scholarly journals Effect of hexadecyltrimethyl-ammonium loaded montmorillonite on the Cu adsorption: adsorption surface sites involved

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
César Fernández Morantes ◽  
Alejandra M Fernández Solarte ◽  
Rosa M Torres Sánchez
Keyword(s):  
Surface Sites ◽  
Adsorption Surface

A theoretical investigation of the adsorption surface sites of the activated MgCl2

2007 ◽  
Vol 270 (1-2) ◽  
pp. 164-170 ◽  
Author(s):  
Dmitry A. Trubitsyn ◽  
Vladimir A. Zakharov ◽  
Ivan I. Zakharov
Keyword(s):  
Theoretical Investigation ◽  
Surface Sites ◽  
Adsorption Surface

Adsorption and desorption of phosphate on Fe2O3: effect of fulvic acid and pH

2008 ◽  
Vol 5 (2) ◽  
pp. 161 ◽  
Author(s):  
Tsanangurayi Tongesayi ◽  
Eric J. Byam ◽  
Sarah B. Keysper ◽  
Michael J. Crounce
Keyword(s):  
Fulvic Acid ◽  
Humic Substances ◽  
Adsorption Mechanism ◽  
Chemical Species ◽  
Adsorption And Desorption ◽  
Surface Sites ◽  
Mineral Oxides ◽  
Adsorption Surface ◽  
Complex Adsorption ◽  
Desorption Mechanism

Environmental context. Adsorption controls the mobility of chemical species like nutrients in the soil and water environments and forms the basis for some of the methods of treating contaminated waters. Nutrients are introduced into environments where there are large quantities of humic substances adsorbed onto mineral oxides in the soil and sediments but no work has specifically focussed on the effect of adsorbed and free humic substances on the mobility of nutrients, and their adsorption and desorption mechanism on surface sites covered with adsorbed humic substances is still obscure. We believe that our findings and the proposed adsorption mechanism will help advance the technologies and methodologies for the removal of nutrients from wastewater. Abstract. The main objective of the present study was to evaluate the effect of adsorbed fulvic acid (FA) on the mobility of phosphate (Pi) using Fe2O3 as the soil or sediment model. The study showed that adsorbed FA increased the amount of adsorbed Pi as a function of time and pH without it being remobilised. We envisage that Pi adsorbs onto both residual cationic surface sites and onto the adsorbed FA and that additional Pi loads onto the adsorption surface as FA–Pi precipitate. Addition of FA to Fe2O3 with adsorbed Pi resulted in the remobilisation of Pi as FA got adsorbed at pH 5.30 and 6.30. At pH 8.30, FA adsorbed without remobilising Pi. FA is a stronger base than the Pi species at pH 5.30 and 6.30 and should adsorb more strongly. At pH 8.30, FA is thought to bind onto adsorbed Pi. The experimental isotherm data could not be completely fitted into the Freundlich equation. This could be due to the complex adsorption mechanism.

Mercury Removal from Wastewater by Steamed Hoof Powder

1999 ◽  
Vol 40 (7) ◽  
pp. 109-116 ◽  
Author(s):  
M. H. Ansari ◽  
A. M. Deshkar ◽  
P. S. Kelkar ◽  
D. M. Dharmadhikari ◽  
M. Z. Hasan ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Adsorption Capacity ◽  
Adsorption Process ◽  
Adsorption Equilibrium ◽  
Light Metal ◽  
Mercury Removal ◽  
High Adsorption ◽  
Surface Sites ◽  
Ph Values ◽  
High Adsorption Capacity

Steamed Hoof Powder (SHP), size < 53μ, was observed to have high adsorption capacity for Hg(II) with >95% removal from a solution containing 100 mg/L of Hg(II) with only 0.1% (W/V) concentration of SHP. The SHP has good settling properties and gives clear and odour free effluent. Studies indicate that pH values between 2 and 10 have no effect on the adsorption of Hg(II) on SHP. Light metal ions like Na+, K+, Ca2+ and Mg2+ up to concentrations of 500 mg/L and heavy metals like Cu2+, Zn2+, Cd2+, Co2+, Pb2+, Ni2+, Mn2+, Cr3+, Cr6+, Fe2+ and Fe3+ up to concentrations of 100 mg/L do not interfere with the adsorption process. Anions like sulphate, acetate and phosphate up to concentrations of 200 mg/L do not interfere. Chloride interferes in the adsorption process when Hg(II) concentration is above 9.7 mg/L. The adsorption equilibrium was established within two hours. Studies indicate that adsorption occurs on the surface sites of the adsorbent.

Work function studies of propylene, acetylene, hydrogen and nitrogen chemisorption on molybdenum

1982 ◽  
Vol 47 (11) ◽  
pp. 2996-3003
Author(s):  
Zdeněk Bastl
Keyword(s):  
Work Function ◽  
Surface Topography ◽  
Surface Coverage ◽  
Dissociative Chemisorption ◽  
Complete Coverage ◽  
Surface Sites ◽  
Function Change ◽  
Work Function Change

The work function changes of vacuum deposited molybdenum films caused by the chemisorption of propylene, acetylene, hydrogen and nitrogen were measured using the Kelvin vibrating capacitor method. During the hydrocarbon chemisorption, the work function increased in a low surface coverage region but decreased at the higher surface coverages. The saturation values of the work function changes corresponding to complete coverage of the surface by chemisorbed propylene and acetylene equal -0.08 eV and -0.42 eV, respectively. The observed dependences of the work function change on surface coverage are interpreted by the dissociative chemisorption of hydrocarbons on a limited number of surface sites which are simultaneously the sites of preferred adsorption. The extent of dissociation decreases in the adsorption with the increasing surface coverage. The results of the study of the work function changes induced by the hydrogen and nitrogen chemisorption enabled to draw several conclusions on the surface topography of the used films.

A topological quantum-chemical study of the chemisorption of carbon monoxide on the fcc (112) surfaces of Ni, Pt, Pd, Rh, and Ir

1990 ◽  
Vol 55 (8) ◽  
pp. 1907-1919
Author(s):  
Jiří Pancíř ◽  
Ivana Haslingerová
Keyword(s):  
Carbon Monoxide ◽  
Quantum Chemical ◽  
Co Adsorption ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Dissociative Chemisorption ◽  
Frontier Orbitals ◽  
Surface Sites ◽  
Charged Surfaces ◽  
Topological Quantum

A semiempirical quantum-chemical topological method is applied to the study of the fcc (112) surfaces of Ni, Pt, Pd, Rh, and Ir and the nondissociative as well as dissociative chemisorption of carbon monoxide on them. On Ni, dissociative chemisorption is preferred to linear capture, whereas on Pd and Pt, linear capture is preferred although dissociative chemisorption is also feasible. On Rh and, in particular, on Ir, dissociative chemisorption is energetically prohibited. The high dissociative ability of the Ni surface can be ascribed to a rather unusual charge alteration and to the degeneracy of the frontier orbitals. Negative charges at the surface level are only found on the Ni and Pt surfaces whereas concentration of positive charges is established on the Rh and Ir surfaces; the Pd surface is nearly uncharged. Metals with negatively charged surfaces seem to be able to dissociate molecules of carbon monoxide. It is demonstrated that CO adsorption can take place on all metal surface sites, most effectively in the valley of the step. In all the cases studied, the attachment to the surface is found to be energetically more favourable for the carbon than for the oxygen.

DNP-SENS Formulation Protocols To Study Surface Sites in Ziegler–Natta Catalyst MgCl2 Supports Modified with Internal Donors

2021 ◽  
Author(s):  
Alexander Yakimov ◽  
Jun Xu ◽  
Keith Searles ◽  
Wei-Chih Liao ◽  
Giuseppe Antinucci ◽  
...  
Keyword(s):  
Surface Sites ◽  
Natta Catalyst ◽  
Ziegler Natta Catalyst

Production of Free Radicals Arising from the Surface Activity of Minerals and Oxygen. Part I. Iron Mine Ores

1985 ◽  
Vol 5 (6) ◽  
pp. 1061-1078 ◽  
Author(s):  
Dominique Costa ◽  
Joelle Guignard ◽  
Roger Zalma ◽  
Henri Pezerat
Keyword(s):  
Surface Activity ◽  
Iron Ore ◽  
Particle Surface ◽  
Radical Oxygen Species ◽  
Lung Cancers ◽  
Surface Sites ◽  
Iron Mine ◽  
Mineral Dusts ◽  
Trapping Agent ◽  
Excess Incidence

The excess incidence of lung cancers observed in many metal mines probably is not only correlated with radioactivity but also with the inhaled dusts. In an attempt to determine a possible mechanism of carcinogenicity related to the surface activity of dusts, using the spin-trapping agent and ESR spectroscopy, one can demonstrate that some mineral dusts from iron ore mines are very active in an oxidative process in aqueous medium, implying the formation of radical oxygen species on reducing surface sites of the solid. This reducing surface activity of the dusts depends on the presence of Fe2+ ion in the lattice and on the process of activation and passivation of the surface sites. The more simple process of activation is the dissolution of the oxidized coating on the particle surface. Among the oxides, oxyhydroxides, carbonates, and silicates, the magnesium-iron phyllosilicates (chlorite, biotite, berthierine) appear the most active. The siderite FeCO3 is also active, but the iron oxides and oxyhydroxides are generally nonactive.

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