Electrometallurgical recovery of nickel and vanadium from spent desulphurization catalysts using an acidic leaching–electrolysis technique

Spent desulphurization catalysts are considered a major secondary source of valuable metals. The contents of nickel and vanadium present in these catalysts, accompanied by environmental rules, have attracted scientists to explore diverse options for their effective processing. The electrometallurgy recovery of Ni and V from the spent desulphurization Ni-Mo-V/Al₂O₃ catalyst is described in this study. Using flat plate graphite electrodes, the electrochemical deposition of Ni and V from spent catalyst in an acid solution (HNO₃/H₂SO₄) was investigated. By the central composite design of the response surface methodology, the effect of the operating factors was examined and optimized. At the ideal conditions of reaction temperatures of 84.0 and 42.0°C, electrolysis times of 5.6 and 4.4 h, liquid/solid ratios of 22.7 and 15.4 ml/g, and current densities of 229.0 and 255.6 A/m², respectively, the recovery efficiencies of Ni and V were 81.96% and 93.07%. The statistical analysis revealed that the expected data (R² = 0.9984 and R² = 0.9883) were in good agreement with the observed data (R² = 0.9984), with an average variation from experimental data of 0.78% and 0.65% for the optimum conditions of Ni and V recovery, respectively. It shows that the Ni and V nanoparticles deposited have a spherical form with purities of 84.39% and 90.76%, respectively. Because of its great efficiency and purity, the current study can provide a dependable procedure for extracting Ni and V from solid waste.     

Influence of ammonium salt formation on the activity and selectivity of the 12-molybdophosphate heteropolyacid catalyst prepared by solid–solid interaction in the ammoxidation of 2-methylpyrazine

The ammonium salt of 12-molybdophosphoric acid has been prepared by the solid-state interaction of the ammonium salts of molybdenum and phosphorus. The catalysts obtained by pretreatment of the precursor at various temperatures, have been characterized by nitrogen adsorption, X-ray diffraction (XRD), Fourier-transformed infrared (FTIR) spectroscopy and temperature-programmed decomposition (TPD) of the catalysts. Ammoxidation of 2-methylpyrazine has been carried out on these catalysts. The amount of ammonium salt present in the catalyst has been correlated with the activity and selectivity of the catalysts.     

Novel Pd–Au/TiO2 catalyst for the selective catalytic reduction of NOx by H2

Novel Pd–Au/TiO₂ catalyst exhibited high catalytic activity with a wide temperature window for the selective catalytic reduction of NO_x by H₂ in the presence of oxygen. The synergetic effect between Pd and Au contributes to the formation of Pd⁰ and Pd–Au alloy, thus promoting the NO_x reduction to proceed.     

Novel MoO3/CeO2–ZrO2 catalyst for the selective catalytic reduction of NOx by NH3

A series of MoO₃-doped CeO₂–ZrO₂ catalysts were investigated for the selective catalytic reduction of NO_x by NH₃ (NH₃-SCR). It was found that the added MoO₃ significantly enhanced the activity of CeO₂–ZrO₂ catalyst for NH₃-SCR of NO_x in a wide temperature range and the optimum MoO₃ loading is 5%. The highly dispersed MoO₃ not only resulted in more Lewis acid and Brønsted acid sites formed on the catalyst surface, but also increased the redox property of the catalyst, all of which account for the enhanced SCR activity.     

Enhanced alkali resistance of CeO2/SO42 −–ZrO2 catalyst in selective catalytic reduction of NOx by ammonia

Ceria catalysts supported on sulfated zirconia showed a remarkable resistance towards alkali metal poisoning in selective catalytic reduction of NO by NH₃. TPD results revealed sulfation treatment of supports produced massive acid sites on the surface of catalysts. Adequate acidity was of importance for the enhanced resistance to alkali metal ions. The introduction of potassium did not affect the crystalline phases and morphology of catalysts, but it could lead to higher surface areas of samples.     

Greenhouse tomato–cucumber yield and soil N leaching as affected by reducing N rate and adding manure: a case study in the Yellow River Irrigation Region China

The effect of reducing N rate fertilization and manure addition on greenhouse vegetable yields and soil N leaching was studied in a greenhouse tomato?Ccucumber rotation system in the Yellow River Irrigation Region of Ningxia Plain, North China. The treatments were: 1-no fertilizers, 2-conventional fertilization, 3-reduced fertilizer application, and 4-reduced fertilizer application + regulation of soil C/N ratio applied by the high C/N ratio of dairy manure. The results indicated that reduced fertilizer application in tomato and cucumber season had no significant influence on vegetable yield comparing with control. The amounts of leachate had no significant differences under all fertilizer treatments at the same investigated period. In comparison with conventional fertilization, both total N and NO₃?CN leaching decreased in the low fertilizer treatments. The cumulative total N and NO₃?CN leached from fertilizers N were less than 9?% during the tomato?Ccucumber rotation system. NO₃?CN was the predominant form of leaching N, represented about 70?% of total N in the leachate. Soluble organic N represented 14.7?C33.3?% of total N leached. Vegetable yields did not increase significantly as applied N rates increased. However, soil N leaching increased largely with N rates. Reducing fertilizer N rate while adding dairy manure regulated soil C/N ratio could be appropriate fertilization practices for reducing soil N leaching and achieving high vegetable yields in the greenhouse systems.     

Wear-resistant Ti–Al–Ni–C–N coatings produced by magnetron sputtering of SHS-targets in the DC and HIPIMS modes

The hard wear-resistant nanocomposite Ti–Al–Ni–C–N coatings were deposited by direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HIPIMS) in the Ar, Ar+15%N_2, and Ar+25%N₂ atmospheres. The structure of coatings was analyzed using the X-ray diffraction analysis, glow discharge optical emission spectroscopy, and scanning electron microscopy. Mechanical and tribological properties were measured using the nanoindentation and scratch testing as well as by tribological testing using the “pin-on-disc” scheme. Electrochemical corrosion resistance and oxidation resistance of coatings were investigated. The results suggest that the coatings are based on the FCC phases TiCN and Ni₃Al with crystallites size ~3 and ~15 nm, correspondingly. DCMS coatings with optimal composition were characterized by hardness 34 GPa, stable friction coefficient <0.26 and wear rate <5 × 10^-6 mm³N^-1m^-1. Application of HIPIMS mode allowed the increase of adhesion strength, tribological properties and corrosion resistance of coatings.     

Inter-ligand interactions and the selective formation of the unusual metal–N3(adenine) bond in ternary copper(II) complexes with N-benzyliminodiacetato(2−) ligands

A novel mixed-ligand copper(II) complex with N-(p-methoxybenzyl)-iminodiacetato(2−) ligand (MOBIDA) and adenine (AdeH) of formula [Cu(MOBIDA)(AdeH)(H₂O)]·H₂O has been obtained. Its crystal structure reveals the selective formation of a rare Cu–N3(AdeH) bond, closely related to those reported by first time for compounds of general formula [Cu(B)(AdeH)(H₂O)]·H₂O, with B=N-benzyl- or N-(p-methylbenzyl)-iminodiacetato(2−) ligands. Appropriate structural comparison reveals that the copper(II) coordination by less basic N3 heterocyclic donor of the nucleobase is controlled by a molecular recognition process involving the formation of an intra-molecular inter-ligand N7(imidazole-like)–H⋯O(carboxyl) bond and the inter-molecular inter-ligand π,π-stacking interaction between six membered rings of benzyl (MOBIDA) and AdeH. This stack generates multi-stacked infinite chains along the b-axis of the crystal.