Kinetics and adsorption behaviour of salicylate on α-alumina in aqueous medium

Das, Manash R.; Sahu, Omprakash; Borthakur, P. C.; Mahiuddin, Sekh

doi:10.1016/j.colsurfa.2004.02.010

Cited by 19 publications

(27 citation statements)

References 21 publications

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“…5,11 The shift in peak position was observed due to distortions of the salicylate structure upon adsorption on goethite surfaces. 21 The bands attributed to ν(CC) vibration were shifted from about 1623, 1593, 1487, 1458, and 1303 cm −1 in aqueous salicylate to 1610, 1574, 1477, 1462, and 1265 cm −1 once adsorbed, respectively.…”

Section: 21mentioning

confidence: 99%

“…The formation of this M-M 1 surface complex has almost no effect on the geometry of the planar sixmembered ring due to its strong intramolecular hydrogen bond. 11,31 Furthermore, this intramolecular hydrogen bond may, in turn, jeopardize the strength of the Fe−salicylate interactions, resulting in a relative weak inner-sphere complex.…”

Section: 21mentioning

confidence: 99%

“…5,7 Hence, the most plausible configuration would be in monodentate coordination involving an oxygen atom from the carboxylate. 5,11,12 To justify the proposed surface complex, we employed the quantum chemical calculations for the adsorbed salicylate in five possible configurations including two M-M, one M-B, and two B-B structures (Figure 4). The M-M complexes interacted with the surface iron involving an oxygen atom of the carboxylate.…”

Section: 21mentioning

confidence: 99%

“…Some researchers suggest the M-B structure on TiO 2 involved both ph−OH and COO − groups. 8,9 Meanwhile, the B-B complexes were hypothesized by Jankovićet al 10 Upon salicylate adsorption on aluminum (hydr)oxides, surface configurations such as mononuclear mondentate (M-M), 5,11,12 M-B, 9 and B-B 5,12 were proposed. The inconsistency in the proposed surface complex motivated our research in molecularscale understanding of salicylate adsorption.…”

Section: ■ Introductionmentioning

confidence: 99%

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Molecular-Scale Study of Salicylate Adsorption and Competition with Catechol at Goethite/Aqueous Solution Interface

2013

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Insights into the adsorption mechanisms of salicylate on goethite, especially its competition with catechol, can further our understanding of the fate and transport of natural organic matter analogues in the environment. The adsorption process was investigated using multiple complementary techniques including batch adsorption experiments, flow-cell ATR-FTIR measurement, and DFT calculations. The macroscopic results show that increasing pH and ionic strength had an adverse effect on salicylate adsorption because of electrostatic interactions. Salicylate formed an inner-sphere complex in a mononuclear monodentate configuration with carboxylate bound to the iron atom on goethite surface within pH 5−9. The electrostatic outer-sphere complex could be observed under high salicylate concentrations and low ionic strength. In the competitive adsorption of salicylate and catechol, their individual interfacial complexes coexisted and competed with each other. The surface salicylate could be replaced by catechol during adsorption under neutral and basic pH conditions. Accordingly, the macroscopic adsorption capacity of salicylate was depressed in the binary system.

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Section: 21mentioning

confidence: 99%

Section: 21mentioning

confidence: 99%

Section: 21mentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Molecular-Scale Study of Salicylate Adsorption and Competition with Catechol at Goethite/Aqueous Solution Interface

2013

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“…However, detailed understanding has been impeded by the lack of structure/reaction characterization. 4,5,8,11 While water dissociation has been observed on many cation-terminated surfaces or surfaces with defects, 3,[12][13][14][15][16][17] dissociation pathways remain an open question. As a result, we have little direct evidence that open metal sites (e.g., exposed cations at oxygen vacancies) are effective in dissociating water molecules.…”

Section: Introductionmentioning

confidence: 99%

Water Reaction Mechanism in Metal Organic Frameworks with Coordinatively Unsaturated Metal Ions: MOF-74

et al. 2014

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Water dissociation represents one of the most important reactions in catalysis, essential to the surface and nano sciences [e.g., Hass et al., Science, 1998, 282, 265-268; Brown et al., Science 2001, 294, 67-69; Bikondoa et al., Nature 2005, 5, 189-192]. However, the dissociation mechanism on most oxide surfaces is not well understood due to the experimental challenges of preparing surface structures and characterizing reaction pathways. To remedy this problem, we propose the metal organic framework MOF-74 as an ideal model system to study water reactions. Its crystalline structure is well characterized; the metal oxide node mimics surfaces with exposed cations; and it degrades in water. Combining in situ IR spectroscopy and first-principles calculations, we explored the MOF-74/water interaction as a function of vapor pressure and temperature. Here, we show that, while adsorption is reversible below the water condensation pressure (~19.7 Torr) at room temperature, a reaction takes place at ~150 ˚C even at low water vapor pressures. This important finding is unambiguously demonstrated by a clear spectroscopic signature for the direct reaction using D 2 O, which is not present using H 2 O due to strong phonon coupling. Specifically, a sharp absorption band appears at 970 cm -1 when D 2 O is introduced at above 150 ˚C, which we attribute to an O-D bending vibration on the phenolate linker. Although H 2 O undergoes a similar dissociation reaction, the corresponding O-H mode is too strongly coupled to MOF vibrations to detect. In contrast, the O-D mode falls in the phonon gap of the MOF and remains localized. First-principles calculations not only positively identify the O-D mode at 970 cm -1 but derive a pathway and kinetic barrier for the reaction and the final configuration: the D (H) atom is transferred to the oxygen of the linker phenolate group, producing the notable O-D absorption band at 970 cm -1 , while the OD (or OH) binds to the open metal sites. This finding explains water dissociation in this case and provides insight into the long-lasting question of MOF-74 degradation. Overall, it adds to the understanding of molecular water interaction with cation-exposed surfaces to enable development of more efficient catalysts for water dissociation.2

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Silicon Incorporation Reduces the Reactivity of Short-range Ordered Aluminosilicates Toward Organic Acids

Lenhardt

Stein

Rennert

2023

Clays and clay miner.

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The structure and composition of short-range ordered aluminosilicates (SROAS) may control their affinity for organic acids with potential effects on soil organic matter stabilization. Adsorption mechanisms of model organic acids were studied to resolve the effect of Si incorporation. Adsorption of oxalic, salicylic, and octanoic acid on Al-rich (Al:Si = 3.7) and Si-rich (Al:Si = 1.4) SROAS was quantified by analyses of dissolved organic carbon using catalytic high-temperature combustion. The initial pH of 5 and 6.5 increased to 6.3–8.2 during adsorption of oxalic and salicylic acid, demonstrating hydroxyl release by ligand exchange. Minor changes in pH indicated weak interactions of octanoic acid with both SROAS. Adsorbates were characterized by Fourier-transform infrared spectroscopy. Asymmetric stretching of carboxylate groups at 1720 and 1700 cm–1, and symmetric stretching at 1430 cm–1 evinced the formation of chelate complexes for oxalic acid. An absorption band centered at 1545 cm–1 indicated partial inner-sphere binding of salicylic acid on both SROAS. Silicon-rich SROAS adsorbed 80–90% less than Al-rich SROAS, suggesting that adsorption of oxalic and salicylic acid was controlled by surface aluminol groups. Fast kinetics of oxalate adsorption on Al sites was studied by a conductivity-based stopped-flow technique. Ligand exchange proceeded at a rate constant of 3.5 s–1 (25°C), similar to solute Al complexation, with an activation energy of up to 34.1 kJ mol–1. A slow process with a rate constant of 0.13 s–1 (25°C) was attributed to diffusion of oxalate at the surface or into SROAS particles. As supported by structural characterization of Si-rich SROAS, the much lower susceptibility of Si-rich SROAS to ligand exchange relates to Al speciation. The formation of tetrahedral Al precludes its complexation by carboxyl groups.

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Kinetics and adsorption behaviour of salicylate on α-alumina in aqueous medium

Cited by 19 publications

References 21 publications

Molecular-Scale Study of Salicylate Adsorption and Competition with Catechol at Goethite/Aqueous Solution Interface

Molecular-Scale Study of Salicylate Adsorption and Competition with Catechol at Goethite/Aqueous Solution Interface

Water Reaction Mechanism in Metal Organic Frameworks with Coordinatively Unsaturated Metal Ions: MOF-74

Silicon Incorporation Reduces the Reactivity of Short-range Ordered Aluminosilicates Toward Organic Acids

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