Electrochemical pre-treatment of effluents containing chlorinated compounds using an adsorbent

Electrochemical pre-treatment of industrial wastewater to remove refractory and/or toxic organic components, making them more amenable to biological treatment, is likely to be more cost-effective than using a physical or chemical process for complete organic removal. This paper demonstrates the use of a carbon-based adsorbent material that preferentially removes chlorinated organic compounds. Electrochemical regeneration of the adsorbent is shown to be a quick, easy and cheap process, because the adsorbent is both highly electrically conducting and non-porous. High regeneration rates over a number of cycles were obtained by passing a charge of 25 C g⁻¹ through a bed of adsorbent particles, at a current density of 20 mA cm⁻² for 10 min. The energy required to remove a kg of COD from an industrial wastewater was calculated to be 27 kWh.     

SOLUBILITY OF CO2 AND H2S IN A HINDERED AMINE SOLUTION

The solubility of H₂S and CO₂ in aqueous solutions of the sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP), was determined at 40 and 100°C. Partial pressures of C)₂ ranged from approximately 2 to 6000 kPa and of H₂S from 2 to 2200 kPa. The solubility results were compared with previously reported acid gas solubilities in aqueous monoethanolamine (MEA) solutions.     

The selectivity of porous catalysts: parallel reactions

The influence of intraparticle mass diffusion on the overall and relative rates of the parallel reactions A → B and A → C is examined for the case of an isothermal catalyst particle with no external concentration or temperature gradients. Calculations for three pairs of reaction orders: (0,1), (0,2) and (1,2), show that internal concentration gradients can cause the yield of the product formed in the higher-order reaction to decrease by as much as 80 percent. Extension of the analysis to other reaction orders is discussed. Criteria for close approach to various asymptotic limits are presented, together with an asymptotic expression which allows the maximum effect of pore diffusion on selectivity to be estimated for any pair of reaction orders.     

Chemical reactivity of CO and CO2 at a Cu(110)-Cs surface

Carbon dioxide and carbon monoxide undergo reactive chemisorption with cesium modified Cu(110) and Cu(110)-O surfaces and via the anionic intermediate CO ₂ ^– (a) form a surface carbonate. The CO ₂ ^– (a) species was characterised by VEELS and XPS at low temperature (80 K) and the surface carbonate at 295 K. For cesium modified Cu(110) surfaces chemisorption of carbon monoxide gives rise to electron energy loss peaks (v _co) as low as 1450 cm^–1 at 295 K.     

Assessing the reliability of ordered categorical scales using kappa-type statistics

Methods for the analysis of reliability of ordered categorical scales are discussed, focussing on the limitation of the single summary-weighted kappa coefficients. A symmetric matrix of kappa-type coefficients is suggested as an alternative. The method is proposed as being suitable for ordinal scale where there is no underlying continuum. Their application is illustrated using two data sets from reliability studies. If, instead, distances between categories can be specified, a weighted mean of the matrix terms can be used as a summary measure. This is equal to a weighted kappa coefficient with squared weights, provided distances between adjacent categories are equal. When a study design corresponds to a one-way random effects model, estimates of precision of kappa-type coefficient, including the coefficients described here, can be obtained using the delta-method, bootstrap resampling by subjects or jack-knifing by subjects. In the case of interobserver reliability studies, where there may be systematic differences between observers, the investigator may wish to generalise to a population of observers and subjects. In this case, jack-knifing by observer and subject is suggested. Empirical comparisons are made between standard error estimates based on the delta-method, on jack-knifing by subjects and a two-way jack-knife by subjects and observers. The results suggest that standard errors based on the delta-method or jack-knifing by subject alone may be overly precise.     

A dislocation model for the two critical stress intensities required for threshold fatigue crack propagation

We have examined the variations, with decreasing load ratio, of threshold peak and cyclic stress intensities required for fatigue crack growth in stage I (mainly mode II loading) using a simple model simulating dislocation motion near a crack tip. In this model the crack grows by dislocations running into the crack during loading and unloading phases. Initially we have studied the behaviour of a crack with a dislocation source relatively far away from the crack tip. Crack propagation rates showed a Paris regime at high ΔK, and an abrupt threshold value ΔK_th below which no crack growth occurred. The variation with load ratio of the peak (K_th) and cyclic (ΔK_th) stress intensities at the fatigue threshold showed that two different processes controlled the behaviour. At high load ratios dislocations are generated readily during loading and the threshold is controlled by the need for sufficient unloading to allow dislocations to run back into the crack, so that the criterion ΔK ≥ ΔK∗ results. At negative load ratios it is the generation of dislocations during the loading phase that controls the threshold condition, since once generated, the large unloading and reversed loading easily forces dislocations back to the crack. Under these conditions the threshold criterion becomes K_max ≥ K∗.     

Chromium distribution between liquid iron and molten basic slags

An equilibrium study was made of the distribution of chromium and oxygen between liquid iron, containing less than 1 pct Cr, and simple slags of the CaO(MgO)-SiO₂-FeO-Cr₂O₃ type in the temperature range 1526° to 1734°C The effects of slag oxidation, temperature, and basicity were observed.     

Optics clustered to output unique solutions: a multi-laser facility for combined single molecule and ensemble microscopy

Optics clustered to output unique solutions (OCTOPUS) is a microscopy platform that combines single molecule and ensemble imaging methodologies. A novel aspect of OCTOPUS is its laser excitation system, which consists of a central core of interlocked continuous wave and pulsed laser sources, launched into optical fibres and linked via laser combiners. Fibres are plugged into wall-mounted patch panels that reach microscopy end-stations in adjacent rooms. This allows multiple tailor-made combinations of laser colours and time characteristics to be shared by different end-stations minimising the need for laser duplications. This setup brings significant benefits in terms of cost effectiveness, ease of operation, and user safety. The modular nature of OCTOPUS also facilitates the addition of new techniques as required, allowing the use of existing lasers in new microscopes while retaining the ability to run the established parts of the facility. To date, techniques interlinked are multi-photon/multicolour confocal fluorescence lifetime imaging for several modalities of fluorescence resonance energy transfer (FRET) and time-resolved anisotropy, total internal reflection fluorescence, single molecule imaging of single pair FRET, single molecule fluorescence polarisation, particle tracking, and optical tweezers. Here, we use a well-studied system, the epidermal growth factor receptor network, to illustrate how OCTOPUS can aid in the investigation of complex biological phenomena.     

Understanding urban residential end uses of water

The 'end use' of water is a breakdown of the total household water usage such as water used for toilets, showers, washing machines, taps, lawn watering, etc. Understanding end uses of water will enable water planners, water authorities and household owners determine where water is used/wasted, how much and how often. This paper describes the end uses of water from a number of single-family homes in Greater Melbourne, Australia. The study involves the analysis of water consumption data recorded at 5-s intervals from logged households collected by Yarra Valley Water in Melbourne in 2004. The study determines how much water is used for outdoor and indoor purposes in a single-family home in Melbourne and compares the water usage during winter and summer. Hourly patterns of major end uses of water are also developed. The aim of this study is to improve the understanding of the end uses of water and to assist where to focus water conservation efforts that would be most effective financially and environmentally, and be acceptable to everyone.     

Using multiple endmember spectral mixture analysis to retrieve subpixel fire properties from MODIS

The Moderate-Resolution Imaging Spectroradiometer (MODIS) sensors on NASA's Terra and Aqua satellites image most of the Earth multiple times each day, providing useful data on fires that cannot be practically acquired using other means. Unfortunately, current fire products from MODIS and other sensors leave large uncertainties in measurements of fire sizes and temperatures, which strongly influence how fires spread, the amount and chemistry of their gas and aerosol emissions, and their impacts on ecosystems. In this study, we use multiple endmember spectral mixture analysis (MESMA) to retrieve subpixel fire sizes and temperatures from MODIS, possibly overcoming some limitations of existing methods for characterizing fire intensities such as estimating the fire radiative power (FRP). MESMA is evaluated using data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) to assess the performance of FRP and MESMA retrievals of fire properties from a simultaneously acquired MODIS image, for a complex of fires in Ukraine from August 21, 2002. The MESMA retrievals of fire size described in this paper show a slightly stronger correlation than FRP does to fire pixel counts from the coincident ASTER image. Prior to this work, few studies, if any, had used MESMA for retrieving fire properties from a broad-band sensor like MODIS, or compared MESMA to higher-resolution fire data or other measures of fire properties like FRP. In the future, MESMA retrievals could be useful for fire spread modeling and forecasting, reducing hazards that fires pose to property and health, and enhancing scientific understanding of fires and their effects on ecosystems and atmospheric composition.