The role of metal ion-ligand interactions during divalent metal ion adsorption

Eldridge, Daniel S.; Crawford, Russell J.; Harding, Ian H.

doi:10.1016/j.jcis.2015.04.056

Cited by 30 publications

(11 citation statements)

References 52 publications

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“…The first Ni(II) adsorption equilibrium study compared the adsorption capacity of chitosan to CTS– g –GMA–PDEAEMA without pH adjustment (i.e., tertiary amine groups were not protonated). It is important to mention that it has been established in the literature that pH plays an important role in the adsorption capacities of different materials [28,29,30,31], however in our particular system, due to the nature of the CO 2 (gas) it was not possible to control the pH. These trials (Figure 6) suggested that the initial CTS– g –GMA–PDEAEMA was not as strong an adsorbent as pure chitosan despite the addition of 1.35 PDEAEMA chelation sites for every one chitosan chelation site.…”

Section: Resultsmentioning

confidence: 99%

CO2-Responsive Graft Modified Chitosan for Heavy Metal (Nickel) Recovery

et al. 2017

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Abstract:Chitosan was chemically functionalized with poly(diethylaminoethyl methacrylate) (PDEAEMA) using a grafting to approach to produce a CO 2 -responsive material for adsorbing metals from wastewater streams. A need for improved economical and greener approaches to recover heavy metals from wastewater streams exists due to increasing resource scarcity. Chitosan is currently used as an adsorbent for heavy metals but suffers from some properties that can be disadvantageous to its effectiveness; it is difficult to effectively disperse in water (which limits available surface area) and to regenerate. We set out to improve its effectiveness by grafting CO 2 -responsive tertiary amine containing polymers onto the chitosan backbone, with the goals of preparing and assessing a new type of adsorbent based on a novel concept; using carbon dioxide switchable polymers to enhance the performance of chitosan. PDEAEMA chains prepared by nitroxide-mediated polymerization were grafted onto chitosan functionalized with glycidyl methacrylate. In carbonated water, the grafted chitosan displayed improved dispersibility and exhibited a Ni(II) adsorption capacity higher than several other chemically functionalized chitosan variants reported in the literature with the regenerated material having a higher capacity than all physical and chemical derivatives reported in the literature. The results of this study validate the continued development of this material for applications in heavy metal removal and recovery from wastewater streams.

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Section: Resultsmentioning

confidence: 99%

CO2-Responsive Graft Modified Chitosan for Heavy Metal (Nickel) Recovery

et al. 2017

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“…Interestingly, the zeta potential vs pH slope for all the samples containing Hf were, to a first approximation, similar. This is a common result for colloidal systems which are chemically and physically similar but have different isoelectric points due to slight variations in, for example, surface site density 49,58,62,67,68 . We thus further ascribe the result here as indicating that once Hf is present at the surface, the nature of that surface has changed in a similar fashion regardless of the amount of Hf present.…”

Section: Accepted Manuscriptmentioning

confidence: 85%

“…Zeta potential is a parameter often used to probe the properties of an emulsion's surface. 33,35,46,49,58 It can be used to indicate the influence of adsorbed drugs on surface properties 35,37,51,59,60 as well as an indicator for particle stability. 36,41,46,61 Emulsions, for example, are more likely to be stable if the absolute zeta potential is high.…”

Section: Zeta Potentialmentioning

confidence: 99%

“…Note that several researchers have found changes in i.e.p. to be directly proportional to the surface concentration (see, for example, Schwartz et al 62 ; Harding 49 and Eldridge et al 58 ). Although the increase shown in Table 2 is monotonic, it is not proportional; with a small amount of Hf (0.5 mg mL -1 ) having a disproportionate effect on the i.e.p.…”

Section: Insert Table 2 About Herementioning

confidence: 99%

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Physical Characterization of Halofantrine-Encapsulated Fat Nanoemulsions

Haidar

Harding

Bowater

et al. 2019

Journal of Pharmaceutical Sciences

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We report the colloidal characterisation of halofantrine (Hf) laden soybean oil (SBO) fat emulsions. Hf increased the zeta potential, at all pH values, of the fat emulsions. Concomitant with this, the isoelectric point (i.e.p.) of the emulsion increased to higher pH values. The emulsion was destabilised by a small amount of Hf; interestingly, however, this was ameliorated by increasing the amount of Hf. The particle size and polydispersity of the fat emulsion reflected this with a small Hf concentration resulting in a significant increase in both particle size and polydispersity, but less so as the Hf concentration was increased. Emulsions lost stability as the pH approached the i.e.p. and this effect was greatest for the small Hf concentration emulsions. Cryogenic transmission electron microscopy showed the presence of beading or string like behaviour leading to gross distortions of the spherical shape for highly unstable emulsions. We conclude that to maintain good stability for Hf laden SBO emulsions, the pH of the emulsion should be kept away from its isoelectric point, and also that the drug concentration should be maintained at a relatively high value.

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“…In plants, polymerization of H 4 SiO 4 to colloidal and amorphous silica and/or polysilicic acid occurs in both rhizodermis and endodermis of rice roots ( Yoshida et al, ; Yeo et al, ). Since such polymerization is facilitated by H + ions ( Yoshida et al, ; Yeo et al, ), it might be assumed that in root tissues at slightly acidic pH, interaction of Ca 2+ with Si‐forms follows the same mechanism as described for silica surfaces ( Dove and Nix , ; Dishon et al, ; Eldridge et al, ). At alkaline conditions, the main type of interaction between charged silicic acid and Ca 2+ appears to be an electrostatic attraction, which is further supported by the findings that in vitro silicic acid and Ca 2+ react at a 1 : 2 ratio ( Dishon et al, ).…”

Section: Discussionmentioning

confidence: 99%

High monosilicic acid supply rapidly increases Na accumulation in maize roots by decreasing external Ca²⁺ activity

Bosnić

Pavlićević

Nikolić

et al. 2018

J. Plant Nutr. Soil Sci.

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Both calcium (Ca2+) and silicon (Si) improve plant performance under salt (NaCl) stress. Although these two mineral elements share numerous similarities, the information on how their extracellular interactions in the root apoplast affect uptake of sodium (Na+) is still lacking. Here, we investigated the effect of high Si supply in the bioavailable form of monosilicic acid (H4SiO4) on the activity of Ca2+ in the external root solution, and subsequent root uptake and compartmentation of Na in maize (Zea mays L.). In the short‐term experiments (6 h), 14‐d‐old maize plants were exposed to various concentrations of Ca2+ at three different pH‐values (6.5, 7.5, and 8.5) and two Si concentrations, i.e., low (1 mM) and high (4 mM) supply of H4SiO4. The activity of Ca2+ and Na+ in the external solution as well as the root concentrations of total and cell sap and BaCl2‐exchangeble apoplastic fractions of both elements were analyzed. The pH of the nutrient solution affected neither the ion activities nor the root accumulation of both Ca2+ and Na+. At higher pH values (7.5 and 8.5) the interactions of Ca2+ and Si at high Si supply led to a decrease of Ca2+ activity and, hence, an increase of Na+ : Ca2+ activity ratio in the external root solution. Concomitantly, despite the elevated exchangeable apoplastic fraction of both Ca2+ and Na+, the total and cell sap concentrations were remarkably decreased for Ca2+ and increased for Na+ by the addition of 4 mM H4SiO4. This work demonstrates that at high Si supply extracellular Ca‐Si interactions leading to lowered activity of Ca2+ might rapidly compromise the ameliorative effect of Ca2+ on Na+ accumulation in roots. Practically, Si over‐fertilization of saline and, in particular, sodic soils may further promote the accumulation of Na+ in root tissues hours after Si application and, hence, increase a potential risk of Na+ toxicity.

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The role of metal ion-ligand interactions during divalent metal ion adsorption

Cited by 30 publications

References 52 publications

CO2-Responsive Graft Modified Chitosan for Heavy Metal (Nickel) Recovery

CO2-Responsive Graft Modified Chitosan for Heavy Metal (Nickel) Recovery

Physical Characterization of Halofantrine-Encapsulated Fat Nanoemulsions

High monosilicic acid supply rapidly increases Na accumulation in maize roots by decreasing external Ca²⁺ activity

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The role of metal ion-ligand interactions during divalent metal ion adsorption

Cited by 30 publications

References 52 publications

CO2-Responsive Graft Modified Chitosan for Heavy Metal (Nickel) Recovery

CO2-Responsive Graft Modified Chitosan for Heavy Metal (Nickel) Recovery

Physical Characterization of Halofantrine-Encapsulated Fat Nanoemulsions

High monosilicic acid supply rapidly increases Na accumulation in maize roots by decreasing external Ca2+ activity

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Product

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High monosilicic acid supply rapidly increases Na accumulation in maize roots by decreasing external Ca²⁺ activity