Biosorption of copper ions from dilute aqueous solutions on base treated rubber (Hevea brasiliensis) leaves powder: kinetics, isotherm, and biosorption mechanisms

The effciency of sodium hydroxide treated rubber (Hevea brasiliensis) leaves powder (NHBL) for removing copper ions from aqueous solutions has been investigated. The e?ects of physicochemical parameters on biosorption capacities such as stirring speed, pH, biosorbent dose, initial concentrations of copper, and ionic strength were studied. The biosorption capacities of NHBL increased with increase in pH, stirring speed and copper concentration but decreased with increase in biosorbent dose and ionic strength. The isotherm study indicated that NHBL fitted well with Langmuir model compared to Freundlich and Dubinin-Radushkevich models. The maximum biosorption capacity determined from Langmuir isotherm was 14.97 mg/g at 27°C. The kinetic study revealed that pseudo- second order model fitted well the kinetic data, while Boyd kinetic model indicated that film diffusion was the main rate determining step in biosorption process. Based on surface area analysis, NHBL has low surface area and categorized as macroporous. Fourier transform infrared (FT-IR) analyses revealed that hydroxyl, carboxyl, and amino are the main functional groups involved in the binding of copper ions. Complexation was one of the main mechanisms for the removal of copper ions as indicated by FT-IR spectra. Ion exchange was another possible mechanism since the ratio of adsorbed cations (Cu2+ and H+) to the released cations (Na+, Ca2+, and Mg2+) from NHBL was almost unity. Copper ions bound on NHBL were able to be desorbed at > 99% using 0.05 mol/L HCl, 0.01 mol/L HNO3, and 0.01 mol/L EDTA solutions.

Study on the Evaporation Kinetics of Zinc and Lead in Zn-Pb-Bearing Dust Pellets Mixed with Coal Powder

The study on the evaporation kinetics of zinc and lead in the pellets made of ZnPbbearing dust mixed with carbon ,in nitrogen atmosphere at the temperature range between 1 100 and 1 300 , shows that the reduction temperature has a significant effect on the evaporation rates of zinc and lead and that both the particle size of coal powder and the extra carbon content have no effect on the evaporation rates . The obtained activation energies for the evaporation of zinc and lead are 7942 kJ/mol and 8874kJ/mol respectively. The evaporation rate of zinc is controlled by the reaction between zinc oxide and CO while that of lead is controlled by lead volatilization and the diffusion of gaseous lead through gas boundary layer covering the surface of liquid lead.

Oxidation pathway and kinetics of titania slag powders during cooling process in air

The oxidation pathway and kinetics of titania slag powders in air were analyzed using differential scanning calorimetry(DSC)and thermogravimetry(TG).The oxidation pathway of titania slag powder in air was divided into three stages according to their three exothermic peaks and three corresponding mass gain stages indicated by the respective non-isothermal DSC and TG curves.The isothermal oxidation kinetics of high titania slag powders of different sizes were analyzed using the ln-ln analysis method.The results revealed that the entire isothermal oxidation process comprises two stages.The kinetic mechanism of the first stage can be described as f(α) = 1.77(1-α) [-ln (1-α)]^((1.77-1)/1.77),f(α)= 1.97(1-α) [-ln (1-α)]^((1.97-1)/1.97),and f (α) = 1.18(1-α) [-ln (1-α)]^((1.18-1)/1.18).The kinetic mechanism of the second stage for all samples can be described as f (α)=1.5(1-α)^(2/3)[1-(1-α)^(1/3)]^(-1).The activation energies of titania slag powders with different sizes(d_(1)<0.075 mm,0.125 mm<d_(2)<0.150 mm,and 0.425 mm<d_(3)<0.600 mm)for different reaction degrees were calculated.For the given experimental conditions,the rate-controlling step in the first oxidation stage of all the samples is a chemical reaction.The rate-controlling steps of the second oxidation stage are a chemical reaction and internal diffusion(for powders d_(1)<0.075 mm)and internal diffusion(for powders 0.125 mm<d_(2)<0.150 mm and 0.425 mm<d_(3)<0.600 mm).

A Study on Synthesis Kinetics of YBa_2Cu_3O_x High Tc Superconductor Powder

The synthesis kinetics of YBa_2Cu_30_x supercon- ductor was studied through comparing the calcina- tion (sintering) processes of different kinds of powders. It was shown that the temperature of synthesis of YBa_2Cu_30_x phase can be lowered from 950℃ to 800℃ through direct calcination of multiphase powder with uniform chemical com- position. The stress which is caused by the volume change during synthetic reaction breaks the particles. It facilitates the formation of highly active superfines of superconductor.

Kinetics of Reduction of Iron Oxide in CaO-SiO_2-Al_2O_3-Fe_tO Slags with Graphite Powder

The reduction rate of Fe^tO in CaOSiO_2Al_2O_3Fe_tO slags with graphite powder has been determined in an alumina crucible at 1 673-1 823 K. The effects of temperature, slag basicity and Fe_tO content on the reduction rate have also been discussed. Test results show that the reduction rate increases with the increase of temperature or Fe_tO concentration in slags, and the reduction rate has a parabolic relation with slag simple basicity or optical basicity. The maximum reduction rate is observed around CaO/SiO_2=1.5 of molten slags. The reaction order is 1.26 or 1.31, and the reduction activation energy is 126.8 or 129.7 kJ/mol respectively in regard to Fe_tO content or Fe_tO activity calculated by using regular solution model. The reduction rate of Fe_tO in CaOSiO_2Al_2O_3Fe_tO slags with graphite powder is in the range of 0.15×10^-4-0.86×10^-4 molO/cm^2·s.

Microstructural evolution and sintering kinetics during spark plasma sintering of Fe and Al blended powder

The reaction diffusion between Fe and Al during spark plasma sintering(SPS)was studied.Microstructural evolution wasinvestigated by X-ray diffraction(XRD)and scanning electron microscopy(SEM)and the sintering kinetics was disclosed.The maininterphase of the SPS sample was Fe2Al5at773-873K.Ball-milling enabled a large number of lattice defects and grain boundariesthus the reaction kinetics was accelerated,although the direct current can also promote those defects.After milling,the phasetransformation kinetics was improved from0.207before mill to4.56×10-3.Besides,this work provided more details for thegeneration of Joule heating.The resistance offered to the electric path was considered to be the source of Joule heating,andparticularly the resistance offered by the different contact interfaces of die,punch,graphite foil and the sample played a leading rolefor the generation of Joule heating during spark plasma sintering.

Acute Toxicity and Toxicokinetics of Tongguan Powder in Rats

[Objectives]To evaluate the acute toxicity and toxicokinetics of Tongguan Powder in rats,and provide references for clinical safe medication.[Methods]The classical acute toxicity test method was used,rats were given different doses of Tongguan Powder through the mouth and nasal cavity to observe the symptoms of toxicity,and make a record of the food intake,weight changes,and death.After the medication,blood was taken from each group of rats at different time points,and the plasma levels of benzoyl aconitine(BA),benzoyl hypaconine(BH)and benzoyl mesaconine(BM)were determined by the liquid chromatography tandem-mass spectrometry(LC-MS/MS),and the toxicokinetic parameters were fitted with the aid of DAS software.[Results]Rats were given Tongguan Powder 3.75 g/kg(equivalent to 54 times the human daily dose)in the nasal cavity of rats.Rats were observed with reactions such as scratching and sneezing;rats were given Tongguan Powder LD50 and 95%confidence limit of 4.15(3.53-4.71)g/kg through the oral administration,which is equivalent to 60 times the human daily dose,rats showed slow weight gain,decreased food intake,decreased voluntary activities,prone,black stools,etc.One hour after nasal administration of Tongguan Powder,the plasma concentration of benzoyl aconitine and benzoyl hypaconine was below the lower limit of detection,and benzoyl mesaconine could not be detected at any time point;one hour after the oral administration of Tongguan Powder,the plasma concentration of the three components reached the maximum,the exposure level of benzoyl hypaconine was higher than that of benzoyl aconitine and benzoyl mesaconine;there was no gender difference in the kinetic parameters.[Conclusions]The toxicity of Tongguan Powder in nasal administration is much lower than that of intragastric administration.The target organs and mechanism of toxicity need to be further studied.

Kinetics and corrosion products of aqueous nitrate reduction by iron powder without reaction conditions control

Although considerable research has been conducted on nitrate reduction by zero-valent iron powder （Fe^0）, these studies were mostly operated under anaerobic conditions with invariable pH that was unsuitable for practical application. Without reaction conditions （dissolved oxygen or reaction pH） control, this work aimed at subjecting the kinetics of denitrification by microscale Fe^0 （160-200 mesh） to analysis the factors affecting the denitrification of nitrate and the composition of iron reductive products coating upon the iron surface. Results of the kinetics study have indicated that a higher initial concentration of nitrate would yield a greater reaction rate constant. The reduction rate of nitrate increased with increasing Fe^0 dosage. The reaction can be described as a pseudo-first order reaction with respect to nitrate concentration or Fe^0 dosage. Experimental results also suggested that nitrate reduction by microscale Fe^0 without reaction condition control primarily was an acid-driven surface-mediated process, and the reaction order was 0.65 with respect to hydrogen ion concentration. The analyses of X-ray diffractometry and X-ray photoelectron spectroscopy indicated that a black coating, consisted of Fe2O3, Fe3O4 and FeO（OH）, was formed on the surface of iron grains as an iron corrosion product when the system initial pH was lower than 5. The proportion of FeO（OH） increased as reaction time went on, whereas the proportion of Fe3O4 decreased.

Crystallization Kinetics and Magnetic Properties of Fe_(73.5)Si_(13.5)B_9Cu_1Nb_1V_2 Nanocrystalline Powder Cores

Amorphous ribbons of the alloy Fe73.5 Si13.5B9Cu1Nb1V2 were prepared by the standard single copper wheel melt spinning technique in the air atmosphere. The crystallization kinetics of amorphous ribbons was analyzed by non-isothermal differential scanning calorimetry （DSC） measurements. The crystallization activation energies of amorphous ribbons calculated by using Kissinger model were 364 and 337 kJ/mol for the first and the second crystallization, respectively. The Avrami exponent n was calculated from the Johnson- Mehl-Avrami （ MA） equation. The value of the Avrami exponent showed that the crystallization mechanism in the non-isothermal primary crystallization of amorphous ribbons was all shapes growing from small dimensions controlled by diffusion at decreasing nuclectcn rate. The variation of soft magnetic properties of nanocrystalline Fe73.5 Si13.5B9Cu1Nb1V2 alloy powder cores s a tunction of milling times has been investigated. It is found that the effective permeability of the cores shows high frequency stability and decreases with the increase of milling times. The quality factor increases with increasing frequency in lower frequency range, and reaches a maximum at the frequency of 80 kHz then decreases gradually with increasing frequency.

Kinetics and mechanism of titanium hydride powder and aluminum melt reaction

Based on the measurement of the released hydrogen gas pressure （PH2）, the reaction kinetics between TiH2 powder and pure aluminum melt was studied at various temperatures. After cooling the samples, the interface of TiH2 powder and aluminum melt was studied. The results show that the-time curves have three regions; in the first and second regions, the rate of reaction conforms zero and one order, respectively; in the third region, the hydrogen gas pressure remains constant and the rate of reaction reaches zero. The main factors that control the rate of reaction in the first and second regions are the penetration of hydrogen atoms in the titanium lattice and the chemical reaction between molten aluminum and titanium, respectively. According to the main factors that control the rate of reaction, three temperature ranges are considered for the reaction mechanism： （a） 700-750°C, （b） 750-800°C, and （c） 800-1000°C. In the first temperature range, the reaction is mostly under the control of chemical reaction; at the temperature range of 750 to 800°C, the reaction is controlled by the diffusion and chemical reaction; at the third temperature range （800-1000°C）, the dominant controlling mechanism is diffusion.

Kinetics of the Thermal Decomposition of Magnesium Salicylate Powder in Air

Simultaneous thermogravimetry-differential thermal analysis （TG-DTA） was used to study the kinetics and the degradation of magnesium salicylate（ C14H10MgO6 ） in air. The results show that the decomposition proceeds through two steps. The kinetics of the first decomposition step was studied. The activation energies were calculated by using the Friedman and Flynn Wall Ozawa（FWO） methods, and the most probable kinetic model function was estimated using the multiple linear regression method. The values of the correlated kinetic parameters for the first decomposition step are E = 152.97 kJ/mol, lg（A/S^-1 ） = 10. 78, f（α） = （ 1 - α）^n（ 1 ＋Kcatα）, n =0. 691, and Kcat = 1. 3048.

KINETICS OF PREPARATION OF ULTRAFINE TiN POWDER BY HIGH FREQUENCY PLASMA

The reaction kinetie model for the synthesis of ultrafine TiN powder from vapour phase sys- tem TiCl_4-NH_3-H_2-N_2 in the high frequency plasma reactor was proposed as follows: 1/V((dn_(TiCl_4))/dt)=0.852e^(-63.2·RT)P_(TiCl_4) The majority of factors influenced upon the reaction rate were analysed,so as to provide the theoretical basis for improving quality of TiN powder and for optimizing the design of plasma reactor.

Thermal Decomposition Reaction Kinetics Model of Powdered Bastnaesite

The thermal decomposition procedure of powdered bastnaesite from Mianning was investigated, and TG DTA curves of bastnaesite were tested in atmosphere. According to the model provided by Criado, the kinetics data were calculated and treated with thermal analysis techniques, and kinetics curves of thermal decomposition reaction of powdered bastnaesite were drawn. Comparing these curves with the standard curves and combining with the previous research results of kinetics parameter calculation, the results confirmed that the reaction mechanism was nucleation and nuclei growth, and its differential and integral forms of reaction kinetics model can be expressed as: f(α)=(1-α) and g(α) =-ln(1- α ) respectively.

Curing Kinetics, Mechanical Properties and Thermal Stability of Epoxy/Graphene Nanoplatelets(GNPs) Powder Coatings

Epoxy/graphene nanoplatelets（GNPs） powder coatings were fabricated using ultrasonic predispersion of GNPs and melt-blend extrusion method. The isothermal curing kinetics of epoxy/GNPs powder coating were monitored by means of real-time Fourier transform infrared spectroscopy（FT-IR） with a heating cell. The mechanical properties of the epoxy/GNPs cured coatings had been investigated, by evaluating their fracture surfaces with field-emission scanning electron microscopy（FE-SEM） after three-point-bending tests. The thermal stability of the epoxy/GNPs cured coatings was studied by thermo-gravimetric analysis（TGA）. The isothermal curing kinetics result showed that the GNPs would not affect the autocatalytic reaction mechanism, but the loading of GNPs below 1.0 wt % additive played a prompting role in the curing of the epoxy/GNPs powder coatings. The fracture strain, fracture toughness and impact resistance of the epoxy/GNPs cured coatings increased dramatically at low levels of GNPs loading（1 wt %）, indicating that the GNPs could improve the toughness of the epoxy/GNPs powder coatings. Furthermore, from FE-SEM studies of the fracture surfaces, the possible toughening mechanisms of the epoxy/GNPs cured coatings were proposed. TGA result showed that the incorporation of GNPs improved the thermal stability of the cured coatings. Hence, the GNPs modified epoxy can be an efficient approach to toughen epoxy powder coating along with improving their thermal stability.

Removal of aqueous Ni(Ⅱ) with carbonized leaf powder: Kinetics and equilibrium

Nickel is a heavy metal which has the potential threaten to human＇s health and attracts public concern recently. The carbonized leaf powder is expected as suitable adsorbent for Ni（II） removal became of the composition of some beneficial groups. In this work, carbonized leaf powder was evaluated for its adsorption performance towards Ni（II）. According to the results, adsorbent component, dosage, initial solute concentration, solution pH, temperature and contact time can significantly affect the efficiency of Ni（II） removal. Sips model fits the test results best, and the adsorption capacity towards Ni（II） is determined around 37.62 mg/g. The thermodynamic behaviors reveal the endothermic and spontaneous nature of the adsorption. The free adsorption energy （fluctuate around 8 kJ/mol） predicted by D-R model indicates that the adsorption capacity originated from both physical and chemical adsorption. Room temperature （15-25 ℃） is suitable for Ni（II） removal as well as low energy consumption for temperature enhancement. Further conclusions about the mechanism of chemical adsorption are obtained through analysis of the FT-IR test and XRD spectra, which indicates that the adsorption process occurs predominantly between amine, carbonate, phosphate and nickel ions.

Oxidation Kinetics of Ilmenite Powder in Fluidized Bed

The oxidation kinetics of Panzhihua ilmenite was studied in a fluidized bed in the temperature range of 1053-1153 K. Within this temperature interval, the reaction can be expressed: From the experimental results, it was clarified that the intrinsic chemical reaction is the rate-controlling step.

Kinetics Researches of La1-x SrxMnO3 Powder by Microwave Synthesis

The La1 -xSrxMnO3 is the cathode materials of SOFC, which is the key part of SOFC.The production technology of La1 -xSrxMnO3 materials is widely studied with efficiency, saving energy and environment friend.Microwave synthesis was used to produce La1 -xSrxMnO3.The kinetics course of synthesizing La1-xSrxMnO3 materials by microwave technology was discussed.Using DTA-TGA and XRD analysis, the process and principle of solid reaction were examined.The results show that the reaction time and grain size of raw materials are important factor.When reaction time increases from 4 to 15 min, the crystal structure of La1 -xSrxMnO3 formes gradually.Through analysis of kinetics model, the reaction principle of La1-xSrxMnO3 was gained by microwave synthesis and the kinetics equation was built.

Isothermal thermo-analytical study and decomposition kinetics of non-activated and mechanically activated indium tin oxide(ITO) scrap powders treated by alkaline solution

Isothermal decomposition process of chemically transforming indium tin oxide（ITO） powders into indium（III） hydroxide powders was investigated. Two types of powders were analyzed, i.e., non-activated and mechanically activated. It has been found that in the case of activated sample, shorter induction periods appear, which permits growth of smaller crystals, while in the case of non-activated sample, long induction periods appear, characterized by the growth of larger crystals. DAEM approach has shown that decomposition processes of non-activated and mechanically activated samples can be described by contracting volume model with a linear combination of two different density distribution functions of apparent activation energies（Ea）, and with first-order model, with a single symmetrical density distribution function of Ea, respectively. It was established that specific characteristics of particles not only affect the mechanism of decomposition processes, but also have the significant impact on thermodynamic properties.

Synthesis kinetics of Mg_2Sn in Mg-Sn powder mixture using non-isothermal differential scanning calorimetry

The non-isothermal heating process of Mg-Sn powder mixture was studied by differential scanning calorimetry(DSC) technique and the synthesis kinetics of Mg2Sn was evaluated by the model-free and model-fitting methods.The activation energy and conversion function of Mg2Sn synthesis reaction are calculated to be 281.7 kJ/mol and g(α)=[-ln(1-α)] 1/4,respectively.The reaction mechanism of 2Mg+Sn→Mg2Sn under non-isothermal condition is regarded as "nucleation and growth" .During the non-isothermal heating process,the phase transformation occurred in the Mg-Sn powder mixture was analyzed by XRD and the microstructure evolution of Mg2Sn was observed by optical microscopy,which is in good agreement with the reaction mechanism of 2Mg+Sn→ Mg2Sn deduced from the kinetic evaluation.

Synthesis and grain growth kinetics of in-situ FeAl matrix nanocomposites(Ⅱ):Structural evolution and grain growth kinetics of mechanically alloyed Fe-Al-Ti-B composite powder during heat treatment

Morphological changes,structural evolutions and grain growth kinetics of mechanically alloyed(MAed)Fe50Al50,Fe42.5Al42.5Ti5B10 and Fe35Al35Ti10B20(mole fraction,%)powders were investigated by XRD and SEM,when being isothermally annealed at 1 073-1 373 K.The effect of different Ti and B addition on the grain growth of FeAl phase was also discussed.The results show that the nanocrystalline FeAl and in-situ TiB2/FeAl nanocomposite powders can be synthesized by subsequent heat treatment.Besides the relaxation of crystal defects and lattice stress,the transformation from Fe-based solid solution into B2-FeAl and TiB2 occurs upon heating of the MA-processed alloys.Although the grain growth takes place,the grain sizes of both FeAl and TiB2 are still in nanometer scale.The activation energies for the nanocrystalline FeAl growth in the three alloys are calculated to be 534.9,525.6 and 1 069.6 kJ/mol respectively,according to kinetics theory of nanocrystalline growth.Alloys with different TiB2 contents exhibit unequal thermal stability.The presence of higher content TiB2 plays significant role in the impediment of grain growth.