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n-Capric Acid anchored Silanized-Silica-Gel; Its application to sample clean up of Th(IV) sorbed as a dinuclear species in quantified H-bonded-dimeric-metal-trapping-cores

Abstract

Selective separation, preconcentration and recovery of Th(IV) from aqueous solutions were investigated using reusable (>800 cycles @95% recovery) n-capric acid (nCA) impregnated silanized-silica-gel (SSG-nCA), through batch-column adsorption methods. SSG-nCA is a porous material (Pore volume: 2.21 mL g-1) of high Brunauer–Emmett–Teller (BET) surface area (1820 m2g-1). Dimethyldichlorosilane (DMDCS) binds SG skeleton-unit-cells (i.e.,{Si(OSi)4.xH2O}θ=2.4) via–{SiO2}n=12-O-Si(Me)2-O-{SiO2}n=12 3-D networking to produce SSG through intra-particular silanization reaction. In SSG-nCA hydrophobic-long-hydrocarbon-chain of nCA being hooked at hydrophobic surface of SSG generates 121 µmol g-1 H-bonded-dimeric-metal-trapping-cores (HBDMTC), projected towards hydrophilic mobile phase. It showed significant Th(IV) sorption (Break through Capacity (BTC): 235±15 μmol g-1; minimum sorption-equilibrium time:> 12 minutes; high recovery(> 95% from large sample volume, 1000 mL) and high preconcentration factor(PF:192)). The ascertained dimeric-aqua-{Th2(OH)2(H2O)2}6+ sorbed species, anchored with an appreciable binding energy (-38.37 eV per mole) at optimum pH 5.0±0.4. Along with the existing standard methodology, density functional theory (DFT) based computation has been done for characterization of both the extractor and extracted species. The sorption process was endothermic (+ΔH), entropy-gaining (+ΔS) and spontaneous (-ΔG) in nature. It was found effective in presence of 0.125-0.150 mmol mL-1 Na/K salts of coexisting ions. Sequential separation of Zr(IV), U(VI), Ce(IV), Th(IV) was achieved by exploiting the differences in pH for extraction (Zr(IV) at pH 2.5 and U(VI), Ce(IV), Th(IV) at pH 5.0±0.4) followed by their selective elution from respective extracted portion (Zr(IV):4M HNO3 and U(VI):0.6M CH3COOH, Ce(IV):1M CH3COOH, Th(IV):0.5 HNO3).

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Publication details

The article was received on 02 Mar 2017, accepted on 16 May 2017 and first published on 16 May 2017


Article type: Paper
DOI: 10.1039/C7NJ00694B
Citation: New J. Chem., 2017, Accepted Manuscript
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    n-Capric Acid anchored Silanized-Silica-Gel; Its application to sample clean up of Th(IV) sorbed as a dinuclear species in quantified H-bonded-dimeric-metal-trapping-cores

    B. Mandal, M. Chaterjee, D. roy, R. sarkar, B. Srivastava, S. Banerjee, S. mondal and M. K. Barman, New J. Chem., 2017, Accepted Manuscript , DOI: 10.1039/C7NJ00694B

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