Optimization of Preparation of Fe_(3)O_(4)-L by Chemical Co-Precipitation and Its Adsorption of Heavy Metal Ions

To address the serious pollution of heavy metals in AMD,the difficulty and the high cost of treatment,Fe_(3)O_(4)-L was prepared by the chemical co-precipitation method.Based on the single-factor and RSM,the effects of particle size,total Fe concentration,the molar ratio of Fe^(2+)to Fe^(3+)and water bath temperature on the removal of AMD by Fe_(3)O_(4)-L prepared by chemical co-precipitation method were analyzed.Static adsorption experiments were conducted on Cu^(2+),Zn^(2+)and Pb^(2+)using Fe_(3)O_(4)-L prepared under optimal conditions as adsorbents.The adsorption properties and mechanisms were analyzed by combining SEM-EDS,XRD and FTIR for characterization.The study showed that the effects of particle size,total Fe concentration and the molar ratio of Fe^(2+)to Fe^(3+)are larger.Obtained by response surface optimization analysis,the optimum conditions for the preparation of Fe_(3)O_(4)-L were a particle size of 250 mesh,a total Fe concentration of 0.5 mol/L,and a molar ratio of Fe^(2+)to Fe^(3+)of 1:2.Under these conditions,the removal rates of Cu^(2+),Zn^(2+),and Pb^(2+)were 94.52%,88.49%,and 96.69%respectively.The adsorption of Cu^(2+),Zn^(2+)and Pb^(2+)by Fe_(3)O_(4)-L prepared under optimal conditions reached equilibrium at 180 min,with removal rates of 99.99%,85.27%,and 97.48%,respectively.The adsorption reaction of Fe_(3)O_(4)-L for Cu^(2+)and Zn^(2+)is endothermic,while that for Pb^(2+)is exothermic.Fe_(3)O_(4)-L can still maintain a high adsorption capacity after five cycles of adsorption-desorption experiments.Cu^(2+),Zn^(2+)and Pb^(2+)mainly exist as CuFe_(2)O_(4),Zn(OH)2,ZnFe_(2)O_(4)and PbS after being adsorbed by Fe_(3)O_(4)-L,which is the result of the combination of physical diffusion,ion exchange and surface complexation reaction.

Thermodynamic equilibrium theory-guided design and synthesis of Mg-doped LiFe_(0.4)Mn_(0.6)PO_(4)/C cathode for lithium-ion batteries

Mn-rich LiFe_(1-x)Mn_(x)PO_(4)(x>0.5),which combines the high operation voltage of LiMnPO_(4)with excellent rate performa nce of LiFePO4,is hindered by its sluggish kinetic properties.Herein,thermodynamic equilibrium analysis of Mn^(2+)-Fe^(2+)-Mg^(2+)-C_(2)O_(4)^(2-)-H_(2)O system is used to guide the design and preparation of insitu Mg-doped(Fe_(0.4)Mn_(0.6))_(1-x)Mg_(x)C_(2)O_(4)intermediate,which is then employed as an innovative precursor to synthesize high-performance Mg-doped LiFe_(0.4)Mn_(0.6)PO_(4).It indicates that the metal ions with a high precipitation efficiency and the stoichiometric precursors with uniform element distribution can be achieved under the optimized thermodynamic conditions.Meanwhile,accelerated Li+diffusivity and reduced charge transfer resistance originating from Mg doping are verified by various kinetic characterizations.Benefiting from the contributions of inherited homogeneous element distribution,small particle size,uniform carbon layer coating,enhanced Li+migration ability and structural stability induced by Mg doping,the Li(Fe_(0.4)Mn_(0.6))_(0.97)Mg_(0.03)PO_(4)/C exhibits splendid electrochemical performance.

Preparation of MnxNi0.5-xZn0.5Fe2O4 Nanorods by the Co-precipitation Method

MnxNi0.5-xZn0.5Fe2O4 nanorods were successfully synthesized by the thermal treatment of rod-like precursors that were fabricated by the co-precipitation of Mn2＋, Ni2＋, and Fe2＋ in the lye. The phase, morphology, and particle diameter were examined by the X-ray diffraction and transmission electron microscopy. The magnetic properties of the samples were studied using a vibrating sample magnetometer. nanorods with a diameter of 35 nm and an The results indicated that pure Ni0.5-xZn0.5Fe2O4 aspect ratio of 15 were prepared. It was found that the diametei of the MnxNi0.5-xZn0.5Fe2O4（0≤x≤0.5） samples increased, the length and the aspect .ratio decreased, with an increase in x value. When x=0.5, the diameter and the aspect ratio of the sample reached up to 50 nm and 7-8, respectively. The coercivity of the samples first increased and then decreased with the increase in the x value. The coercivity of the samples again increased when the x value was higher than 0.4. When x=0.5, the coercivity of the MnxNi0.5-xZn0.5Fe2O4 sample reached the maximal value （134.3 Oe） at the calcination temperature of 600 ℃. The saturation magnetization of the samples first increased and then. decreased with the increase in the x value. When x=0.2, the saturation magnetizat：ion of the sample reached the maximal value （68.5 emu/g） at the calcination temperature of 800 ℃.

Electrochemical performance of Ti^(4+)-doped LiFePO_4 synthesized by co-precipitation and post-sintering method

Ti4+-mixed FePO4·xH2O precursor was prepared by co-precipitation method,with which Ti4+ cations were added in the process of preparing FePO4·xH2O to pursue an effective and homogenous doping way.Ti4+-doped LiFePO4 was prepared by an ambient-reduction and post-sintering method using the as-prepared precursor,Li2CO3 and oxalic acid as raw materials.The samples were characterized by scanning electron microscopy (SEM),X-ray diffractometry (XRD),electrochemical impedance spectroscopy (EIS),and electrochemical charge/discharge test.Effects of Ti4+-doping and sintering temperature on the physical and electrochemical performance of LiFePO4 powders were investigated.It is noted that Ti4+-doping can improve the electrochemical performance of LiFePO4 remarkably.The Ti4+-doped sample sintered at 600 ℃ delivers an initial discharge capacity of 150,130 and 125 mA·h/g with 0.1C,1C and 2C rates,respectively,without fading after 40 cycles.

Recovery of magnetite from FeSO_4·7H_2O waste slag by co-precipitation method with calcium hydroxide as precipitant

Proper utilization of the FeSO4·7H2O waste slag generated from TiO2 industry is an urgent need, and Fe3O4 particles are currently being widely used in the wastewater flocculation field. In this work, magnetite was recovered from ferrous sulphate by a novel co-precipitation method with calcium hydroxide as the precipitant. Under optimum conditions, the obtained spherical magnetite particles are well crystallized with a Fe304 purity of 88.78%, but apt to aggregate with a median particle size of 1.83 μm. Magnetic measurement reveals the obtained Fe304 particles are soft magnetic with a saturation magnetization of 81.73 A-m2/kg. In addition, a highly crystallized gypsum co-product is obtained in blocky or irregular shape. Predictably, this study would provide additional opportunities for future application of low-cost Fe3O4 particles in water treatment field.

Co-Precipitation Synthesis and Spectral Characteristics of Long Afterglow Phosphor Y_2O_2S:Sm^(3+), Mg^(2+), Ti^(4+)

Y2O2S：Sm^3＋, Mg^2＋, Ti^4＋ phosphor was synthesized by co-precipitation method. The crystalline structure of all synthesized phosphors was investigated by XRD. The result showed that all synthesized phosphors had a hexagonal crystal structure, which was the same as Y2O2S. The emission spectrum and excitation spectrum were measured, and the effect of Sm^3 ＋ molar ratio on the spectra was discussed. The emission spectra of the phosphors showed three emission peaks due to typical transitions of Sm^3 ＋ （4G5/2→6HJ ,J = 5/2, 7/2, 9/2）, and the emission peaks at 606 nm was stronger than others. With the increase of Sm^3 ＋ molar ratio, the emission intensity was strengthened. The excitation peaks were ascribed to the representative energy transition 4f→4f of Ti^4＋ phosphor prepared by co-precipitation method was Sm^3＋ ions. The results indicated that the Y2O2S ： Sm^3＋ , Mg^2＋ , an efficient long afterglow phosphor.

Synthesis of LaPO_4:Ce,Terbium by Co-Precipitation Method

The synthesis of precursor of green phosphors, LaPO4: Ce, Tb, by means of co-precipitation with cocurrent flow feed was studied. The effects of the reaction temperature, the kind and concentration of the acid in the bottom water, and the charging rate on the physical properties, such as particle size, were investigated. It is found that the particle size of the powder is controllable by adjusting acidity in bottom water and charging rate. The powder with diameter size of 3 to 5μm was obtained. Its XRD and SEM were analyzed. XRD patterns of the as-prepared green phosphor powders display the typical peaks of CePO4. SEM shows that the morphology of powders is ball-shaped.

Preparation and Microstructure of Spinel Zinc Ferrite ZnFe_2O_4 by Co-precipitation Method

Spinel zinc ferrites ZnFe2O4, prepared by co-precipitation method using the zinc nitrate Zn（NO3）2·6H2O and ferric nitrate Fe（NO3）3·2H2O as the raw materials, were characterized by the thermo gravimetric analysis （TG） and differential scanning calorimeter （DSC）, X-ray diffraction （XRD） and scanning electron microscope （SEM）. The influence of synthesis conditions, such as Zn/Fe molar ratio, pH value, the sintering temperature and time, on the microstructures was detailedly investigated. The relationships between the microstructures and the synthesis conditions were discussed. The results show that the pure spinel zinc ferrites ZnFe2O4 are formed when the Zn/Fe molar ratio is 1.05∶2 at pH=8.5 or Zn/Fe molar ratio is 1∶2 at Ph=9-10, and the precursors are sintered at 1100 ℃ for 4 h. Especially no other phases are observed when the Zn/Fe molar ratio is 1∶2 at pH=10 and the precursor is sintered above 700 ℃ for 4 h. The higher sintering temperature and longer sintering time contribute to grain growth.

Synthesis of M1-3xAl2O4:Eu2+x/Dy3+ 2x(M^2+= Sr^2+, Ca^2+ and Ba^2+) phosphors with long-lasting phosphorescence properties via co-precipitation method

The long afterglow fluorescent material of M1-3xAl2O4:Eu2+ x/Dy3+2x(M2+= Sr2+, Ca2+ and Ba2+) phosphors are successfully synthesized by calcining precursor obtained via co-precipitation method at 1300oC for 4 h with reducing atmosphere (20% H2 and 80% N2). The phase evolution, morphology and afterglow fluorescent properties are systematically studied by the various instruments of XRD, FE-SEM, PLE/PL spectroscopy and fluorescence decay analysis. The PL spectra shows that the Sr1-3xAl2O4:Eu2+x/Dy3+ 2x phosphors display vivid green emission at s519 nm (4f65d1!4f7 transition of Eu2+) with monitoring of the maximum excitation wavelength at s334 nm (8S7=2!6IJ transition of Eu2+), among which the optimal concentration of Eu2+ and Dy3+ is 15 at.% and 30 at.%, respectively. The color coordinates and temperature of Sr1-3xAl2O4:Eu2+ x/Dy3+ 2x phosphors are approximately at (s0.27, s0.57) and s6700 K, respectively. On the above basis, the M0:55Al2O4:Eu2+ 0:15/Dy3+ 0:3 (M2+= Ca2+ and Ba2+) phosphors is obtained by the same method. The PL spectra of these phosphors shows the strongest blue emission at s440 nm and cyan emission at s499 nm under s334 nm wavelength excitation, respectively, which are blue shifted comparing to Sr1??3xAl2O4:Eu2+ x/Dy3+ 2x phosphors. The color coordinates and temperatures of M0:55Al2O4:Eu2+ 0:15/Dy3+ 0:3 (M2+= Ca2+ and Ba2+) phosphors are approximately at (s0.18, s0.09), s2000 K and (s0.18, s0.42), s11600 K, respectively. In this work, long afterglow materials of green, blue and cyan aluminates phosphors with excellent properties have been prepared, in order to obtain wide application in the field of night automatic lighting and display.

Physical Properties Study of Zn_(0.5)Mn_(0.5−x)Li_(2x)Fe_(2)O_(4) Nanoparticle Series that Prepared by Co-Precipitation Method

Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) was afforded by utilizing co-precipitation method. The structural and optical characteristics were analyzed for the samples employing X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and Ultraviolet-visible spectrophotometer (UV-Vis). XRD revealed that the structure of certain nanoparticles is a cubic spinel with space group (Fd-3m) and crystallite size in the scale 124 - 150 nm. Lattice parameter was determined to increments with Li+1 and that may occur due to the larger ionic radius of the Li1+ ion. FTIR spectroscopy confirmed the form of spinel ferrite and explicated the properties of absorption bands approximately 593, 1111, 1385, 1640, 2922 and 3430. The energy band gap was estimated for all samples with diverse ratios and was observed in the range of 2.58 - 2.52 eV.

Antibacterial and anti-flaming PA6 composite with metathetically prepared nano AgCl@BaSO_(4) co-precipitates

In this study,a facile and environmentally friendly method with low energy consumption for preparing nanoscale AgCl and BaSO4 co-precipitates(AgCl@BaSO_(4) co-precipitates)was developed based on the metathetical reaction.Then,the dried co-precipitates were melt-compounded with polyamide 6(PA6)resins at a specified mass ratio in a twin-screw extruder.The results demonstrated that in the absence of any coating agent or carrier,the nanoparticles of AgCl@BaSO_(4) co-precipitates were homogeneously dispersed in the PA6 matrix.Further analysis showed that after the addition of AgCl@BaSO_(4) co-precipitates,the antibacterial performance,along with the flame-retardance and anti-dripping characteristics of PA6,was enhanced significantly.In addition,the PA6 composites possessed high spinnability in producing pre-oriented yarn.

Fluorescent Comparison of Sr_2CeO_4 Prepared from Carbonate and Oxalate Precursor

A blue-emitting phosphor powder, Sr_2CeO_4, was synthesized after heat-treatment to carbonate and oxalate precursors, which were obtained by co-precipitation reactions with respective ammonium compounds as precipitants. The phase formation and chemical purity of Sr_2CeO_4 powders were studied on XRD, TGA and XPS techniques. Their fluorescent performances were investigated and compared. The photoluminescence emission spectra for the phosphor prepared from respective precursors are similar, having a broad band with the peak at about 470 nm. However, their fluorescent intensities are different after heat-treatment at same conditions. The optimum condition to achieve superior Sr_2CeO_4 phosphor is confirmed.

Synthesis and electrochemical performances of spherical LiFePO_4 cathode materials for Li-ion batteries

Spherical LiFePO4 and LiFePO4/C composite powders for lithium ion batteries were synthesized by a novel processing route of co-precipitation and subsequent calcinations in a nitrogen and hydrogen atmosphere. The precursors of LiFePO4, LiFePO4/C composite and the resultant products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and the electrochemical performances were investigated by galvanostatic charge and discharge tests. The precursors composed of amorphous Fe3(PO4)2·xH2O and crystalline Li3PO4 obtained in the co-precipitation processing have a sphere-like morphology. The spherical LiFePO4 derived from the calcinations of the precursor at 700 ℃ for 10 h in a reduction atmosphere shows a discharge capacity of 119 mAh·g-1 at the C/10 rate, while the LiFePO4/C composite with 10wt.% carbon addition exhibits a discharge capacity of 140 mAh·g-1. The electrochemical performances indicate that the LiFePO4/C composite has a higher specific capacity and a more stable cycling performance than the bare olivine LiFePO4 due to the carbon addition enhancing the electronic conductivity.

Preparation of Nano-MnFe2O4 and Its Catalytic Performance of Thermal Decomposition of Ammonium Perchlorate

Nano-MnFe2O4 particles were synthesized by co-precipitation phase inversion method and low-temperature combustion method respectively, using MnCl2, FeCl3, Mn（NO3）2, Fe（NO3）3, NaOH and C6H8O7. X-ray diffraction （XRD）, transmission electron microscope （TEM）, Fourier transform infrared spectroscopy （FT-IR）, thermogravim-etry-differential thermal analysis （TG-DTA） and differential scanning calorimetry （DSC） were used to characterize the structure, morphology, thermal stability of MnFe2O4 and its catalytic performance to ammonium perchlorate. Results showed that single-phased and uniform spinel MnFe2O4 was obtained. The average particle size was about 30 and 20 nm. The infrared absorption peaks appeared at about 420 and 574 cm-1, and the particles were stable below 524 ℃. Using the two prepared catalysts, the higher thermal decomposition temperature of ammonium perchlorate was decreased by 77.3 and 84.9 ℃ respectively, while the apparent decomposition heat was increased by 482.5 and 574.3 J？g？1. The catalytic mechanism could be explained by the favorable electron transfer space provided by outer d orbit of transition metal ions and the high specific surface absorption effect of MnFe2O4 particles.

Effect of Cu Loading to Catalytic Selective CO Oxidation of CuO/CeO₂–Co₃O₄

This work studied CuO/CeO2-Co3O4 with wt% Ce:Co ratio 95:5 for selective CO oxidation with effect of? wt% Cu loading. The catalysts were prepared by co-precipitation. Characterizations of catalysts were carried out by XRD and BET techniques. The results showed a good dispersion of CuO for 5 wt% Cu loading catalysts and showed high specific surface area of catalyst. For selective CO oxidation, both 5CuO and 30CuO catalysts could remove completely CO in the presence of excess hydrogen at 423 K and 20CuO could eliminate CO completely at 443 K. Moreover, considering the selectivity to CO oxidation, the 5CuO catalyst has shown the highest selectivity of 85% while the 30CuO catalyst obtains the selectivity of 65% at the reaction temperature of 423 K.

The Electrical and Optical Properties of Zn0.5Li2xMg0.5-xFe2O4 Lithium Doped Nanoparticle Prepared by Coprecipitation Method

In this study, nano ferrite materials were produced to replace costive industrial materials [1]. Ferrite nanoparticles are the interesting material due to their rich and unique physical and chemical properties. They find applications in catalysis, bio-processing, medicine, magnetic recording, adsorption, devices etc. Using co-participation method, five nano ferrite samples Zn0.5Mg0.5-xLi2xFe2O4 (x = 0.00, 0.10, 0.20, 0.30 and 0.40) were prepared. The electrical and optical properties of the Zn0.5Mg0.5-xLi2xFe2O4 samples were studied using the Ultraviolet-visible (UV-Vis) spectroscopy. The results verified that the formation of the absorption coefficient of the five samples of Zn0.5Mg0.5-xLi2xFe2O4 increased with the increase of Lithium (Li2x). The energy band gap of the Zn0.5Mg0.5-xLi2xFe2O4 samples ranged from 3.28 to 3.12 eV [1]. The extinction coefficient (K) for five samples of Zn0.5Li2xMg0.5-xFe2O4 increased with the increase of Lithium (Li2x) at 338 nm from 0.074 to 0.207. The high magnitude of optical conductivity is (1.34 × 1012 sec-1) and the maximum value of electrical conductivity is 42 (Ω.cm)-1. This may due to the electrical and optical properties of lithium.

Synthesis and electrochemical performances of high-voltage LiNi_0.5Mn_1.5O_4 cathode materials prepared by hydroxide co-precipitation method

Spherical cathode material LiNi_0.5Mn_1.5O_4 for lithium-ion batteries was synthesized by hydroxide co- precipitation method. X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electrochemical mea- surements were carried out to characterize prepared LiNi_0.5Mn_1.5O_4 cathode material. SEM images show that the LiNi_0.5Mn_1.5O_4 cathode material is constituted by micro-sized spherical particles （with a diameter of around 8 μm）. XRD patterns reveal that the structure of prepared LiNi_0.5Mn_1.5O_4 cathode material belongs to Fd3m space group. Electrochemical tests at 25℃show that the LiNi_0.5Mn_1.5O_4 cathode material prepared after annealing at 600 ℃ has the best electrochemical performances. The initial discharge capacity of prepared cathode material delivers 113.5 mAh·g-1 at 1C rate in the range of 3.50-4.95 V, and the sample retains 96.2% （1.0C） of the initial capacity after 50 cycles. Under different rates with a cutoff voltage range of 3.50-4.95 V at 25℃, the dis- charge capacities of obtained cathode material can be kept at about 145.0 （0.1C）, 126.8 （0.5C）, 113.5 （1.0C） and 112.4mAh·g-1 （2.0C）, the corresponding initial coulomb efficiencies retain above 95.2% （0.1C）, 95.0% （0.5C）, 92.5% （1.0C） and 94.8% （2.0C）, respectively.

Recovery of magnetite from waste ferrous sulfate using polyethylene glycol(PEG) as a dispersant

The effect of PEG dispersant on the magnetic separation of magnetite（Fe3O4） synthesized from ferrous sulfate solution via co-precipitation method with calcium hydroxide as the precipitant was investigated. The results indicated that a PEG dispersant could significantly affect Fe3O4 recovery. Adding PEG during the preparation of Fe3O4 was unfavorable for Fe3O4 recovery. When the PEG-6000 concentration was increased from 0 to 8 g/L, the iron grade and median particle size of the Fe3O4 product decreased from 65.58% and 2.35 μm to 57.79% and 1.35 μm, respectively. However, adding PEG during the wet milling of the mixed product promoted the subsequent recovery of Fe3O4. When the amount of PEG-200 increased from 0% to 4% of the powder mass, the grade of iron in the Fe3O4 product increased from 65.58% to 68.32%. While the relative molecular mass of PEG at an amount of 4% of the powder mass increased from 200 to 20000, the grade of iron was reduced from 68.32% to 66.70%.

Structural characterization and optical properties of long-lasting CaAl2O4：Eu2＋,Nd3＋ phosphors synthesized by microwave-assisted chemical co-precipitation

The present paper reported the structural and luminescent properties of Eu^（2＋） and Nd^（3＋） doped CaAl_2O_4 phosphor. The samples were prepared by microwave-assisted chemical co-precipitation（MA-CCP）, a synthesis technique which is suitable for small and uniform particle that could be used directly without grinding. The effects of different microwave temperatures on structure and photoluminescence behavior were studied. Formation of a phosphor and phase purity were confirmed by X-ray diffraction technique（XRD） with variable microwave temperatures. XRD analysis showed that the phosphors prepared by MA-CCP method at the temperature of 750, 900oC, respectively and solid-state reaction（SSR） method at 1300oC consisted of impurities. Commission Internationale de L＇Eclairage（CIE） color coordinates of CaAl_2O_4：Eu^（2＋）,Nd^（3＋） were suitable as blue light emitting phosphor. Excitation and emission peaks of the samples prepared by different methods in this study were almost the same. The images of SEM showed that the size of the phosphors prepared by MA-CCP method reached a submicrometer.

Ultrasound-assisted co-precipitation synthesis of mesoporous Co_(3)O_(4)–CeO_(2)composite oxides for highly selective catalytic oxidation of cyclohexane

The one-step highly selective oxidation of cyclohexane into cyclohexanone and cyclohexanol as the essential intermediates of nylon-6 and nylon-66 is considerably challenging.Therefore,an efficient and low-cost catalyst must be urgently developed to improve the efficiency of this process.In this study,a Co_(3)O_(4)–CeO2 composite oxide catalyst was successfully prepared through ultrasound-assisted co-precipitation.This catalyst exhibited a higher selectivity to KA-oil,which was benefited from the synergistic effects between Co^(3+))/Co^(2+))and Ce^(4+)/Ce^(3+)redox pairs,than bulk CeO2 and/or Co_(3)O_(4).Under the optimum reaction conditions,89.6%selectivity to KA-oil with a cyclohexane conversion of 5.8%was achieved over Co_(3)O_(4)–CeO2.Its catalytic performance remained unchanged after five runs.Using the synergistic effects between the redox pairs of different transition metals,this study provides a feasible strategy to design high-performance catalysts for the selective oxidation of alkanes.