scholarly journals Oxygen as an exchangeable ligand in soil

1980 ◽  
Vol 52 (1) ◽  
pp. 34-44
Author(s):  
Erkki Aura
Keyword(s):  
Ligand Exchange ◽  
Lewis Acids ◽  
Ph Value ◽  
Exothermic Reaction ◽  
Exchange Equilibrium ◽  
Covalent Character ◽  
Lewis Bases ◽  
Pka Value ◽  
Al And Fe Oxides ◽  
The Relationship

An attempt was made to clarify the adsorption of oxygen ligands onto the Al- and Fe-oxides in the soil. In the ligand exchange the central ions Al3+ and Fe3+ of the oxides are Lewis acids or electron acceptors and the ligands are Lewis bases or electron donors. The binding of ligand oxygen by the central ion is primarily dependent on the nucleophilic strength of the ligand oxygen. The proton is a hard Lewis acid as are Al3+ and Fe3+. The pKa-value of the acid corresponding to the anion shows the ability of ligand oxygen to bind a proton and also the ability to bind Al3+ and Fe3+. The greater the nucleophilic strength of the ligand, the more covalent the nature of the bond between ligand oxygen and the central ion. However, the covalent character of this bond does not make the adsorption of a ligand by oxides an exothermic reaction. The entropy changes in adsorption determine the exchange equilibrium of the anions. The nucleophilic strength of ligand oxygen also determines the rate of exchange. If an anion has a high nucleophilic strength, it is rapidly adsorbed by oxides but the desorption is slow. The theory explains the relationship between the adsorption of anions to oxides and the pH-value in the equilibrum solution. The theory also illuminates the factors, which determine the leaching of an anion from the soil and the uptake rate of an anion from the soil by plants.

Spontaneous bond dissociation cascades induced by Ben clusters (n = 2,4)

2021 ◽  
Author(s):  
Eva Vos ◽  
Inés Corral ◽  
M. Merced Montero-Campillo ◽  
Otilia Mó ◽  
José Elguero ◽  
...  
Keyword(s):  
Lewis Acids ◽  
Lewis Bases ◽  
Bond Dissociation ◽  
Multireference Methods

Be4 clusters are very powerful Lewis acids leading to the total dissociation of all the bonds of the Lewis bases interacting with them. The product of the bond dissociation cascade possesses a hyper-coordinated center. Multireference methods are needed to correctly describe these complexes.

Building new discrete supramolecular assemblies through the interaction of iso-tellurazole N-oxides with Lewis acids and bases

2017 ◽  
Vol 203 ◽  
pp. 187-199 ◽  
Author(s):  
Peter C. Ho ◽  
Hilary A. Jenkins ◽  
James F. Britten ◽  
Ignacio Vargas-Baca
Keyword(s):  
Electron Acceptor ◽  
Lewis Acids ◽  
Heterocyclic Carbenes ◽  
Supramolecular Assemblies ◽  
Triphenyl Phosphine ◽  
Tellurium Atom ◽  
Lewis Bases ◽  
Acids And Bases ◽  
Lewis Acids And Bases

The supramolecular macrocycles spontaneously assembled by iso-tellurazole N-oxides are stable towards Lewis bases as strong as N-heterocyclic carbenes (NHC) but readily react with Lewis acids such as BR3 (R = Ph, F). The electron acceptor ability of the tellurium atom is greatly enhanced in the resulting O-bonded adducts, which consequently enables binding to a variety of Lewis bases that includes acetonitrile, 4-dimethylaminopyridine, 4,4′-bipyridine, triphenyl phosphine, a N-heterocyclic carbene and a second molecule of iso-tellurazole N-oxide.

Pyridinediimine Iron Dicarbonyl Complexes with Pendant Lewis Bases and Lewis Acids Located in the Secondary Coordination Sphere

2013 ◽  
Vol 2013 (22-23) ◽  
pp. 4008-4015 ◽  
Author(s):  
Zachary Thammavongsy ◽  
Micah E. LeDoux ◽  
Andrew G. Breuhaus-Alvarez ◽  
Takele Seda ◽  
Lev N. Zakharov ◽  
...  
Keyword(s):  
Coordination Sphere ◽  
Lewis Acids ◽  
Lewis Bases ◽  
Secondary Coordination Sphere

scholarly journals Effect of hydrothermal pretreatment of corn stover with pH adjustment on properties of pulp and hydrolysate

BioResources ◽  
2020 ◽  
Vol 15 (3) ◽  
pp. 6826-6839
Author(s):  
Junjun Kong ◽  
Ling Zhang ◽  
Ziyi Niu ◽  
Rina Wu ◽  
Gaosheng Wang
Keyword(s):  
Sodium Hydroxide ◽  
Corn Stover ◽  
Ph Value ◽  
Major Product ◽  
Hydrothermal Pretreatment ◽  
Raw Material ◽  
High Yield ◽  
Pulp Yield ◽  
Industrial Utilization ◽  
The Relationship

In view of environmental and economic issues, co-production technology with pulp as the major product is an important developmental direction in biorefinery. In this paper, high-yield pulp was prepared by hydrothermal pretreatment with controlled pH and subsequent mechanical refining using corn stover as raw material. By adding acetic acid or sodium hydroxide, the properties of the hydrolysate and the pulp were altered. Reducing the pH during hydrothermal pretreatment resulted in more cellulose and hemicellulose being released, while less lignin was released. Increased pH led to more lignin being released, while dissolution of carbohydrates did not change significantly. A maximum pulp yield at pH 5.84 of hydrolysate was obtained when 3.0% sodium hydroxide was used. The strength of pulp is highly related to the removal of lignin during hydrothermal pretreatment. The relationship between pH value in hydrothermal pretreatment and the physical properties of the pulp was established and could be further used for prediction and as guidance for process control. Moreover, the results could be used to develop technologies for industrial utilization of agricultural straw to co-generate fiber and other bio-based products.

scholarly journals Characteristics of cows’ cicatricial metabolism of different linearity

2021 ◽  
Vol 213 (10) ◽  
pp. 75-80
Author(s):  
E. Razhina
Keyword(s):  
Statistical Data ◽  
Ph Value ◽  
Rumen Fluid ◽  
Point Of View ◽  
Ideal Line ◽  
Microsoft Office ◽  
Relationship Of ◽  
First Time ◽  
The Relationship ◽  
Veterinary Laboratory

Abstract. The aim of this work is to investigate the relationship between indicators of cicatricial digestion and linearity of cows. Methods. The research was carried out in the breeding enterprises of the Sverdlovsk region on the livestock of Ural-type cows. Cicatricial fluid was collected with an oropharyngeal rubber probe, and a wooden yaw was also used. Cicatricial content was assessed at the Chelyabinsk Interregional Veterinary Laboratory. The pH value was determined by the electrometric method, VFA – in the Markgam apparatus, ammonia – by the microdiffusion method. Ciliates – in Goryaev’s chamber and under a microscope, bacteria – under a microscope with the addition of sodium chloride solution. Statistical data processing was carried out in the Microsoft Office Excel 2010 program. Results. In terms of the number of ciliates and bacteria in the rumen fluid, the Montwick Chieftain cows, characterized by high productive qualities, had an advantage. In terms of pH and VFA, the Vis Back Ideal line was the best. There were no significant differences between the groups in terms of the amount of ammonia in the rumen. The best animals from the point of view of influence on cicatricial metabolism were the animals of the Vis Back Ideal and Montwick Chieftain lineage. Scientific novelty. Studies have shown that linearity is associated with cicatricial digestion in cows. The relationship of bull lines with indicators of cicatricial metabolism of cows has been determined for the first time. The food in the rumen is digested due to the action of bacteria, ciliates, and fungi. An environment has been created in the rumen for the active development of microflora. Bacteria are able to synthesize amino acids and vitamins. The proventriculus can contain up to 50 species of ciliates.

scholarly journals A review of anaerobic landfill bioreactor using leachate recirculation to increase methane gas recovery

2021 ◽  
Vol 894 (1) ◽  
pp. 012013
Author(s):  
M A Budihardjo ◽  
B S Ramadan ◽  
E Yohana ◽  
Syafrudin ◽  
F Rahmawati ◽  
...  
Keyword(s):  
Alternative Energy ◽  
Ph Value ◽  
Biogas Production ◽  
Future Research ◽  
Leachate Recirculation ◽  
Methane Gas ◽  
Gas Recovery ◽  
Development Plans ◽  
Waste Degradation ◽  
The Relationship

Abstract Municipal Solid Waste (MSW) treatment with anaerobic landfill bioreactor utilizes landfill as a place of biodegradation and produces methane gas which can be used as renewable alternative energy source. Anaerobic landfill bioreactor technology is a landfill development method that can increase waste degradation and increase biogas production. The increase of biogas and the removal of pollutants from leachate needs to pay attention to the factors that influence the success of anaerobic landfill bioreactor, including pH value, temperature, water content, and COD concentration after recirculation, and methane production. The relationship between these factors was discussed in depth in this paper. The method used is a narrative review where metadata is obtained from Google Scholar and Web of Science. This study explains the development of an anaerobic landfill bioreactor and conducts a synthesis for future research development plans by leachate recirculation.

scholarly journals Non-Covalent Interactions Involving Alkaline-Earth Atoms and Lewis Bases B: An ab Initio Investigation of Beryllium and Magnesium Bonds, B···MR2 (M = Be or Mg, and R = H, F or CH3)

Inorganics ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 35 ◽  
Author(s):  
Ibon Alkorta ◽  
Anthony Legon
Keyword(s):  
Ab Initio ◽  
Lewis Acids ◽  
Alkaline Earth ◽  
Basis Set ◽  
Covalent Bonds ◽  
Lewis Bases ◽  
Complete Basis Set ◽  
Definition Of ◽  
The Individual ◽  
Equilibrium Dissociation

Geometries, equilibrium dissociation energies (De), intermolecular stretching, and quadratic force constants (kσ) determined by ab initio calculations conducted at the CCSD(T)/aug-cc-pVTZ level of theory, with De obtained by using the complete basis set (CBS) extrapolation [CCSD(T)/CBS energy], are presented for the B···BeR2 and B···MgR2 complexes, where B is one of the following Lewis bases: CO, H2S, PH3, HCN, H2O or NH3, and R is H, F or CH3. The BeR2 and MgR2 precursor molecules were shown to be linear and non-dipolar. The non-covalent intermolecular bond in the B···BeR2 complexes is shown to result from the interaction of the electrophilic band around the Be atom of BeR2 (as indicated by the molecular electrostatic potential surface) with non-bonding electron pairs of the base, B, and may be described as a beryllium bond by analogy with complexes such as B···CO2, which contain a tetrel bond. The conclusions for the B···MgR2 series are similar and a magnesium bond can be correspondingly invoked. The geometries established for B···BeR2 and B···MgR2 can be rationalized by a simple rule previously enunciated for tetrel-bonded complexes of the type B···CO2. It is also shown that the dissociation energy, De, is directly proportional to the force constant, kσ, in each B···MR2 series, but with a constant of proportionality different from that established for many hydrogen-bonded B···HX complexes and halogen-bonded B···XY complexes. The values of the electrophilicity, EA, determined from the De for B···BeR2 complexes for the individual Lewis acids, A, reveal the order A = BeF2 > BeH2 > Be(CH3)2—a result that is consistent with the −I and +I effects of F and CH3 relative to H. The conclusions for the MgR2 series are similar but, for a given R, they have smaller electrophilicities than those of the BeR2 series. A definition of alkaline-earth non-covalent bonds is presented.

scholarly journals TiO2 Nano Flowers Based EGFET Sensor for pH Sensing

Coatings ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 251
Author(s):  
Chih-Chiang Yang ◽  
Kuan-Yu Chen ◽  
Yan-Kuin Su
Keyword(s):  
Ph Value ◽  
Ph Sensor ◽  
High Sensitivity ◽  
Experimental Result ◽  
Ph Sensing ◽  
Voltage Reference ◽  
Ph Sensors ◽  
Oxide Substrate ◽  
Ph Range ◽  
The Relationship

In this study, pH sensors were successfully fabricated on a fluorine-doped tin oxide substrate and grown via hydrothermal methods for 8 h for pH sensing characteristics. The morphology was obtained by high-resolution scanning electron microscopy and showed randomly oriented flower-like nanostructures. The TiO2 nanoflower pH sensors were measured over a pH range of 2–12. Results showed a high sensitivity of the TiO2 nano-flowers pH sensor, 2.7 (μA)1/2/pH, and a linear relationship between IDS and pH (regression of 0.9991). The relationship between voltage reference and pH displayed a sensitivity of a 46 mV/pH and a linear regression of 0.9989. The experimental result indicated that a flower-like TiO2 nanostructure extended gate field effect transistor (EGFET) pH sensor effectively detected the pH value.

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