Effect of bio-sludge concentration on the efficiency of sequencing batch reactor (SBR) system to treat wastewater containing Pband Ni

The removal efficiency of sequencing batch reactor (SBR) system with synthetic industrial estate wastewater (SIEWW) containing Ni²⁺ or Pb²⁺ was increased with the increase of mixed liquor suspended solids (MLSS). But, the sludge volume index (SVI) of the system was increased up to higher than 100 mL/g under MLSS of up to 4000 mg/L. Also, the effluent NO₃⁻ was decreased with the increase of MLSS. The heavy metals (Ni²⁺ or Pb²⁺), BOD₅, COD and TKN removal efficiencies of SBR system with SIEWW containing 5 mg/L heavy metal (Ni²⁺ or Pb²⁺) under MLSS of 3000 mg/L were 83–85%, 96–97%, 95–96% and 83–94%, respectively. The increase of heavy metal (Ni²⁺ or Pb²⁺) concentrations of SIEWW from 5 to 50 mg/L were not significantly effected to both COD and BOD₅ removal efficiencies (they were reduced by only 4–5%), but they were strongly effected to both TKN and heavy metals removal efficiencies (they were reduced by 15 and 20–30%, respectively). Both Ni²⁺ and Pb²⁺ could repress the growth of both nitrification and denitrification bacteria. And Ni²⁺ was more effective than Pb²⁺ to reduce the heavy metals removal efficiency. The SBR system could be applied to treat the industrial estate wastewater (IEWW) containing both Pb²⁺ and Ni²⁺ even the heavy metals concentrations was up to 5 mg/L, but the removal efficiency was quite low and excess bio-sludge did not produce. However, the system efficiency could be increased with the increase of BOD₅ concentration of the wastewater. The Pb²⁺, Ni²⁺, COD, BOD₅ and TKN removal efficiencies of the system with IEWW containing 500 mg/L BOD₅, 5 mg/L Ni²⁺ and 5 mg/L Pb²⁺ under HRT of 3 days were 85.68 ± 0.31%, 87.03 ± 0.21%, 86.0 ± 0.5%, 94.04 ± 0.4% and 90.5 ± 0.9%, respectively. And the effluent SRT, SS and SVI of the system were 44.7 ± 0.6 days, 150 ± 6 mg/L and 100 mL/g, respectively.     

Effect of vacuum magnetic annealing on the structural and physical properties of the Ni and Al co-doped ZnO films

About 300 nm-thick Zn_0.87Al_0.06Ni_0.07O, Zn_0.83Al_0.06Ni_0.11O and Zn_0.81Al_0.04Ni_0.15O films were deposited on glass substrates at 300 K by co-sputtering ZnO:Al and Ni targets. The films were annealed in vacuum at 673 K for 2 h under a magnetic field of 4.8 × 10⁴ A/m applied along the film plane and then were cooled down to room temperature without magnetic field. All the films have a wurtzite structure and consist of thin columnar grains perpendicular to the substrate. The annealing promotes the (002) orientation growth in the film growing direction for the Zn_0.87Al_0.06Ni_0.07O and Zn_0.83Al_0.06Ni_0.11O films as well as the (100) orientation growth for the Zn_0.81Al_0.04Ni_0.15O film. The annealing results in a slight increase in the grain size. A weak Ni diffraction peak was detected for the annealed films with high Ni content. The annealing enhances the room temperature ferromagnetism of the films. A temperature dependence of magnetization confirms that the Curie temperature is above 400 K for the annealed films. The films magnetically annealed exhibit an anisotropic magnetization behavior. The annealed Zn_0.87Al_0.06Ni_0.07O film has the lowest resistivity (8.73 × 10⁻³ Ω cm), the highest free electron concentration (1.73 × 10²⁰ cm^− 3) and Hall mobility (4.16 cm²V^− 1 s^− 1). A temperature dependence of the resistivity from 50 K to 300 K reveals that the carrier transport mechanism is Mott's variable range hopping in the low temperature range and thermally activated band conduction in the high temperature range.     

Peculiarities of the Ni ions in the crystal lattice of Bi12SiO20:Ni

Absorption measurements are taken over a wide spectral range which includes the visible, near and far IR region (500-22,272 cm⁻¹). The exponential absorption edge parameters σ(T), σ₀, W_d and g are calculated for undoped and Ni doped Bi₁₂SiO₂₀ at room temperature. The dopant nickel ion is double-charged and occupies the tetrahedral sites in the crystal lattice of doped sillenite. The energy level structure of the Ni²⁺ ion in Bi₁₂SiO₂₀:Ni (BSO:Ni) is also presented. The crystal field parameter Dq and the Racah parameters B and C are calculated. It is established that the Jahn-Teller effect displays very strong influence in a distored tetrahedral Ni²⁺ complex. The two-photon absorption of BSO:Ni is studied in far IR region.     

The influence of Na2CO3 content and Ni concentration on the physicochemical properties of nanometer Y-substituted nickel hydroxide

Nanometer Y-substituted nickel hydroxide was prepared by supersonic co-precipitation method with Na₂CO₃ as a buffer and NiCl₂ as a nickel source. The crystal structure, morphology, particle size distribution and electrochemical performance affected by the buffer (Na₂CO₃) content and Ni²⁺ concentration are characterized. The results indicate most of the samples are co-existence with α and β phases and the proportion of α-Ni(OH)₂ increases with the increase of Na₂CO₃, but decreases with the increase of Ni²⁺ concentration. The primary particles of samples are nanometer particles and the shape of primary particles transform from acicular to quasi-spherical with increasing Na₂CO₃ content, but converse process for the increase of Ni²⁺ concentration. The average particle size decreases initially and then increases. Complex electrodes were prepared by mixing 8 wt.% nickel hydroxides with commercial micro-size spherical nickel. The discharge capacities of samples increase initially and then decrease with increasing Na₂CO₃ content or decreasing Ni²⁺ concentration. When Na₂CO₃ content is 0.08 g and Ni²⁺ concentration is 0.2 mol/L, the sample has better electrochemical performance, such as larger discharge capacity (316.3 mAh/g at 0.2 C rate), lower charge voltage and higher discharge plateau, than those of other samples.     

Finite size effect on Ni doped nanocrystalline NixZn1 − xFe2O4 (0.1 ≤ x ≤ 0.5)

Nanocrystalline nickel ferrite with different concentration of Ni and Zn (Ni_xZn_1 − xFe₂O₄ where x = 0.1, 0.3, 0.5) were synthesized using chemical co-precipitation method. The effect of doping ion concentration on physical properties like crystalline phase, crystallite size, particle size, and saturation magnetization are investigated. The X-ray diffraction pattern confirms the synthesis of single crystalline Ni_xZn_1 − xFe₂O₄ nanoparticles. The lattice parameter decreases with increase Ni content resulting in reduction of lattice strain. HRTEM images revealed that the as-prepared nanoparticles were crystalline with particle size distribution in 10-30 nm range. The saturation magnetization show the superparamagnetic nature of sample for x = 0.1 and x = 0.3 whereas for x = 0.5, the material is ferromagnetic. The saturation magnetization value is 23.95 emu/gm for Ni_0.1Zn_0.9Fe₂O₄ sample and it increases with increase in Ni content.     

Ni 2p X-ray photoelectron spectroscopy study of nanostructured nickel oxide

Herein the detailed analysis of the Ni 2p X-ray photoelectron spectra of nanostructured nickel oxide samples with three different average crystallite sizes is reported. The observed main line broadening and the increase in the relative intensity of the ∼1.5 eV satellite structure are discussed taking into account the large surface to volume ratio, high concentration of Ni²⁺ vacancies and enhancement in the Ni 3d-O 2p hybridization. The influence of these factors on the possible local and non-local screening mechanisms accompanying the photoemission of Ni 2p core level electron is analyzed on the basis of the Ni₇O₃₆ cluster calculations.     

Characterization of Al/Ni multilayers and their application in diffusion bonding of TiAl to TiC cermet

The Al/Ni multilayers were characterized and diffusion bonding of TiAl intermetallics to TiC cermets was carried out using the multilayers. The microstructure of Al/Ni multilayers and TiAl/TiC cermet joint was investigated. The layered structures consisting of a Ni₃(AlTi) layer, a Ni₂AlTi layer, a (Ni,Al,Ti) layer and a Ni diffusion layer were observed from the interlayer to the TiAl substrate. Only one AlNi₃ layer formed at the multilayer/TiC cermet interface. The reaction behaviour of Al/Ni multilayers was characterized by means of differential scanning calorimeter (DSC) and X-ray diffraction. The initial exothermic peak of the DSC curve was formed due to the formation of Al₃Ni and Al₃Ni₂ phases. The reaction sequence of the Al/Ni multilayers was Al₃Ni → Al₃Ni₂ → AlNi → AlNi₃ and the final products were AlNi and AlNi₃ phases. The shear strength of the joint was tested and the experimental results suggested that the application of Al/Ni multilayers improved the joining quality.     

Ascorbate electro-oxidation by modified electrodes: Polypyrrole and polypyrrole/Ni(OH)2 composite thin films

The present paper describes the utilization of polypyrrole and the composite of polypyrrole doped with nickel hydroxide modified electrodes toward the catalytic oxidation of ascorbate. Films were potentiostatically deposited onto a glassy carbon surface and Fluor-doped tin oxide glass for different times. The physical characterization was performed using the low angle X-ray diffraction technique. Furthermore, the films were electrochemically characterized using cyclic voltammetry. The X-ray diffraction results show the existence of different polymorphic phases of nickel hydroxide in the polymer matrix, and the β-Ni(OH)₂ phase appears to be dominant. The cyclic voltammetry profile in KOH solution shows the presence of two redox peaks that are related to the Ni^II/Ni^III and Ni^III/Ni^II couples, at approximately 0.5 and 0.35 V, respectively. The reversible electro-oxidation of ascorbate was observed on the surface of the polypyrrole and composite films. The analytical curves obtained using voltammetric techniques show a linear relationship between the faradaic current and the increase of the ascorbic acid concentration. The sensitivity of these films, which is obtained from the slope of the analytical curves, shows that the composite film is more electroactive than the polypyrrole film: 133.4 mA L mol^− 1 cm^− 2 and 83.8 mA L mol^− 1 cm^− 2, respectively. The rate constants of the catalytic ascorbate electro-oxidation were also reported, where the mean values were found to be 217.74 M^− 1 s^− 1 and 54.37 M^− 1 s^− 1, for the composite and polypyrrole films, respectively. The low cost of polypyrrole doped with Ni(OH)₂ composite electrodes presents a more selective and high sensitivity to determine ascorbic acid concentration.     

Formation of Ni2Si silicide in Ni/Si bilayers by ion beam mixing

We have studied ion mixing in Ni-Si(1 1 1) bilayers using noble gas ions. Thin Ni films of 45 nm thickness, deposited on a Si (1 1 1) substrate, were irradiated with 175 keV Kr and 110 keV Ar ions at the same fluence of 4×10¹⁶ ions/cm² at room temperature. The formation of the mixing and the elemental depth profile were investigated by Rutherford backscattering spectrometry. In the Ar irradiated sample, there was no structural change. On the other hand, we have noted the formation of Ni₂Si for the sample irradiated with Kr ions. X-ray diffraction measurements confirmed the formation of the Ni₂Si phase. The surface morphology of the Kr irradiated sample was also studied by scanning electron microscopy.     

Magnetic properties of epitaxial thin films and bulk of Eu(Ni,Mn)O3 perovskites

Magnetic properties of EuNi_xMn_1 − xO₃ were studied in bulk form and, for a specific composition (x = 1/3), as epitaxial thin film. Paramagnetic properties are interpreted as a VanVleck contribution of the ⁷F Eu³⁺ configuration, showing linear decrease of the effective moment and VanVleck susceptibility as x(Ni) increases. The ordered state was studied for three particular compositions which describe different regimes: canted-antiferromagnetism for x(Ni) = 1/4 and ferromagnetism for x(Ni) = 1/2, the composition x(Ni) = 1/3 being at the frontier of both regimes. Nominal composition x(Ni) = 1/3 was chosen for epitaxial films, since it corresponds to a critical concentration for which a maximum number of pairs Mn³⁺-Mn⁴⁺ and optimal double-exchange interactions are found. The coercive field is enhanced, and the field dependence of T_max is reduced as if the coherent ferromagnetic phase is favoured at the boundary of the magnetic domains.     

Efficient way of precipitation to synthesize Ni-ion stabilized tetragonal zirconia nanopowders

Nickel ions (Ni²⁺) stabilized tetragonal zirconia (t-ZrO₂) nanopowders have been synthesized at constant pH as well as increasing (direct process) and decreasing (reverse process) the pH of the precursor solution step by step, using hydrazine hydrate (N₂H₅OH) as a precipitating agent. The constant pH (at 10) process has a promising effect on the stability of t-ZrO₂ over the direct and reverse processes. The maximum solubility limit of Ni²⁺ in ZrO₂ is less than 20 mol%. XRD results of the Ni²⁺-ZrO₂ systems revealed that the minimum concentrations of Ni²⁺ for stabilizing t-ZrO₂ at 700 °C and 800 °C are 10 mol% and 20 mol%, respectively. Decrease in cell volume and crystallite size lead to higher strain with the incorporation of Ni²⁺ ions that causes the stabilization of t-ZrO₂ up to 800 °C while synthesized using constant pH process.     

Development of graded Ni-YSZ composite coating on Alloy 690 by Pulsed Laser Deposition technique to reduce hazardous metallic nuclear waste inventory

Alloy 690 based ‘nuclear waste vitrification furnace’ components degrade prematurely due to molten glass-alloy interactions at high temperatures and thereby increase the volume of metallic nuclear waste. In order to reduce the waste inventory, compositionally graded Ni-YSZ (Y₂O₃ stabilized ZrO₂) composite coating has been developed on Alloy 690 using Pulsed Laser Deposition technique. Five different thin-films starting with Ni80YSZ20 (Ni 80 wt% + YSZ 20 wt%), through Ni60YSZ40 (Ni 60 wt% + YSZ 40 wt%), Ni40YSZ60 (Ni 40 wt% + YSZ 60 wt%), Ni20YSZ80 (Ni 20 wt% + YSZ 80 wt%) and Ni0YSZ100 (Ni 0 wt% + YSZ 100 wt%), were deposited successively on Alloy 690 coupons. Detailed analyses of the thin-films identify them as homogeneous, uniform, pore free and crystalline in nature. A comparative study of coated and uncoated Alloy 690 coupons, exposed to sodium borosilicate melt at 1000 °C for 1-6 h suggests that the graded composite coating could substantially reduced the chemical interactions between Alloy 690 and borosilicate melt.     

Influence of isovalent ion substitution on the electrochemical performance of LiCoPO4

LiCo_1−xM_xPO₄ (M = Mg²⁺, Mn²⁺ and Ni²⁺; 0 ≤ x ≤ 0.2) compounds have been synthesized by solid-state reaction method and studied as cathode materials for secondary lithium batteries. LiCoPO₄ exhibits a discharge plateau at ∼4.7 V with an initial discharge capacity of 125 mAh/g and on cycling capacity falls. Substitution of Co²⁺ with Mg²⁺/Mn²⁺/Ni²⁺ in LiCoPO₄ has an influence on the initial discharge capacity and on cycling behaviour. The capacity retention of LiCoPO₄ is improved by manganese substitution. Among the manganese substituted phases, LiCo_0.95Mn_0.05PO₄ shows good reversible capacity of ∼50 mAh/g.     

Effect of Ni addition on formation of amorphous and nanocrystalline phase during mechanical alloying of Al-25 at.%Fe-(5,10) at.%Ni powders

Al-Fe-Ni ternary powder mixtures containing 25 at.%Fe-5 at.%Ni and 25 at.%Fe-10 at.%Ni were mechanically alloyed by a high-energy planetary ball mill. Structural evolution of these powders during milling was investigated by X-ray diffraction technique and transmission electron microscopy. Almost complete amorphous phase in Al₇₀Fe₂₅Ni₅ system is observed at the early milling stage. The amorphous phase transforms into metallic compound Al₅(Fe,Ni)₂ and then the compound changes to ordered Al(Fe,Ni) phase. The last milling products in Al₇₀Fe₂₅Ni₅ system are amorphous phase plus nanocrystalline of the disordered Al(Fe,Ni) phase changed from the ordered Al(Fe,Ni) phase. During milling of Al₆₅Fe₂₅Ni₁₀ system, α-Al and α-Fe solid solutions formed at the early stage change to the ordered Al(Fe,Ni) compound and at last the ordered phase changes to the disordered Al(Fe,Ni) phase. Ten percent of Ni addition promotes retardation of the formation of the amorphous phase.     

Al and Ni co-doped ZnO films with room temperature ferromagnetism,low resistivity and high transparence

Zn_0.91Al_0.07Ni_0.02O and Zn_0.90Al_0.05Ni_0.05O films of about 250 nm thick were deposited on glass substrates at 300 K by co-sputtering with ZnO:Al and Ni targets. The films were annealed in vacuum at 673 K for 2 h and then cooled down to room temperature under a magnetic field of 4.8 × 10⁴ A m⁻¹ applied along the film plane. After this process the films showed room temperature ferromagnetism, a resistivity of about 2 × 10⁻³ Ω cm and an average transmittance of 75% in the visible wavelength range. The films have a wurtzite structure with the c-axis orientation in the film growing direction and consist of thin columnar grains perpendicular to the substrate. A temperature dependence of the resistivity from 2 K to 300 K reveals that the carrier transport mechanism is thermally activated band conduction above 150 K and Mott's variable range hopping below 70 K.     

Synergistic Coupling of Ni Nanoparticles with Ni3C Nanosheets for Highly Efficient Overall Water Splitting

Exploring earth‐abundant bifunctional electrocatalysts with high efficiency for water electrolysis is extremely demanding and challenging. Herein, density functional theory (DFT) predictions reveal that coupling Ni with Ni₃C can not only facilitate the oxygen evolution reaction (OER) kinetics, but also optimize the hydrogen adsorption and water adsorption energies. Experimentally, a facile strategy is designed to in situ fabricate Ni₃C nanosheets on carbon cloth (CC), and simultaneously couple with Ni nanoparticles, resulting in the formation of an integrated heterostructure catalyst (Ni–Ni₃C/CC). Benefiting from the superior intrinsic activity as well as the abundant active sites, the Ni–Ni₃C/CC electrode demonstrates excellent bifunctional electrocatalytic activities toward the OER and hydrogen evolution reaction (HER), which are superior to all the documented Ni₃C‐based electrocatalysts in alkaline electrolytes. Specifically, the Ni–Ni₃C/CC catalyst exhibits the low overpotentials of only 299 mV at the current density of 20 mA cm^?2 for the OER and 98 mV at 10 mA cm^?2 for the HER in 1 m KOH. Furthermore, the bifunctional Ni–Ni₃C/CC catalyst can propel water electrolysis with excellent activity and nearly 100% faradic efficiency. This work highlights an easy approach for designing and constructing advanced nickel carbide‐based catalysts with high activity based on the theoretical predictions.     

Characterization of electrochemically deposited Cu-Ni black coatings

Electrochemically deposited Cu-Ni black coatings on molybdenum substrate from ethylenediaminetetraacetic acid (EDTA) bath solution are shown to exhibit good optical properties (α=0.94, ε = 0.09). The deposit is characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Cu is present in metallic and +2 oxidation states in the as-prepared Cu-Ni black coating, whereas Ni²⁺ as well as Ni³⁺ species are observed in the same coating. Cu and Ni are observed in their metallic state after 10 and 20 min sputtering. X-ray initiated Auger electron spectroscopy (XAES) of Cu and Ni also agrees well with XPS investigations.     

Synthesis and characterizations of nano-sized Ni(OH)2 and Ni(OH)2/poly(vinyl alcohol) nano composite

Nano-sized Ni(OH)₂ was synthesized by a co-precipitation method. Peaks between 500 and 750 cm⁻¹ in Fourier transform infrared spectroscopy (FTIR) confirmed the presence of metal hydroxide stretching. Thermo gravimetric analysis inferred that 69 wt% residue remained above 750 °C. High-resolution transmission electron microscopy analysis of Ni(OH)₂ revealed its size ranged from 80 to 110 nm with smooth morphology. Scanning electron microscopy inferred that pure Ni(OH)₂ has nano rod-like morphology and higher weight percentage of aniline-intercalated Ni(OH)₂ has agglomerated structure. UV–Vis spectrum detected the presence of Ni²⁺ ions at 210 nm and the existence of amino group in the basal spacing of Ni(OH)₂ was not clearly appeared in the spectrum. Photoluminescence (PL) inferred that aniline-intercalated Ni(OH)₂ showed higher PL intensity than the pristine poly(vinyl alcohol) its and nano composite.     

Synthesis of CuCr and CuCrAg alloy with nano-ceramic dispersion by mechanical alloying and consolidation by laser assisted sintering

Cu-4.5Cr and Cu-4.5Cr-3Ag (in wt%) alloys without or with 10 wt% nanocrystalline Al₂O₃ and ZrO₂ dispersion have been synthesized by mechanical alloying or milling and consolidated by laser assisted sintering in Ar atmosphere. Microstructural characterization by scanning and transmission electron microscopy and phase analysis by X-ray diffraction suggest that the alloyed matrix undergoes significant grain growth after sintering while the dispersoids retain their ultrafine size and uniform distribution in the matrix. The dispersion of nano-Al₂O₃ is more effective than that of nano-ZrO₂ in enhancing the mechanical properties due to the smaller initial particle size of Al₂O₃ than that of ZrO₂. In general, laser sintering of mechanically alloyed Cu-4.5Cr and Cu-4.5Cr-3Ag alloys with 10 wt% nanocrystalline Al₂O₃ at 100 W laser power and 1-2 mm s⁻¹ scan speed yields the optimum combination of high density (7.1-7.5 mg m⁻³), hardness (165-225 VHN), wear resistance and electrical conductivity (13-20% IACS).     

Ni-doped vertically aligned zinc oxide nanorods prepared by hybrid wet chemical route

Ni-doped zinc oxide (Ni:ZnO) nanorods were synthesized by incorporating nickel in vertically aligned ZnO nanorods. Ni was evaporated onto ZnO nanorods and the composite structure was subjected to rapid thermal annealing for dispersing Ni in ZnO nanorods. The optical band gap decreased with increasing amount of Ni incorporation. The origin of the photoluminescence peak at ∼ 400 nm was related to the defect levels introduced due to substitution of Ni²⁺ in the Zn²⁺ site with annealing. The Raman spectra indicated the presence of the characteristic peak at ∼ 436 cm^− 1 which was identified as high frequency branch of E₂ mode of ZnO. The Fourier Transformed Infrared spectra indicated the existence of the distinct characteristic absorption peak at 481 cm^− 1 for ZnO stretching modes. Current-voltage characteristics indicated that the current changed linearly with voltage for both the doped and undoped samples.