Herminio Sastre

Heavy metal removal in packed beds using apple wastes

Abstract Agricultural waste from apple-juice processing and cider production was used to remove heavy metal cations from solutions. This residual lignocellulosic biomass contains acidic groups with cation exchange properties which can be enhanced by means of chemical modification. The removal/ recovery of copper, zinc and nickel ions in packed beds was studied, the variables considered being the influence of chemical treatment, particle size and metal concentration in the solutions percolated. The apple waste showed most affinity for copper ions and the efficiency of the heavy metal removal was greatly increased after the apple waste had been treated with phosphorus (V) oxychloride. After exhaustion of the waste, the metals were eluted with hydrochloric acid, and after subsequent washing the waste was ready for re-use.

Catalytic hydrodechlorination of tetrachloroethylene over red mud.

Hydrodechlorination of tetrachloroethylene was investigated using red mud (RM, a by-product in the production of alumina by the Bayer process) as the catalyst. Use of RM as a hydrodechlorination catalyst is of interest from an industrial point of view because its cost is much lower than that of commercial catalysts. Hydrodechlorination reactions were carried out in a continuous fixed bed reactor. The influence of catalyst sulfiding, temperature (50-350 degrees C), pressure (2-10MPa), hydrogen flow rate and the presence of solvents (hexane, heptane, benzene and toluene) on the reaction was studied. Sulfided red mud is active as a hydrodechlorination catalyst, conversion of tetrachloroethylene increases as the pressure and temperature increase. The solvents did not influence the conversion, nor were side reactions involving the solvent observed. The kinetics of the reaction was studied at 350 degrees C and 10MPa, conditions for which mass transfer limitations were negligible. A good fit of a Langmuir-Hinselwood model to the experimental data was obtained.

Combustion of methane over palladium catalyst in the presence of inorganic compounds: inhibition and deactivation phenomena

Abstract The influence of the presence of different inorganic gases, often found in methane-containing industrial off-gases (NH3, NO2, H2, H2O, SO2, H2S, CO and CO2) on the catalytic combustion of methane over a Pd/Al2O3 catalyst is studied in the present work, in a range of concentrations corresponding to typical industrial emissions, such as those of coke oven facilities. Results show that the effect of SO2 and H2S on the catalyst is similar, both compounds causing partially irreversible poisoning, whereas water (present in the feed or formed by combustion of H2 or CH4) causes reversible inhibition in the absence of sulphur compounds. Nitrogen-containing compounds increase methane conversion in the absence of sulphur-containing compounds, but ammonia has the opposite effect when sulphur compounds are present. The other compounds studied do not affect appreciably the catalytic combustion of methane.

A new method for enhancing the performance of red mud as a hydrogenation catalyst

Abstract A new method is presented for improving the performance of red mud as a hydrogenation catalyst (a residue from the production of alumina by the Bayer process that contains iron oxides), based on the method developed by K.C. Pratt and V. Christoverson, Fuel 61 (1982) 460. The activation method consists essentially in dissolving red mud in a mixture of aqueous hydrochloric and phosphoric acids, boiling the resulting solution, adding aqueous ammonia until pH=8, and filtering, washing, drying and calcining the resulting precipitate. The catalyst thus obtained is characterised, and after sulphidation, tested (activity and life) for the hydrogenation of a light fraction of an anthracene oil. The catalytic performance is compared with that of sulphided untreated red mud and sulphided red mud activated by the method of Pratt and Christoverson. This activation method has proved to be more effective in improving the performance of red mud as a hydrogenation catalyst than the method of Pratt and Christoverson, since the activated catalyst presents a slightly higher level of activity and a markedly extended active life.

Kinetic study of the gas-phase hydrogenation of aromatic and aliphatic organochlorinated compounds using a Pd/Al2O3 catalyst

The hydrodechlorination of dichloromethane (DCM), tetrachloroethylene (TTCE), chlorobenzene (CBZ) and 1,2-dichlorobenzene (DCBZ), all of them alone and in mixtures, over a commercial Pd/Al(2)O(3) catalyst in a continuous packed-bed reactor was studied in the present work. Results indicate that the reaction kinetics for the single compounds are pseudo-first order kinetics. The reactivity of the compounds studied is very different. So, whereas aromatic compounds and tetrachloroethylene can be fully converted at the operation conditions reported in this work, dichloromethane conversions are lower than 30% in all the cases. The hydrodechlorination of mixtures of organochlorinated compounds shows important inhibition effects, these effects increase as the number of chlorine atoms in the molecule increase. Reaction kinetics for the hydrogenation of mixtures can be represented by a Langmuir-Hinshelwood model.

Anaerobic thermophilic treatment of cattle manure in UASB reactors

Cattle manure was characterised after filtration through a 1-mm sieve and subsequently treated in a 9-l volume Upflow Anaerobic Sludge Blanket (UASB) reactor made of transparent PVC at a thermophilic temperature (55°C). Different Hydraulic Retention Times (HRT)(22.5, 16, 10.6, 8.9 and 7.3 days) were employed and organic matter, total solids and metals were determined, as was the production of biogas. After screening, the COD of the manure subjected to anaerobic thermophilic treatment varied between values of 33,382 and 45,513 mgO2 l-1. The highest percentage of COD removal obtained was 79.7% for an HRT of 22.5 days and there was a fraction refractory to biodegradation of 11%, calculated using Chen & Hashimoto’s model. Finally, the results obtained at a thermophilic temperature were compared with those obtained at a mesophilic temperature (obtained in a previous work). The reduction in COD was slightly greater under mesophilic conditions, though the main advantage of thermophilic anaerobic treatment is the faster inactivation of viruses and bacteria.

Catalytic hydrogenation of anthracene oil with red mud

Abstract Red mud, and red mud activated by dissolution in hydrochloric acid and reprecipitation with ammonia, were tested as catalysts for the hydrogenation of an anthracene oil in a trickle-bed reactor. Conversion data were determined for the different polyaromatic compounds in the anthracene oil. Red mud shows appreciable catalytic activity, which is enhanced by the activation. Although both red mud and activated red mud are less active than a commercial Ni-Mo/γ-alumina hydrotreating catalyst, the difference in activity is smaller when conversion to hydroaromatics instead of total conversion of reactants is considered.

The influence of hydraulic residence time on the treatment of cattle manure in UASB reactors

Cattle manure from farms in the autonomous community of Asturias, Spain, was characterised and subsequently treated, after filtration through a 1 mm sieve, in upflow anaerobic sludge blanket laboratory reactors. The volume generated per cow and day varied between 50-55 litres (obtained through a survey of 400 farms), the manure being used on Asturian farms up until now as a fertiliser. After screening, the COD of the manure employed varied between 33,000 and 56,000 mgO2l-1. The highest percentage of COD removal obtained was 75.5% for a hydraulic residence time of 22.5 days. Gas production varied between values of 0.20-0.39 m3gas kg-1 COD removed, with a methane content of up to 64%. There was a fraction refractory to biodegradation of 11%.

Life cycle analysis of municipal solid waste management possibilities in Asturias, Spain

Directive 1994/62 concerning packaging and packaging waste and Directive 1999/31 related to waste disposal will substantially modify the management and treatment of Municipal Solid Waste (MSW) in Europe. In this study, a life cycle analysis has been carried out of the different possibilities of managing Municipal Solid Waste in Asturias. The “Integrated Waste Management” (IWM-1) model was employed, analysing the different alternatives for collection and treatment of MSW. This model predicts overall environmental burdens of MSW management systems and includes a parallel economical model. The sources of costs in the different systems of collection and treatment of MSW were considered in the economical analysis, as well as the sources of resource gathering that may be obtained via the sale of recovered materials. What emerges from this study is the soundness of management strategies based on biological treatment technologies in comparison with thermal treatments, together with the need to increase the level of collection at source.

Characterization and deactivation studies of an activated sulfided red mud used as hydrogenation catalyst

Abstract Red mud is a residue in the production of alumina by the Bayer process that contains oxides of Fe and Ti, active as hydrogenation catalyst in sulfided form, and whose catalytic activity can be improved by the activation method proposed by Pratt and Christoverson. The development of its activity and selectivity with reaction time was studied for the hydrogenation of a light fraction of an anthracene oil, and compared with untreated sulfided red mud. Catalyst samples were collected at different reaction times, and their texture, morphology and composition characterized by nitrogen adsorption, SEM and SEM–EDX. The loss of catalytic activity of activated sulfided red mud is slower than for untreated sulfided red mud. The main cause of this decrease in catalytic activity is the loss of surface area and superficial Fe.