Hydrometallurgical leaching and kinetic modeling of low-grade manganese ore with banana peel in sulfuric acid

Manganese was leached from a low-grade manganese ore(LGMO)using banana peel as the reductant in a dilute sulfuric acid medium.The effects of banana peel amount,H2SO4 concentration,reaction temperature,and time on Mn leaching from the complex LGMO were studied.A leaching efficiency of~98%was achieved at a leaching time of 2 h,banana peel amount of 4 g,leaching temperature of 120°C,manganese ore amount of 5 g,and sulfuric acid concentration of 15vol%.The phase,microstructural,and chemical analyses of LGMO samples before and after the leaching process confirmed the successful leaching of manganese.Furthermore,the leaching process followed the shrinking core model and the leaching rate was controlled by a surface chemical reaction(1−(1−x)^1/3=kt)mechanism with an apparent activation energy of 40.19 kJ·mol^−1.

Phase, Microstructure and Beneficiation of Manganese Ore by Acid Leaching

In this research work, sawdust was used as a reducing agent for sulphuric acid leaching of manganese ore from Prang Ghar, Lower Mohmand Agency, Pakistan. X-ray diffraction of the powdered sample indicated the presence of Hausmannite (Mn3O4), Calcium Aluminum Silicate Hydrate, Silica (SiO2) and Hematite (Fe2O3). X-ray diffraction and the energy dispersive spectroscopic analysis show that the manganese ore sample was siliceous in nature. In the present study, six process parameters were investigated i.e. the particle size of the ore, leaching temperature, time duration, Mn ore amount, sulphuric acid concentration and amount of sawdust. Manganese extraction of 88.93 (wt%) was achieved for a leaching time of 60 minutes at 120°C using 5% (v/v) H2SO4 concentration for 10 g Mn ore and 5 g sawdust. The results demonstrate that sawdust is a low cost, renewable and non-hazardous reducing agent in comparison to other available reagents.

Synthesis and Characterization of Cr Doped ZnO Nanocrystals

Samples of chromium doped ZnO were synthesized using co-precipitation technique at room temperature. Structural and optical properties of Cr doped ZnO samples were investigated by X-ray diffraction technique (XRD and UV-Visible spectroscopy (UV-Vis) respectively. X-ray diffraction (XRD) patterns confirm that the samples have hexagonal (wurtzite) structure with no additional peak which suggests that Cr ions go to the regular Zn sites in the ZnO crystal structure. The lattice constants were calculated using X-ray diffraction data and it is found that lattice parameters decrease with increasing Cr content. The average grain size was calculated using Scherrer’s formula for pure and Cr doped ZnO samples and it is observed that grain size is in the range 11 to17 nm. Band gap of Zn1–xCrxO samples has been evaluated using UV-Vis spectrometer. It is found that the band gap decreases as Cr increases;it is attributed to the s-d and p interactions and the smaller average grain size. It indicates that incorporation of Cr ions into the ZnO matrix. The chemical species of the grown crystals were identified by Fourier transform infrared spectroscopy (FTIR). From FTIR spectra it is observed that IR peaks corresponding to the Zn-O bands. Such results are presented in this paper quantitatively and qualitatively.

Role of Substrate Temperatures on Structural, Optical, Wetting and Electrical Transport Properties of CdS Thin Films

Cadmium sulphide thin films were deposited on the glass substrate via simple spray pyrolysis technique. The substrate temperatures (Ts) have been varied from 250℃ to 350℃ and concentration of precursor’s solution of cadmium chloride and thiourea was optimized. The X-ray patterns and morphological studies of CdS thin films indicated that films are crystalline in nature with hexagonal crystal structure. The grain size calculated and found to be 250.12 to 349.61 nm. The optical spectra exhibited high transmittance and band gap varied from 2.41 eV to 2.39 eV. The angle of contact measured and found to be hydrophilicity behaviour. The electrical conductivity and thermoelectric power have been measured with two probe method. It was found that CdS thin films were semiconducting in nature with n-type.

The Crystallographic and Optical Studies on Cobalt Doped CdS Nanoparticles

The samples of Cd1?- xCoxS with compositions x = 0.0 & 0.6 were prepared by Co-precipitation route at room temperature. XRD analysis confirms that the samples have cubic structure with no impurity phases. The lattice parameter, volume cell, X-ray density and grain size were calculated using XRD data. It is found that lattice parameter, volume of unit cell and X-ray density decrease with enhancing Co content. It is due to the smaller ionic radius of Co than the Cd. It is well noticed that the grain size increases with increasing Co content, it may be owing to the good synthesis technique. The functional groups and chemical interaction were determined by FTIR spectra. From FTIR spectra, it is investigated that absorption bands show the presence of resonance interaction between vibrational modes of oxide ions in the crystal. The energy band gap of Co doped CdS samples was calculated using UV-Vis analysis. It is observed that energy band gap decreases with increasing Co content owing to the sp-d exchange interaction between Co and CdS atoms.

Physical Characterization of Ionic Liquid-Modified Polyvinyl Alcohol and Sodium Thiocyanate Polymer Electrolytes for Electrochemical Double-Layer Capacitor Application

Novel gel polymer electrolytes(GPEs)composed of polyvinyl alcohol(PVA)and sodium thiocyanate were developed via a solution casting technique.An ionic liquid(IL),1-ethyl-3-methyl-imidazolium tricyanomethanide([EMIM][TCM]),was doped into a polymer–salt complex system(PVA+NaSCN)to further enhance the conductivity.IL-doped polymer electrolyte(ILDPE)films were characterized using X-ray diffraction(XRD),polarized optical microscopy(POM),Fourier-transform infrared(FTIR)spectroscopy,and conductivity measurements.XRD was performed to check the degree of crystallinity and amorphicity of the ILDPE films,and the amorphicity of GPEs increased with the increase of the IL content.POM was employed to evaluate the changes in the surface morphology due to the inclusion of salt and IL in the PVA.The compositional nature of the GPE films was examined via FTIR studies.The electrical and electrochemical properties were characterized by cyclic voltammetry and electrochemical impedance spectroscopy.The maximum conductivity for the GPE film was estimated to be 1.10×10^(-5) S/cm for 6%(mass fraction)of IL in the polymer–salt complex.The ionic transference number was approximately 0.97.An electrochemical double-layer capacitor(EDLC)was built from optimized GPE films and reduced graphene oxide-based electrodes.The specific capacitance calculated from the cyclic voltammograms of the EDLC cells was 3 F/g.

Investigation of magnetoelectric effect in lead free K0.5Na0.5NbO3–BaFe12O19 novel composite system

Lead-free magnetoelectric composites(1-x)K0.5Na0.5NbO3–(x)BaFe12O19(x = 30, 40, and 50 wt%) are synthesized using solid state reaction method. X-ray diffraction(XRD) patterns confirm formation of diphase composites. Field emission scanning electron microscopy(FE-SEM) gives information about grain size, connectivity, and microstructure of constituent phases. Dielectric parameters of composite samples are studied as a function of temperature and the transition temperatures corresponding to both the constituent phases are observed in the composite samples. Dielectric constant has been found to decrease with addition of ferrite. Room temperature multiferroic behaviour has been confirmed using P–E and M–H hysteresis loops and magnetoelectric measurement. Polarization is found to decrease;however, magnetization increases with ferrite weight percentage. The highest αME of 4.08 mV/(cm·Oe) is obtained for x = 30 wt% composite and it is realized that ferrite content significantly affects magnetoelectric behaviour.

Metamorphic Temperature Investigation of Coexisting Calcite and Dolomite Marble Examples from Nikani Ghar Marble and Nowshera Formation,Peshawar Basin,Pakistan

Using marble samples from the Nikani Ghar marble and Nowshera Formation from Northern Pakistan the determination of the temperature of metamorphism was undertaken with the help of calcite-dolomite solvus geothermometer. Two types of marbles, that is, calcite-dolomite marble and quartz-bearing calcite-dolomite marble were selected. Petrographic and scanning electron microscope analysis of dolomite samples indicated different grain sizes. X-ray diffraction technique indicated the calcites MgCO3 content up to 7.93 mol.%. Nikani Ghar marble samples have shown lower contents of MgCO3 as compared to samples from Nowshera Formation. The calcite-dolomite-quartz marble has also showed relatively lower MgCO3 content and hence rather low temperature （-500 ℃）. The temperature reached during peak metamorphism of the investigated marble occurrence, based on calcitedolomite solvus was 628 ℃. Metamorphic temperatures derived from the present study were shown as a linear graph and values were in good agreement with the published literature.

The effects of electron irradiation on the optical properties of the organic semiconductor polypyrrole

The optical properties of polypyrrole （Ppy） thin films upon 2 MeV electron beam irradiation changes with different doses. The induced changes in the optical properties for Ppy thin films were studied in the visible range 300 to 800 nm at room temperature. The optical band gap of the pristine Ppy was found to be 2.19 cV and it decreases up to 1.97 eV for a 50 kGy dose of 2 MeV electron beam. The refractive index dispersion of the samples obeys the single oscillator model. The obtained results suggest that electron beam irradiation changes the optical parameters of Ppy thin films.

Structural,morphological,optical and photoluminescent properties of spray-deposited ZnSe thin film

ZnSe thin films are successfully deposited by spray pyrolysis deposition technique. Deposited thin films are characterized by X-ray diffraction study, and it reveals that spray-deposited ZnSe thin films are polycrystalline with hexagonal crystal structure. Surface morphology is carried out by scanning electron microscopy. It shows cotton-like morphology, and optical properties, such as absorbance, transmittance, reflectance, band gap, refrac- tive index, extinction coefficient are studied. Photoluminescence shows strong emission at 497 nm. Also, spray- deposited ZnSe thin films are hydrophilic in nature, which is shown by contact angle meter.

Preparation by chemical co-precipitation, spectral and electrical characteristics of neodymium orthophosphate nanoparticles

Nanoparticles of neodymium orthophosphate （NdPO4） were prepared through a facile wet co-precipitation technique. The X-ray diffraction （XRD） studies revealed the material belonging to monoclinic monazite phase with crystallite size of 30.8 nm. Scanning electron microscopic studies showed that the material was composed of a large number of agglomerated spherical particles having grain size of 92 nm. Thermogravimetric analysis suggested that the structural phase transition was seen above 800 °C. The spectroscopic investigations were carried out using Fourier transform infrared spectroscopy （FTIR）. UV-VIS-NIR ab-sorption spectrophotometer showed various transitions from the ground state 4I9/2 to various excited states within the 4f shell and the optical band gap came out to be 3.3 eV. The dielectric constant （ε′）, dielectric loss （tanδ） and ac conductivity ln（σac） were measured in the frequency range of 5 kHz to 1 MHz and in the temperature range of 40 to 500 °C. The dielectric measurement suggested that there was a shift in the value of transition temperature （Tc）, thereby indicating relaxor behaviour of the material. The activation energy value decreased with increase in frequency, thereby suggesting the role of mixed ionic-polaronic conduc-tivity.

Optical properties of electrochemically synthesized polypyrrole thin films:the electrolyte effect

Polypyrrole thin films are prepared by the potentiostatic mode of electrodeposition at ＋0.7 V versus a saturated calomel electrode （SCE）. The polypyrrole films are prepared in the presence of different electrolytes such as： p-toluene sulphonic acid （PTS）, oxalic acid and H2SO4. The prepared films are characterized by UV- vis absorption spectroscopy and normal reflectance measurements. The electrochemically synthesized films are semiconductor in nature. The band gap energy ofpolypyrrole thin films is found to be 1.95, 1.92 and 1.79 eV for H2 SO4, oxalic acid and p-toluene sulphonic acid, respectively. The normal reflectance spectroscopy of polypyrrole films shows that the maximum reflectance is in the presence of p-toluene sulphonic acid; this is may be due to a more distinct microstructure than the others. The optical constants such as the extinction coefficient, refractive index, optical conductivity, etc. are calculated and studied with various electrolytes.

Dielectric relaxation and modulus spectroscopy analysis of(Na_(0.47)K_(0.47)Li_(0.06))NbO_(3) ceramics

We have investigated the structure,dielectric and electrical properties of lead-free polycrystalline (Na_(0.47)K_(0.47)Li_(0.06))NbO_(3) ceramics as a function of temperature and frequency in order to understand the intrinsic contribution of grain/bulk and grain boundary effects toward the dielectric response as well as the electrical conduction mechanism in the samples fabricated by microwave sintering method.X-ray diffraction analysis exhibits perovskite structure with orthorhombic symmetry,which is well supported by the Raman spectroscopic analysis.A minor secondary impurity phase of tungsten bronze structure was observed for samples sintered at 1050℃,which gets weaker for samples sintered at 1150℃.Dielectric permittivity was enhanced by 50%,although there was a reduction in the dielectric loss by about 50%at Curie temperature(450℃)for samples sintered at 1150℃.Complex impedance spectroscopic analysis indicated non-Debye-type dielectric relaxation present in the samples,and this phenomenon followed thermally activated process related to hopping mechanism.Nyquist plot showed the negative temperature coefficient of resistance,characteristic of the samples.

Evaluation of structure,dielectric and electrical properties of(Li/Ta/Sb)modified(Na,K)NbO_(3) lead-free ceramics with excess Na concentration

Polycrystalline perovskite structured Li_(0.04)(Na_(0.54+x) K_(0.46))_(0.96)(Nb_(0.81)Ta_(0.15)Sb_(0.04))O_(3) ceramics with x¼0:00,0.005 and 0.01 mole excess Na concentration were prepared by solid state sintering method.The present study relates the role of excess Na addition with the stoichiometry,density,structure,dielectric and ferroelectric properties of the samples.X-ray diffraction(XRD)pattern exhibits single phase orthorhombic structure.The characteristic Raman modes were observed due to translational modes of cations and vibrational modes of NbO_(6) octahedra and no structural phase transition were observed.This confirms the formation of single phase perovskite structure and is consistent with XRD results.The dielectric permittivity increases about two times,while dielectric loss decreases by four times for χ=0.01 composition.The electrical measurements carried by Complex Impedance spectroscopic analysis suggest negative temperature coefficient of resistance(NTCR)behavior.

Effect of neodymium doping on structural,microscopic and electrical properties of barium phosphate system

Neodymium-doped barium phosphate(NdBP)was prepared as single crystal by room temperature solution technique known as gel encapsulation technique.Single crystal X-ray diffraction shows that the crystal belongs to orthorthombic system.The flower type morphology was observed by scanning electron microscope(SEM)and the stoichiometric composition of the prepared crystal was observed by energy dispersive X-ray analysis(EDAX).The presence of functional group and other groups was studied by Fourier transform infrared spectroscopy(FTIR).The electrical properties of these materials like dielectric constant(ε′),dieletric loss(tan σ)and ac conductivity[ln(σac)]was studied at different temperatures ranging from 40℃ to 420℃ in the frequency range of 5 kHz to 1 MHz.The activation energy values decreases with increase in frequency suggesting that the conduction mechanism is because of hopping of charge carriers.

The influence of monomer concentration on the optical properties of electrochemically synthesized polypyrrole thin films

Polypyrrole （PPy） thin films were deposited on stainless steel and ITO coated glass substrate at a constant deposition potential of 0.8 V versus saturated calomel electrode （SCE） by using the electrochemical polymerization method. The PPy thin films were deposited at room temperature at various monomer concentrations ranging from 0.1 M to 0.3 M pyrrole. The structural and optical properties of the polypyrrole thin films were investigated using an X-ray diffractometer （XRD）, FTIR spectroscopy, scanning electron microscopy （SEM）, and ultravioletvisible （UV-vis） spectroscopy. The XRD results show that polypyrrole thin films have a semi crystalline structure. Higher monomer concentration results in a slight increase of crystallinity. The polypyrrole thin films deposited at higher monomer concentration exhibit high visible absorbance. The refractive indexes of the polypyrrole thin films are found to be in the range of 1 to 1.3 and vary with monomer concentration as well as wavelength. The extinction coefficient decreases slightly with monomer concentration. The electrochemically synthesized polypyrrole thin film shows optical band gap energy of 2.14 eV.

Effect of Sodium Metasilicate on Structural, Optical, Dielectric and Mechanical Properties of ADP Crystal

For the first time, sodium metasilicate （SMS） doped ammonium dihydrogen phosphate （ADP） crystal was grown by slow evaporation solution technique. The unit cell parameters of grown crystal were deter- mined by means of single crystal X-ray diffraction technique. The qualitative analysis of SMS doped ADP crystal was carried out using energy dispersive X-ray and Fourier transform infrared analysis. The in- crease in optical transparency of doped ADP crystal was ascertained in the range of 200-900 nm using the UV-visible spectral analysis. The vital optical constants were evaluated using the transmittance data to explore various optical device applications of crystal. The assertive influence of SMS on mechanical and dielectric behavior of ADP crystal was investigated by means of Vickers microhardness analysis and dielectric studies, respectively. The enhancement in second harmonic generation （SHG） efficiency of SMS doped ADP crystal with reference to potassium dihydrogen phosphate （KDP） and ADP was confirmed from Kurtz-Perry SHG test. The Kerr lensing nonlinearity in SMS doped ADP crystal was identified by means of Z-scan analysis and the third order nonlinear optical susceptibility （χ3） was found to be 6.19 × 10-5 esu, which vitalizes its application for laser stabilization systems.

High energy storage density with ultra-high efficiency and fast charging-discharging capability of sodium bismuth niobate lead-free ceramics

Ceramics-based capacitors with excellent energy storage characteristics,fast charging/discharge rate,and high efficiency have received significant attention.In this work,Na0.73Bi0.09NbO3(NBN)ceramics were processed through solid-state sintering route.The investigated ceramics were crystallized in a single perovskite phase.Dense microstructure,with small average grain size(~0.92 mm)is obtained for the investigated ceramics.A high dielectric constant>1000 accompanied by a low dielectric loss was achieved for these ceramics at ambient temperature.A recoverable energy density~0.92 J/cm3 and ultra-high efficiency of 96.33%at 138 kV/cm were obtained at room temperature.Furthermore,a lower discharging time of 0.14 ms was also achieved.This material is a suitable candidate for power pulsed applications.