Gas-phase controlled mass transfer in a foam-bed reactor

Gas-phase controlled absorption of ammonia in foams made of solutions of sulphuric acid has been studied experimentally. Effects of gas-phase concentration of ammonia and type of surfactant on the performance of the foam-bed reactor are investigated. Gas-phase controlled absorption from a spherical bubble is anaylzed using the asymptotic value of Sherwood number (Sh = 6.58), for both negligible as well as significant changes in the volume of the bubble. The experimental data are shown to be in good agreement with the single-stage model of the foam-bed reactor using these asymptotic sub-models, as well as the diffusion-in-sphere analysis available in literature. Influence of effective diffusivity on the time dependence of fractional gas absorption has been found to be unimportant for foam columns with large times of contact. The asymptotic sub-models have been compared and use of the rigid-sphere asymptotic sub-model is recommended for foam columns of practical relevence.

Substrate integrated Lead-Carbon hybrid ultracapacitor with flooded, absorbent glass mat and silica-gel electrolyte configurations

Lead-Carbon hybrid ultracapacitors (Pb-C HUCs) with flooded, absorbent-glass-mat (AGM) and silica-gel sulphuric acid electrolyte configurations are developed and performance tested. Pb-C HUCs comprise substrate-integrated PbO2 (SI-PbO2) as positive electrodes and high surface-area carbon with graphite-sheet substrate as negative electrodes. The electrode and silica-gel electrolyte materials are characterized by XRD, XPS, SEM, TEM, Rheometry, BET surface area, and FTIR spectroscopy in conjunction with electrochemistry. Electrochemical performance of SI-PbO2 and carbon electrodes is studied using cyclic voltammetry with constant-current charge and discharge techniques by assembling symmetric electrical-double-layer capacitors and hybrid Pb-C HUCs with a dynamic Pb(porous)/PbSO4 reference electrode. The specific capacitance values for 2 V Pb-C HUCs are found to be 166 F/g, 102 F/g and 152 F/g with a faradaic efficiency of 98%, 92% and 88% for flooded, AGM and gel configurations, respectively.

The Freshwater Biological Association at Wray Castle: Recollections of its first director

In 1937 the Development Commission provided an annual grant to the Freshwater Biological Association to pay for a director and secretary. The author moved to the Lake District in the same year, and at that time T.T. Macan was working on invertebrates; K.R. Allen on fish; C.H. Mortimer on chemistry and physics of the aquatic environment, and Marie Rosenberg on phytoplankton. They were backed by George Thompson as laboratory assistant and Rosa Bullen as secretary. The work of the Association continued and expanded throughout the Second World War with some far-reached discoveries made. For example, the recovery of lake sediment cores and the examination of diatom remains, so starting the discipline of archaeo-limnology. Also, a hydrological survey of the Windermere catchment area found significant traces of sulphuric acid in rain gauges. This was more than 30 years before "acid rain" became fashionable.

South Lancashire Fisheries Advisory Committee 30th June, 1976.

This is the report from the South Lancashire Fisheries Advisory Committee meeting, which was held on the 30th June, 1976. The report contains sections on Mitton Fishery, fisheries activities, and the pollution of Trawden Water and Colne Water due to a spillage of sulphuric acid into Colne Water on 15th June, 1975. The section on fisheries activities includes Langcliffe Hatchery; fish monitoring stations; re-stocking by North West Water Authority; investigations into stocked brown trout and fish mortalities. The Fisheries Advisory Committee was part of the Regional Water Authorities, in this case the North West Water Authority. This preceded the Environment Agency which came into existence in 1996.

Recovery of Ce(IV) and Th(IV) from rare earths(III) with Cyanex 923

Solvent extraction of Ce(IV), Th(IV) with Cyanex 923 in n-hexane from sulphuric acid medium was studied with the dependence of the extraction on acidity and temperature being investigated. The Ce(IV) and Th(IV) extraction mechanism was proposed by slope analysis and the IR spectra of purified Cyanex 923 saturated with Ce(IV) were employed to determine the composition of the Ce(IV) complex. The equilibrium constant and thermodynamic functions of Th(IV) extraction were calculated and the characteristics of the stripping of Ce(IV), Th(IV) from the loaded organic phase were studied. (C) 1998 Elsevier Science B.V. All rights reserved.

Solvent extraction of scandium(III) by Cyanex 923 and Cyanex 925

The extraction equilibria of Sc(III), Zr(IV), Ti(IV), Th(IV), Fe(III) and Lu(III) from sulphuric or hydrochloric acid media by Cyanex 923 (mixture of straight chain alkylated phosphine oxides) and Cyanex 925 (mixture of branched chain alkylated phosphine oxides) were studied at various aqueous acidities. The extractant Cyanex 923 demonstrated better scandium loading and selectivity for TI(IV). Fe(III) and Lu(III) than Cyanex 925. The effects of extractant concentration on the extractions of sulphuric acid and Sc(III) by Cyanex 923 were examined. The stoichiometries of the extraction reactions were postulated based on slope analysis. The experimental results indicate that Cyanex 923 can be employed to recover scandium directly from the hydrolytic mother solution arising from TiO2 production via the sulphate process. The parameters studied were scandium loading capacity, phase ratio, concentrations of Ti(IV) scrubbing and Sc(III) stripping agents. A new solvent extraction technology of scandium recovery was developed. The purity of the final Sc(III) product is above 95% with a yield > 94%. (C) 1998 Elsevier Science B.V.

Corrosion inhibition of mild steel in acidic solution by some oxo-triazole derivatives

The oxo-triazole derivative (DTP) was synthesized and its inhibiting action on the corrosion of mild steel in sulphuric acid was investigated by means of weight loss, potentiodynamic polarization, EIS and SEM. The results revealed that DTP was an excellent inhibitor and the inhibition efficiencies obtained from weight loss experiment and electrochemical experiment were in good agreement. Potentiodynamic polarization studies clearly revealed that DTP acted essentially as the mixed-type inhibitor. Thermodynamic and kinetic parameters were obtained from weight loss of the different experimental temperatures, which suggested that at different temperatures (298-333 K) the adsorption of DTP on metal surface obeyed Langmuir adsorption isotherm model. (C) 2009 Elsevier Ltd. All rights reserved.

Effects of different seed pretreatments on germination of ten Calligonum species

In order to determine the optimum seed pre??sowing treatments and patterns of germination,a greenhouse experiment was conducted to study the effects of abrasion,sulphuric acid,boiling water,cold stratification and seed exudate treatments on the germination of ten Calligonum species.The results showed that the response of seed germination to the different pretreatments was similar for all ten Calligonum species.The abrasion,sulphuric acid and cold stratification treatments significantly promoted overall germinability.Compared with the control,the exudate treatment significantly decreased the percent germination,hampered the rate of germination and bolstered dormancy for almost all species.The cold stratification treatment can break the dormancy of viable Calligonum seeds and increased the germination,but it has a little lethal effect on viable seeds probably as well as the boiling water treatments.The germinaton patterns performed significant difference between the pre-sowing treatments for all ten Calligonum species,and the speed and percent germination of the Calligonum species can be greatly increased by mechanical scarification or sulphuric acid treatments.The results showed that seeds of C.junceum have strong ability of germinating.

The influence of alkali metal chlorides on the loss of water from glass-ionomer dental cements

The water loss behaviour of a clinical glass-ionomer dental cement has been studied with and without the addition of alkali metal chlorides. Dehydrating conditions were provided by placing specimens in a desiccator over concentrated sulphuric acid. Cements were prepared using either pure water or an aqueous solution of metal chloride (LiCl, NaCl, KCl) at 1.0 mol/dm(3). In addition, NaCl at 0.5 mol/dm(3) was also used to fabricate cements. Disc-shaped specimens of size 6 mm diameter x 2 mm thickness were made, six performulation, and cured at 37 degrees C for 1 hour They were then exposed to desiccating conditions, and the mass measured at regular intervals. All formulations were found to lose water in a diffusion process that equilibrated after approximately 3 weeks. Diffusion coefficients ranged from 2.27 (0.13) x 10(9) with no additive to 1.85 (0.07) x 10(9) m(2)/s with 1.0 mol/dm(3) KCl. For the salts, diffusion coefficients decreased in the order LiCl > NaCl > KCl. There was no statistically significant difference between the diffusion coefficients for 1.0 and 0.5 mol/dm(3) NaCl. For all salts at 1.0 mol/dm(3) and also additive-free cements, equilibrium losses were, with statistical limits, the same, ranging from 6.23 to 6.34%. On the other hand, 0.5 mol/dm(3) NaCl lost significantly more water 7.05%.

An investigation into the behaviour of concrete containing seawater-neutralised bauxite refinery residues in silage effluent

The farm production of silage as a winter-feed supplement is widespread. However, the bins in which silage is produced are subject to acidic and microbial attacks. Both these types of attack can lead to a weakening and failure of the concretes, especially on the outer lip of the open side of the silage pit. Consequently, the development of an acid-resistant concrete that can extend the life span of silage bins on farms could lead to considerable cost savings for farmers and, hence, can improve farm productivity. This paper reports on test results of an investigation into the behaviour of concrete containing seawater-neutralised bauxite refinery residues (Bauxsol™) exposed to sulphuric acid environments in the laboratory and to silage effluents. The concrete manufactured had a fixed water–cement ratio of 0.55 and natural sand was replaced with the Bauxsol™ at 0%, 5%, 10%, 15% and 20% by cement mass. Results indicated that the use of Bauxsol™ as a sand replacement material improved the behaviour of concrete both in sulphuric acid in the laboratory as well as in the silage effluent. Consequently, it is concluded that the Bauxsol™ can be used to replace 10% of natural sand to produce concrete that is resistant to silage effluents, providing an extended service life over conventional concretes used in silage pits.

Preparation and characterisation of cellulose nanofibres

Two different procedures were compared for the preparation of cellulose nanofibres from flax and microcrystalline cellulose (MCC). The first involved a combination of high energy ball milling, acid hydrolysis and ultrasound, whilst the second employed a high pressure homogenisation technique, with and without various pre-treatments of the fibrous feedstock. The geometry and microstructure of the cellulose nanofibres were observed by SEM and TEM and their particle size measured using image analysis and dynamic light scattering. Aspect ratios of nanofibres made by microfluidisation were orders of magnitude greater than those achieved by acid hydrolysis. FTIR, XRD and TGA were used to characterise changes to chemical functionality, cellulose crystallinity and thermal stability resulting from the approaches used for preparing the cellulose nanofibres. Hydrolysis using sulphuric acid gave rise to esterification of the cellulose nanofibres, a decrease in crystallinity with MCC, but an increase with flax, together with an overall reduction in thermal stability. Increased shear history of flax subjected to multiple passes through the microfluidiser, raised both cellulose nanofibril crystallinity and thermal stability, the latter being strongly influenced by acid, alkaline and, most markedly, silane pretreatment.

Biorefining of perennial ryegrass for the production of nano-fibrillated cellulose

This study has demonstrated biorefining steps for ryegrass and silage at a pilot scale to extrude fibre cake for the production of nanofibrillated cellulose (NFC), a potentially green biomaterial for replacing conventional fillers in the manufacture of polymer composites. Further treatments of processed ryegrass fibres with mechanical shearing, microfluidising, hydrochloric acid (HCl)/ sulphuric acid and a four stage {ethylenediaminetetra-acetic acid, sodium hydroxide, sodium hypochlorite and HCl} hydrolysis yielded 43.8, 36.1, 25.6 and 39.8 kg t21 DM of NFCs respectively. The NFCs were characterised using microscopy, X-ray diffraction, dynamic light scattering, spectroscopy and thermogravimetry. The NFC had diameters from 3.0–9.1 nm and length 308 nm– 4.6 mm. NFC-polyvinyl alcohol composites containing NFC (5 wt%) exhibited enhanced Young’s modulus and thermal stability by factors of 2.5 and 2 respectively compared with control. The mass, energy, water and chemical balances of the four process steps were assessed to evaluate technical feasibility and also to provide baseline production data for scaling up. The microfluidised product has been identified as the best NFC product, but production cost needs to be reduced.

In situ FTIR spectroscopic studies of the oxidation of CO adsorbates on Ru(0 0 0 1) electrodes under open circuit conditions

This paper reports the first observation, using in situ FTIR spectroscopy, of the oxidation of CO adsorbates on the Ru(0001) electrode to CO under open circuit (oc) conditions in both perchloric acid and sulphuric acid solution at 20 and 55 °C. While the significant oc oxidation of the adsorbed CO on the Ru(0001) electrode was observed in perchloric acid solution, much less oc oxidation took place in sulfuric acid solution due to the specific adsorption of bisulfate at the Ru surface which inhibits the surface oxidation and reduces the reactivity of the surface towards the oxidation of CO . The oc oxidation of the CO depends strongly on the oxygen concentration in the solution and the temperature. The data so obtained are compared to those observed at the gas|solid interface, as well as to those obtained from the electro-oxidation of CO , and possible new catalytic oxidation reaction mechanisms are discussed. In addition, it is shown that the C-O frequency of the adsorbed CO may be used as an effective probe of the open circuit potential. © 2003 Elsevier B.V. All rights reserved.

Assessment of hydrogen sulfide removal from biogas using a field scale anoxic biotrickling filter.

Hydrogen sulphide is one of the most toxic and corrosive compound present in swine-derived biogas streams.In this study, afield scale biotrickling filter for the removal of hydrogen sulfide was investigated.A Biofilter packed with supporting biofilm materials was fed continuously with a proprietary nutrient solution and operatedfor over 73days. The system has been operating with a H2S inlet concentrations ranging from 1,000to 3,000 ppm.Significant removal efficiencies >95% was demonstrated. pH of the stock feeding solution decreased from 6.2 to as low as 3.5within couple days.The resulting drop in pH provided circumstantial evidence to support biological H2 Soxidation to sulphuric acid by sulfide-oxidizers. Sulfur precipitation was also observed to occur. The results suggested that H2S removal from biogas stream can be efficiently achieved using portable, low cost and maintenance free biotrickling filters.

Toxicity of Effluent from a Titanium Dioxide Factory on some Marine Animals

Toxicity of effluent from a titanium dioxide factory containing sulphuric acid residue with soluble iron metallic salts and insoluble material such as silica, etc. on fishes, decapods and molluscs was studied. The effluent caused changes in pH and oxygen depletion of the sea water. Sublethal effects of the precipitate of ferrous salts were also studied. Dilutions of effluent up to 1:150 were LC100 for all organisms used while 1:200 dilution was LC50 for fishes at 36 hr and for other organisms at 48 hr. But death of organisms at this concentration was caused by pH changes and oxygen depletion and did not account for the effects of the precipitate. Below this level precipitation started soon after mixing with sea water causing death of organisms by choking their gills and siphons. Dilutions,< 1:1000 were 96 hr LCO.