This article describes a newly designed block copolymer based aqueous biphasic system (ABS, composed of two immiscible aqueous phases) which is further utilized to study extraction behavior of three iodine species viz., I2, I-, and IO4-. Phase diagram and tie line data reveals the potential working range of this new biphasic system. Fluorescence, dynamic light scattering, transmission electron microscopy (TEM) and conductance data establish the micellar arrangement in solutions of this particular block copolymer. Elemental iodine is easily soluble in copolymer solution due to charge transfer complexation. Polymer phase of the ABS is found to have species dependent selectivity of extraction for the three different iodine species. Two non toxic, non flammable dyes 3,6-diamino-10-phenylphenazinium chloride (DPC) and haematoxylin are introduced for the first time to detect iodide and periodate species respectively in the copolymer medium. This journal is © The Royal Society of Chemistry 2015.

KAMALIKA SEN

Chemistry

P SAMADDAR

A CHAKRABORTY

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

RSC Advances

Calcium is an essential element for our living. Different calcium species show interesting interplay in our body. A slow accumulation of calcium oxalate species in the body turns out to be painful as it forms stone in the kidneys and gall bladder. Therefore extraction of different calcium species has been taken up in this study. The micellar activity of different water soluble polymers and their role in aqueous biphasic systems (ABS) make them attractive for species dependent extraction of calcium. In the present study, we report the possibility of extractions of three different Ca species viz., calcium acetate, calcium lactate and calcium oxalate extractions in polyethylene glycol (PEG) and a block copolymer (PPG-PEG-PPG) using ABS with varying pH conditions of the salt rich phase. It has also been suggested that calcium oxalate species can potentially be extracted in micellar medium of PEG #12000 and PPG-PEG-PPG. A correlation of the extent of extraction has been drawn with the aggregation number of the polymer medium. © 2018 Elsevier B.V.

Journal of Molecular Liquids

Micelle mediated extraction of calcium species in aqueous biphasic systems: A mechanism steered by aggregation number

The present study aims at the generation of a triblock copolymer vs sodium sulfate aqueous biphasic system (ABS), its application toward extraction of molybdenum species, and finally purification and regeneration of the block copolymer. The ABS was characterized for its biphasic region by constructing the phase diagram using turbidometric titration methods. Extractions were monitored using the spectrophotometric method directly in the block copolymer medium. Complete extraction of molybdenum species was observed in this method. Interference from other closely related metal ions in the extraction process was found to be negligible excepting oxo and polyoxometallates of vanadium and tungsten. Regeneration of the polymer was done using a thermoseparation technique followed by successive treatment with ion exchange resins. ∼87% of the pure triblock copolymer could be regenerated as a result of such treatment. © 2018 American Chemical Society.

Journal of Chemical and Engineering Data

Thermoseparative Regeneration of Triblock Copolymer after Aqueous Biphasic Extraction of Molybdate Species

A new aqueous biphasic system (ABS) was designed by mixing aqueous solutions of tri-block copolymer polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol (PPG-PEG-PPG) with a nontoxic ionic liquid tris (2-hydroxyethyl) methyl-ammonium methyl sulfate. Well defined phase diagram validated with Merchuk equation along with suitable tie-lines was obtained by turbidometric titration method at 298&nbsp;K. The tie-line lengths and slope of tie lines were calculated and the results were validated using Othmer-Tobias and Bancroft equations. The newly designed ABS has been used to perform the extraction studies of cholesterol, zinc and Zn-cholesterol complex at different pHs of the solution. Zn-cholesterol complex was found to be formed at an acidic pH (1.5). The stability constant value of Zn-cholesterol complex was obtained in ethanolic medium, pristine polymer medium and in the ABS extracted polymer rich phase using Benesi-Hildebrand equation. The aggregation number of PPG-PEG-PPG solution obtained after extraction of cholesterol and Zn-cholesterol complex in ABS was found to be greater in comparison to the pristine copolymer solution. Kinetic spectrophotometric studies were also supporting higher stability of Zn-cholesterol complex in the ABS extracted polymer rich phase. Zn-cholesterol complex formation in acidic micellar medium (pH&nbsp;1.5) also falls in the pH range of normal human stomach and may offer a suitable method of zinc supplementation by absorption via cell membrane that resembles with the polymeric micellar aggregation. © 2016 Elsevier B.V.

Ionic liquid vs tri-block copolymer in a new aqueous biphasic system for extraction of Zn-cholesterol complex

In this work we have designed a simple, eco-friendly, one-pot method for the synthesis of palladium nanopartides of quantum dot dimension (PdQDs) using a non-toxic, biocompatible block co polymer which functions as a reducing and stabilizing agent during the synthesis. The entire synthesis is free from any especial experimental set up and reaction conditions. These QDs were characterized by several well know characterization techniques such as UV-vis spectroscopy (UV-vis), transmission electron microscopy (TEM), Fourier transform infra-red spectroscopy (FTIR), dynamic light scattering (01,S), and potential measurements. The transformation of a yellow solution into dark brown solution was indicative of the formation of the PdQDs. The kinetics of this reaction was monitored using a time scan absorption measurement which reveals a sigmoidal curve, a signature of noble metal nanoparticles. The rate of nucleation and growth were calculated using Finke and Watzky model. The synthesized colloidal PdQDs were employed for the reduction of environmentally toxic Cr(VI) to safer Cr(III). The reaction was catalyzed by the PdQDs in presence of acetic acid and was dependent on the concentration of both. The order and rate constant of the reduction reaction was calculated. A comparatively faster and complete reduction of Cr(VI) to Cr(III) using this catalysis was achieved at room temperature in presence gamma irradiation, thus making the method more effective in its approach for bulk remediation of Cr(VI). (C) 2017 Elsevier B.V. All rights reserved.

Reactive and Functional Polymers

On the kinetics of block copolymer mediated palladium quantum dot synthesis: Application in reduction of Cr(VI) to Cr(III)

In this work we have designed a simple, eco-friendly, one-pot method for the synthesis of palladium nanoparticles of quantum dot dimension (PdQDs) using a non-toxic, biocompatible block co polymer which functions as a reducing and stabilizing agent during the synthesis. The entire synthesis is free from any especial experimental set up and reaction conditions. These QDs were characterized by several well know characterization techniques such as UV–vis spectroscopy (UV–vis), transmission electron microscopy (TEM), Fourier transform infra-red spectroscopy (FTIR), dynamic light scattering (DLS), and ξ potential measurements. The transformation of a yellow solution into dark brown solution was indicative of the formation of the PdQDs. The kinetics of this reaction was monitored using a time scan absorption measurement which reveals a sigmoidal curve, a signature of noble metal nanoparticles. The rate of nucleation and growth were calculated using Finke and Watzky model. The synthesized colloidal PdQDs were employed for the reduction of environmentally toxic Cr(VI) to safer Cr(III). The reaction was catalyzed by the PdQDs in presence of acetic acid and was dependent on the concentration of both. The order and rate constant of the reduction reaction was calculated. A comparatively faster and complete reduction of Cr(VI) to Cr(III) using this catalysis was achieved at room temperature in presence γ irradiation, thus making the method more effective in its approach for bulk remediation of Cr(VI). © 2017 Elsevier B.V.

Solutions of polyvinyl alcohol have been found to show fluorescence emission upon excitation (λex = 300 nm, λem = 420 nm). The site of luminescence generation has been attributed to its tendency to form organized micelles in solution which result in an electron dense region in the hydrophilic zone. The expected micellar size was evaluated using dynamic light scattering and the cmc was predicted from the conductance measurements. The spectral changes of the PVA solution were spectacular in the presence of different oxidation states of the metal ions Cr(III)/(VI), Mn(II)/(VII) and Fe(II)/(III). The spectral studies indicated a weak ground state complexation of PVA micelles with the lower oxidation state metal ions. However for the higher oxidation state species both ground and excited state fluorescence quenching were observed. The present system offers a simple and cost effective method of species dependent metal ion sensing. ©2014 Elsevier B.V. All rights reserved.

Organized polyvinyl alcohol assemblies: Eligible luminescent centers for species dependent metal sensing

Polyvinylpyrrolidone (PVP) forms aqueous biphasic systems with tri-block co-polymers, surfactants and salts. The phase diagrams of PVP-salt and PVP-surfactant systems were constructed by a turbidometric titration method at 296 K. Density measurements of the phase forming solutions at this temperature also led to an attractive outcome of the formation of two tri-phasic systems among the components of our study (Na-tartrate + PVP + Triton-X-100 and Na-tartrate + PVP + PPG-PEG-PPG). We also constructed a spreadsheet reflecting the relationship between miscibility and the possibility of phase separation between the components, consisting of the seven phase forming solutions to open up different possibilities of ABS formation. Some completely new biphasic systems were obtained as well as the process of gel formation of a PVA solution in the presence of salt and polymer solutions was also observed. The applications of some of the developed ABSs are described for the recovery of an antibiotic drug, amoxicillin and a catalyst, molybdenum disulphide. © The Royal Society of Chemistry 2014.

Phase separation in aqueous systems for realizing virtually significant extractions

An aqueous biphasic system (ABS) was obtained after mixing an amino acid (l-proline) solution (5 mol·kg-1) with a 0.90 g·g -1 solution of nonionic surfactant (Triton X-100). The phase diagram of the system was constructed at 296 K. The system was found to work in a more efficient and economic way when the surfactant is enriched with a cosolute, isoamyl alcohol in a ratio of 2:1. The addition of isoamyl alcohol results in a decrease in density of the surfactant phase, much below the density of a dilute solution of proline (0.1 mol·kg-1). This results in very low consumption of the amino acid for the design of the ABS. The tolerance of the ABS toward changes in pH and concentrations have been found to improve drastically in the presence of the cosolute. When sodium alginate is used as a complexing agent, the developed system shows a pH-dependent separation for the alkaline earth metal ions Mg2+, Ca2+, Sr2+, and Ba2+ from one another. Detection of these metal ions after their separations has been achieved with eriochrome black T (EBT; for Mg2+ at pH 9.5) and arsenazo III (for Ca2+, Sr2+, and Ba 2+ at pH 7.2) using absorption spectrometry. As different pH values are suitable for the complexation and extraction of different alkaline earths, it is possible to have a sequential separation of the individual elements from a mixture as and when required. © 2014 American Chemical Society.

L -proline based aqueous biphasic system: Design and application to isolate the alkaline earths

The present article reports on the speciation of As(v) and As(iii) using aqueous biphasic extraction based on a polyethylene glycol-salt system. For the detection of these inorganic arsenicals the salts of As(v) and As(iii) are converted to their respective arsenomolybdenum blues having the formulae [AsVMo4V Mo8VIO 40]7- and [AsIIIMo4V Mo8VIO40]9- and measured for their absorption spectra at 820 nm. These blue species are different in their extraction behaviour with the aqueous biphasic system. Once the blue solutions are formed they could further find application in the speciation of nitrite and nitrate in aqueous solution. A high molecular weight polymer, polyvinyl alcohol (PVA) was found to have a better efficiency to differentiate the nitrite and nitrate species. Kinetic studies show a proper decay rate of the As-blues with nitrite and no sensitivity for the nitrate species in PVA medium. This has been attributed to the structural property of PVA and its changes in the presence of the heteroplyacids. The results have been explained on the basis of changes in structural topology as revealed by the scanning electron microscope images. © The Royal Society of Chemistry 2013.

Competent arsenicals: Aqueous biphasic extractions and their application in nitrate/nitrite speciation

Fluorescence in poly(ethylene glycol) (PEGs 400-12000) solutions is reported here for the first time. PEG solutions form a vesicular organization with the hydrophilic groups attached at both ends which arrange themselves beyond a particular concentration and offer electron-dense regions at the center of the vesicle. These vesicles provide an inherent site for fluorescence generation in PEG solutions. Fluorescence emission was observed at ∼380 nm with an excitation wavelength of 300 nm. PEG of molecular weight 6000 was found to show maximum emission intensity at a particular concentration. The formation of PEG vesicles (∼1 nm size) was confirmed by dynamic light scattering (DLS) and confocal laser microscopy. On addition of metal ions the polymeric vesicle breaks up to monomeric PEG, and hence, the fluorescence intensity decreases with a red shift. Fluorescence lifetime measurements indicate the nature of complexation of the metals with PEG. Since PEGs are used as one of the phases in aqueous biphasic systems (ABS) of liquid-liquid extractions, the nature of the fluorescence emission spectrum of the PEG phase after extraction was studied. Metal extraction in the PEG-rich phase of an ABS leads to quenching of fluorescence in PEG. © 2012 American Chemical Society.

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ISSN	2046-2069