Browsing by Author "Amal, R"

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    Characterisation of dense gypsum slude from waste acid
    (Institution of Chemical Engineers in Australia, 2001-09-23) Halim, CE; Bickert, G; Amal, R
    The treatment of acid waste liquors is often carried out in a conventional neutralisation circuit using lime as reagent. The High Density Sludge (HDS) process improves this technology by recycling conditioned thickener underflow to modify the precipitate particle formation, leading to an increase in the density of the settled solids. The treatment of sulphuric acid was examined using conventional lime treatment and the HDS process, in both batch and continuous mode. The HDS process produced sludge of significantly higher density than the conventional process. Particle size analysis of the solids indicated some variation between conventional and HDS solids. Particle chord length distribution and SEM examination indicated no change in particle shape. Both precipitates exhibited a flat leaf type shape. There was little difference between the conventional and HDS solids from XRD analysis, which indicated a gypsum (CaSO4.2H2O) crystal form. The results suggest that for gypsum, the HDS process alters the particle structure by removing free water molecules, giving a more compact sludge of higher density. This seems to be partially achieved by shearing of the gypsum particles in the conditioning tank, causing compaction of the gypsum sludge. © The Authors.
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    Expanding the applications of the ilmenite mineral to the preparation of nanostructures: TiO2 nanorods and their photocatalytic properties in the degradation of oxalic acid
    (Wiley-Blackwell, 2013-01-14) Tao, T; Chen, Y; Zhou, D; Zhang, HZ; Liu, S; Amal, R; Sharma, N; Glushenkov, AM
    The mineral ilmenite is one of the most abundant ores in the Earth's crust and it is the main source for the industrial production of bulk titanium oxide. At the same time, methods to convert ilmenite into nanostructures of TiO2 (which are required for new advanced applications, such as solar cells, batteries, and photocatalysts) have not been explored to any significant extent. Herein, we describe a simple and effective method for the preparation of rutile TiO2 nanorods from ball-milled ilmenite. These nanorods have small dimensions (width: 520 nm, length: 50100 nm, thickness: 25 nm) and possess large specific surface areas (up to 97 m2?g-1). Dissolution/hydrolysis/precipitation is proposed as a growth mechanism. The nanorods were found to have attractive photocatalytic properties in the degradation of oxalic acid. Their photocatalytic activity is close to that of the benchmark Degussa P25 material and better than that of a commercial high-surface-area rutile powder. © 2013, Wiley-Blackwell
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    Experimental validation of proton transverse relaxivity models for superparamagnetic nanoparticle MRI contrast agents.
    (Institute of Physics, 2010-01-22) Carroll, MRJ; Woodward, RC; House, MJ; Teoh, WY; Amal, R; Hanley, TL; St Pierre, TG
    Analytical models of proton transverse relaxation rate enhancement by magnetic nanoparticles were tested by making measurements on model experimental systems in a field of 1.4 T. Proton relaxivities were measured for five aqueous suspensions of iron oxide (maghemite) nanoparticles with nominal mean particle sizes of 6, 8, 10, 11, and 13 nm. Proton relaxivity increased with mean particle size ranging from 13 s(-1) mM Fe-1 for the 6 nm sample, up to 254 s(-1) mM Fe-1 for the 13 nm sample. A strong correlation between the measured and predicted values of the relaxivity was observed, with the predicted values being consistently higher than the measured values. The results indicate that the models give a reasonable agreement with experimental results and hence can be used as the basis for the design of new magnetic resonance imaging contrast and labelling agents. © 2010, Institute of Physics
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    Reconstructing Cu nanoparticle supported on vertical graphene surfaces via electrochemical treatment to tune the selectivity of CO2 reduction toward valuable products
    (ACS Publications, 2022-04-07) Ma, ZP; Tsounis, C; Toe, CY; Kumar, PV; Subhash, B; Xi, SB; Yang, HY; Zhou, SJ; Lin, ZH; Wu, KH; Wong, RJ; Thomsen, L; Bedford, NM; Ng, YH; Han, ZJ; Amal, R
    Reconstructing a catalyst with tunable properties is essential for achieving selective electrochemical CO2 reduction reaction (CO2RR). Here, a reduction–oxidation–reduction (ROR) electrochemical treatment is devised to advisedly reconstruct copper nanoparticles on vertical graphene. Undercoordinated sites and oxygen vacancies constructed on the Cu active sites during the ROR treatment enhance the CO2RR activity. Moreover, by varying the oxidation potential while maintaining the reduction potential during the ROR treatment, CO2RR selectivity can be tuned between *COOH- and *OCHO-derived products. Specifically, rich grain boundaries are formed on the ROR catalyst with a high oxidation potential (+1.2 VRHE), favoring the *COOH/*OCCO adsorption and leading C–C coupling to *COOH-derived products, while the catalyst undergoing ROR at a low oxidation potential (+0.8 VRHE) lacks grain boundaries, resulting in highly selective formate (*OCHO-derived) production. Our findings are evidenced by combined in situ and ex situ characterizations and theoretical calculations. © 2022 American Chemical Society
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    Removal of water impurities by hydrous oxides
    (Institution of Engineers, Australia, Institution of Chemical Engineers & Royal Australian Chemical Institute, 1991-09-19) Amal, R; Raper, JA; Waite, TD
    In this study, the effects of adsorbed fulvic acid, a naturally occurring organic acid, on the kinetics of hematite aggregation and on the resulting structure of hematite aggregates are investigated. A model based on colloid stability theory which also accounts for the structure of the aggregates formed is used to describe the aggregation kinetics of these adsorbed particles. The study of aggregate structure shows that the fractal dimensions of hematite aggregates which are partially acid molecules are higher than those obtained with no adsorbed fulvic acid The scattering exponents obtained from static light scattering experiments of these aggregates range from 2.83 +- to 3.42 +- 0.1.