Complexation of Nickel Ions by Boric Acid or (Poly)borates

Boric acid catalysed hydrolysis of peroxyacids

This study shows for the first time that boric acid catalyses the hydrolysis of peroxyacids, resulting in an approximately 12-fold increase in hydrolysis rate for both peracetic acid (PAA) and 3-chloroperbenzoic acid (MCPBA) when 0.1 M boric acid is present. The maximum rate of hydrolysis occurs at pH 9 and pH 8.4 for PAA and MCPBA respectively. In contrast, carbonate buffer does not enhance the rate of PAA hydrolysis. The reaction was followed by measuring the initial rate of hydrogen peroxide formation using a specific Ti(iv) complexation method. The study of the hydrolysis reaction requires the presence of 2 × 10^-5 M each of ethylenediaminetetraacetic acid (EDTA) and ethylenediamine tetramethylene phosphonic acid (EDTMP) in all solutions in order to chelate metal ions across the full pH range (3 to 13) that would otherwise contribute to peroxyacid decomposition. Catalysis of peroxyacid hydrolysis is most likely effected by the triganol boric acid acting as a Lewis acid catalyst, associating with the peroxide leaving group in the transition state to reduce the leaving group basicity. The products of the reaction are the well characterised monoperoxoborate species and the parent carboxylic acid. Analysis of the pH and borate dependence data reveals that in addition to a catalytic pathway involving a single boric acid molecule, there is a significant pathway involving either (a) two boric acid molecules or (b) the polyborate species, B₃O₃(OH)₄ ^-. Knowledge about catalytic mechanisms for the loss of peroxyacids through hydrolysis is important because they are widely used in reagents in a range of oxidation, bleaching and disinfection applications.

Removal of empty capsids from adeno-associated virus preparations by multimodal metal affinity chromatography

Separation of empty and full adeno-associated virus capsids by multimodal metal affinity chromatography was investigated using a positively charged metal affinity ligand. A subpopulation of empty capsids eluted first, followed by full capsids, and later by more empty capsids and debris. Empty and full capsid composition of chromatography fractions was evaluated by cesium chloride density gradient centrifugation followed by stratigraphic flow analysis of the centrifuge tube contents, monitored by intrinsic fluorescence. Columns charged with barium, calcium, magnesium, zinc, manganese, and ferric ions gave similar results with respect to capsid separation. Charging with cupric ions maintained resolution between early-eluting empty capsids and full capsids but caused them to elute at lower conductivity. Empty and full capsids were fractionated with Tris-borate gradients, sodium chloride gradients, and magnesium chloride gradients. Recovery of full serotype 9 capsids was 100% with complete elimination of empty capsids. All metal ions bound contaminant subsets that required sodium hydroxide for removal. Columns charged with ferric iron and manganese bound more contaminants than all other metals. Columns charged with calcium, magnesium, barium, and copper bound the least. Contaminant binding on zinc-charged columns was intermediate between the two groups.

Electrochemical deposition of nickel targets from aqueous electrolytes for medical radioisotope production in accelerators: a review

This paper reviews reported methods of the electrochemical deposition of nickel layers which are used as target materials for accelerator production of medical radioisotopes. The review focuses on the electrodeposition carried out from aqueous electrolytes. It describes the main challenges related to the preparation of suitable Ni target layers, such as work with limited amounts of expensive isotopically enriched nickel; electrodeposition of sufficiently thick, smooth and free of cracks layers; and recovery of unreacted Ni isotopes from the irradiated targets and from used electrolytic baths.

Abiotic Synthesis of Nucleoside 5'-Triphosphates with Nickel Borate and Cyclic Trimetaphosphate (CTMP)

While nucleoside 5'-triphosphates are precursors for RNA in modern biology, the presumed difficulty of making these triphosphates on Hadean Earth has caused many prebiotic researchers to consider other activated species for the prebiotic synthesis of RNA. We report here that nickel(II), in the presence of borate, gives substantial amounts (2-3%) of nucleoside 5'-triphosphates upon evaporative heating in the presence of urea, salts, and cyclic trimetaphosphate (CTMP). Also recovered are nucleoside 5'-diphosphates and nucleoside 5'-monophosphates, both likely arising from 5'-triphosphate intermediates. The total level of 5'-phosphorylation is typically 30%. Borate enhances the regiospecificity of phosphorylation, with increased amounts of other phosphorylated species seen in its absence. Experimentally supported paths are already available to make nucleosides in environments likely to have been present on Hadean Earth soon after a midsized 10²¹ to 10²³ kg impactor, which would also have delivered nickel to the Hadean surface. Further, sources of prebiotic CTMP continue to be proposed. Thus, these results fill in one of the few remaining steps needed to demystify the prebiotic synthesis of RNA and support a continuous model from atmospheric components to oligomeric RNA that is lacking only a mechanism to obtain homochirality in the product RNA.

Simultaneous Adsorption of 4,6-Dimethyldibenzothiophene and Quinoline over Nickel and Boron Modified Gamma-Al2O3 Adsorbent

The simultaneous adsorption of quinoline and 4,6-dimethyldibenzothiophene over adsorbents, based on alumina modified with boron and nickel under ambient temperature and pressure, was studied. The adsorbents were characterized by BET specific surface area, a potentiometric method for the determination of acid strength, electrophoretic migration, and X-ray diffraction. The results showed that the adsorbent containing nickel had better adsorption capacity than the adsorbent modified with nickel and boron, which was attributed to its greater acidity and ability to generate π-complexation between the adsorbent and the molecules. In terms of selectivity, quinoline was more adsorbed than 4,6-dimethyldibenzothiophene in all systems, due to the basic nature of quinoline. The experimental data in all cases were adjusted by three kinetic models (Yoon–Nelson, Yan and Thomas), and the regression coefficients in all models were close to one. Finally, the values of the kinetic constant obtained by the Thomas model were used to relate the adsorption capacity results.

Influence of organic matter and CO2 supply on bioremediation of heavy metals by Chlorella vulgaris and Scenedesmus almeriensis in a multimetallic matrix

This research evaluated the influence of organic matter (OM) and CO₂ addition on the bioremediation potential of two microalgae typically used for wastewater treatment: Chlorella vulgaris (CV) and Scenedesmus almeriensis (SA). The heavy metal (HM) removal efficiencies and biosorption capacities of both microalgae were determined in multimetallic solutions (As, B, Cu, Mn, and Zn) mimicking the highest pollutant conditions found in the Loa river (Northern Chile). The presence of OM decreased the total biosorption capacity, specially in As (from 2.2 to 0.0 mg/g for CV and from 2.3 to 1.7 mg/g for SA) and Cu (from 3.2 to 2.3 mg/g for CV and from 2.1 to 1.6 mg/g for SA), but its influence declined over time. CO₂ addition decreased the total HM biosorption capacity for both microalgae species and inhibited CV growth. Finally, metal recovery using different eluents (HCl, NaOH, and CaCl₂) was evaluated at two different concentrations. HCl 0.1 M provided the highest recovery efficiencies, which supported values over 85% of As, 92% of Cu, and ≈100% of Mn and Zn from SA. The presence of OM during the loaded stage resulted in a complete recovery of As, Cu, Mn, and Zn when using HCl 0.1 M as eluent.

Effects of CO3 2- and OH- on the solubility, metastable zone width and nucleation kinetics of borax decahydrate

Measurements of the solubility and metastable zone width (MZW) of borax decahydrate in sodium carbonate and sodium hydroxide aqueous were obtained. The onsets of nucleation were detected by the turbidity technique with the temperature range from 285 to 315 K. The results showed that the solubility of borax gradually decreased and the MZW broadened with the mass percentage of sodium carbonate increasing from 0% up to 9.22%. Correspondingly, the solubility and MZW had the same trend with the addition of sodium hydroxide. Meanwhile, the nucleation parameters of borax were determined and analysed to explain the trends obtained. Applying the classical three-dimensional nucleation theory approach, it was found that the addition of carbonate and hydroxide ions led to the values of solid-liquid interfacial energy (γ) increasing, which indicated the CO₃ ^2- and OH^- ions adsorbed on the nuclei but suppressed nucleation rate.