NiCo 2 O 4 was used as microwave absorber for the first time. • The NiCo 2 O 4 /paraffin composite shows excellent microwave absorbing property. • The microwave absorbing mechanism was discussed. Quasione-dimensional NiCo 2 O 4 nanostructure was synthesized by a precipitation-thermal decomposition process. The diameters and special ratios of the NiCo 2 O 4 fibers are 0.2–0.5 μm and 20–50, respectively. The mesoporous structure with a surface area of 54.47 m 2 g − 1 and average pore-size of 12.5 nm for the NiCo 2 O 4 was obtained. The relative complex permittivity and permeability of paraffin/50 wt.% NiCo 2 O 4 composite were measured in the frequency range of 2–18 GHz, and the microwave absorbing property of the composite was evaluated. An excellent reflection loss (RL) of −35.76 dB at 14.86 GHz with a composite thickness of 1.50 mm and effective bandwidth (RL < −10 dB) of 11.18 GHz were obtained, which is related to the thickness, impedance matching and morphology of the absorber.

Influence of sodium dodecyl sulfate on the fabrication of zinc oxide nanoparticles

Dispersive ZnO nanoparticles with a primary particle size of about 70 nm and an average agglomerate size of about 2.0 μm were synthesized via the precipitation-thermal decomposition route using ZnSO4 and Na2CO3 as the reactants and sodium dodecyl sulfate (SDS) as the surface modification agent. The presence of minor amounts of SDS in the formation of hydrozicite (Zn5(CO3)2(OH)6) precursor changed the agglomeration size of ZnO from 9.7 to 2.0 μm and the primary particle size of ZnO from about 45 to 70 nm. Molecular simulation based on the DISCOVER model and COMPASS force field indicated that SDS was adsorbed on the surface of Zn5(CO3)2(OH)6 mainly via the coulomb and hydrogen bond interactions.

Amorphous “Ti3N4” and Formation of Nanocrystalline TiN

ABSTRACTThe existence of Ti3N4 was proposed as the first product of the thermal decomposition of precipitates obtained in ammonolysis reactions of titanium(IV) dialkylamides. The evidence is re-evaluated and further evidence is presented to demonstrate that these materials are probably TiN contaminated with carbon. However, this precursor system is demonstrated to be a good route to finely divided, nanocrystalline TiN powders.