Calcinated hydrotalcite—a sorbent for purifying uraniferous waters

Timoshenko, T. G.; Kosorukov, A. A.; Pshinko, G. N.; Гончарук, В. В.

doi:10.3103/s1063455x09040079

Cited by 14 publications

(7 citation statements)

References 6 publications

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“…49 Being negatively charged, the first two species are expected to be attracted to the positively charged surface where ligand exchange would subsequently result in 1 E and 2 E surface complexes (scheme S4a,b). Previous research 5,6,50 has shown that U adsorption does not decline until the point of zero charge of HTC is approached with the extent of adsorption not being significantly different between pH 7.0 and 9.5, which is consistent with the findings of this work.…”

Section: +supporting

confidence: 92%

“…Efficient capture and containment of U, transuranics, daughter radionuclides, and other contaminants from U mining, processing wastewater, and nuclear accidents is an essential component to ensure an environmentally and socially responsible operational lifecycle of the U industry. − Although a number of conventional technologies such as ion exchange are available to address one or more contaminants, few technologies are able to efficiently capture a range of geochemically diverse contaminants often present and to rapidly convert them into a stable, solid form. Layered-double hydroxide (LDH) anionic clays, specifically hydrotalcite (HTC, {[Mg 1– x ,Al x ](OH) 2 }A x / m – m – · n H 2 O, e.g., A = 1/2SO 4 2– , 1/2CO 3 2– or 1NO 3 – ), have been investigated extensively over a wide range of pH, ionic strengths, and with various ligands (EDTA, citrate, carbonate, nitrate, and sulfate), to be effective U scavengers under controlled laboratory settings. − However, few studies have been able to test HTCs on actual, real-life U-containing samples. Recent research undertaken by CSIRO tested the in situ formation of HTCs as a broad spectrum repository for a range of cationic and anionic contaminant species on Heathgate Resources’ Beverley North (South Australia) in situ recovery (ISR) barren mine lixiviant and on tailings pond water from ERA’s Ranger Mine (Northern Territory).…”

Section: Introductionmentioning

confidence: 99%

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Mechanisms of Uranyl Sequestration by Hydrotalcite

et al. 2017

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Since the advent of large-scale U mining, processing, and enrichment for energy or weapons production, efficient capture and disposal of U, transuranics, and daughter radionuclides has constituted an omnipresent challenge. In this study, we investigated uranyl (UO 2 2+ ) sequestration by hydrotalcite (HTC) as a coprecipitation or surface adsorption reaction scenario. The master variables of the study were pH (7.0 and 9.5) and CO 2 content during the reactions (CO 2 -rich, CO 2 r vs CO 2 -depleted, CO 2 p). In addition, we compared the outcomes of U–HTC coprecipitation reactions between pristine salt precursors and barren U mine wastewater (lixiviant). Extended X-ray absorption fine structure spectra revealed that uranyl adsorbs on the HTC surface as inner-sphere complexes in CO 2 r and CO 2 p systems with U–Mg/Al interatomic distances of ∼3.20 and ∼3.35 Å indicative of single-edge ( 1 E) and double-edge ( 2 E) sharing complexes, respectively. Partial coordination of uranyl by carbonate ligands in CO 2 r systems does not appear to hinder surface complexation, suggesting ligand-exchange mechanisms to be operative for the formation of inner-sphere surface complexes. Uranyl symmetry is maintained when coprecipitated with Al and Mg from synthetic or barren lixiviant solutions, precluding incorporation into the HTC lattice. Uranyl ions, however, are surrounded by up to 3–5 Mg/Al atoms in coprecipitated samples interfering with HTC crystal growth. Future research should explore the potential of Fe(II) or Mn(II) to reduce U(VI) to U(V), which is conducive for U incorporation into octahedral crystal lattice positions of the hydroxide sheet.

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Section: +supporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Mechanisms of Uranyl Sequestration by Hydrotalcite

et al. 2017

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“…Heat-treated form of a LDH is shown in (2) to absorb anions from aqueous media to restore its initial structure, which is confirmed with the results of our X-ray diffraction studies [4,13]. It has been found that pH 0 values of 3 to 4 are optimal for adsorption ( Figure 9), and single-charged anions have less effect on the rate of recovery of chromate ions: they actually cause no reduction in HCO 3 − sorption in the range of up to 7 mgeqv./dm 3 and NO 3 − sorption in the range of up to 0.2 M, whereas the effects of SO 4 2− are more pronounced: sulphate ions in the dose of 30 mg/dm 3 reduce the rate of recovery of Cr(VI) by 20% ( Figure 10).…”

Section: Journal Of Chemistrysupporting

confidence: 85%

“…Layered double hydroxides (LDHs) built of positively charged brucite-like layers linked by exchangeable anions are rather promising in this context [2,3]. Inorganic hydrotalcite adsorbents containing carbonate anions in the interlayer space may be successfully used for sorption of cationic forms of uranyl ions from aqueous media [4,5]. However, sorption of uranyl ions with such sorbents is substantially reduced in presence of HCO 3 − and CO 3 2− in aqueous solutions.…”

Section: Introductionmentioning

confidence: 99%

Layered Double Hydroxides as Effective Adsorbents for U(VI) and Toxic Heavy Metals Removal from Aqueous Media

Pshinko

2013

Journal of Chemistry

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Capacities of different synthesized Zn,Al-hydrotalcite-like adsorbents, including the initial carbonate [Zn4Al2(OH)12]·CO3·8H2O and its forms intercalated with chelating agents (ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and hexamethylenediaminetetraacetic acid (HMDTA)) and heat-treated form Zn4Al2O7, to adsorb uranium(VI) and ions of toxic heavy metals have been compared. Metal sorption capacities of hydrotalcite-like adsorbents have been shown to correlate with the stability of their complexes with the mentioned chelating agents in a solution. The synthesized layered double hydroxides (LDHs) containing chelating agents in the interlayer space are rather efficient for sorption purification of aqueous media free from U(VI) irrespective of its forms of natural abundance (including water-soluble bi- and tricarbonate forms) and from heavy metal ions. [Zn4Al2(OH)12]·EDTA·nH2O is recommended for practical application as one of the most efficient and inexpensive synthetic adsorbents designed for recovery of both cationic and particularly important anionic forms of U(VI) and other heavy metals from aqueous media. Carbonate forms of LDHs turned out to be most efficient for recovery of Cu(II) from aqueous media withpH0≥7owing to precipitation of Cu(II) basic carbonates and Cu(II) hydroxides. Chromate ions are efficiently adsorbed from water only by calcinated forms of LDHs.

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“…The formation of layered-double hydroxide (LDH) minerals, specifically hydrotalcite (HTC), an Mg-Al rich LDH form ([Mg 1−x Al x ](OH) 2 A x/m − m− •nH 2 O, A = anion), has previously been investigated as a solid phase, preformed sorbent for U removal over a range of pH, ionic strength, and in the presence of co-existing U ligands [9][10][11][12][13][14][15] . Nanoscale polymetallic HTC formed in situ in wastewaters via a bespoke, self-assembly mechanism may incorporate U, daughter radionuclides and other contaminants as fundamental building blocks within or at the edges of the metal hydroxide and interlayers, respectively [16][17][18][19][20][21][22] .…”

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confidence: 99%

Engineered mineralogical interfaces as radionuclide repositories

Douglas

Reddy

Saxey

et al. 2023

Sci Rep

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Effective capture of fugitive actinides and daughter radionuclides constitutes a major remediation challenge at legacy or nuclear accident sites globally. The ability of double-layered, anionic clay minerals known as hydrotalcites (HTC) to contemporaneously sequester a range of contaminants from solution offers a unique remedy. However, HTC do not provide a robust repository for actinide isolation over the long term. In this study, we formed HTC by in-situ precipitation in a barren lixiviant from a uranium mine and thermally transformed the resulting radionuclide-laden, nanoscale HTC. Atomic-scale forensic examination of the amorphized/recrystallised product reveals segregation of U to nanometre-wide mineral interfaces and the local formation of interface-hosted mineral grains. This U-phase is enriched in rare earth elements, a geochemical analogue of actinides such as Np and Pu, and represents a previously unreported radionuclide interfacial segregation. U-rich phases associated with the mineral interfaces record a U concentration factor of ~ 50,000 relative to the original solute demonstrating high extraction and concentration efficiencies. In addition, the co-existing host mineral suite of periclase, spinel-, and olivine-group minerals that equate to a lower mantle, high P–T mineral assemblage have geochemical and geotechnical properties suitable for disposal in a nuclear waste repository. Our results record the efficient sequestering of radionuclides from contaminated water and this novel, broad-spectrum, nanoscale HTC capture and concentration process constitutes a rapid solute decontamination pathway and solids containment option in perpetuity.

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Calcinated hydrotalcite—a sorbent for purifying uraniferous waters

Cited by 14 publications

References 6 publications

Mechanisms of Uranyl Sequestration by Hydrotalcite

Mechanisms of Uranyl Sequestration by Hydrotalcite

Layered Double Hydroxides as Effective Adsorbents for U(VI) and Toxic Heavy Metals Removal from Aqueous Media

Engineered mineralogical interfaces as radionuclide repositories

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