Co-precipitation Temperature Research Articles

Optimized synthesis of cysteine-functionalized nanocrystalline hydroxyapatite for synchronous decontamination of Cd(II) and Pb(II)

The synchronous removal of toxic heavy metals (e.g., cadmium (Cd), lead (Pb), and etc.) from the contaminated water environment is an urgent demand in the pollution control field. Herein, an innovative adsorbent synthesis idea was proposed and a series of cysteine-functionalized nanohydroxyapatite (CysHAP) composites were prepared by adopting different reaction temperatures, cysteine/HAP ratios, and synthesis methods. According to the single factor tests, a co-precipitation temperature of 25 °C with a molar cysteine/HAP ratio of 2.0 was selected to synthesize the optimum CysHAP2.0–25 composite. Multiple characterization results showed that cysteine markedly altered the morphology, crystallinity, and crystal structure of HAP, leading to the formation of CysHAP2.0–25 composite with a superior dispersity, a smaller crystal size, a higher specific surface area, and a greater number of binding sites. Compared with HAP-25, the CysHAP2.0–25 composite exhibited a better Cd(II) sorption performance and a 100% Pb(II) removal in a wide range of solution pH and background electrolyte concentration. The removal performance of CysHAP2.0–25 composite towards Cd(II) was suppressed by the coexisting aqueous components with an obviously stronger inhibiting action of humic acid (HA) than low molecular weight organic acids (LMWOAs) and mixed inorganic components (IC). Pb(II) slightly reduced the sorption ratio of Cd(II) and forced Cd(II) to bind on the -SOx sites derived from sulfhydryl oxidation. In contrast, Cd(II) had no impact on the sorption behaviors of Pb(II). Overall, the synthesized CysHAP2.0–25 composite could be potential applied for the purification of Cd- and Pb-bearing water systems.

Adsorption of Methylene Blue by Magnetic Activated Carbon/Chitosan Composites Prepared from Spent Coffee Grounds : Kinetic, Equilibrium and Thermodynamic Study


 Spent coffee grounds were used as the main ingredient for the composing of magnetic activated carbon/chitosan (MACC) composites and synthesized using the coprecipitation method. The SEM-EDX characterization was used to understand elemental identification and morphology of the adsorbent before the MACC was applied for the removal of methylene blue (MB) from aqueous solution. Magnetic activated carbon/chitosan was fabricated with the subsequent circumstances: the molar ratio of ferrous/ferric ions was 0.02 mol : 0.01 mol, coprecipitation temperature at 60°C for 5 h. Adsorption parameters for MB were investigated. The adsorption by MACC was evaluated thermodynamically for the discharge of MB from an aqueous solution as adsorption reckon on temperature. Calculations of thermodynamic parameters were conducted. Batch adsorption experiments were operated at 308 K; 318 K and MB concentration of 5-50 mg L-1 to investigate the adsorption behavior. According to the results, MACC has a porous structure. The adsorption process is more reactive upon raising the temperature, a process commonly known as endothermic. Based on R2values, the adsorption of MB onto MACC was found best fitted to Freundlich model. The maximum adsorption capacity of the MACC was counted as 24.5 mg/g. The adsorption process is spontaneous, which was concluded from the calculation of thermodynamic parameters.

Synthesis of a Nickel-Rich LiNi0.6Mn0.2Co0.2O2 Cathode Material Utilizing the Supercritical Carbonation Process

This study aims to develop a novel efficient process for the synthesis of a nickel-rich LiNi0.6Mn0.2Co0.2O2 cathode material for lithium-ion batteries utilizing supercritical CO2. In this work, the effect of operating parameters including the amount of chelating agent, coprecipitation temperature, and sintering temperature on the composition, structure, and electrochemical performance of Ni0.6Mn0.2Co0.2CO3 precursors and LiNi0.6Mn0.2Co0.2O2 cathode materials is investigated through systematic characterization and electrochemical testing. When using 1.5 M NH4OH at 60 °C for 8 h followed by sintering at 850 °C for 12 h in air, the LiNi0.6Mn0.2Co0.2O2 cathode material delivers an initial discharge capacity of 176.3 mAh g–1 at 60 mA g–1 with a capacity retention of 94.9% after 50 cycles. This work demonstrates the application of carbon capture and utilization for battery material synthesis with the advantages of no caustic precipitating agent, no impurity introduction, and good electrochemical performance compared with a conventional carbonate coprecipitation process.

Magnetic Core-Shell Iron Oxides-Based Nanophotocatalysts and Nanoadsorbents for Multifunctional Thin Films.

In recent years, iron oxides-based nanostructured composite materials are of particular interest for the preparation of multifunctional thin films and membranes to be used in sustainable magnetic field adsorption and photocatalysis processes, intelligent coatings, and packing or bio-medical applications. In this paper, superparamagnetic iron oxide (core)-silica (shell) nanoparticles suitable for thin films and membrane functionalization were obtained by co-precipitation and ultrasonic-assisted sol-gel methods. The comparative/combined effect of the magnetic core co-precipitation temperature (80 and 95 °C) and ZnO-doping of the silica shell on the photocatalytic and nano-sorption properties of the resulted composite nanoparticles were investigated by ultraviolet-visible (UV-VIS) spectroscopy monitoring the discoloration of methylene blue (MB) solution under ultraviolet (UV) irradiation and darkness, respectively. The morphology, structure, textural, and magnetic parameters of the investigated powders were evidenced by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET) measurements, and saturation magnetization (vibrating sample magnetometry, VSM). The intraparticle diffusion model controlled the MB adsorption. The pseudo- and second-order kinetics described the MB photodegradation. When using SiO2-shell functionalized nanoparticles, the adsorption and photodegradation constant rates are three–four times higher than for using starting core iron oxide nanoparticles. The obtained magnetic nanoparticles (MNPs) were tested for films deposition.

In-situ synthesis of reduced graphene oxide/aluminium oxide nanopowders for reinforcing Ti-6Al-4V composites

Carbon nanomaterials (such as graphene, carbon nanotubes and nano-diamond) are widely used to synthesize metal matrix composites to strengthen metals such as Ti, Al and Cu. However, severe aggregation of these nano-scale reinforcements within the metal matrix has been a serious issue to achieve good performance metal matrix composites. In this study, we employed an in-situ co-precipitation method to decorate reduced graphene oxides with aluminium oxide nanoparticles (i.e. rGONs@Al2O3), which were then introduced into Ti-6Al-4 V matrix using the processes of ball milling and spark plasma sintering. Effects of co-precipitation temperature on the characteristics of rGONs/Al2O3 nanopowders, and their concentrations on microstructures and mechanical properties of the composites were systemically investigated. Characterization results revealed that γ-Al2O3 nanoparticles were uniformly wrapped with rGONs fakes, and numbers and sizes of Al2O3 nanoparticles were decreased with the increase of co-precipitation temperature. The rGONs@Al2O3 nanoparticles were uniformly coated onto the surfaces of the Ti-6Al-4 V powders, thus achieving a much finer grain size of matrix after the sintering process. As the content of rGONs@Al2O3 was increased, the strength of the composites was enhanced, whereas the elongation was slightly decreased. Due to effects of grain refinement and effective load transfer, the composite of 0.5 wt% rGONs@Al2O3 has achieved a high yield strength and an ultimate tensile strength of 950 MPa and 1022 MPa, which were ~120.4% and ~117.1% of the TC4 matrix, respectively. The fracture morphology was a mixture of cleavage fracture and ductile fracture.

Effects of co-precipitation temperature on structure and properties of La and Y doped cerium zirconium mixed oxides

Due to the oxygen storage and release properties, cerium zirconium mixed oxides are recognized as the key material in automotive three-way catalysts. To reveal the effects of co-precipitation temperature on structure, physical and chemical properties of multi-doped cerium zirconium mixed oxides, a series of La and Y doped cerium zirconium mixed oxides (CZLYs) were synthesized via a co-precipitation method, and the physical and chemical properties of CZLYs were systemically characterized by XRD, N2 adsorption–desorption, TEM, XPS, oxygen storage capacity (OSC) and hydrogen temperature programmed reduction (H2-TPR). The results show that co-precipitation temperature is an important parameter to influence the crystal size, oxygen storage capacity and thermal stability of CZLYs. When the co-precipitation temperature was 60 °C, the best redox properties and thermal stability of CZLYs were obtained. After thermal treatment at 1100 °C for 10 h, the specific surface area and oxygen storage capacity of the corresponding aged sample were 15.42 m2/g and 497.7 μmol/g, respectively. In addition, a mechanism was proposed to reveal the effects of co-precipitation temperature on the structure and properties of CZLYs.

PREPARATION OF ATO NANOPOWDERS WITH Co-PRECIPITATION AND THEIR LASER-REFLECTION PROPERTIES

Antimony tin oxide (ATO) nanoparticles were prepared using co-precipitation with tin chloride and antimony chloride as the main raw materials. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and ultraviolet-visible spectrophotometry were used to characterize the crystal structure, morphology and laser reflectivity. The effects of the pH value, co-precipitation reaction temperature, calcination temperature and calcination time on the laser reflectivity of ATO nanoparticles were studied. The results show that, compared with the undoped SnO2 powder, the reflectivity of a Sb-doped ATO powder at a laser wavelength of 1.06 µm is significantly reduced, and with an increase in the Sb doping, the reflectivity of the ATO powder at 1.06 µm first decreases and then increases. When the Sb/Sn molar ratio is 2/10, the reflectivity decreases to the lowest point, which is caused by the high concentration of Sb5+. ATO powders (Sb/Sn = 2/10) prepared at a titration-end-point pH of 2, co-precipitation temperature of 70 °C, calcination temperature of 800 °C and calcination time of 6 h have the lowest laser reflectivity at the laser wavelength of 1.06 µm, which is less than 0.02 %.

Morphologic, structural, and magnetic characterization of cobalt ferrite nanoparticles synthesized at different temperatures

In this study we report on the synthesis and characterization of cobalt ferrite (CoFe2O4) nanoparticles (NPs), synthesized by chemical co-precipitation in alkaline medium. Two samples were synthesized at two different temperatures, 35 and 90 oC. Both samples were characterized by Transmission Electron Microscopy (TEM), x-ray diffraction (XRD), and room-temperature (RT) magnetization. Two samples showed superparamagnetic behavior (SPM) at RT. TEM reveals morphological mean diameter increasing 5.8 nm to 10.4 nm, with the increase of the co-precipitation temperature. XRD confirm the inverse cubic spinel structure. The RT magnetization curves were analyzed by the first-order Langevin function averaged out by a lognormal distribution function of magnetic moments. This analysis showed saturation magnetization and magnetic moment increases from 60.2 to 74.8 emu/g and from 3.9 x 103 to 8.2 x 103 mB, respectively.

The effect of co-precipitation temperature on the crystallite size and aggregation/agglomeration of GdFeO3 nanoparticles

The effect of co-precipitation temperature on the crystallite size and aggregation/agglomeration of GdFeO3 nanoparticles

Coprecipitation Temperature Effects of Morphology-Controlled Nickel Hexacyanoferrate on the Electrochemical Performance in Aqueous Sodium-Ion Batteries.

Coprecipitation effortlessly fabricated nickel hexacyanoferrate (NiHCF) with outstanding rate capability and stability for aqueous batteries. Citrate-aided coprecipitation decelerated the crystallization, assembling cubic-shaped powder based on separation between nucleation and growth. This study revealed that coprecipitation temperature determined the electrochemical performance. With lower temperatures, smaller particles with more water were formed by predominant nucleation, resulting in low crystallinity and capacity of 58 mAh g-1 . Expanded surface area reduced electrode/electrolyte interface charge-transfer resistance and showed excellent rate capability (79 % of initial capacity at 100 C-rate). However, poor cyclability was obtained. At elevated temperatures, nuclei growth and dehydration occurred, and thus highly crystalline large particles were formed. In turn, NiHCF delivered excellent capacity of 76 mAh g-1 at 1 C-rate but exhibited inferior rate performance because of longer diffusional path. Meanwhile, normal coprecipitation at 70 °C induced irregular-shaped tiny particles, presenting 93 % retention of initial capacity at 100 C-rate.

Synthesis method of novel Gd2O3@Fe3O4 nanocomposite modified by dextrose capping agent

In current study, gadolinium oxide was heterogeneously formed on the surface of iron oxide nanoparticles and further modified with dextrose capping agent to be used in biomedical applications, especially for contrast enhancement in MR images. First, two types of iron oxide nanoparticles were prepared at 25 and 80 °C via simple coprecipitaion method. Then, gadolinium oxide nanoparticles were synthesized through a consecutive precipitation process on previously formed iron oxide seeds in an aqueous media and subsequent annealing at 300 °C. Finally, dextrose was used as capping agent to stabilize nanocomposites in a colloidal suspension. X-ray diffraction (XRD), Scanning and Transmission electron microscopy, Dynamic Laser Scattering (DLS), Fourier-Transform Infrared Spectroscopy (FTIR), and Magnetometery (VSM) techniques were employed for nanocomposites investigation and MTT-assay method used for viability assessment of colloidal samples. Measurements based on Scherrer equation from XRD patterns showed that increasing coprecipitation temperature resulted bigger iron oxide crystallites. The iron oxide crystallite size was increased from 15.1 to 28.1 nm. Precipitation process led to gadolinium oxide formation with 30.7 and 38.8 nm crystallite sizes, respectively. TEM images revealed that iron oxide agglomerates were encapsulated in gadolinium oxide surroundings. Hydrodynamic size of the coated nanoparticles with dextrose was 208 and 247 nm. In VSM examinations, nanocomposites did not display coercive field and the saturation magnetization was 1.93 emu/g. MTT-assay results showed 80% viability in 285 μg nanocomposites containing 96.9 μg [Fe] and 11.4 μg [Gd].

Field Dependence of the Magnetization at Increasing Size: An Empirical Approach for Cobalt Ferrite Nanoparticles

This paper reports on the synthesis and characterization (morphological and magnetic) of cobalt ferrite nanoparticles in alkaline medium at increasing co-precipitation temperature (30 °C, 50 °C, and 95 °C). Transmission electron microscopy reveals morphological mean diameter (diameter dispersity) increasing (decreasing), with the increase of the co-precipitation temperature, from 6.9 to 10.4 nm (0.19-0.12) while describing the particle size histogram using a log-normal distribution function. Hysteresis curves (M versus H) recorded at 5, 100, and 300 K reveal cycles progressively closing while increasing the temperature. In the range of temperature of our investigation, the M versus H data can be successfully curve fit by a phenomenological model including both ferrimagnetism and superparamagnetism, from which the content of the latter (p), the coercivity (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> ), the squareness ratio (M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> /M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FM</sup> ), and the magnetic mean diameter (diameter dispersity) can be extracted. The magnetic mean diameter (diameter dispersity) increases (decreases), with the increase of the co-precipitation temperature, from 5.2 to 9.1 nm (0.39-0.26) while averaging out the superparamagnetic contribution using a log-normal distribution function.

Effects of surface hydroxyl groups induced by the co-precipitation temperature on the catalytic performance of direct synthesis of isobutanol from syngas

A series of Zn-Cr oxides catalysts with different content of surface hydroxyl groups were prepared at different co-precipitation temperature. These catalysts were used for direct synthesis of isobutanol from syngas with an aim to investigate the effect of co-precipitation temperature on the catalytic activity of Zn-Cr catalysts. The co-precipitation temperature had a strong influence on surface OH groups leading to the different activities of ZnCr catalysts. Catalysts characterizations by XPS, XRD, H2-TPR, CO2-TPD, in situ FTIR of CO absorption and DFT calculation clearly revealed that the surface OH groups played important role in the adsorption and activation of CO. The adsorption energy of CO is intensified by the presence of surface OH, and it is easier to form formats than carbonates owning to the low activation barrier and reaction energy. Therefore, selectivity for alcohols showed an increased tendency with increasing the surface OH content on catalysts. Among all ZnCr catalysts, catalyst prepared at 60 °C (ZC-60) showed the best catalytic performance due to the highest concentration of surface OH groups.

Optimization red emission of SrMoO4: Eu3+ via hydro-thermal co-precipitation synthesis using orthogonal experiment

In the present study, the SrMoO4:Eu3+ phosphors has been synthesized through hydro-thermal co-precipitation method, and single factor and orthogonal experiment method was adopted to find optimal synthesis condition. It is interesting to note that hydro-thermal temperature is a prominent effect on the luminescent intensity of SrMoO4:Eu3+ red phosphor, followed by co-precipitation temperature, calcining time, and the doping amount of Eu3+. The optimal synthesis conditions were obtained: hydro-thermal temperature is 145 °C, co-precipitation temperature is 35 °C, the calcining time is 2.5 h, and the doping amount of activator Eu3+ is 25%. Subsequently, the crystalline particle size, phase composition and morphology of the synthesized phosphors were evaluated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The results show that these phosphors possess a scheelite-type tetragonal structure, and the particle size is about 0.2 μm. Spectroscopic investigations of the synthesized phosphors are carried out with the help of photo-luminescence excitation and emission analysis. The studies reveal that SrMoO4: Eu3+ phosphor efficiently convert radiation of 394 nm–592 and 616 nm for red light, and the luminescence intensity of SrMoO4:Eu3+ phosphors is improved. SrMoO4:Eu3+ phosphors may be a potential application for enhancing the efficiency of white LEDs.

Methanol formation from carbon dioxide hydrogenation using Cu/ZnO/Al2O3 catalyst

Abstract Methanol synthesis was performed using a copper-based catalyst (Cu/ZnO/Al2O3) and the coprecipitation method in a fixed bed reactor. The experimental parameters, including gas hourly space velocity, coprecipitation temperature, and reaction temperature, were examined to obtain the optimal conditions for methanol synthesis. A lower precipitation temperature when preparing the catalyst is propitious for obtaining higher Cu dispersion, smaller Cu crystal size, and higher methanol synthesis activity. The optimal temperature range for methanol synthesis was 180–200°C. The most observable space–time yield was 9.33 g/kg-cat/h, which was obtained using a Cu/ZnO/Al2O3 (45/45/10 mol%) catalyst when the reaction temperature was 200°C, CO2 conversion equaled 13%, and methanol yield was 2.7% at 7 bar. The lifespan was more than 120 h. Characterization of the catalyst was performed with accelerated surface area and porosimetry, an X-ray diffractometer, and temperature program reduction.

CO2 sorbents derived from capsule-connected Ca-Al hydrotalcite-like via low-saturated coprecipitation

This work presents the synthesis of Ca-Al mixed oxides derived from Ca-Al-CO3 layered double hydroxides (LDHs), which were prepared using a low-saturated coprecipitation method at high constant pH. Compared to the high-saturated coprecipitation method, a better CO2 adsorption capacity and stability were obtained from the mixed oxides. This was attributed to the novel capsule-connected structure of LDHs nanoparticles, smaller crystal size of CaO, and uniform distribution of CaO and Al2O3. The effect of the coprecipitation temperature, Ca/Al ratio and methanol modification on the CO2 capture performance of Ca-Al mixed oxides was also investigated. The mixed oxides with 2:1 Ca/Al ratio modified by methanol showed a much greater stability with carbonation capacity of about 56.7 wt% after 30 carbonation/calcination cycles. A double exponential model was fitted to the CO2 adsorption curves, providing a good explanation for the disparity between CO2 uptakes with different Ca/Al ratios.

Mo promoted Ni-Al2O3 co-precipitated catalysts for green diesel production

Three Mo promoted Ni-Al2O3 co-precipitation catalysts with practically the same composition (49–52%wtNi, 6-7%wtMo) were prepared using three different co-precipitation modes: co-precipitation at room temperature using ammonia as precipitating agent as well as co-precipitation at higher temperature (110 °C) using ammonia or urea as precipitating agent. The corresponding un-promoted catalysts were also synthesized for comparison. The catalysts were exhaustively characterized using various techniques and evaluated for the selective deoxygenation (SDO) of natural triglycerides using two different feedstocks: sunflower oil (SO) and waste cooked oil (WCO). The catalytic tests were performed under solvent free conditions in a semi-batch reactor at 310 °C, hydrogen pressure 40 bar and very high reactant volume to catalysts mass ratio (100 mL/1 g).The promoting action of the Mo(VI) and Mo(IV) well dispersed oxidic phases, was demonstrated in all cases. This was attributed to the impressive decrease in the size of the nickel nanoparticles and to the inhibition of the formation of the catalytically inactive nickel aluminate. Moreover, the Mo (VI) and Mo(IV) oxidic phases affect the network of the SDO favoring the hydrodeoxygenation of the intermediate alcohols with respect to the decarbonylation of intermediate aldehydes.The catalyst prepared at high co-precipitation temperature using ammonia as precipitating agent was proved to be the most efficient for the SDO of SO. An almost complete transformation of SO into n-C15, n-C16, n-C17, n-C18 (green diesel: 97% of liquid products) was obtained under the above mentioned conditions. This catalyst was proved to be very stable. The catalyst prepared at room co-precipitation temperature using ammonia as precipitating agent was proved to be the most efficient for the SDO of WCO (green diesel: 76% of liquid products). Its improved efficiency with respect to the other Mo promoted catalysts was attributed to its smaller pore size which prohibits the blockage of active sites located inside the corresponding pores by bulky compounds present in WCO.

Study on preparation of CNTs-Cu composites materials by hydrazine hydrate reduction-solid state sintering process

ABSTRACTIn this paper, the 8% CNTs-Cu and 16% CNTs-Cu composite powders were synthesized by chemical co-precipitation method, in which hydrazine hydrate was used as reductant. The parameters of precipitation process are chosen as follows: co-precipitation temperature was set as 70°C, stirring rate was set to be 600 rpm, pH was designed as 10, dripping reaction time was 120 min and the drying temperature was 50°C. Carbon nanotubes (CNTs), Copper sulfate, sodium hydroxide and hydrazine hydrate were used as raw materials. 8% CNTs-Cu composite bulks were prepared by a solid-phase sintering process under the condition that molding temperature was 800°C, while 16% CNTs-Cu composite bulks cannot be prepared by the same method.

Study on preparation of CNTs-Cu composites materials by chemical coprecipitation hydrogen reduction solid state sintering process

ABSTRACTThe CNTs-CuO composite powders were synthesized by chemical co-precipitation method, when the co-precipitation temperature was set as 70°C, stirring rate was set to 1000 rpm, pH was 10, drip reaction time was 120 min and the drying temperature was 50°C. Carbon nanotubes (CNTs), Copper sulfate, sodium hydroxide were used as raw materials. 8%CNTs-Cu and 16%CNTs-Cu composite powders were synthesized by hydrogen reduction, reduced at 300°C for 2h. 8%CNTs-Cu composite bulk were prepared by a solid-phase sintering process when the molding temperature was 800°C, while 16%CNTs-Cu composite bulk cannot be prepared by the same method.

Influence of co-precipitation temperature on microstructure and electrochemical properties of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode materials for lithium ion batteries

The layered Li-rich Mn-based cathode materials Li[Li0.2Mn0.54Ni0.13Co0.13]O2 were prepared by using co-precipitation technique at different temperatures, and their crystal microstructure and particle morphology were observed and analyzed by XRD and SEM. The electrochemical properties of these samples were investigated by using charge-discharge tests, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV), respectively. The results indicated that all samples are of high purity. When the precursors were co-precipitated at 50 °C, their cathode materials have the most uniform and full particles and exhibit the highest initial discharge capacity (289.4 mAh/g at 0.1C), the best cycle stability (capacity retention rate of 91.2 % after 100 cycles at 0.5C), and the best rate performance. The EIS results show that the lower charge transfer resistance of 50 °C sample is responsible for its superior discharge capacity and rate performance.