414 research outputs found
Agricultural waste in the synthesis of coral ceramic pigment
No full textThis work reports the results of an evaluation of the use of rice husk ash as the source of silica in thepreparation of coral ceramic pigments. ZrSiO4eFe2O3 inclusion pigments have been synthesized by solidstate reactions evaluating the effect of the mineralizer and both silica and iron oxide precursors on thereactivity of the system. The colour developed in the derived ceramic glazes has been compared with thecolour developed in comparative pigments prepared from pure SiO2
The Environmental Friendly Route to Obtain Sodium Silicate Solution from Rice Husk Ash: A Comparative Study with Commercial Silicates Deflocculating Agents
No full textSodium silicate solutions were synthesized treating Rice Husk Ash (RHA) with sodium hydroxide solutions at low molar concentrations (1–4 M). During the study the operative conditions were optimized. Raman spectroscopy was used to check the chemical nature of the silicates solutions obtained by comparison with commercial ones. The defocculating efciency of the synthesized solutions was checked by rheological measures on clay suspensions (solid content 60 and 65 wt%). Some fndings of the study permit to confrm that the extraction of SiO2 increases by increasing NaOH concentration. The alkaline attack (NaOH solution) at 1.5 and 2 M show the best results for SiO2/Na2O ratio close to 2, this ratio is widely used as defocculating agents in ceramic sector using commercial silicates. The 0.5wt% content resulted the optimum dosage for all additives. In particular, the viscosity values obtained using the silicates synthetized from RHA are lower than those corresponding to the commercial products. The defocculating capability behaves similar, or even better, than commercial ones. This valorization of matter from RHA allows the obtainment of high added value products that can play role of “green” substitutes of commercial ones
The circular economy of agro and post‐consumer residues as raw materials for sustainable ceramics
No full textThe circular economy in the area of waste management implies their re‐use as a raw material in different production cycles. Both the qualitative and quantitative characteristics of the residues from the agro sector and those of the products of the ceramics sector make possible to think of a feasible application. This review will illustrate some examples of recycling of residues deriving from animal and vegetable sectors (and two post consume products, spent coffee grounds, and packaging glass cullet), studied by the authors, falling within the concept of urban and agricultural sustainable development. Not only the most traditional products such as glass‐ceramics, glazes, bricks, but also the most innovative lightweight aggregates for plant structures or in and out soil cultivation, as well as additives such as deflocculants for ceramic suspensions, which will be illustrated from the design/production, characterization, and comparison with commercial products
Comparison of Three Manufacturing Techniques for Sustainable Porous Clay Ceramics
No full textThis study proposes different manufacturing techniques (manual pelletization, powder pressing, and “shell scaffold”) to obtain lightweight clay ceramics containing recovery raw materials. The sintering in an electrical furnace (1000 °C, 1 h processing time) was conducted by traditional firing from room temperature, for pressed and shell-scaffold samples, while the flash heating (i.e., samples directly put at 1000 °C) was used only for the pellets. The porous materials (porosity 40–80%), functionalized with nutrients (K and P) in amounts to confer the fertilizer capability, gave suitable results in terms of pH (6.7–8.15) and electrical conductivity (0.29–1.33 mS/cm). Thus, such materials can be considered as feasible lightweight clay ceramics, with a positive
effect on the soil. These findings permit us to hypothesize a potential use in green roofs or in agronomic applications
Preliminary Study on Sustainable NPK Slow-Release Fertilizers Based on Byproducts and Leftovers: A Design-of-Experiment Approach
No full textIn this study, an organic nitrogen-based coating was developed based on black soldier fly (BSF) prepupae reared on
poultry dejections and deposited on ceramic lightweight aggregates (LWAs), containing phosphorous (P) and potassium (K) from
agroresidues, leading to a complete nitrogen, phosphorus, and potassium (NPK) fertilizer. To obtain a resistant coating with good
adhesion to LWAs, different plasticizing agents were tested (e.g., glycerol, cellulose, and polyethylene glycol). The coating
formulation was optimized through a design-of-experiment (DoE) approach to correlate the effect of each mixture component on
the coating’s performance. BSF biomass was characterized through chemical and thermal routes, as well as the final coated LWAs,
confirming their general agreement to fertilizer’s requirements. Release tests in static conditions highlighted the barrier action of the
coating, preventing uncontrolled release of potassium and phosphorus contained in the LWAs as well as the release of nitrogen after
21 days (near to 20%). Germination and growth tests indicated a valuable increase of the growth index, whereas the germination
process is limited by the coating barrier effect. This work proposes a new product in the field of slow-release fertilizers designed by
rational methodologies and innovative materials based on waste valorization, fully in agreement with a circular economy perspectiv
Valorization of polishing and glazing ceramic sludges in new blended cement
No full textThe productive ceramic cycle generates environmental pollution from both the process and depuration treatment. In particular, residues coming from polishing and glazing sludges due to their chemical composition cause technological problems in internal recycle. The present work, developed in the framework of the LITCAR network, has the aim to study the possibility to recover ceramic sludges as new constituents for innovative blended cements. These residues seem very promising thanks to their similarity to pozzolanic materials usually employed in cement fabrication according to European standard EN 197/1
Valorization of agro-industrial wastes in lightweight aggregates for agronomic use: Preliminary study
No full textThis research was focused on the valorization of agro industrial waste/by products available in the local industry with the kilometer zero (km 0) concept, as a replacement of virgin raw materials (clay) to elaborate lightweight aggregates (LWAS). The alternative raw materials were employed as pore forming agent, in order to reduce sintering temperature and energy consumption of the furnace. The three technical nutrients studied were provided for local food industries: sludge from wastewater treatment plant from brewery industry (SB), meat-bone meal (MBM) and corn cob (CC). These materials were characterized in terms of chemical (XRF and elemental analysis - CHNS) and mineralogical (XRD) composition, as well as their thermal behavior (TGA/DTA/DSC) and LOI. For the production of LWAS different percentage of waste/by product (0, 5, 10 and 15%) were mixed with three types of clays (white, black and red) in two different clay-based mixtures. With the addition of water were produced approximately spherical pellets and thermal treated at two different temperatures (900 and 1000°C) for 1 hour. Technological parameters such as bulk and absolute density, total porosity, water absorption capacity, pH, electrical conductivity and organic matter content were measured, to determine their potential use in agriculture. XRD and scanning electron microscope (SEM) were performed for the characterization of different samples. The results indicate the potential for manufacturing high quality lightweight aggregates for agronomic purposes, using relatively simple processing and low sintering temperature that contribute to the reduction of greenhouse gases to the atmosphere
Sintering and phase formation of ceramics based on pre-treated municipal incinerator bottom ash
No full textCeramics, based on 60 wt% of municipal incinerator bottom ashes (MIBA) and 40 wt% of industrial clays, were prepared by using two fractions of pre-treated ashes (above and under 2 mm) and three different industrial clays.
The obtained six compositions with amounts of CaO from 12 to 14 wt%, with SiO2/Al2O3 ratio ranging from 3.5 to 1.6 and with Al2O3/CaO ratio - from 1.25 to 1.75 were investigated and characterized.
These compositions were located in the crystallization field of anorthite (CaO.Al2O3.2SiO2); the ceramics with high SiO2/Al2O3 ratio are near to the eutectic with SiO2, while with low ratio – closer to the anorthite stoichiometry.
The phase transformation and the subsequent melting were studied by non-isothermal DTA-TG analysis, while the densification process - by contactless optical dilatometry. Then, the optimal sintering temperatures and times were evaluated by isothermal dilatometric runs at different temperatures.
At high SiO2/Al2O3 ratio the sintering temperature is lower but the sintering range is very narrow. This behavior can be explained by the formation of too high amount of liquid phase at the eutectic temperature. On the contrary, at lower ratio, the sintering temperature increases but, notwithstanding the decrease of viscosity and shorter sintering time, the densification range becomes wider. This last result is a very important technological finding with a view to industrial transferability.
Additional tests performed demonstrated that a preliminary thermal treatment of ash with elevated residual organic phase is necessary, which leads to a lower firing shrinkage and to a shorter sintering time
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