Dissolution Kinetics of Sulfate from Schwertmannite Under Variable pH Conditions

Sulfate mobilization was investigated under controlled laboratory conditions. Microbially synthesized schwertmannite (14.7 m²/g specific surface area with 4.7 Fe:S molar ratio) was interacted at room temperature for 4 months with aqueous solutions between pH 5 and 8. More than 50% of the solid-phase sulfate was released during the initial 2 months and the rate was positively influenced by pH due to the competition of hydroxyl ions for SO₄ ²⁻. More than 90% of the solid-phase sulfate was released within 4 months at pH 8. Infrared spectra demonstrate diminution and splitting of SO₄ ²⁻ adsorption bands, indicating possible structural changes within the solid phase as a result of SO₄ ²⁻ release. Transformation of schwertmannite to goethite was triggered by pH increase and was primarily responsible for the sulfate mobilization. Thus, schwertmannite that interacts with neutral to alkaline water can add significantly to the sulfate load of a stream.     

L-menthol-based initiators for atom transfer radical polymerization of styrene

Two new atom transfer radical polymerization (ATRP) initiators, 2-isopropyl-5-methylcyclohexyl 2-bromopropanoate ( 1 ) and 2-Isopropyl-5-methylcyclohexyl 2-bromo-2-methylpropanoate ( 2 ), have been synthesized by the reaction of 2-bromopropanoyl bromide and 2-bromo-2-methylpropanoyl bromide, respectively, with L-menthol and characterized by ¹H and ¹³C NMR and FTIR spectroscopic studies. ATRP of styrene has successfully been carried out in a control manner using these initiators along with catalyst/ligand system consisting of Cu(I)Br/N,N,N ^/,N ^/,N ^//-pentamethyldiethylenetriamine. Polymerizations have yielded polystyrenes (PSts) of controlled molecular weight with low polydispersity index having a menthyl end group, as confirmed by ¹H NMR and gel permeation chromatography [GPC]. The controlled nature of the polymerization has also been confirmed by kinetic study of the polymerization process monitored via ¹H NMR and GPC. Initiator 2 has evolved as most efficient among the two. The obtained end-functional PSt has also been used as a macroinitiator for homochain extension with styrene and heterochain extension with methyl methacrylate to produce PSt-b-PMMA, showing the living nature of the polymerization process. In comparison with the PSt sample prepared using widely used initiator ethyl-2-bromo-isobutyrate with almost the same molecular weight and polydispersity, initiator 2 -made L-menthyl-capped PSt has shown higher light transmission properties of its dichloromethane solution at ~259 nm, higher thermal stability, lower glass transition temperature, a broad melting temperature, and higher surface roughness over its film. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47964.     

SEPARATION OF THE CARRIER FREE RADIOISOTOPES OF LANTHANIDE SERIES ELEMENTS

ABSTRACT

The various methods of separation of carrier free lanthanide elements have been briefly described.     

Production of no-carrier-added 97Ru from 11B-activated natural yttrium target and its subsequent separation using liquid–liquid extraction

Production of no-carrier-added (NCA) ⁹⁷Ru was investigated from the ¹¹B-induced reaction on the natural Y target. Bombardment of 40 MeV B-beam on the ^natY foil (2.8 mg/cm²) produced 17.4 kBq activity of ⁹⁷Ru in 7.5 h along with the minute production of ⁹⁶Tc and ^93mMo. Separation of NCA ⁹⁷Ru from the bulk was performed by liquid–liquid extraction (LLX). Liquid cation exchanger di-(2-ethylhexyl)phosphoric acid (HDEHP) dissolved in cyclohexane was used in combination with the aqueous solution of HNO₃. Optimum separation of NCA ⁹⁷Ru from the bulk Y was achieved at 1% HDEHP and 10^?5 M HNO₃ that led to a high separation factor of ~10⁵.     

Environmental Stability of Schwertmannite: A Review

Mine Water and the Environment - Schwertmannite is sensitive to changes in geochemical, thermal, and microbial conditions. Changes in aqueous pH beyond its stability, i.e. pH 2.5–4.5,...     

Membrane properties of sulfonated polytriazoles with molecular branching

The incorporation of branching units in the polymer is beneficial in improving many of the polymer properties. This article deals with the synthesis of branched sulfonic acid–based copolytriazoles (PTHPSH-XX) to prepare freestanding membranes. The copolymers were synthesized by the click reaction of 1,4-bis(prop-2-ynyloxy)benzene, 1,3,5 tris[2-trifluoromethyl-4(4-azidophenyl) phenoxy]benzene (B₃), and 4,4′-diazido-2,2′-stilbene disulfonic acid disodium salt. The chemical constructions of the subsequent copolymers were established by Fourier-transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. The copolymers showed high thermal stability, low water absorption, and outstanding structural robustness in their hydrated state. The presence of branching segments (B₃) in the copolymers contributed to improved peroxide radical resistance and proton conductivity (71–192 mS/cm measured at 90°C) in comparison with their linear analogs. In addition, the membranes exhibited reasonably good set of mechanical properties (TS = 71–53 MPa, YM = 2.76–2.33 GPa). The membranes exhibited phase-separated morphology in their transmission electron microscope images with ionic domains of 20–160 nm.     

Sulfonated co-poly(ether imide)s with alkyne groups: Fabrication of crosslinked membranes and studies on PEM properties including MFC performance

A new diamine monomer having alkyne side-groups (DADAF) has been successfully synthesized, and it was used to prepare a series of sulfonated co-polyimides (DFN-XX) when reacted with 1,4,5,8-naphthalenetetracarboxylic dianhydride along with different mole% of 4,4′-diaminostilbene-2,2′-disulfonic acid. The membrane was made from the copolymers by solution casting route, and one of the copolymers DFN-70 was used to prepare crosslinked membranes by adding a different amount of 1,6-hexanediazide during solution casting step. The morphological transformation from non-crosslinked S-coPI to crosslinked S-coPI was observed by employing transmission electron microscopy, atomic force microscopy, and small-angle X-ray scattering analyses. Compared to the non-crosslinked DFN-XX membranes, crosslinked DFN-70 copolymer membranes showed low water uptake and improved mechanical and peroxide radical stability. Also, crosslinked DFN-70 copolymer membranes showed significantly higher proton conductivities (0.004-0.06 S cm⁻¹) compared to those of DFN-70 (0.003-0.05 S cm⁻¹) particularly, at 80°C when the relative humidity increased from 40% to 98%. Furthermore, crosslinked DFN-70 copolymer membranes exhibited significantly enhanced performance in a microbial fuel cell (MFC) as compared to those of non-crosslinked DFN-70 membrane.     

Video retrieval using salient foreground region of motion vector based extracted keyframes and spatial pyramid matching

Multimedia Tools and Applications - Despite enormous research efforts devoted by the research community to effectively and precisely perform video matching and retrieval among heterogeneous videos...