Search

The mining industry is one of the largest sources of environmental concern globally. Herein we report for the first time the application of highly porous 3D-printed sorbents containing high amounts (50 wt%) of red mud, a hazardous waste derived from the alumina industry, for the remediation of acid mine drainage (AMD). The sorption capacity of the inorganic polymers was initially evaluated for the simultaneous removal of five metal(loid) elements, namely Cu(II), Ni(II), Zn(II), Cd(II) and As(V) in synthetic wastewater. The effect of the initial concentration, pH and contact time were assessed, reaching removal efficiencies between 64% and 98%, at pH 4 and initial concentration of 50 mg L -1 of each cation, after 24 h of contact time. The 3D-printed lattices were then used for the remediation of the real AMD water samples, and the role of adsorption and acidic neutralization was investigated. Lattices were also successfully regenerated and reused up to five cycles without compromising their performance. This work paves the way for the use of an industrial waste derived from the production of alumina as raw material for the management of the hazardous AMD., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Fly ash (FA) from biomass combustion and biological sludge (S), both wastes from the pulp and paper industry, were granulated in different proportions (90% FA+10% S, and 70% FA+30% S w/w, dry weight basis, dw) and used to recover the functionality of soils affected by mining activities (Aljustrel, Iberian Pyrite Belt), with and without the application of municipal solid waste compost (MSWC). Application doses of both mixtures were 2.5, 5.0 and 10% (w/w, dw). These materials corrected soil acidity to circumneutral values and increased extractable P and K concentrations. A significant increase in soil organic matter (from 0.6 to 0.8-1.5% w/w, dw) and N content (from 0.04 to 0.09-0.12% w/w, dw) was also observed, but only when MSWC was applied. The soil was already heavily contaminated with Cu, Pb and Zn and the application of amendments did not increase their pseudo-total concentrations. The CaCl 2 extractable fractions of both Cu and Zn decreased to very low values. The improvement in soil quality, compared to fertilizer only treatment, was further evidenced by the increase in some soil enzymatic activities (dehydrogenase, β-glucosidase and cellulase), with a better response for the granules with the higher proportion of biological sludge, as well as by the decrease in the soil-water extract toxicity towards different organisms (Daphnia magna, Thamnocephalus platyurus, and Pseudokirchneriella subcapitata). Agrostis tenuis germinated and grew during the first month only in the amended pots, but, after that, a considerable phytotoxic effect was evident. This was mainly attributed to salt stress or to some specific ionic toxicity. In conclusion, to establish a long-term plant cover in mining soils amended with biomass ash-based materials, the selection of plants with higher resistance to salinity and/or the stabilization of the amendments, to reduce their soluble salt content, is recommended., (Copyright © 2019. Published by Elsevier B.V.)

This paper presents results about the characterisation of the biomass fly ashes sourced from a thermal power plant and from a co-generation power plant located in Portugal, and the study of new cement formulations incorporated with the biomass fly ashes. The study includes a comparative analysis of the phase formation, setting and mechanical behaviour of the new cement-fly ash formulations based on these biomass fly ashes. Techniques such as X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), thermal gravimetric and differential thermal analysis (TG/DTA), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and environmental scanning electron spectroscopy (ESEM) were used to determine the structure and composition of the formulations. Fly ash F1 from the thermal power plant contained levels of SiO(2), Al(2)O(3) and Fe(2)O(3) indicating the possibility of exhibiting pozzolanic properties. Fly ash F2 from the co-generation plant contained a higher quantity of CaO ( approximately 25%). The fly ashes are similar to class C fly ashes according to EN 450 on the basis of chemical composition. The hydration rate and phase formation are greatly dependant on the samples' alkali content and water to binder (w/b) ratio. In cement based mortar with 10% fly ash the basic strength was maintained, however, when 20% fly ash was added the mechanical strength was around 75% of the reference cement mortar. The fly ashes contained significant levels of chloride and sulphate and it is suggested that the performance of fly ash-cement binders could be improved by the removal or control of these chemical species.