Preliminary investigation of mixed adsorbents for the removal of copper and methylene blue from aqueous solutions

With most recent studies being focused on the development of
advanced chemical adsorbents, this paper investigates the possibility of
using two natural low-cost materials for selective adsorption. Multiadsorbent
systems containing tea waste and dolomite have been tested for
their effectiveness in the removal of copper and methylene blue from
aqueous solutions. The effects of contact time, solution pH and
adsorption isotherms on the sorption behaviour were investigated. The
Langmuir and Freundlich isotherms adequately described the adsorption of
copper ions and methylene blue by both materials in different systems.
The highest adsorption capacities for Cu and MB were calculated as 237.7
at pH 4.5 and 150.44 mg.g‒1 at pH 7 for DO and TW+DO respectively. Tea
waste (TW) and dolomite (DO) were characterized by Fourier transform
infrared spectroscopy, scanning electron microscopy and Energy dispersive
X-ray analysis. The removal of Cu and MB by dolomite was mainly via
surface complexation while physisorption was responsible for most of the
Cu and MB adsorption onto tea waste. Identifying the fundamental mechanisms and behaviour is key to the development of practical multi-adsorbent packed columns.

Electron-impact excitation of the astrophysically important singly ionized Fe-peak ions Sc and Ti

In this work we report on the evaluation of electron-impact collision strengths and Maxwellian averaged effective collision strengths for the lowly-ionized Fe-peak elements Sc II and Ti II using the parallel R-matrix package RMATRX II.

Electron-Impact Excitation of Fe-peak Ions for Astrophysical Applications

This paper discusses one of the major outstanding problems in atomic collision physics, namely the accurate theoretical treatment of electron scattering from open d-shell systems, and explores how this issue has been addressed over recent years with the development of the new parallel R-matrix suite of codes. It focuses on one code in particular - the new parallel R-matrix package PRMAT, which has recently been extended to account for relativistic fine-structure effects. This program facilitates the determination of accurate electron-impact excitation rates for complex open 3d-shell systems including the astrophysically important Fe-peak ions such as Ni II, Fe II and Fe III. Results are presented for collision strengths and Maxwellian averaged effective collision strengths for the optically forbidden fine-structure transitions of Ni II. To our knowledge this is the most extensive calculation completed to date for this ion.

Temperature and Pressure Induced Structural Changes of Cobalt (II) in a Phosphonium Based Ionic Liquid

In this paper the temperature and pressure induced paramagnetic switching of cobalt (II) complex in binary mixture of phosphonium based ionic liquid [P6,6,6,14]SCN and [Co(NCS)2], is reported. This arises from a structural change in the coordination of the cobalt (II) center from tetrahedral [Co(NCS)4]2- to octahedral [Co(NCS)6]4- when mobile thiocyanate ions are added. These properties are reflected in the abrupt change of conductivity behavior of the magnetic ionic liquid. Therefore, as demonstrated herein the reversible switching in coordination of cobalt from tetrahedral to octahedral can be easily monitored at ambient as well as elevated pressure by tracking the dc-conductivity changes.

DRIFT and DRUV spectroscopy methods for studying the interaction of metal compounds with native cellulose

Dissertação de mestrado, Qualidade em Análises, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015

Synthesis and structural characterization of new Piano-stool Ruthenium(II) complexes bearing 1-Butylimidazole heteroaromatic ligand

New cationic ruthenium(II) complexes with the formula [Ru(eta(5)-C5H5)(LL)(1-BuIm)] [Z], with (LL) = 2PPh(3) or DPPE, and Z = CF3SO3-, PF6-, BPh4-, have been synthesized and fully characterized. Spectroscopic and electrochemical studies revealed that the electronic properties of the coordinated 1-butylimidazole were clearly influenced by the nature of the phosphane coligands (LL) and also by the different counter ions. The solid state structures of the six complexes determined by X-ray crystallographic studies, confirmed the expected distorted three-legged piano stool structure. However the geometry of the 1-butylimidazole ligand was found considerably different in all six compounds, being governed by the stereochemistry of the mono and bidentate coligands (PPh3 or DPPE).

An experimental investigation of dechanneling in copper single crystals

This investigation comprises a comparison of experimental and theoretical dechanneling of MeV protons in copper single crystals. Dechanneling results when an ion's transverse energy increases to the value where the ion can undergo small impact parameter collisions with individual atoms. Depth dependent dechanneling rates were determined as functions of lattice temperature, ion beam energy and crystal axis orientation. Ion beam energies were IMeV and 2MeV,temperatures ranged from 35 K to 280 K and the experiment was carried out along both the (lOa) and <110) axes. Experimental data took the form of aligned and random Rutherford backscattered energy spectra. Dechanneling rates were extracted from these spectra using a single scattering theory that took explicit account of the different stopping powers experienced by channeled and dechanneled ions and also included a correction factor to take into account multiple scattering effects along the ion's trajectory. The assumption of statistical equilibrium and small angle scattering of the channeled ions allows a description of dechanneling in terms of the solution of a diffusion like equation which contains a so called diffusion function. The diffusion function is shown to be related to the increase in average transverse energy. Theoretical treatments of increase in average transverse energy due to collisions of projectiles with channel electrons and thermal perturbations in the lattice potential are reviewed. Using the diffusion equation and the electron density in the channel centre as a fitting parameter dechanneling rates are extracted. Excellent agreement between theory and experiment has been demonstrated. Electron densities determined in the fitting procedure appear to be realistic. The surface parameters show themselves to be good indicators of the quality of the crystal.

Fast atom bombardment mass spectrometry studies of ruthenium (II) polypyridy coordination complexes and of group V Triptycenes and related complexes

In order to investigate the use of Fast Atom Bombardment Mass Spectrometry (FAB-MS) as a tool for structural characterization, two groups of complexes are analyzed. The first group is a set of ruthenium(II) coordination complexes containing bidentate polypyridyl ligands. The positive and negative ion FAB-MS spectra are found to be sufficient to allow for an almost complete characterization of the central metal atom, the ligands and the counter anions contained in the intact complex. An unusual observation of mUltiply charged ions in the positive ion FAB-MS spectra (i.e. [RUL 3 ]2+) is explained to be as a result of the oxidative quenching of the excited state of the doubly charged ion by the matrix, 3-nitrobenzyl alcohol. An analysis of a mixture shows that the technique is a good one for identifying components therein. A group of triptycene and related complexes containing Group V elements is also analyzed by FAB-MS and the results. in terms of relative abundances of fragment ions, are found to be consistent with known metal-carbon bond strengths.

Investigations into the determinations of hydride-forming elements

Analytical methods for the determination of trace amounts of germanium, tin and arsenic were established using hydride generation coupled with direct current plasma atomic emission spectrometry. A continuous gas flowing batch system for the hydride generation was investigated and was applied to the determination of germanium(Ge), tin(Sn), antimony(Sb) and lead(Pb) (Preliminary results suggest that it is also applicable to arsenic)As) ). With this system, the reproducibility of signals was improved and the determination was speeded up, compared with the conventional batch type hydride generation system. Each determination was complete within one minute. Interferences from a number of transition metal ions, especially from Pd(II), Pt(IV), Ni(II), Cu(II), Co(II), and Fe(II, III), have proven to be very serious under normal conditions, in the determination of germanium, tin, and arsenic. These interference effects were eliminated or significantly reduced in the presence of L-cystine or L-cysteine. Thus, a 10-1000 fold excess of Ni(II), Cu(II), Co(II), Fe(II), Pt(IV), Pd(II), etc. can be tolerated without interference, In the presence of L-cystine or L-cysteine, compared with absence of interference reducing agent. The methods for the determination of Ge, Sn, and As were examined by the analyses of standard reference materials. Interference effects from the sample matrix, for example, in transition metal-rich samples, copper, iron and steel, were eliminated by L-cystine (for As and Sn) and by LI cysteine (for Ge). The analysis of a number of standard reference materials gave excellent results of As and Sn contents in agreement with the certified values, showing there was no systematic interference. The detection limits for both germanium and tin were 20 pg ml- I . Preliminary studies were carried out for the determination of antimony and lead. Antimony was found to react with NaBH4, remaInIng from the previous determinations, giving an analytical signal. A reversed injection manner, i.e., injection of the NaBH4 solution prior to the analyte solution was used to avoid uncertainty caused by residual NaBH4 present and to ensure that an excess of NaB H4 was available. A solution of 0.4% L-cysteine was found to reduce the interference from selected transition metal ions, Co(II), Cu(II), Ni(II) and Pt(IV). Hydrochloric acid - hydrogen peroxide, nitric acid - ammonium persulphate, and potassium dichromate malic acid reaction systems for lead hydride generation were compared. The potassium dichromate - malic acid reaction medium proved to be the best with respect to reproducibility and minimal interference. Cu(II), Ni(II), and Fe(II) caused strong interference In lead determinations, which was not reduced by L-cysteine or Lcystine. Sodium citrate, ascorbic acid, dithizone, thiosemicarbazide and penicillamine reduced interferences to some extent. Further interference reduction studies were carried out uSIng a number of amino acids, glycine, alanine, valine, leucine and histidine, as possible interference reducing agents in the determination of germanium. From glycine, alanine, valine to leucine, the interference reduction effect in germanium determinations decreased. Histidine II was found to be very promising In the reduction of interference. In fact, histidine proved more efficient than L-cystine and L-cysteine In the reduction of interference from Ni(II) in the determination of germanium. Signal enhancement by easily ionized elements (EIEs), usually regarded as an interference effect in analysis by DCP-AES, was studied and successfully applied to advantage in improving the sensitivity and detection limit in the determination of As, Ge, Sn, Sb, and Pb. The effect of alkali and alkaline-earth elements on the determination of the above five hydride forming elements was studied. With the appropriate EIE, a signal enhancement of 40-115% was achieved. Linear calibration and good reproducibility were also obtained in the presence of EIEs. III

High-Spin and Emissive Molecular Materials: Synthesis and Characterization of New Polynuclear Ni(II) Complexes from the Use of Aromatic Schiff Bases as Bridging Ligands

The employment of the bridging/chelating Schiff bases, N-salicylidene-4-methyl-o-aminophenol (samphH2) and N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2), in nickel cluster chemistry has afforded eight polynuclear Ni(II) complexes with new structural motifs, interesting magnetic and optical properties, and unexpected organic ligand transformations. In the present thesis, Chapter 1 deals with all the fundamental aspects of polynuclear metal complexes, molecular magnetism and optics, while research results are reported in Chapters 2 and 3. In the first project (Chapter 2), I investigated the coordination chemistry of the organic chelating/bridging ligand, N-salicylidene-4-methyl-o-aminophenol (samphH2). The general NiII/tBuCO2-/samphH2 reaction system afforded two new tetranuclear NiII clusters, namely [Ni4(samph)4(EtOH)4] (1) and [Ni4(samph)4(DMF)2] (2), with different structural motifs. Complex 1 possessed a cubane core while in complex 2 the four NiII ions were located at the four vertices of a defective dicubane. The nature of the organic solvent was found to be of pivotal importance, leading to compounds with the same nuclearity, but different structural topologies and magnetic properties. The second project, the results of which are summarized in Chapter 3, included the systematic study of a new optically-active Schiff base ligand, N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2), in NiII cluster chemistry. Various reactions between NiX2 (X- = inorganic anions) and nacbH2 were performed under basic conditions to yield six new polynuclear NiII complexes, namely (NHEt3)[Ni12(nacb)12(H2O)4](ClO4) (3), (NHEt3)2[Ni5(nacb)4(L)(LH)2(MeOH)] (4), [Ni5(OH)2(nacb)4(DMF)4] (5), [Ni5(OMe)Cl(nacb)4(MeOH)3(MeCN)] (6), (NHEt3)2[Ni6(OH)2(nacb)6(H2O)4] (7), and [Ni6(nacb)6(H2O)3(MeOH)6] (8). The nature of the solvent, the inorganic anion, X-, and the organic base were all found to be of critical importance, leading to products with different structural topologies and nuclearities (i.e., {Ni5}, {Ni6} and {Ni12}). Magnetic studies on all synthesized complexes revealed an overall ferromagnetic behavior for complexes 4 and 8, with the remaining complexes being dominated by antiferromagnetic exchange interactions. In order to assess the optical efficiency of the organic ligand when bound to the metal centers, photoluminescence studies were performed on all synthesized compounds. Complexes 4 and 5 show strong emission in the visible region of the electromagnetic spectrum. Finally, the ligand nacbH2 allowed for some unexpected organic transformations to occur; for instance, the pentanuclear compound 5 comprises both nacb2- groups and a new organic chelate, namely the anion of 5-chloro-2-[(3-hydroxy-4-oxo-1,4-dihydronaphthalen-1-yl)amino]benzoic acid. In the last section of this thesis, an attempt to compare the NiII cluster chemistry of the N-naphthalidene-2-amino-5-chlorobenzoic acid ligand with that of the structurally similar but less bulky, N-salicylidene-2-amino-5-chlorobenzoic acid (sacbH2), was made.

Decarboxylative Generation of Carbenes for the Synthesis of N-Heterocyclic Carbene Copper(I) Complexes - Applications in the Oxidative Coupling of 2-Naphthols

Le présent mémoire décrit la synthèse et l’utilité de complexes Cu-NHC. En premier lieu, la synthèse de complexes de cuivre porteurs de ligand(s) de type carbène-N-hétérocyclique (NHC) via une génération décarboxylative de carbènes sera présentée. En effet, de précédents rapports font état de l’utilisation de carboxylates d’imidazol(in)ium en tant que précurseurs carbéniques sous conditions thermolytiques. Ainsi, la présente étude montre l’utilisation de ces espèces zwitterioniques pour la synthèse de complexes de cuivre(I) mono- et bis-NHC comportant divers substituants et contre-ions. Une seconde partie du projet se concentrera sur l’évaluation de complexes Cu-NHC en tant que catalyseurs pour la synthèse de 2,2’-binaphtols via une réaction de couplage oxydatif de naphtols. L’objectif de ce projet de recherche est d’étudier les effets de variations structurales de différents complexes Cu-NHC afin de construire un processus catalytique plus efficace. Les effets de la structure du catalyseur sur la réaction de couplage ont été évalués en variant son contre-ion, le nombre de ligands NHC se coordonnant au cuivre, ainsi que la nature des substituants du ligand.

Novel M(II) beta-diketiminate complexes for the polymerization of lactide

Des ligands diketimines porteurs de substituants N-benzyl, N-9-anthrylmethyl et N-mesitylmethyl (nacnacBnH, nacnacAnH, and nacnacMesH) ont été synthétisés par condensation d’une amine et d’acétyl acétone ou son monoacétal d’éthylène glycol. La chlorination de la position 3 a été effectuée à l’aide de N-chlorosuccinimide conduisant à la formation des ligands ClnacnacBnH et ClnacnacAnH. Cette même position 3 a également été substituée par un groupement succinimide par lithiation du nacnacBnH, suivi de la réaction avec le N-chlorosuccinimide (3-succinimido-nacnacBnH). Les ligands N-aryl nacnacippH et nacnacNaphH (ipp = 2-isopropylphenyl, Naph = 1-naphthyl) ont été préparés selon les procédures reportées dans la littérature. La réaction de ces ligands avec Zn(TMSA)2 (TMSA = N(SiMe3)2) conduit à la formation des complexes nacnacAnZn(TMSA) et ClnacnacBnZn(TMSA). La protonation avec l’isopropanol permet l’obtention des complexes nacnacAnZnOiPr et ClnacnacBnZnOiPr. La réaction avec Mg(TMSA)2 permet quant à elle la formation des complexes nacnacAnMg(TMSA), nacnacMesMg(TMSA), ClnacnacBnMg(TMSA) et ClnacnacAnMg(TMSA). La protonation subséquente à l’aide du tert-butanol permet l’obtention du nacnacMesMgOtBu et du ClnacnacBnMgOtBu, alors que l’on observe uniquement une décomposition avec les ligands possédant des substituants N-anthrylmethyl. La réaction de ces diketimines avec Cu(OiPr)2 conduit aux dimères hétéroleptiques [nacnacBnCu(μ-OiPr)]2 et [3-Cl-nacnacBnCu(μ-OiPr)]2 lors de l’usage des ligands stériquement peu encombrés. Lors de l’utilisation de ligands plus encombrés, la stabilisation du complexe hétéroleptique par dimérisation n’est plus possible, conduisant, par un échange de ligand, à la formation des complexes homoleptiques Cu(nacnacipp)2 et Cu(nacnacNaph)2. Les complexes homoleptiques Cu(nacnacBn)2 et Cu(3-succinimido-nacnacBn)2 ont été obtenus à partir des ligands N-benzyl. Les ligands encore plus encombrés tels que nacnacAnH, nacnacMesH ou ceux comportant des substituants N-methylbenzyl ne présentent alors plus de réactivité avec le Cu(OiPr)2. La plupart des complexes ont été caractérisés par Diffraction des Rayons X. Les complexes homoleptiques ainsi que ceux de TMSA sont monomériques, alors que ceux formés à partir d’alkoxides se présentent sous forme de dimères à l’état solide. Tous les complexes d’alkoxides ainsi que les nacnacAnMg(TMSA)/BnOH et ClnacnacAnMg(TMSA)/BnOH présentent une réactivité modérée à haute en matière de polymérisation du rac-lactide (90% de conversion en 30 secondes à 3 heures). Le nacnacAnZnOiPr permet la synthèse d’un polymère hautement hétérotactique (Pr = 0.90) quand le ClnacnacBnMgOtBu/BnOH génère un polymère isotactique à -30°C (Pr = 0.43). Tous les autres catalyseurs produisent des polymères atactiques avec une légère tendance hétérotactique (Pr = 0.48 – 0.55). Les complexes hétéroleptiques [nacnacBnCu(μ-OiPr)]2 et [3-Cl-nacnacBnCu(μ-OiPr)]2 se révèlent être de très bons catalyseurs pour la polymérisation du rac-lactide présentant une conversion complète du monomère à température ambiante, en solution, en 0,5 à 5 minutes. Le [nacnacBnCu(μ-OiPr)]2 est actif en présence ou absence d’isopropanol, agissant comme agent de transfert de chaine à haute activité (k2 = 32 M–1•s–1) dans le dichlorométhane. Dans l’acétonitrile, le THF, le dichloromethane et le toluène, [nacnacBnCu(μ-OiPr)]2 conduit à une étroite polydispersité, possédant respectivement des kobs = 2.4(1), 5.3(5), 3.6-4.4 and 10(1) min–1. Aucune réaction parasite, telle qu’une trans-esterification, une épimerisation ou une décomposition du catalyseur, n’a été observée. Les complexes homoleptiques en présence d’alcool libre semblent présenter un équilibre avec une petite quantité de leurs équivalents hétéroleptiques, permettant une polymérisation complète, en moins de 60 min, à température ambiante. Tous les catalyseurs de cuivre présentent un haut contrôle de la polymérisation avec une polydispersité égale ou inférieure à 1.1. Les polymères obtenus sont essentiellement atactiques, avec une légère tendance à l’hétérotacticité à température ambiante et -17°C. Le [nacnacBnCu(μ-OiPr)]2 polymérise également la -butyrolactone (BL), l’-caprolactone (CL) et la -valerolactone (VL) avec des constantes respectivement égales à kobs = 3.0(1)•10–2, 1.2–2.7•10–2, et 0.11(1) min–1. Les homopolymères présentent une étroite polydispersité d’approximativement 1.1. Les polymérisations par addition séquentielle ont mis en évidence une trans-estérification (non observée dans les homopolymérisations) si BL ou CL sont introduits après un bloc lactide.

Fabrication Of Potentiometric Sensors For The Determination Of Certain Metal Ions

In this study Fabrication of Potentiometric sensors for the determination of certain metal ions, presents the synthesis and characterization of seven ionophores, their use in the fabrication of potentiometric sensors and the results and discussion of fourteen sensors developed for the determination of five transition metal ions. As part of the present investigations a total of fourteen potentiometric sensors have been developed and fabricated. A three fold approach has been taken in developing he sensors, PVC plasticized membrane sensor, carbon paste electrode and chemically modified carbon paste electrode. All the sensors are highly useful in the determination of metal ions such as manganese, nickel, copper, mercury and lead. A through analytical study has been carried out with respect to each other developed. Based on these studies, optimum conditions have been developed for the quantitative determinations of the selected metal ions using the sensors. Systematic application studies have also been carried out for all the developed sensors and the results revealed that the presently developed sensors are far superior than most of the sensors reported.

Preparation and characterisation of certain II-VI, I-III-VI2 semiconductor thin films and transparent conducting oxides

There is an increasing demand for renewable energies due to the limited availability of fossil and nuclear fuels and due to growing environmental problems. Photovoltaic (PV) energy conversion has the potential to contribute significantly to the electrical energy generation in the future. Currently, the cost for photovoltaic systems is one of the main obstacles preventing production and application on a large scale. The photovoltaic research is now focused on the development of materials that will allow mass production without compromising on the conversion efficiencies. Among important selection criteria of PV material and in particular for thin films, are a suitable band gap, high absorption coefficient and reproducible deposition processes capable of large-volume and low cost production. The chalcopyrite semiconductor thin films such as Copper indium selenide and Copper indium sulphide are the materials that are being intensively investigated for lowering the cost of solar cells. Conversion efficiencies of 19 % have been reported for laboratory scale solar cell based on CuInSe2 and its alloys. The main objective of this thesis work is to optimise the growth conditions of materials suitable for the fabrication of solar cell, employing cost effective techniques. A typical heterojunction thin film solar cell consists of an absorber layer, buffer layer and transparent conducting contacts. The most appropriate techniques have been used for depositing these different layers, viz; chemical bath deposition for the window layer, flash evaporation and two-stage process for the absorber layer, and RF magnetron sputtering for the transparent conducting layer. Low cost experimental setups were fabricated for selenisation and sulphurisation experiments, and the magnetron gun for the RF sputtering was indigenously fabricated. The films thus grown were characterised using different tools. A powder X-ray diffractometer was used to analyse the crystalline nature of the films. The energy dispersive X-ray analysis (EDX) and scanning electron microscopy i (SEM) were used for evaluating the composition and morphology of the films. Optical properties were investigated using the UV-Vis-NIR spectrophotometer by recording the transmission/absorption spectra. The electrical properties were studied using the two probe and four probe electrical measurements. Nature of conductivity of the films was determined by thermoprobe and thermopower measurements. The deposition conditions and the process parameters were optimised based on these characterisations.

Zeolite-encapsulated Co(II), Ni(II) and Cu(II) complexes as catalysts for partial oxidation of benzyl alcohol and ethylbenzene

Co(II), Ni(II) and Cu(II) complexes of dimethylglyoxime and N,N-ethylenebis(7-methylsalicylideneamine) have been synthesized in situ in Y zeolite by the reaction of ion-exchanged metal ions with the flexible ligand molecules that had diffused into the cavities. The hybrid materials obtained have been characterized by elemental analysis, SEM, XRD, surface area, pore volume, magnetic moment, FTIR, UV-Vis and EPR techniques. Analysis of data indicates the formation of complexes in the pores without affecting the zeolite framework structure, the absence of any extraneous species and the geometry of encapsulated complexes. The catalytic activities for hydrogen peroxide decomposition and oxidation of benzyl alcohol and ethylbenzene of zeolite complexes are reported. Zeolite Cu(II) complexes were found to be more active than the corresponding Co(II) and Ni(II) complexes for oxidation reactions. The catalytic properties of the complexes are influenced by their geometry and by the steric environment of the active sites. Zeolite complexes are stable enough to be reused and are suitable to be utilized as partial oxidation catalysts.