191 research outputs found
Alkali activation for management of construction and demolition wastes coming from earthquake
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Addition of WEEE glass to metakaolin based geopolymeric binder: a cytotoxicity study
Waste Electrical and Electronic Equipment (WEEE) types of glass, including Cathode Ray Tube (CRT) glass, are now separately collected in European Union 28 (EU28) zone. Due to the high level of Pb and Ba in their compositions, this type of waste finds its way to the disposal. In the present research, a geopolymer matrix based on metakaolin is used to blend in fine powder panel and funnel glass from personal computer (PC) and television (TV) monitors. Such waste glass, which cannot be directed to glass melting furnaces, is safely incorporated into a geopolymer matrix. The consolidation of the geopolymeric matrix containing the waste glass was followed by pH and conductibility up to 28 days of curing. Scanning electron microscope equipped with energy dispersive spectroscopy (SEM/EDS) was used to obtain information on the microstructure of the consolidated products. Cytotoxicity tests helped the environmental evaluation of these materials
Effects on Folsomia candida Willem, 1902 of products resulting from anaerobic digestion of biomass tested at different soil pH
In recent years, it has become increasingly important to reduce the production and impact of wastes on the environment, and to save and restore natural resources. A way of disposing industrial, agro-industrial and urban wastes is their treatment by anaerobic digestion, with the production of biogas and residual organic material. The latter is commonly called digestate and can be used in agriculture as fertilizer, soil improver or adsorbent material, but only scarce or no evaluations of its biological effects on soil organisms are presently available. The aim of the present research was to study the effects of digestate, when added to soils with different pH values, on the survival and reproduction of the collembolan Folsomia candida. The digestate investigated in this study was obtained from agro-industrial wastes mixed with biological sludge. We exposed springtails to two different concentrations of digestate (2.5%; 5%) in two artificial soils with pH values of 6 and 4.5. The addition of digestate resulted in an increase of experimental-soil pH values, depending on the concentration and original pH value of the artificial soil used. The negative effects of digestate detected on the survival and reproduction of F. candida was mainly attributed to pH values > 6. The high pH value, however, does not explain by itself the strong decrease in number of juveniles in the experimental soil when the highest concentration of digestate was combined with the highest pH value reached: in this case it is possible to assume a combined effect of pH and other digestate characteristics such as nitrogen content and salinity, currently under study
Design of inorganic polymer mortar from ferricalsialic and calsialic slags for indoor humidity control
Amorphous silica and alumina of metakaolin are used to adjust the bulk composition of black (BSS) and white (WSS) steel slag to prepare alkali-activated (AAS) mortars consolidated at room temperature. The mix-design also includes also the addition of semi-crystalline matrix of river sand to the metakaolin/steel powders. The results showed that high strength of the steel slag/metakaolin mortars can be achieved with the geopolymerization process which was particularly affected by the metallic iron present into the steel slag. The corrosion of the Fe particles was found to be responsible for porosity in the range between 0.1 and 10 ÎĽm. This class of porosity dominated (~31 vol %) the pore network of B compared to W samples (~16 vol %). However, W series remained with the higher cumulative pore volume (0.18 mL/g) compared to B series, with 0.12 mL/g. The maximum flexural strength was 6.89 and 8.51 MPa for the W and B series, respectively. The fracture surface ESEM observations of AAS showed large grains covered with the matrix assuming the good adhesion bonds between the gel-like geopolymer structure mixed with alkali activated steel slag and the residual unreacted portion. The correlation between the metallic iron/Fe oxides content, the pore network development, the strength and microstructure suggested the steel slag's significant action into the strengthening mechanism of consolidated products. These products also showed an interesting adsorption/desorption behavior that suggested their use as coating material to maintain the stability of the indoor relative humidity
Waste Cork in Metakaolin–Geopolymer Matrix: Physico-Mechanical Characterization
Cork powdery waste (CW) from agglomerated cork caps manufacturing is commonly
transported to waste-to-energy plants, although it could be locally exploited for lightweight building
materials. The transformation of CW into a geopolymer formulation to obtain a novel composite
formulation suitable for insulating panels is presented in this contribution. The geopolymer mix
was based on metakaolin added to NaOH and Na silicate solutions, to which 2.4, 4.8 and 9.1 wt%
(calculated upon dry metakaolin) of CW in the form of as-received powdery waste were added.
No pre-treatments were performed on CW and no thermal curing was conducted for the alkaliactivated product that was consolidated at room temperature to improve product sustainability. The
insulating panel presented an apparent density of about 1.521 to 0.990 ± 0.001 g/cm3
, combined
with a total porosity in the range of 35.61 to 56.22 ± 0.003 % for 2.4 to 9.1 wt% of CW, respectively,
and this was dependent upon ageing time. The values of its mechanical properties (compressive
strength ranged from 2.5 to 1.5 MPa at 28 and 90 days of curing time, complying with UNI EN 998-2)
and thermal insulating properties (thermal conductivity around 0.1146 W/mK) indicated that the
highest percentage of CW in the formulations, i.e., 9.1 wt%, was suitable to obtain self-standing
insulating panels
Effects of LED Lights and New Long-Term-Release Fertilizers on Lettuce Growth: A Contribution for Sustainable Horticulture
The horticulture sector has been directed by European guidelines to improve its practices
related to environmental sustainability. Moreover, the practice of horticulture in urban areas is
increasing since it provides fresh products that are locally produced. At the same time, horticulture
needs to implement circular economy approaches and energy-efficient models. Therefore, to address
these issues, this study investigated the effects of an integrated fertilizer-box-based cultivation
system equipped with LED lights and coated porous inorganic materials (C-PIMs), which was
applied as fertilizer, on Lactuca sativa L. growth. Two different types of lightweight aggregates were
formulated considering agri-food and post-consumer waste, and they were enriched with potassium
and phosphorus. Involving waste in the process was part of their valorization in the circular economy.
Using PIMs as fertilizers enabled the controlled release of nutrients over time. The tests were carried
out in controlled conditions using two LED lighting systems capable of changing their light spectrum
according to the growth phases of the plants. The effects of two different lighting schemes on the
growth of lettuce plants, in combination with different amounts of aggregates, were studied. The
results showed that increasing the amount of C-PIMs statistically improved the lettuce growth in
terms of dry biomass production (+60% and +34% for two different types of PIM application) when
the plants were exposed to the first LED scheme (LED-1). Plant height and leaf areas significantly
increased when exposed to the second LED scheme (LED-2), in combination with the presence of
C-PIMs in the soil. The analysis of the heavy metal contents in the lettuce leaves and the soil at the
end of the test revealed that these elements remained significantly below the legislated thresholds.
The experimental achievements of this study identified a new approach to improve the environmental
sustainability of horticulture, especially in an urban/domestic context
Synthesis of WEEE-based geopolymers and their cytotoxicity
Alkali activated metakaolin-based geopolymer materials were used to blend in fine powder glasses from waste electric and electronic equipment. In particular, glasses from funnel and panel parts of cathode ray tubes were recovered and re-utilized, thus obtaining GPVFNL and GPVBa enriched geopolymers. The materials were characterized by means of Fourier Transform InfraRed spectroscopy (FT-IR), and in order to avoid health risk for humans, cytotoxicity was preliminarily assessed by means of MTT test towards NIH-3T3 murine fibroblast cell line. The synthetized geopolymers showed an important anti-bacterial activity vs. Escherichia col
Geopolymer matrix for the inertization of gold mine tailings
The mining industry produces a huge amount of solid waste materials during mining’s lifetime. Solid mine tailings typically contain many sulfide minerals and heavy metals. These fine-grained residues are usually deposited in impounding lakes near mining sites. Sulfides are oxidized in contact with water, which decreases the surrounding pH, and metal oxides are leached into the environment. This leachability causes short- and long-term environmental problems, such as contamination of surface and ground water. There is increasing interest in discovering new methods to manage mine tailings more effectively in the future. This interest is mainly focused on developing low-cost treatment or confinement processes. The possibility of immobilizing several heavy metals from gold mine tailings by reactive geopolymerization technique has been investigated in the present study. The chemical stability of geopolymers synthesized by the alkali activation of metakaolin and blast furnace slag with the addition of 40 to 50 wt% gold mine tailings is demonstrated. The geopolymers were cured at room temperature, and the effects of different Si/Al and Na/Al molar ratios and curing times were investigated. The inertization effectiveness was evaluated by means of leaching tests carried out according to standard EN 12457 after 7 and 28 days and after 18 months. The samples were immersed into the water for 1 day, and the leachable metals in the test solution were determined by ICP-OES.
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Shot-Earth as Sustainable Construction Material: Chemical Aspects and Physical Performance
Soil has long been one of the most widely used building materials globally. The evolution of soil-based construction materials has seen steady improvement over the centuries, even as traditional materials have given way to newer options like reinforced concrete. Nonetheless, soil-based construction has maintained its relevance and, in recent decades, has garnered increased attention due to sustainability concerns and renewed research interest. Among the innovative earth-based materials, shot-earth (SE) stands out as one of the most advanced. Research on SE has facilitated efficient handling of soil variability in mix design and provided structural engineers with relevant models for dimensioning and detailing reinforced SE constructions. This paper focuses on studying the durability characteristics of various types of SE to ascertain their ability to withstand environmental degradation over their intended lifespan. The tests conducted indicate that SE can serve as a viable construction material in numerous real-life scenarios, offering a sustainable alternative to existing materials
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