Luis F. Vilches

Use of FGD gypsum in fire resistant panels

Gypsum from power plant flue gas desulphurization units (FGD gypsum) is a combustion by-product produced in high quantities. In this paper, gypsum panels composed of 100% FGD gypsum from two power plants have been subjected to different physico-chemical (density, pH, humidity), mechanical (flexural and compressive strength, surface hardness, impact resistance), fire resistance and environmental tests (leaching and radioactivity). The results obtained have been compared with the requirements established in some European standards for commercial gypsum and other standards for similar products. In addition, the panels manufactured have been compared with commercial gypsum panels in order to determine the recycling possibilities of this kind of material in this application.

Recycling potential of coal fly ash and titanium waste as new fireproof products

This paper studies the possibilities for joint recycling of fly ash (FA) from the combustion of coal in power plants and the waste of the first attack on ilmenite in the production of titanium dioxide (RTi). Studies have been made of the insulating properties of plates composed mainly of FA, together with RTi waste, subjecting them to thermal exposure using standardized fire-resistance tests, with a view to potential use as insulating and fireproof components of fire-resistant items such as fireproof doors and firewalls. Other physical and chemical properties of these products have also been determined in order to characterize their mechanical properties. In addition, given the nature of the raw materials used in the manufacture of the product, an environmental study has been carried out to assess their environmental impact and to compile an ecotoxicological report on the material prepared.

Use of co-combustion bottom ash to design an acoustic absorbing material for highway noise barriers

The present study aims to determine and evaluate the applicability of a new product consisting of coal bottom ash mixed with Portland cement in the application of highway noise barriers. In order to effectively recycle the bottom ash, the influence of the grain particle size of bottom ash, the thickness of the panel and the combination of different layers with various particle sizes have been studied, as well as some environmental properties including leachability (EN-12457-4, NEN-7345) and radioactivity tests. Based on the obtained results, the acoustic properties of the final composite material were similar or even better than those found in porous concrete used for the same application. According to this study, the material produced presented no environmental risk.

Ammonium Ion Adsorption and Settleability Improvement Achieved in a Synthetic Zeolite-Amended Activated Sludge

Abstract Municipal wastewater treatment plants typically exhibit two classic problems: high ammonium concentration in water after conventional biological treatment and, in some cases, poor activated sludge sediment ability. Potential solutions to these problems were investigated by adding a synthetic zeolite obtained from coal fly ash to different steps of activated sludge treatment. The experimental results for ammonium removal fit well with the theoretical adsorption isotherms of the Freundlich model with a maximum adsorption capacity of 13.72 mg·g −1 . Utilization of this kind of zeolite to improve activated sludge sediment ability is studied for the first time in this work. It is found that the addition of the zeolite (1 g·L −1 ) to an activated sludge with settling problems significantly enhances its sediment ability and compact ability. This is confirmed by the sludge volume index (SVI), which was reduced from 163 ml·g −1 to 70 ml·g −1 , the V 60 value, which was reduced from 894 ml·L −1 to 427 ml·L −1 , and the zeta potential (ζ), which was reduced from −19.81 mV to −14.29 mV. The results indicate that the addition of this synthetic zeolite to activated sludge, as an additional waste management practice, has a positive impact on both ammonium removal and sludge settleability.

Solar photocatalytic treatment of landfill leachate using a solid mineral by-product as a catalyst

The treatment of municipal solid waste landfill leachate in a pilot plant made up of solar compound parabolic collectors, using a solid industrial titanium by-product (WTiO(2)) containing TiO(2) and Fe(III) as a photocatalyst, was investigated. In the study evidence was found showing that the degradation performed with WTiO(2) was mainly due to the Fe provided by this by-product, instead of TiO(2). However, although TiO(2) had very little effect by itself, a synergistic effect was observed between Fe and TiO(2). The application of WTiO(2), which produced coupled photo-Fenton and heterogeneous catalysis reactions, achieved a surprisingly high depuration level (86% of COD removal), higher than that reached by photo-Fenton using commercial FeSO(4) (43%) in the same conditions. After the oxidation process the biodegradability and toxicity of the landfill leachate were studied. The results showed that the leachate biodegradability was substantially increased, at least in the first stages of the process, and again that WTiO(2) was more efficient than FeSO(4) in terms of increasing biodegradability.

Application Of Synthetic Zeolites To The Depuration Of A Waste Landfill Leachate

In this paper the application of synthetic zeolites to the decontamination of a highly contaminated municipal waste landfill leachate has been studied. Thus, the reduction of organic matter (COD), total KjeMhal nitrogen (TKN), suspended solids and metals contents in the diluted leachate were measured after two different treatments. One of them consisted in a two-stage process: a physiochemical coagulation-flocculation treatment combined with the zeolite treatment. Two synthetic zeolites have been tested: a commercial zeolite and one obtained after a coal fly ash alkaline hydrothermal process (CV-Z). The results showed that the physico-chemical treatment using aluminium sulphate and an organic flocculent yielded an important reduction in the leachate COD, not improved by the zeolite treatment, Nevertheless, zeolites, especially CV-Z, clearly produced a strong reduction in the leachate nitrogen content. In addition, although the leachate metal concentrations are not very high, the zeolite addition also improved the metal removal. In the light of the low metal content in the leachate, a new treatment in one stage was used in a second phase. This treatment achieved an important improvement in the COD reduction, though the TKN nitrogen removal was somewhat worse than in the two stage process.

Development of fly ash boards with thermal, acoustic and fire insulation properties

This paper presents an experimental analysis on a new board composed of gypsum and fly ashes from coal combustion, which are mutually compatible. Physical and mechanical properties, sound absorption coefficient, thermal properties and leaching test have been obtained. The mechanical properties showed similar values to other commercial products. As far as the acoustic insulation characteristics are concerned, sound absorption coefficients of 0.3 and 0.8 were found. The board presents a low thermal conductivity and a fire resistance higher than 50 min (for 4 cm of thickness). The leaching of trace elements was below the leaching limit values. These boards can be considered as suitable to be used in building applications as partitions.

Radiological, Leaching, and Mechanical Properties of Cocombustion Fly Ash in Cements

AbstractWastes are used increasingly as construction materials to make the building industry more sustainable. In this regard, the European standards indicate the characteristics to be met by fly a...

Assessing durability properties of noise barriers made of concrete incorporating bottom ash as aggregates

Abstract This research analyses the durability of a noise barrier using coal bottom ashes as aggregates in a high proportion (80%wt of bottom ash). A concrete noise barrier is composed by a combination of a porous sound absorbing face and a standard concrete in order to increase the mechanical properties of the barrier. The bottom ash was sieved at 2.5 mm, a porous concrete with the coarse fraction of bottom ashes and a standard concrete with the fine fraction of bottom ashes were made. This paper analyses the water absorption, resistance to acid attacks, resistance to sulphate attacks and resistance to freeze-thaw cycles, determining mechanical and acoustical properties of the porous concrete. When the materials are subjected to acid and sulphate attacks, the compressive strength is reduced to 20% and the noise absorption to 40% from initial baseline. When all the materials are subjected to freeze-thaw cycles, a mass loss higher than 15% at 30–40 cycles was observed, the compressive strength of materials with a high particle size drops at 20–30 cycles for natural and bottom ashes aggregates, and the noise absorption of bottom ash materials present a lower drop than natural aggregates.

Valorisation of a by-product from the TiO2 pigment industry for its application in advanced oxidation processes

AbstractThe aim of this study was to find a recycling use for waste material (WTiO2) that results from the extraction process of TiO2 from ilmenite in the pigment industry. In view of its high TiO2 content, the photocatalytic activity of this material was tested in the degradation of humic and fulvic acid substances (HFAs) and showed low levels of photoactivity, as was the case for the commercial photocatalyst Aeroxide TiO2 P25 (P25). However, due to its high Fe3+ content, an important application was observed for WTiO2 as an HFA coagulant and catalyst in Fenton and photo-Fenton processes. A two-stage process of coagulation and photo-Fenton treatment was subsequently designed and conducted at laboratory and small pilot scale. High percentages (above 95%) were obtained in total organic carbon (TOC) removal.