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Dispersive Solid–Liquid Microextraction Based on the Poly(HDDA)/Graphene Sorbent Followed by ICP-MS for the Determination of Rare Earth Elements in Coal Fly Ash Leachate. METALS 2022. [DOI: 10.3390/met12050791] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A dispersive solid-phase microextraction (DSPME) sorbent consisting of poly(1,6-hexanediol diacrylate)-based polymer microspheres, with embedded graphene microparticles (poly(HDDA)/graphene), was synthesized by microfluidic emulsification/photopolymerization and characterized by optical microscopy and X-ray fluorescence spectrometry. This sorbent was applied for simple, fast, and sensitive vortex-assisted DSPME of rare earth elements (RREs) in coal fly ash (CFA) leachate, prior to their quantification by inductively coupled plasma mass spectrometry (ICP-MS). Among nine DSPME variables, the Plackett–Burman screening design (PBD), followed by the central composite optimization design (CCD) using the Derringer desirability function (D), identified the eluent type as the most influencing DSPME variable. The optimum conditions with maximum D (0.65) for the chelating agent di-(2-ethylhexyl) phosphoric acid (D2EHPA) amount, the sorbent amount, the eluting solvent, the extraction temperature, the centrifuge speed, the vortexing time, the elution time, the centrifugation time, and pH, were set to 60 μL, 30 mg, 2 M HNO3, 25 °C, 6000 rpm, 1 min, 1 min, 5 min, and 4.2, respectively. Analytical validation of the DSPME method for 16 REEs (Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) in CFA leachate samples estimated the detection limits at the low ppt level, the recovery range 43–112%, and relative standard deviation within ± 22%. This method was applied to a water extraction procedure (EP) and acetic acid toxicity characteristic leaching procedure (TCLP) for leachate of CFA, from five different coal-fired thermoelectric power plants. The most abundant REEs in leachate (20 ÷ 1 solid-to-liquid ratio) are Ce, Y, and La, which were found in the range of 22–194 ng/L, 35–105 ng/L, 48–95 ng/L, and 9.6–51 μg/L, 7.3–22 μg/L, 2.4–17 μg/L, for EP and TCLP leachate, respectively. The least present REE in TCLP leachate was Lu (42–125 ng/L), which was not detected in EP leachate.
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Rubinos DA, Spagnoli G. Assessment of red mud as sorptive landfill liner for the retention of arsenic (V). JOURNAL OF ENVIRONMENTAL MANAGEMENT 2019; 232:271-285. [PMID: 30481641 DOI: 10.1016/j.jenvman.2018.09.041] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 09/08/2018] [Accepted: 09/11/2018] [Indexed: 06/09/2023]
Abstract
The sorption of AsV on red mud (bauxite residue), produced in the ALCOA-San Cibrao factory (Spain), was assessed in view of its potential use as sorptive liner of landfills for the attenuation of As-rich leachates. The operating parameters evaluated, using batch-type procedures, comprised the effects of time, solution pH, AsV concentration (sorption isotherm) and presence of phosphate on the AsV sorption. The results showed that the red mud efficiently sorbed AsV. The sorption was fast, with a major fraction of initial AsV being removed in a few minutes or hours of contact, depending on AsV concentration. The kinetic process was well described by the pseudo-second order equation, which points to chemisorption is involved, whereas surface (film) diffusion chiefly governs the rate of AsV sorption for the red mud system. Sorption of AsV was strongly pH-dependent. Maximum removal (>98%) was observed at slightly acidic pH (pHmax = 5.5-6), while AsV sorption considerably decreased at both highly acidic and alkaline pH. The percentages of sorbed AsV decreased with the increasing solution AsV concentration, and the AsV sorption capacity (up to 43.5 mmol/kg) of the red mud was higher (∼4 -fold) at pH ∼6 than at pH ∼9.2 (natural pH of the red mud). The presence of P at equimolar or 1:10 As/P molar ratios reduced AsV sorption by ∼20% and 30%, respectively. Simulations of AsV migration taking into account the effects of dispersion and diffusion through an hypothetical red mud liner, using the sorption parameters and the geotechnical-hydraulic conductivity characteristics of the RM, predicted a deeper migration of AsV in the liner at pH∼9.2 than at pH∼6 and a minimum thickness of ∼90 cm and ∼20 cm, respectively, for a RM liner to decrease the solution AsV concentration from highly toxic 1 mM to a safe <0.133 μM (<10 μg/L) level, after a 35-years period.
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Affiliation(s)
- David A Rubinos
- Freelance Researcher & Consultant, Reboiras 39, 15981 A Coruña, Spain.
| | - Giovanni Spagnoli
- BASF Construction Solutions GmbH, Dr.-Albert-Frank-Straße 32, 83308 Trostberg, Germany.
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