Malcolm Hobday

The use of low rank brown coal as an ion exchange material: 1. Basic parameters and the ion exchange mechanism

Abstract The cation exchange properties of three Victorian brown coals were investigated. Coal from the Yallourn North Extension (YNE) behaved differently from the Loy Yang (LY) and Yallourn (Y) coals. All coals showed increased cation exchange capacity (CEC) as solution pH was increased, but the YNE coal exhibited a CEC double that of the other coals for all cations except sodium. The solution pH for YNE coals was consistently two pH units above that for the other coals. These observations were explained in terms of the different sodium contents of the coals. A simple model is proposed to explain the pH dependence of coal ion exchange properties.

Free-radical involvement in the drying and oxidation of victorian brown coal

Abstract The technique of electron spin resonance spectroscopy has been used to study the changes in free-radical nature and content of brown coals as a result of vacuum drying the coal at various temperatures, and exposing the dried coal to either air at room temperature or oxygen at 105 °C. Free-radical concentrations increased during the vacuum-drying process and this is thought to be a result of organic functional group breakdown. Free-radical concentrations in dry coals following air or oxygen exposure have been found to vary with exposure time. The observations can be explained in terms of free-radical involvement in the oxidation process.

The use of low rank coal-based adsorbents for the removal of nitrophenol from aqueous solution

Abstract A range of Victorian brown coal based materials (Yallourn brown coal, grus, briquette char, power station char and an activated carbon) have been assessed as potential adsorbents for the removal of organics from aqueous wastes. The compound 4-nitrophenol has been used as the adsorbate. The influence of adsorbent dosage levels, particle size, and the presence of buffer solution components, other electrolytes, and pH on the kinetics of adsorption of nitrophenol have been investigated. For some adsorbents, pH changes in the acidic region appear to have little influence on adsorption rates of nitrophenol, but for chars, reduced pH conditions appear to reduce adsorption rates. In the alkaline pH range, leaching from some of the adsorbents occurs, with the extent of leaching reducing as the carbon content of the adsorbent increases. Adsorption capacities for Yallourn coal, grus, briquette char and power station char using nitrophenol in phosphate buffer have been measured. The technique of differential pulse polarography has been shown to be useful as a means of measuring nitrophenol adsorption in situ for concentrations up to 30 mg l −1 .

The use of low rank brown coal as an ion exchange material: 2. Ionic selectivity and factors affecting utilization

Victorian brown coals from Loy Yang, Yallourn and Yallourn North Extension open cut mines were studied. When these coals are used as ion exchange materials, their ionic selectivities follow the Irving-Williams order for metals from the first transition metal series i.e. Mn Zn. The cation exchange capacity (CEC) of the coal for a particular metal in a mixture of metals is lower than in a single metal solution, presumably due to the relative increase in ionic strength in the mixed metal situation. The solid:liquid ratio has also been shown to influence CEC, with maximum CEC occurring at low solid:liquid ratios. Temperature has a marginal influence on CEC, at least over the range 25–70 °C, whereas the presence of non-aqueous solvents can have a significant influence.

Novel copper materials based on the self-assembly of organophosphonic acids and bidentate amines

The hydrothermal synthesis and crystal structure of seven new supramolecular, heterocyclic adducts of copper organophosphonates are presented. Compounds 1–4, [CuX(D)2][C6H5P(O)(OH)2] [C6H5P(O)2(OH)], where D = 1,10-phenanthroline (phen) and X = Cl (1), Br (2), I (3), and NCS (4), are ionic in nature and possess a monoclinic structure, with the copper(II)-halide bond lying along a two-fold crystallographic axis. The crystals exhibit an alternating, lamellar structure in which 1-D ‘ribbons’ of [CuX(phen)2]+ cations are interleaved with 2-D ‘sheets’ of anionic [C6H5P(O)(OH)2][C6H5P(O)2(OH)]− dimers. The ribbons are associated through π–π bonding of the heterocyclic rings, and the acid sheets through a combination of π–π bonding of the aromatic rings, and hydrogen-bonding between the PO and P–OH of neighbouring acid dimers. Analogous derivatives have also been prepared by the reaction of [Cu(phen)2]Br with benzylphosphonic acid (5), [Cu(2,2′-bipy)2]I with phenylphosphonic acid (6) and [Cu(phen)2]I with phenylsulfonic acid (7). These complexes did not produce crystals suitable for single-crystal analysis. However, compounds (5) and (7) are thought to have similar structures to 1–4, whilst compound (6) has a different (2 : 2 : 3) ratio of copper : phosphonate : amine. Thus the supramolecular structure is robust for phenyl- and benzyl-phosphonic acids, with Cl, Br, I and NCS copper(II)phen complexes, and slightly varied by the presence of phenylsulfonic acid, but is not observed in the presence of 2,2′-bipy.

PRELIMINARY TOXICITY ASSESSMENT OF WATER AFTER TREATMENT WITH UV-IRRADIATION AND UVC/H2O2

Photooxidation (UV radiation) and enhanced photooxidation (UVC/H2O2) are water treatment technologies which remove aquatic natural organic matter (NOM) by photodegradation, producing lower molecular weight components and CO2. Since these technologies are being investigated for the treatment of drinking water, knowledge of the potential toxicity of the photooxidation by-products is vital. The potential toxicity of UVA-, UVB-, UVC-irradiated, and UVC/H2O2-treated aquatic NOM in two spot samples from two Australian reservoirs was analysed in two spot samples using Vibriofischeri in the Microtox test, African green monkey kidney cells (AS/NZS 4020:1999), and Daphnia carinata in an acute immobilisation test. Toxicity was not apparent for both the Microtox procedure and cytotoxicity analyses for the UVC-irradiated and UVC/H2O2-treated NOM samples, while UVA- and UVB-irradiated water samples were non-toxic to D. carinata. In contrast, acute toxicity was observed for UVC- and UVC/H2O2-treated water samples. The observed toxicity was attributed to photooxidative degradation of NOM-metal binding sites, which resulted in the release of bioavailable copper ions, as evidenced by higher concentrations of free copper ions in photooxidised water. As the total copper concentrations of the two raw water samples were well below the Australian Water Quality Guidelines for metals in domestic supplies, the release of copper from photooxidised NOM is unlikely to cause health concerns in these samples.

Free radical involvement in the oxidation of Victorian brown coal

Abstract Electron spin resonance spectroscopy has been used to investigate free radical involvement in the oxidation of Victorian brown coal. Fresh, wet Yallourn brown coal exhibits two superimposed e.s.r. signals due to organic free radicals. The free radicals responsible for the narrow signal interact reversibly with atmospheric oxygen while the broad signal changes intensity dramatically during prolonged exposure to air. Coal:oxygen complex formation may explain these observations. Results also suggest that the free radical content of brown coal increases as a consequence of vacuum drying.

Supramolecular bidentate amine derivatives of copper(ii) organophosphonatesElectronic Supplementary Information (ESI) available: 3D images for compound 1 and compound 2. See http://www.rsc.org/suppdata/ce/b4/b400064a/

Four novel complexes of copper(II) with organophosphonic acids and bidentate amines: [CuDn((OH)O2PR)][(OH)O2PR)]·(H2O)x, where D = 1,10-phenanthroline (C12H8N2 or phen) or 2,2′-bipyridyl (C10H8N2 or 2,2′-bipy), n = 1 or 2, R = C6H5 or CH2C6H5, and x = 0, 1, 4 or 7, have been synthesised by hydrothermal reactions at 160 °C. A combination of structural studies and various analytical techniques indicate that for species where D = phen and R = C6H5 (1), and where D = phen and R = CH2C6H5 (2), the compounds are crystalline ionic materials possessing triclinic and monoclinic structures, respectively. The crystal structures of (1) and (2) are supramolecular and contain ribbons of [Cu(phen)2((OH)O2PR)]+ cations, interleaved between H-bonded sheets of organophosphonate anions and water molecules. The data compiled for the 2,2′-bipy derivatives (3–4) are somewhat different from the phen species, indicating there is only one amine ligand for each copper atom. Powder XRD, FTIR, TGA, UV-Vis, and XPS data consistent with the formulations are presented.

E.p.r. study of organic free radicals in Victorian brown coal

The signals at g≈2 in the e.p.r. spectra of Victorian brown coals are attributed to organic free radicals. Mathematical lineshape analysis and variation of linewidth with frequency suggested that the observed signals at low power levels are mainly homogeneously broadened. Power saturation experiments, however, resolved the signals to show the presence of from one to three resonances due to different free radical types.

A pseudo first order rate model for the adsorption of an organic adsorbate in aqueous solution

Five low rank, coal-based adsorbents, i.e. coal, grus, two chars, and an activated carbon were used to adsorb a low molecular weight organic compound from aqueous solution. The rates of adsorption were found to conform to pseudo first order kinetics with good correlation (r2 greater than 0.996). This kinetic model was used to calculate pseudo first order rate constants (k1′ min −1) and relative rate constants (rate constant/unit mass of adsorbent, k1″ min−1 g−1) for the adsorption process. Rate properties have been explained in terms of both a diffusion and chemically controlled rate determining step. Rate constants for the five adsorbents vary as expected on the basis of their physical properties, that is slowest for grus (compressed coal) and fastest for the activated carbon. © 1999 Society of Chemical Industry