Zinc recovery and waste sludge minimization from chromium passivation baths

This work reports the feasibility of applying emulsion pertraction technology (EPT) aiming at zinc recovery and waste minimization in the zinc electroplating processes that include Cr (III) passivation. The assessment consists of firstly the lifetime extension of the passivation baths by selective removal of the tramp ions zinc and iron, and secondly, the recovery of zinc for further reuse. Spent passivation baths from a local industry were tested, being the major metallic content: Cr³⁺ 9000 mg L⁻¹, Zn²⁺ 12,000 mg L⁻¹, Fe³⁺ 100 mg L⁻¹. Working in a Liqui-Cel hollow fiber membrane contactor and using the extractant bis(2,4,4-trimethylpentyl) phosphinic acid, reduction of zinc and iron concentrations below 60 mg L⁻¹ and 2 mg L⁻¹, respectively were obtained, while trivalent chromium, the active metal that generates the passivation layer, was retained in the baths. Zinc was selectively transferred to an acidic stripping phase that in the experimental time reached a concentration of 157,000 mg L⁻¹. Zinc recovery by electrowinning from the acidic stripping phase without any pretreatment of the electrolyte solution provided a purity of 98.5%, matching the lower commercial zinc grade. As a result of the extension of the life time of the passivation bath, significant environmental advantages are derived such as minimization of the volume of hazardous wastes and savings in the consumption of raw materials.     

Reclaimed wastewater: impact on soil-plant system under tropical conditions

This study investigated the ionic speciation of reclaimed urban wastewater (RWW), and the impact of increasing RWW irrigation rates on soil properties and plant nutrition under field conditions. Most RWW elements (>66%) are readily available as NH₄⁺, Ca²⁺, Mg²⁺, K⁺, SO₄²⁻, Cl⁻, H₃BO₃, Mn²⁺ and Zn²⁺, but in imbalanced proportion for plant nutrition. Lead, Cd, Cr and Al in RWW are mostly bounded with DOM or OH⁻.^.Irrigation with RWW decreased soil acidity, which is beneficial to the acidic tropical soil. Although RWW irrigation builds exchangeable Na⁺ up, the excessive Na⁺ was leached out of the soil profile after a rainy summer season (>400 mm). Benefits of the disposal of RWW to the soil under tropical conditions were discussed, however, the over irrigation with RWW (>100% of crop evapotranspiration) led to a nutritional imbalance, accumulating S and leading to a plant deficiency of P and K.     

Tl-208, Pb-212, Bi-212, Ra-226 and Ac-228 adsorption onto polyhydroxyethylmethacrylate-bentonite composite

The adsorption of naturally occurring radionuclides (²⁰⁸Tl⁺, ²¹²Pb²⁺, ²²⁶Ra²⁺, ²¹²Bi³⁺ and ²²⁸Ac³⁺) onto Polyhydroxyethylmethacrylate-bentonite (PHEMA-B) composite was investigated. Experimentally obtained isotherms were evaluated with reference to Langmuir, Freundlich and Dubinin-Radushkevich (DR) models. The adsorption isotherms were L type of Giles classification proving that PHEMA-B had a high affinity adsorbent for the studied radionuclides. The Langmuir adsorption capacities (X_L) were in the order of ²²⁶Ra (2.8 MBq kg⁻¹)>²¹²Bi (0.4 MBq kg⁻¹)>²¹²Pb (0.3 MBq kg⁻¹)>²²⁸Ac and ²⁰⁸Tl (0.2 MBq kg⁻¹). The adsorption process was physical via complex formation after proton exchanger for which the adsorption energies obtained from DR model was evidence. The enthalpy and entropy changes were positive and the negative free enthalpy change was proof for the spontaneity of adsorption. The reusability tests for PHEMA-B for five uses demonstrated that the adsorbent could be reused after complete recovery of the loaded radionuclide ions by 1 M HCl. The chemical structure of the composite did not change after the reuses and storage foregoing.     

Clean hydrometallurgical route to recover zinc, silver, lead, copper, cadmium and iron from hazardous jarosite residues produced during zinc hydrometallurgy

A hydrometallurgical process for treating the hazardous jarosite residue from zinc hydrometallurgy was proposed, for not only detoxifying the residue, but also recovering the contained valuable metal components. The jarosite was initially activated and decomposed by sintering at 650 °C for 1 h. The sintered residue was leached in 6 mol L⁻¹ aqueous NH₄Cl solution at 105 °C, followed by filtration. The leaching extraction of Zn, Pb, Cu, Cd and Ag are more than 95%. During reduction with Zn powder, more than 93% of Pb, Cu, Ag and Cd can be simultaneously recovered. Then the NH₄Cl leaching residue were leached again in 30 wt% aqueous NaOH solution for 1 h at 160 °C, and about 94% of As and 73% of Si were removed from the residue. The final residue was almost completely detoxified, and contains about 55 wt% Fe, which can be used as an iron concentration.     

Fluoride accumulation by plants grown in acid soils amended with flue gas desulphurisation gypsum

The application of flue gas desulphurisation (FGD) gypsum as an acid soil ameliorant was studied in order to establish the possible detrimental effects on plants and animals feeding on them caused by the high fluoride content in this by-product. A greenhouse experiment was conducted under controlled conditions to determine the F accumulation by two plant species (alfalfa (Medicago sativa L.) and ryegrass (Lolium perenne L.)) grown in acid soils amended with different FGD gypsum doses (0-10%). The F concentrations in plant aerial parts were comprised in the range 22-65 mg kg⁻¹, and those in plant roots varied from 49 to 135 mg kg⁻¹. The F contents in the above-ground plant tissues showed to decrease with the FGD gypsum application rate, whereas an inverse trend was manifested by plant roots. The increase in the soil content of soluble Ca as a result of the FGD gypsum addition seemed to play an important role in limiting the translocation of F to plant aerial parts.     

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.     

Microstructures and improved wear resistance of 3D needled C/SiC composites with graphite filler

Three-dimensional (3D) needled carbon/carbon (C/C) composites with a lowest porosity of 15.6% were achieved after 1 cycle of impregnation by phenolic resin slurry containing graphite filler, hot-pressing curing and pyrolysis. Carbon/silicon carbide (C/SiC) composites were obtained by liquid silicon infiltrating C/C composites. The aim was to incorporate cost effectiveness and excellent performance of C/SiC braking material. Using filler content not exceeding 30 wt% in the slurry promised undamaged C/C segments in C/SiC composites. The linear wear rate of C/SiC using 30 wt% filler was 0.33 μm side⁻¹ cycle⁻¹ and displayed a fourfold decrease; its weight wear rate was 2.46 mg side⁻¹ cycle⁻¹ and minus 171%, compared with the previously reported values of C/SiC without filler, at a braking velocity of 28 m/s. Its friction coefficients and friction stability coefficients appeared relative insensitive to changes in braking velocities and displayed higher values at high braking velocities compared with the previous values.     

Emissions of polycyclic aromatic hydrocarbons from fluidized and fixed bed incinerators disposing petrochemical industrial biological sludge

This study investigated the emissions of polycyclic aromatic hydrocarbons (PAHs) from two fluidized bed incinerators (FLBI_A and FLBI_B) and one fixed bed incinerator (FIBI) disposing biological sludge generated from the petrochemical industries in Taiwan. The results of 21 individual PAHs (including low (LM-PAHs), middle (MM-PAHs) and high molecular weight PAHs (HM-PAHs)) were reported. The LM-PAHs mainly dominated the total-PAHs in the stack flue gases, whereas the LM- and HM-PAHs dominated the total-PAHs in the bottom fly, fly ash and WSB effluent. Due to high carcinogenic potencies (= total-BaP_eq concentrations) in the bottom ash (195 ng g⁻¹) and WSB effluent (20,600 ng L⁻¹) of the FIBI, cautious should be taken in treating them to avoid second contamination. Lower combustion efficiency and elevated fuel/feedstock (F/W) ratio for the FIBI led to the highest total emission factor of total-PAHs (38,400 μg kg⁻¹). Lower total-PAH removal efficiencies of wet scrubber (WSB) (0.837–5.89%), cyclone (0.109–0.255%) and electrostatic precipitator (ESP) (0.032%) than those reported elsewhere resulted in high fraction in PAH contributions from the stack flue gases. Lower total-PAH emission factor was found for FLBI_A (2380 μg kg⁻¹ biological sludge) with higher combustion efficiency compared to those for FLBI_B (11,500 μg kg⁻¹) and FIBI (38,400 μg kg⁻¹ biological sludge), implying that combustion efficiency plays a vital role in PAH emissions.     

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).     

Electrical conductivity and Raman imaging of double wall carbon nanotubes in a polymer matrix

Raman spectroscopy is used to access the dispersion state of DWNTs in a PEEK polymer matrix. The interaction of the outer tube with the matrix can be determined from the line shape of the Raman G band. This allows us to distinguish regions where the nanotubes are well dispersed and regions where the nanotubes are agglomerated. The percolation threshold of the electrical conductivity of the double wall carbon nanotubes (DWNTs)/PEEK nanocomposites is found to be at 0.2-0.3 wt%. We find a maximum electrical conductivity of 3 × 10⁻² S cm⁻¹ at 2 wt% loading. We detect nanotube weight concentrations as low as 0.16 wt% by Raman spectroscopy using a yellow excitation wavelength. We compare the Raman images with transmission electron microscopy images and electrical conductivity measurements. A statistical method is used to find a quantitative measure of the DWNTs dispersion in the polymer matrix from the Raman images.     

The influence of Ni nanoparticles and Ni (II) on the growth of Ag dendrites immobilized on the chelating copolymer membrane

Preparation of Ag dendrites on the surface of chelating copolymer membranes (PBAGI), which was synthesized by using the soap-free emulsion copolymerization of n-butylacrylate (BA) and acrylonitrile (AN), as well as 2-methacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester (GMA-IDA) that was used as a chelating group, is presented in this study. The characteristics of polymer membranes were investigated by Fourier transform infrared (FTIR) spectroscopy and elementary analysis (EA). The weight fraction of GMA-IDA in the polymer was 4.2 wt% as revealed by elemental analysis. The chelating group, –N(CH₂COO⁻Na⁺)₂ on the polymer was used to coordinate different amounts of Ni(II), controlled by different chelating times and subsequently reduced to Ni nanoparticles, as templates for growing Ag nanocrystals from 1.67 wt% AgNO₃ aqueous solution with 55.7 ppm poly(vinyl pyrrolidone) (PVP) added. In addition, the effect of Ni²⁺ concentration on the growth of the Ag dendrites was studied. Crystallinity and morphology of Ag dendrites were examined with X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. Amount of Ag dendrites increased with the increasing of Ni nanoparticles on the PBAGI membrane or the dose of Ni²⁺ present in the aqueous solution. Notable, under higher amount of Ni nanoparticles (over 200 mmol Ni²⁺/g PBAGI membrane), Ag dendrites could be successful grown on the membrane. However, higher dose of Ni²⁺ (over 41.3 ppm) might inhibit the growth of Ag dendrites.     

Low temperature luminescence of KMgF3:Eu crystal

Paper presents luminescence spectra and time resolved spectra of KMgF₃:Eu²⁺ system obtained at different temperatures and pressures, under excitation with 325 nm. At temperatures between 200 K and 292 K the spectra consist of sharp line peaked at 27,830 cm⁻¹ related to ⁶P_7/2 → ⁸S_7/2 transition in Eu²⁺ accompanied by the phonon sideband. Under pressure the red spectral shift with the rate equal to −0.6 cm⁻¹/kbar is observed. Luminescence decay is single-exponential with the lifetime equal to 5.2 ms independent of pressure and temperature. The emission spectra obtained at temperatures lower than 125 K consist of 5 sharp lines peaked at 27,590 cm⁻¹, and 27,670 cm⁻¹, 27,722 cm⁻¹, 27,766 cm⁻¹ and 27,809 cm⁻¹, that relative intensity depends on temperature. Pressure shift of these lines was found to be equal to −0.6 cm⁻¹/kbar; the same as ⁶P_7/2 → ⁸S_7/2 transition in Eu²⁺, whereas their lifetime is shorter and is equal to 0.7 ms at 100 K. These new lines disappear at temperature greater than 200 K. We tentatively related them to the luminescence of Eu²⁺-F center (fluorine vacancy with electron) complex.     

Effects of field-manure applications on stratified 17β-estradiol concentrations

The occurrence of the manure-borne estrogen, 17β-estradiol (E2), was investigated in laboratory and field soils. In the laboratory, E2 was applied to soil to simulate concentrations found in swine (Sus scrofa domestica) manure (5000 ng L⁻¹). The aqueous-extracted E2 dissipated in the soil by 98% within 1 h and was not significantly different from background concentrations (18 ng L⁻¹) for the duration of the experiment (64 h). In the field study, soil cores were taken before and several dates after swine manure application. Equivalent porewater concentrations of water-extractable E2 were determined in 0.15-m increments down to the water table (0.70-2.00 m deep). The average frequency of detection for 168 samples was 38% (average = 40 ng L⁻¹ porewater equivalents). Eleven days after manure application there was no significant effect on E2 detection frequency or concentration. However, E2 concentrations significantly increased by 6 months after manure application, and appeared to be related to precipitation. Concentrations then returned to original levels by 17 months after manure application. Manure did not have an immediate effect on E2 occurrence due to the capacity of the soil to rapidly sorb E2. However, it appears that soil may act as a long-term reservoir for E2 in the environment, which may be periodically released through desorption.     

Copper nanowall array grown on bulk Fe-Co-Ni alloy substrate at room temperature as lithium-ion battery current collector

Large-scale copper nanowall array on the bulk Fe-Co-Ni alloy substrate has been prepared in aqueous solution at room temperature via an electroless deposition method. The thickness of the nanowalls is about 15 nm. A possible growth mechanism of the nanowalls was proposed. The effects of reaction temperature, reaction time and the amount of critical agent (Fe³⁺) on the morphology and crystalline phase of the nanowalls were investigated. Furthermore, the electrochemical performance of Sn film supported on the as-prepared copper nanowalls current collector is enhanced in comparison with that on the commercial copper foil when used as anode for Li-ion batteries with the operating voltage window of 0.01-2.0 V (vs. Li). After 20 cycles, the discharge capacity of Sn-Cu nanowalls anode still remained 365.9 mAh g^− 1, that is, 40% retention of the reversible capacity, while the initial charge capacity of Sn film cast on commercial Cu foil was 590 mAh g^− 1, dropping rapidly to 260 mAh g^− 1 only after 10 cycles.     

Growth and spectral properties of Cr:KAl(MoO4)2 crystal

The Cr³⁺:KAl(MoO₄)₂ single crystal was grown by top seeding solution growth method (TSSG). Based on the absorption and emission spectra, the crystal field strength Dq, the Racah parameters B and C, the effective phonon energy ?ω and the Huang-Rhys factor S were calculated: Dq = 1494.8 cm^− 1, B = 585.5 cm^− 1 and C = 3049 cm^− 1, ?ω = 373.8 cm^− 1 and the Huang-Rhys factor S = 3.74, respectively. The value Dq/B = 2.55 indicates that Cr³⁺ ion occupies the strong crystal field site in KAl(MoO₄)₂ crystal. A comparison of crystal field parameters for Cr³⁺:KAl(MoO₄)₂ with other Cr³⁺-doped crystals was presented. The results of spectral measurement show that Cr³⁺:KAl(MoO₄)₂ may be a potential candidate for broadband laser applications.     

Synthesis and structural characterization of Tm:Lu2O3 nanocrystals. An approach towards new laser ceramics

Nanocrystals of Tm³⁺ Thulium doped cubic sesquioxides, Tm:Lu₂O₃, with a maximum size around 30 nm have been synthesized by a modified Pechini sol-gel method. The calcination temperature for the synthesis is 1073 K. Electron microscopy was used to analyze the presence of aggregates, and the type of boundary between the nanocrystals. The linear coefficient of thermal expansion for these nanocrystals has been determined to be around 7.5 × 10⁻⁶ K⁻¹. The growth of the nanocrystals has been studied in terms of temperature and time. Nanocrystals start to grow at temperatures around 1267 K. Finally, the grain growth activation energy of this material has been evaluated to be 76 kJ/mol, indicating a diffusion growth mechanism. Linear thermal expansion of prepared nanocrystals is ≈7.5 × 10⁻⁶ K⁻¹.     

The biochemical response to different Cr and Cd concentrations in soils amended with organic wastes

The effects of adding municipal solid waste (MSW) or poultry manure (PM) on the biochemical properties of a soil polluted with Cr and Cd were studied. Soil was mixed with Cr(NO₃)₃ and Cd(NO₃)₂ to give three concentrations (0, 100, and 250 mg Cr kg⁻¹ and 0, 100, and 250 mg Cd kg⁻¹) in the soil, which was then treated with MSW at a rate of 10% or PM at a rate of 7.6%. The pH and biochemical parameters were measured at 0 and 120 days. An unamended and no-polluted soil was used as control. Compared with the non-polluted soil, for the 250 mg Cd kg⁻¹ treatment the microbial biomass-C, dehydrogenase, urease, β-glucosidase, phosphatase, and arylsulphatase activities decreases 23%, 26.2%, 36%, 34.8%, 18.4%, and 15.8%, respectively, whereas for 250 mg Cr kg⁻¹ treatment the biochemical parameters were slightly lowest than for 250 mg Cd kg⁻¹ treatment. For 250 mg Cr kg⁻¹ soil + 250 mg Cd kg⁻¹ soil treatment, the inhibition percentages of the biochemical parameters increased. After the application of organic wastes in Cr + Cd polluted soil, the inhibition of biochemical properties was greater with the MSW amendment than with PM, possibly due to its higher humic acid concentration.     

Luminescence excitation spectra of TbX3 (X = Cl, Br, I)

A systematic study of the excitation spectrum of TbX₃ (X = Cl⁻, Br⁻, I⁻) is presented in this work. In general, the excitation spectra of TbX₃ can be divided into three major regions: (1) the short-wave host lattice absorption region, (2) the intermediate absorption region where the Tb³⁺ 4f⁸ → 4f⁷5d¹ interconfigurational excitation transition are located, and (3) the long-wave excitation region where the Tb³⁺ 4f⁸ → 4f⁸ intraconfigurational excitation transition are located. The high spin and the low spin components of the Tb³⁺ interconfigurational excitation transition are clearly identified in the case of TbCl₃. The luminescence of TbX₃ (X = Cl⁻, Br⁻, I⁻) is dominated by emission transitions emanating from the Tb³⁺⁵D₄ state. A comparative study of the optical properties of TbX₃ (X = Cl⁻, Br⁻, I⁻) with the properties of the Tb³⁺ ion in several halide host lattices is presented. Further, a comparative study of the fundamental host lattice optical transitions in terbium halides and other halide materials is also presented.     

Absorption and emission properties of Ho doped lead-zinc-borate glasses

This paper reports on the affect of lead content on the absorption and emission spectra of the Ho³⁺ ion doped lead-zinc-borate glasses in the composition (mol%) of (20 − x)PbO-20ZnO-(59 + x)B₂O₃-1.0Ho₂O₃ where x = 0, 5,10,15 of PbO content with λ_exc = 405 nm. The experimental absorption band energies have satisfactorily been correlated with the theoretical results with an r.m.s deviation of zero with the following correction factors obtained by a least square fit analysis: ΔE¹ = 348.495936 cm^− 1, ΔE² = 1.436043 cm^− 1, ΔE³ =  46.481575 cm^− 1, Δξ_4f = − 28.512979 cm^− 1, Δα = 55.508936 cm^− 1, Δβ = − 1394.339908 cm^− 1 and Δγ = 1208.424336 cm^− 1. By applying the Judd-Ofelt intensity parameter Ω₂ has been found to be linearly decreasing with the PbO content from 5 to 10 mol% and then increasing. And also radiative (A, A_T, β, τ_r) characteristic factors of the luminescent transitions (⁵I₈ ← ⁵F_3,4,5 and ⁵S₂) of the glasses have been evaluated. Stimulated emission cross-sections (σ_p^E) of the measured emission transitions of holmium glasses have also been computed.     

Polypyrrole thin films for gas sensors prepared by Matrix-Assisted Pulsed Laser Evaporation technology: Effect of deposition parameters on material properties

Thin films of polypyrrole (PPY) were prepared by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technology from two matrices: water and dimethylsulfoxide (DMSO). The deposition was carried out using a KrF excimer laser (laser fluence F ranged from 0.1 to 0.6 J cm^− 2). This work deals with optimization of two deposition parameters - laser fluence and number of pulses - for both matrices. From the deposition curves, the fluence thresholds, F_th, and maximum growth rates were subsequently determined (water matrix: F_th ~ 0.40-0.45 J cm^− 2, maximum growth rate 0.16 nm pulse^− 1; DMSO matrix: F_th ~ 0.25-0.30 J cm^− 2; maximum growth rate 0.20 nm pulse^− 1). The changes in chemical composition of deposited layers were studied by Attenuated Total Reflection Fourier Transform Infrared spectroscopy. Surface morphology was characterized by Atomic Force Microscopy. A discussion is also presented concerning relationships between laser fluence and chemical composition of deposited layers with respect to their potential application in gas sensors. Finally, the response of a sensor with a MAPLE deposited PPY active layer to air humidity is presented.