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.

Effects of synthesis conditions on layered Li[Ni_(1/3)Co_(1/3)Mn_(1/3)]O_2 positive-electrode via hydroxide co-precipitation method for lithium-ion batteries

Layered Li[Ni1/3Co1/3Mn1/3]O2 was synthesized with complex metal hydroxide precursors that were prepared by a co-precipitation method.The influence of coordination between ammonia and transition-metal cations on the structural and electrochemical properties of the Li[Ni1/3Co1/3Mn1/3]O2 materials was studied.It is found that when the molar ratio of ammonia to total transition-metal cations is 2.7：1,uniform particle size distribution of the complex metal hydroxide is observed via scanning electron microscopy.The average particle size of Li[Ni1/3Co1/3Mn1/3]O2 materials was measured to be about 500 nm,and the tap-density was measured to be approximately 2.37 g/cm3,which is comparable with that of commercialized LiCoO2.XRD analysis indicates that the presently synthesized Li[Ni1/3Co1/3Mn1/3]O2 has a hexagonal layered-structure.The initial discharge capacity of the Li[Ni1/3Co1/3Mn1/3]O2 positive-electrode material is determined to be 181.5 mA·h/g using a Li/Li[Ni1/3Co1/3Mn1/3]O2 cell operated at 0.1C in the voltage range of 2.8-4.5 V.The discharge capacity at the 50th cycle at 0.5C is 170.6 mA·h/g.

Recovery of iron from waste ferrous sulphate by co-precipitation and magnetic separation

Magnetite concentrate was recovered from ferrous sulphate by co-precipitation and magnetic separation. In co-precipitation process, the effects of reaction conditions on iron recovery were studied, and the optimal reaction parameters are proposed as follows： n（CaO）/n（Fe2＋） 1.4：1, reaction temperature 80 ℃, ferrous ion concentration 0.4 mol/L, and the final mole ratio of Fe3＋ to FJ＋ in the reaction solution 1.9-2.1. In magnetic separation process, the effects of milling time and magnetic induction intensity on iron recovery were investigated. Wet milling played an important part in breaking the encapsulated magnetic phases. The results showed that the mixed product was wet-milled for 20 min before magnetic separation, the grade and recovery rate of iron in magnetite concentrate were increased from 51.41% and 84.15% to 62.05% and 85.35%, respectively.

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 ℃.

Measurement of Liquid Concentration Fields Near Interface with Cocurrent Gas-Liquid Flow Absorption Using Holographic Interferometry

Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by ethanol. The influences of the Reynolds number on the measurable interface concentration and on the film thickness were discussed. The results show that CO2 concentration decreases exponentially along the mass transfer direction,and the concentration gradient increases as Reynolds number of either liquid or gas increases. CO2 concentrations fluctuate slightly along the direction of flow; on the whole, there is an increase in CO2 concentration. The investigation also demonstrated that film thickness decreases with the increase of Reynolds number of either of the two phases. Sherwood number representing the mass transfer coefficient was finally correlated as a function of the hydrodynamic parameters and the physical properties.

Fluorescence and preparation of Sr_2(P_2O_7 ):Ce,Tb phosphate by co-precipitation method

The micron-sized Sr2（P2OT）：Ce,Tb green phosphors were prepared by being annealed at different temperatures with its precursors synthesized by co-pre-cipitates of （NH4）2HPO4 at ambient temperature. The phase structure, grain size, surface morphology, and luminescent properties of phosphors were investigated by X-ray diffraction, scanning electron microscope, trans-mission electron microscope, and fluorescence spectrum. The results show that the product of precursor annealed at 1,100 ℃ is Sr2（P2O7）：Ce,Tb, which belongs to ortho-rhombic phase. The powder is spherical and the size dis-tribution is in micron grade. The sample with the molar ratio of Sr/Tb/Ce of 100.0：0.4：0.6 shows the best fluores-cence effect annealed at 1,100 ℃ for 3 h. The phosphors produce green fluorescence by being excitated with ultra-violet radiation of 254 nm wavelength, and the main emission peak is at 547 nm. The Sr2（P2O7）：Ce,Tb phos-phors synthesized by co-precipitation method of precursors at ambient temperature is a kind of efficient green-emitting phosphors.

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.

Oxidative coupling of methane over LaAlO3 perovskite catalysts prepared by a co-precipitation method: Effect of co-precipitation pH value

Oxidative coupling of methane(OCM) was conducted over LaAlO3X catalysts that were prepared by a coprecipitation method using different co-precipitation pH values(X = 6–10). The aim is to investigate the effect of p H values on the catalytic activity of La AlO3 catalysts in this reaction. The results showed that the co-precipitation pH value affected greatly on the formation of chemical species of precipitate precursors in the co-precipitation step, leading to different phases of the finally obtained LaAlO3 catalysts.When the co-precipitation pH value increased up to 8, the lanthanum-related phases such as La2 O3 and La(OH)3 were gradually formed as by-products, preventing the formation of LaAlO3 perovskite crystalline structure and facilitating the formation of oxygen vacancies on catalyst surface. However, at pH value of9 or higher, the lanthanum content in the precipitate precursor was increased greatly. Not LaAlO3 perovskite but lanthanum-related phases were developed as main phases, reducing their catalytic activities in this reaction. Among LaAlO3 catalysts, the one prepared at pH = 8 showed the highest C2 yield due to its well-developed oxygen vacancies and electrophilic lattice oxygen. Therefore, the co-precipitation pH value strongly affected the LaAlO3 catalyst activity in OCM reaction. A precious pH control should be required to prepare various perovskite catalysts for the OCM.

Solution-Phase Synthesis and Characterization of Perovskite LaCoO_3 Nanocrystals via A Co-Precipitation Route

A facile co-precipitation route for the synthesis of well-dispersed LaCoO3 nanocrystals was developed. The asprepared products were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, energy dispersive X-ray spectrometer （EDX）, and laser Raman spectroscopy （LRS）. The resuks showed that modulating the growth parameters, such as the addition of surfactants as well as the adding manner of the precipitator had a significant effect on the overall shape and size of the obtained nanocrystals. The nanorods with the diameter of 20 nm and spherical LaCoO3 nanocrystals with the size of about 25 nm could be obtained at a relatively low calcining temperature of 600℃. Furthermore, the Raman properties of LaCoO3 products obtained at different calcining temperatures were investigated.

Fundamental Study on New Method of Reducing Iron Ore-Coal Pellet in Cocurrent Shaft Furnace

Based on the laboratory experiment of reducing iron ore-coal pellet in oxidizing atmosphere,a new self-heating reduction method of iron ore-coal pellet in the cocurrent shaft furnace(CSF) has been developed.In this process,the pellets and preheated oxygen-enriched air enter the shaft furnace through its top and descend cocurrently in the furnace.Most of the heat required for rising temperature and endothermic reduction of descending pellets is provided by the way that the descending air burns the volatile from pellets and CO from the reduction of iron oxide in pellets.The reduced pellets and high temperature gas are discharged from the lower part.The sensible heat and chemical energy of the off-gas are used to heat the oxygen-enriched air in stove.This process is applicable to the direct reduction of iron pellets and prereduction of iron pellets in smelting reduction with iron bath.

Effects of synthesis conditions on the structural and electrochemical properties of layered LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2 cathode material via oxalate co-precipitation method

The uniform layered LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries was prepared by using （Ni1/3Co1/3Mn1/3）C2O4 as precursor synthesized via oxalate co-precipitation method in air. The effects of calcination temperature and time on the structure and electrochemical properties of the LiNi1/3Co1/3Mn1/3O2 were systemically studied. XRD results revealed that the optimal calcination conditions to prepare the layered LiNi1/3Co1/3Mn1/302 were 950℃ for 15 h. Electrochemical measurement showed that the sample prepared under the such conditions has the highest initial discharge capacity of 160.8 mAh/g and the smallest irreversible capacity loss of 13.5% as well as stable cycling performance at a constant current density of 30 mA/g between 2.5 and 4.3 V versus Li at room temperature.

Co-precipitation/Hydrothermal Synthesis of BiFeO_3 Powder

A coprecipitation/hydrothermal route was utilized to fabricate pure phase BiFeO3 powders using FeCl3·6H2O and Bi（NO3）3·5H2O as starting materials, ammonia as precipitant and NaOH as mineralizer. The synthesized powders were characterized by XRD, SEM and DSC-TG analysis. In the process, single-phase BiFeO3 powders could be obtained at a hydrothermal reaction temperature of 180 ℃, with NaOH of 0.15 mol/L, in contrast to 200 ℃ and 4 mol/L for conventional hydrothermal route. Meanwhile, the micro-morphology of synthesized BiFeO3 powders changed with different reaction temperatures and concentrations of NaOH. The N6el temperature, Curie temperature and decomposition temperature of the synthesized BiFeO3 powders were detected to be 301 ℃, 828 ℃ and 964 ℃, respectively. The hydrothermal reactions mechanism to fabricate BiFeO3 powders were discussed based on the in-situ transformation process.

Effect of Ferric Chloride on the Properties of Biological Sludge in Co-precipitation Phosphorus Removal Process

This paper studied the effect of ferric chloride on waste sludge digestion,dewatering and sedimentation under the optimized doses in co-precipitation phosphorus removal process.The experimental results showed that the concentration of mixed liquid suspended solid(MLSS) was 2436 mg.L-1 and 2385 mg.L-1 in co-precipitation phosphorus removal process(CPR) and biological phosphorous removal process(BPR),respectively.The sludge reduction ratio for each process was 22.6% and 24.6% in aerobic digestion,and 27.6% and 29.9% in anaerobic digestion,respectively.Due to the addition of chemical to the end of aeration tank,the sludge content of CPR was slightly higher than that of BPR,but the sludge reduction rate for both processes had no distinct difference.The sludge volume index(SVI) and sludge specific resistance of BPR were 126 ml.g-1 and 11.7×1012 m.kg-1,respectively,while those of CPR were only 98 ml.g-1 and 7.1×1012 m.kg-1,indicating that CPR chemical could improve sludge settling and dewatering.

Nanostructured yttrium aluminum garnet powders synthesized by co-precipitation method using tetraethylenepentamine

Tetraethylenepentamine(C8H23N5,TEPA) has been used as a novel precipitant to synthesize yttrium aluminum garnet(Y3Al5O12,YAG) precursor from a mixed solution of aluminum and yttrium nitrates via a normal-strike co-precipitation method without controlling the pH value during precipitation process.The original precursor was analyzed by thermogravimetry/differential scanning calorimetry(TG/DSC).The evolution of phase composition and micro-structure of the as-synthesized YAG powders were characterized by X-ray ...

Co-precipitation preparation and burning performance test of delay composition containing barium chromate

In order to optimize the performance of delay composition containing barium chromate,the preparation conditions of barium chromate were optimized,and S/BaCrO 4/KClO 4 delay composition was prepared by co-precipitation using barium chromate as precipitant.Then,the ignition temperature,delay time and other burning performance were tested.The results show that the ignition temperature of S/BaCrO 4/KClO 4 delay composition prepared by co-precipitation method is higher than that by traditional mechanical mixing method;the burning rate is faster and the burning time precision is higher because co-precipitation method can make the components mix more evenly.This co-precipitation method with barium chromate can be extended to the preparation of other mixed explosive agents containing barium chromate.

Effects of Heating Processing on Microstructure and Magnetic Properties of Mn-Zn Ferrites Prepared via Chemical Co-precipitation

The fine powders of Mn-Zn ferrites with uniform size were prepared via chemical co- precipitation method. X-ray diffraction analysis （XRD）, scanning electron microscopy （SEM）, vibrating sample magnetometer （VSM）, frequency dependence of permeability and metallographical microscope were used to investigate the crystal structure, surface topography and magnetic properties of the powders and the sintering samples. The experimental results demonstrate that the precursor powders have formed a pure phase cubic spinel MnxZn1-xfe2O4 while in the reactor and show definite magnetism, which can solve the difficult issue in washing process effectively. When calcined beneath 450 ℃, the powders have intact crystal form and the crystallite size is less than 20 nm. Comparison tests of sintering temperatures show that 1 300 ℃ is the ideal sintering temperature for Mn-Zn ferrites prepared by using the chemical co-precipitation.

Synthesis and electrochemical properties of LiNi_(0.8)Al_(0.2-x)Ti_xO_2 cathode materials by an ultrasonic-assisted co-precipitation method

A new co-precipitation route was proposed to synthesize LiNi0.8A10.2-xTixO2 （x=0.0-0.20） cathode materials for lithium ion batteries, with Ni（NO3）2, Al（NO3）3, LiOH·H2O, and TiO2 as the starting materials. Ultrasonic vibration was used during preparing the precursors, and the precursors were protected by absolute ethanol before calcination in the air. The influences of doped-Ti content, calcination temperature and time, additional Li content, and ultrasonic vibration on the structure and properties of LiNi0.8A10.2-xTixO2 were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and charge-discharge tests, respectively. The results show that the optimal molar fraction of Ti, calcination temperature and time, and additional molar fraction of Li for LiNi0.8A10.2-xTixO2 cathode materials are 0.1,700℃, 20 h, and 0.05, respectively. Ti doping facilitates the formation of the α-NaFeO2 layered structure, and ultrasonic vibration improves the electrochemical performance of LiNi0.8A10.2-xTixO2.

Synthesis of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2 cathode material by chloride co-precipitation method

LiNi0.8Co0.1Mn0.1O2 was prepared by a chloride co-precipitation method and characterized by thermogravimetric analysis, X-ray diffractometry with Rietveld refinement,electron scanning microscopy and electrochemical measurements.Effects of lithium ion content and sintering temperature on physical and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 were also investigated. The results show that the sample synthesized at 750℃with 105%lithium content has fine particle sizes around 200 nm and homogenous sizes distribution.The initial discharge capacity for the powder is 184 mA·h/g between 2.7 and 4.3 V at 0.1C and room temperature.

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,N_(2) adsorption−desorption,TEM,XPS,oxygen storage capacity(OSC)and hydrogen temperature programmed reduction(H_(2)-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℃,the best redox properties and thermal stability of CZLYs were obtained.After thermal treatment at 1100℃for 10 h,the specific surface area and oxygen storage capacity of the corresponding aged sample were 15.42 m^(2)/g and 497.7μmol/g,respectively.In addition,a mechanism was proposed to reveal the effects of co-precipitation temperature on the structure and properties of CZLYs.

Preparation and Characterization of Y_3Sc_2Ga_3O_(12) Nano-Polycrystalline Powders by Co-Precipitation Method

In order to grow high-quality gallium garnet crystals,polycrystalline materials were used as starting materials.YSGG precursor was synthesized by co-precipitation method using aqueous ammonia as a precipitator,and the precursor was then sintered at different temperatures.The results showed that the feasible pH range was 8.3～9.84 in the process of co-precipitation reaction.The YSGG precursor and the powders sintered at different temperatures were characterized by IR,XRD and TEM methods.It was found that the precursor transformed to pure YSGG polycrystalline phase at 800 ℃.YSGG nano-polycrystalline powders sintered at 800～1000 ℃ were well dispersed and the sizes of the YSGG grains were about 40～100 nm.