Soil Chemistry

2003 ◽  
Author(s):  
Anthony S. R. Juo ◽  
Kathrin Franzluebbers
Keyword(s):  
Surface Charge ◽  
Functional Groups ◽  
Soil Chemistry ◽  
Chemical Properties ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Surface Hydroxyl ◽  
Mineral Structure ◽  
Ph Dependent ◽  
Soil Colloids

Soil chemistry deals with the chemical properties and reactions of soils. It is essentially the application of electrochemistry and colloid chemistry to soil systems. Major topics include surface charge properties of soil colloids, cation and anion sorption and exchange, soil acidity, soil alkalinity, soil salinity, and the effects of these chemical properties and processes on soil biological activity, plant growth, and environmental quality. The ability of the electrically charged surface of soil colloids to retain nutrient cations and anions is an important chemical property affecting the fertility status of the soil. There are two major sources of electrical charges on soil organic and inorganic colloids, namely, permanent or constant charges and variable or pH-dependent charges. Permanent or constant charges are the result of the charge imbalance brought about by isomorphous substitution in a mineral structure of one cation by another of similar size but differing valence (see also section 2.3.2). For example, the substitution of Mg2+ for Al3+ that occurs in Al-dominated octahedral sheets of 2:1 clay minerals results in a negative surface charge in smectite, vermiculite, and chlorite. The excess negative charges are then balanced by adsorbed cations to maintain electrical neutrality. Permanent negative charges of all 2:1 silicate minerals arise from isomorphous substitutions. The l:l-type clay mineral, kaolinite, has only a minor amount of permanent charge due to isomorphic substitution. The negative charges on kaolinite originate from surface hydroxyl groups on the edge of the mineral structure and are pH-dependent. Variable or pH-dependent charges occur on the surfaces of Fe and Al oxides, allophanes, and organic soil colloids. This type of surface charge originates from hydroxyl groups and other functional groups by releasing or accepting H+ ions, resulting in either negative or positive charges. Other functional groups are hydroxyl (OH) groups of Fe and/or Al oxides and allophanes and the COOH and OH groups of soil organic matter. Variable-charge soil colloids bear either a positive or a negative net surface charge depending on the pH of the soil. The magnitude of the charge varies with the electrolyte concentration of the soil solution.

scholarly journals Scale-up of a NiMoP/γAl2O3 catalyst for the hydrotreating and mild hydrocracking of heavy gasoil

2019 ◽  
Vol 74 ◽  
pp. 22 ◽  
Author(s):  
Ricardo Prada Silvy
Keyword(s):  
Scale Up ◽  
Catalyst Support ◽  
Chemical Properties ◽  
Pilot Scale ◽  
Solid Particles ◽  
Metallic Surface ◽  
Hydroxyl Groups ◽  
Alumina Surface ◽  
Distribution Profile ◽  
Surface Hydroxyl

This contribution shows the acquired experience during the scale-up of a NiMoP/γAl2O3 catalyst employed for the hydrotreating and mild hydrocracking of heavy gasoil. Three different strategies were adopted for preparing catalyst batches at pilot scale. They consisted on co-impregnation of γ-alumina extrudates with aqueous solutions containing Ni and Mo salts and phosphoric acid in one or two successive steps. The textural, chemical composition, mechanical strength, metallic surface dispersion and elemental radial distribution profile properties were influenced by the impregnation procedure employed. The co-impregnation with diluted Ni, Mo and P solutions in two successive steps is the best way to prepare the catalyst. This procedure provides a catalyst that exhibits better physico-chemical properties and catalytic activity profile than the other impregnation methods investigated. Heat and mass transfer limitations became very important when preparing catalysts in large quantities. The diffusion intra-particle and extra-particle was observed influenced by the density and viscosity properties of the metallic solution, the liquid-solid contact angle, the reactivity of phosphate, polymolybdate and phosphomolybdate species with the alumina surface hydroxyl groups, the raise of temperature produced in the solid particles during the initial impregnation step and the porosity properties of the catalyst support. It was concluded that the fine control of the metal distribution on the alumina surface during the impregnation is crucial for producing highly active uniform catalysts.

Effect of Acid on Surface Hydroxyl Groups on Kaolinite and Montmorillonite

2018 ◽  
Vol 232 (3) ◽  
pp. 409-430 ◽  
Author(s):  
Sarah K. Sihvonen ◽  
Kelly A. Murphy ◽  
Nancy M. Washton ◽  
Muhammad Bilal Altaf ◽  
Karl T. Mueller ◽  
...  
Keyword(s):  
Functional Groups ◽  
Acid Treatment ◽  
Atmospheric Transport ◽  
Magic Angle Spinning ◽  
Resonance Spectroscopy ◽  
Hydroxyl Groups ◽  
Magic Angle ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Angle Spinning

AbstractMineral dust aerosol participates in heterogeneous chemistry in the atmosphere. In particular, the hydroxyl groups on the surface of aluminosilicate clay minerals are important for heterogeneous atmospheric processes. These functional groups may be altered by acidic processing during atmospheric transport. In this study, we exposed kaolinite (KGa-1b) and montmorillonite (STx-1b) to aqueous sulfuric acid and then rinsed the soluble reactants and products off in order to explore changes to functional groups on the mineral surface. To quantify the changes due to acid treatment of edge hydroxyl groups, we use19F magic angle spinning nuclear magnetic resonance spectroscopy and a probe molecule, 3,3,3-trifluoropropyldimethylchlorosilane. We find that the edge hydroxyl groups (OH) increase in both number and density with acid treatment. Chemical reactions in the atmosphere may be impacted by the increase in OH at the mineral edge.

The Effect of Ar/H2 Plasma Pretreatments on Porous K=2.0 Dielectrics for Pore Sealing by Self-Assembled Monolayers Deposition

2012 ◽  
Vol 195 ◽  
pp. 146-149 ◽  
Author(s):  
Y. Sun ◽  
J. Swerts ◽  
P. Verdonck ◽  
A. Maheshwari ◽  
J.L. Prado ◽  
...  
Keyword(s):  
Plasma Temperature ◽  
Self Assembled Monolayers ◽  
Hydroxyl Groups ◽  
K Value ◽  
Oh Groups ◽  
Surface Hydroxyl ◽  
Pore Sealing ◽  
Assembled Monolayers ◽  
Self Assembled ◽  
Low K

Self-assembled monolayers (SAMs) deposition is being recently explored to help sealing the pores of a k=2.0 material. In order to enable a covalent chemical low-k surface functionalization by SAMs, a hydroxyl groups density as high as 1 to 2.5 OH groups/nm2 is required. This surface modification must be carefully controlled to confine the k below 10%. In this paper, the effects of plasma temperature, time and power on the SAMs deposition and plasma-induced damage are investigated. The main findings are that there is always a trade-off between surface hydroxyl groups density and bulk damage. A thick modified layer allows the SAM molecules to penetrate inside the pores which results in a decreased porosity and an increased k value with respect to correspondent plasma-treated pristine substrates.

AN INFRARED STUDY OF THE ADSORPTION OF AMMONIA ON POROUS VYCOR GLASS

1964 ◽  
Vol 42 (4) ◽  
pp. 802-809 ◽  
Author(s):  
N. W. Cant ◽  
L. H. Little
Keyword(s):  
Hydrogen Exchange ◽  
Lone Pair ◽  
Acid Sites ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Infrared Study ◽  
Vycor Glass ◽  
Oh Groups ◽  
Surface Hydroxyl ◽  
Adsorption Sites

The infrared spectrum of ammonia adsorbed on porous glass at 20 °C and 150 °C has been studied in the region 1450–4000 cm−1. No absorption band due to the asymmetric bending mode of ammonia was observed but in the NH stretching region, bands occurred at 3280 cm−1, 3320 cm−1, 3365 cm−1, and 3400 cm−1. The bands at 3320 cm−1 and 3400 cm−1 were easily removed by evacuation and are due to ammonia molecules hydrogen bonded through the nitrogen atom to surface hydroxyl groups. The bands at 3280 cm−1 and 3365 cm−1 were not removed by evacuation even at 150 °C and are due to ammonia molecules held to surface Lewis acid sites by the nitrogen lone-pair electrons. The site for this adsorption is not a surface hydroxyl group. These results are further evidence for the existence of the two adsorption sites proposed by Folman and Yates. Deuteration of the surface OH groups was easily accomplished with D2O vapor at 300 °C and the rate of hydrogen exchange between adsorbed ammonia molecules and surface OD groups was found to be rapid.

Self Terminating Reaction of Dipivaloylmethanate Complexes with Hydroxyl Groups on Oxide Surface

1991 ◽  
Vol 222 ◽  
Author(s):  
Rika Sekine ◽  
Maki Kawai ◽  
Kiyotaka Asakura ◽  
Yasuhiro Iwasawa
Keyword(s):  
Fine Structure ◽  
Photoelectron Spectroscopy ◽  
Oxide Surface ◽  
Hydroxyl Groups ◽  
Adsorbed Species ◽  
Oh Groups ◽  
X Ray ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
X Ray Absorption

ABSTRACTWe have already reported that copper and calcium dipivaloylmethanates [Cu(DPM)2 and Ca(DPM)2 ] reacts selectively and stoichiometrically with surface hydroxyl groups (OH) on SiO2. In order to clarify the structure of the adsorbed species and the origin of the reaction between M(DPM)2 (M=Cu and Ca) and OH groups, the surface adsorbed species are studied by infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and the extended X-ray absorption fine structure (EXAFS). As a result, it was found that H from surface OH has moved into M(DPM)2 after the adsorption, where the four oxygen coordinated structure around Cu still exists in the adsorbed Cu(DPM)2. Introducing water vapor at 673 K to this surface results in the removal of ligand DPM from the adsorbed Cu(DPM)2. At 673 K, Cu atoms decomposed from the adsorbates aggregated on the surface. This fact supports that the interaction between the adsorbed Cu(DPM)2 and SiO2 surface is originated from that between the ligands and the surface.

scholarly journals The effect of hydroxyl functional groups and molar mass on the viscosity of non-crystalline organic and organic–water particles

2017 ◽  
Vol 17 (13) ◽  
pp. 8509-8524 ◽  
Author(s):  
James W. Grayson ◽  
Erin Evoy ◽  
Mijung Song ◽  
Yangxi Chu ◽  
Adrian Maclean ◽  
...  
Keyword(s):  
Functional Groups ◽  
Optical Tweezers ◽  
Molar Mass ◽  
Hydroxyl Groups ◽  
Structure Property ◽  
Strong Function ◽  
Oh Groups ◽  
Carbon Backbone ◽  
Structure Property Relationship ◽  
Dry Conditions

Abstract. The viscosities of three polyols and three saccharides, all in the non-crystalline state, have been studied. Two of the polyols (2-methyl-1,4-butanediol and 1,2,3-butanetriol) were studied under dry conditions, the third (1,2,3,4-butanetetrol) was studied as a function of relative humidity (RH), including under dry conditions, and the saccharides (glucose, raffinose, and maltohexaose) were studied as a function of RH. The mean viscosities of the polyols under dry conditions range from 1.5  ×  10−1 to 3.7  ×  101 Pa s, with the highest viscosity being that of the tetrol. Using a combination of data determined experimentally here and literature data for alkanes, alcohols, and polyols with a C3 to C6 carbon backbone, we show (1) there is a near-linear relationship between log10 (viscosity) and the number of hydroxyl groups in the molecule, (2) that on average the addition of one OH group increases the viscosity by a factor of approximately 22 to 45, (3) the sensitivity of viscosity to the addition of one OH group is not a strong function of the number of OH functional groups already present in the molecule up to three OH groups, and (4) higher sensitivities are observed when the molecule has more than three OH groups. Viscosities reported here for 1,2,3,4-butanetetrol particles are lower than previously reported measurements using aerosol optical tweezers, and additional studies are required to resolve these discrepancies. For saccharide particles at 30 % RH, viscosity increases by approximately 2–5 orders of magnitude as molar mass increases from 180 to 342 g mol−1, and at 80 % RH, viscosity increases by approximately 4–5 orders of magnitude as molar mass increases from 180 to 991 g mol−1. These results suggest oligomerization of highly oxidized compounds in atmospheric secondary organic aerosol (SOA) could lead to large increases in viscosity, and may be at least partially responsible for the high viscosities observed in some SOA. Finally, two quantitative structure–property relationship models (Sastri and Rao, 1992; Marrero-Morejón and Pardillo-Fontdevila, 2000) were used to predict the viscosity of alkanes, alcohols, and polyols with a C3–C6 carbon backbone. Both models show reasonably good agreement with measured viscosities for the alkanes, alcohols, and polyols studied here except for the case of a hexol, the viscosity of which is underpredicted by 1–3 orders of magnitude by each of the models.

STUDIES OF THE DISSOCIATION OF OXIDE SURFACES AT THE LIQUID–SOLID INTERFACE

1966 ◽  
Vol 44 (14) ◽  
pp. 1663-1670 ◽  
Author(s):  
Syed M. Ahmed
Keyword(s):  
Surface Charge ◽  
Double Layer ◽  
Zero Point ◽  
Specific Adsorption ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Charge Densities ◽  
Coulombic Interactions ◽  
Solution Interface ◽  
Effect Of Surface

The dissociation of surface hydroxyl groups of crystalline SiO2, ZrO2, and ThO2, in aqueous suspensions, has been studied as a function of pHs at different ionic strengths of KNO3. The surface groups of quartz dissociate as weak acids, while those of ZrO2 and ThO2 dissociate amphoterically. A reversible double layer is formed at the oxide–solution interface, and H+ and OH− function as the potential-determining ions. Quantitative data have been obtained on (a) surface charge densities, (b) zero point of charge, (c) differential capacities of the double layer on quartz and ZrO2, and (d) the effect of surface charge density and ionic strength on the interfacial tension. The differential capacities indicate specific adsorption of NO3−on ZrO2 and ThO2 while NO3− has zero affinity for quartz surfaces. At low negative charge densities, solvated K+ are adsorbed on quartz and ZrO2 through coulombic interactions while at pHs > 10 specific adsorption of K+ predominates. ThO2 appears to exhibit a greater tendency for the specific adsorption of K+.

scholarly journals Effects of the Covalent Bonding Entrapment of Tetrapyrrole Macrocycles Inside Translucent Monolithic ZrO2 Xerogels

Nano Hybrids ◽  
2014 ◽  
Vol 7 ◽  
pp. 1-34 ◽  
Author(s):  
Eduardo Salas-Bañales ◽  
R. Iris Y. Quiroz-Segoviano ◽  
Fernando Rojas-González ◽  
Antonio Campero ◽  
Miguel A. García-Sánchez
Keyword(s):  
Sol Gel ◽  
Hydroxyl Groups ◽  
Stable Form ◽  
Silica Xerogels ◽  
Oh Groups ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Spectroscopic Characteristics ◽  
Hydrophilic Character ◽  
First Time

While searching for adequate sol-gel methodologies for successfully trapping in monomeric and stable form either porphyrins or phthalocyanines, inside translucent monolithic silica xerogels, it was discovered that the interactions of these trapped tetrapyrrole macrocycles with Si-OH surface groups inhibit or spoil the efficient display of physicochemical, especially optical, properties of the confined species. Consequently, we have developed strategies to keep the inserted macrocycle species as far as possible from these interferences by substituting the surface-OH groups foralkylorarylgroups or trapping these species inside alternative metal oxide networks, such as ZrO2, TiO2, and Al2O3. In the present manuscript, we present, for the first time to our knowledge, a methodology for preserving the spectroscopic characteristics of metal tetrasulfophthalocyanines and cobalt tetraphenylporphyrins trapped inside the pores of ZrO2xerogels. The results obtained are contrasting with analogous silica systems and demonstrate that, in ZrO2networks, the macrocyclic species remain trapped in stable and monomeric form while keeping their original spectroscopic characteristics in a better way than when captured inside silica systems. This outcome imply a lower hydrophilic character linked to the existence of a smaller amount of surface hydroxyl groups in ZrO2networks, if compared to analogous SiO2xerogel systems. The development and study of the possibility of trapping or fixing synthetic or natural tetrapyrrole macrocycles inside inorganic networks suggest the possibility of synthesizing hybrid solid systems suitable for important applications in technological areas such as optics, catalysis, sensoring and medicine

scholarly journals Features of Functionalization of the Surface of Alumina Nanofibers by Hydrolysis of Organosilanes on Surface Hydroxyl Groups

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4374
Author(s):  
Mikhail M. Simunin ◽  
Anton S. Voronin ◽  
Yurii V. Fadeev ◽  
Yurii L. Mikhlin ◽  
Denis A. Lizunov ◽  
...  
Keyword(s):  
Functional Groups ◽  
Simultaneous Thermal Analysis ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Alumina Nanofibers ◽  
High Uniformity ◽  
The Matrix ◽  
Important Approach ◽  
Hydrolysis Of ◽  
Perfect Interface

Small additions of nanofiber materials make it possible to change the properties of polymers. However, the uniformity of the additive distribution and the strength of its bond with the polymer matrix are determined by the surface of the nanofibers. Silanes, in particular, allow you to customize the surface for better interaction with the matrix. The aim of our work is to study an approach to silanization of nanofibers of aluminum oxide to obtain a perfect interface between the additive and the matrix. The presence of target silanes on the surface of nanofibers was shown by XPS methods. The presence of functional groups on the surface of nanofibers was also shown by the methods of simultaneous thermal analysis, and the stoichiometry of functional groups with respect to the initial hydroxyl groups was studied. The number of functional groups precipitated from silanes is close to the number of the initial hydroxyl groups, which indicates a high uniformity of the coating in the proposed method of silanization. The presented technology for silanizing alumina nanofibers is an important approach to the subsequent use of this additive in various polymer matrices.

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