Search results for "Exchange"

Intercalation of [M(ox)3]3− (M=Cr, Rh) complexes into NiIIFeIII-LDH

2010

Abstract Layered Double Hydroxides (LDH) containing paramagnetic NiII and FeIII ions in the hydroxide layers and chromium or rhodium oxalate complexes at the interlayer space were prepared by ion exchange from a NiFe-LDH precursor with sebacate anions between the hydroxide layers. The precursor was synthesized by coprecipitation at controlled pH in order to avoid the formation of solid phases different from LDH. Magnetic studies demonstrated that both LDHs, NiFe–Cr(ox)3 and NiFe–Rh(ox)3, exhibited a behaviour similar to the precursor. Nevertheless, the substitution of intercalated sebacate anions with oxalate complexes compresses the LDH basal spacing, increasing the intensity of dipolar in…

Study of the Interaction Mechanism in the Biosorption of Copper(II) Ions onto Posidonia oceanica and Peat

2012

A systematic approach was used to characterize the biosorption of copper(II) onto two biosorbents, Posidonia oceanica and peat, focusing on the interaction mechanisms, the copper(II) sorption–desorption process and the thermal behavior of the biosorbents. Sorption isotherms at pH 4–6 were obtained and the experimental data were fitted to the Langmuir model with a maximum uptake ( q max ) at pH 6 of 85.78 and 49.69mgg -1 , for P. oceanica and peat, respectively. A sequential desorption (SD) with water, Ca(NO 3 ) 2 , and EDTA was applied to copper-saturated biosorbents. Around 65–70% copper(II) were desorbed with EDTA, indicating that this heavy metal was strongly bound. The reversibility of …

Intercalation of cobalt(II)-tetraphenylporphine tetrasulfonate complex in magnetic NiFe-layered double hydroxide

2013

Abstract Hybrid magnetic multilayers have been synthesized by means of intercalation of [5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato]cobalt(II) (CoTPPS) complex in the interlayer space of a Ni II Fe III layered double hydroxide (LDH), through anion-exchange reaction. A sebacate ( − OOC–(CH 2 ) 8 –COO − ) intercalated NiFe-LDH have been used as precursor, facilitating the anion exchange reaction, thus permitting the inclusion of a paramagnetic macrocycle inside the ferrimagnetic NiFe-LDH layers. The material has been characterized by XRD, FT-IR, SEM, SQUID and ESR. The T c for the hybrid NiFe–CoTPPS, ca. 11–12 K, is very close to that shown by the precursor, despite that the intercala…

Mass spectrometric investigations of the kinetic stability of chromium and copper complexes with humic substances by isotope-labelling experiments

1999

Isotope-labelling exchange experiments were carried out to investigate the kinetic stability of Cr(III) complexes with humic substances (HS). To compare the results with those of an ion, not expected to form kinetically stable HS complexes with respect to its electron configuration, Cu(II) was investigated under the same conditions. HS solutions of different origin were therefore spiked with 53Cr(III) or 65Cu(II) after saturation of HS with chromium and copper of natural isotopic composition. In fractions of metal/HS complexes with different molecular weight, obtained by ultrafiltration and HPLC/ICP-MS using size exclusion chromatography (SEC), respectively, the isotope ratios of chromium a…

Assessment of the influence of counter ions on biosorption of copper cations in brewer's spent grain - Waste product generated during beer brewing pr…

2019

Abstract The influence that conditioning leached ground barley grain (known as “brewer's spent grain” (BSG)) has on the effectiveness of copper cation sorption was analysed. Saturation with counter ions of functional groups present on the grain surface was carried out in hydrochloric acid, sodium hydroxide, sodium and calcium chloride solutions. For comparison, BSG was also conditioned in demineralised water. Spent barley grain is a by-product of the brewing industry which can be used as a biosorbent in the removal of heavy metals from waste water. Emphasis is placed on the effect of competitive sorption of copper and hydrogen cations and the negative influence of a solution alkalinisation …

Gas-phase ion chemistry of protonated melatonin

2009

The gas-phase ion chemistry of protonated melatonin has been investigated by mass spectrometric (MS) techniques involving chemical ionisation, fast atom bombardment and electrospray ionisation. Either naturally-occurring or collision-induced decomposition experiments have been carried out using side chain tetra-deuterium-labelled derivatives, as well as the corresponding N–D derivatives obtained by exchange with D2O. The analysis of experimental results allows definite pathways for the formation of the ion at m/z 174 to be assigned and sheds some more light on the overall fragmentation pathways. Experiments on labelled derivatives evidenced H–D scrambling processes during fragmentation.

A bibliometric review of sukuk literature

2023

Abstract Sukuk (Islamic bonds) are one of the Islamic finance sectors that have experienced the fastest growth during the last decade. Using a quali-quantitative approach known as meta-literature review, the aim of this paper is to survey the sukuk literature over the period 1950–2018. In total we review and analyze 80 papers through bibliometric citation analysis (using HistCite and VOSviewer software) coupled with content analysis. We show the influential aspects of the literature, such as countries, institutions, journals, authors, articles and topics. We also present the co-authorship network and identify three research streams: (1) sukuk overview and growth, (2) sukuk and finance theor…

Isolation of organic material from water.

1985

International competitiveness, job creation and job destruction—An establishment-level study of German job flows

2010

Abstract This study investigates the impact of international competitiveness on net employment, job creation, job destruction, and gross job flows for a representative sample of German establishments from 1993 to 2005. We find a statistically significant but economically small effect of real exchange rate shocks on employment, comparable to the one found in studies for the United States. However, contrary to the United States, the employment adjustment (among surviving firms) operates mainly through the job creation rather than the job destruction rate. Job destruction occurs essentially through discrete events such as restructuring, outsourcing and bankruptcy. We suggest that these finding…

A Scholar in Action in Interwar America: John H. Williams on Trade Theory and Bretton Woods

2009

In this paper we analyse the scientific contributions of Harvard economist John H. Williams as international trade theorist and monetary reformer together with his activities as a Vice President of the Federal Reserve Bank of New York. In the first 2 Sections we first present a succinct overview of Williams’ main contributions to international trade theory and to the interwar debate on the reform of the international monetary system. Particular attention will be devoted to his early academic writings which contained different critical arguments against the two main tenets of classical international economics: the Ricardian theory of comparative advantages and the gold standard. These critic…