Synthesis of solid sodium silicate from waste glass and utilization on one-part alkali-activated materials based on spent oil filtering earth.

Alkali activated materials (AAMs) commonly known as geopolymers are considered ecofriendly substitutes for Portland cement. However, these materials still have a significant environmental impact, owing mainly to the use of activators based on commercial chemical products. In this sense, this research focuses on the production and use of waste glass-derived activators AAMs as an alternative to commercial activators. Using a thermochemical synthesis method, activator compositions were systematically designed to achieve predefined activator modulus (Ms = SiO2/Na2O = 0.5; 1.0 and 1.5). These alternative activators were studied by XRD, FTIR and SEM techniques. Additionally, one-part AAMs were manufactured using spent oil filtration earth (SOFE) as precursor and activator with optimum modulus Ms = 1.0. The influence of the Na2O dosage was studied (10; 20 and 30 g of Na2O per every 100 g of SOFE) as well as the influence of the activator modulus maintaining the optimum dosage of 20 g Na2O per 100 g of SOFE. As a control, two-part AAMs were also synthetized with the optimum dosage and modulus employing commercial activators (NaOH + Na2SiO3 solution). Results indicate that the modulus of the alternative activator and especially the Na2O dosage have a significant influence on the technological properties of AAMs based in SOFE, with an optimum compressive strength (35.8 MPa) for the addition of 20 g of Na2O per every 100 g of SOFE using activator with modulus Ms = 1.0. This research embodies a sustainable approach to AAM production and suggests waste glass as a valuable raw material for sodium silicate synthesis intended for the one-part activation of spent filtering earth from the agri-food industry, aligning with the principles of circular economy and sustainable development goals.

Preparation of Geopolymeric Materials from Industrial Kaolins, with Variable Kaolinite Content and Alkali Silicates Precursors.

In the present work, the development of geopolymeric materials with Na or K based on industrial kaolin samples, with variable kaolinite content and alkaline silicates, is studied. XRF, XRD, FTIR and SEM-EDS have been used as characterization techniques. Three ceramic kaolin samples, two from Algeria and one from Charente (France), have been considered. In particular, chemical and mineralogical characterization revealed elements distinct of Si and Al, and the content of pure kaolinite and secondary minerals. Metakaolinite was obtained by grinding and sieving raw kaolin at 80 µm and then by thermal activation at 750 °C for 1 h. This metakaolinite has been used as a base raw material to obtain geopolymers, using for this purpose different formulations of alkaline silicates with NaOH or KOH and variable Si/K molar ratios. The formation of geopolymeric materials by hydroxylation and polycondensation characterized with different Si/Al molar ratios, depending on the original metakaolinite content, has been demonstrated. Sodium carbonates have been detected by XRD and FTIR, and confirmed by SEM-EDS, in two of these geopolymer materials being products of NaOH carbonation.

Fe3O4@UiO-66-NH2 based on magnetic solid phase extraction for determination of organic UV filters in environmental water samples.

In this work, a nanocomposite structured magnetic metal-organic framework named as Fe3O4@UiO-66-NH2 was prepared via a simple hydrothermal approach. The as-mentioned nanocomposite was characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and the Brunauer-Emmett-Teller (BET) techniques. Using the Fe3O4@UiO-66-NH2 as a nanosorbent, an easy and highly effective approach was developed to preconcentrate nine organic UV filters before gas chromatography-mass spectrometry (GC-MS) analysis. Different conditions influencing the extraction efficiency encompassing the sorbent amount, nature and volume of desorption solvent, desorption time, pH of the sample, and extraction time, were examined. Under the optimal experimental parameters, the Fe3O4@UiO-66-NH2-based magnetic solid phase extraction and GC-MS (MSPE-GC-MS) demonstrated linearity in the range of 0.03-1500 ng/L (R2 ≥ 0.9974) and the reproducibility, expressed as RSD, was ≤7.5%. The limits of detection ranged between 0.01 and 0.07 ng/L and limits of quantification were in the range of 0.03-0.4 ng/L. Finally, the suggested approach was satisfactorily utilized to determine nine organic UV filters in different water samples (analytical recoveries between 86.5% and 104.2%).

Reuse of Oil Refining Sludge Residue Ash via Alkaline Activation in Matrices of Chamotte or Rice Husk Ash.

The aim of this work is to investigate the possibility of reusing ashes obtained by the calcination of industrial sludge from the oil refining industry (ORSA) as a secondary raw material in the manufacture of alkaline activated cements or geopolymers. The incorporation behavior of 5-20 wt.% of residue in binary mixtures with rice husk ash (RHA) or chamotte (CHM) was evaluated. The cements were activated with a sustainable alternative activating solution obtained from NaOH (10 M) and diatomaceous earth. The specimens were cured at room temperature. Physical and mechanical properties were determined, and the reaction products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX). The results indicate that the addition of ORSA (5-20 wt.%) to RHA and CHM improves the mechanical strength of alkaline activated cements with maximum compressive strengths of 30.6 MPa and 15.7 MPa, respectively, after 28 days of curing, with the incorporation of 20 wt.% waste. In these mixtures, the sludge acts as a source of aluminum, promoting the formation of a higher amount of geopolymer gel N-A-S-H in materials using RHA as a precursor and also (N)-(C)-A-S-H gel in cements using CHM.

Effect of L-Glutamic Acid on the Composition and Morphology of Nanostructured Calcium Phosphate as Biomaterial.

Calcium phosphate (CaP) with several chemical compositions and morphologies was prepared by precipitation using aqueous solutions of L-Glutamic acid (H2G) and calcium hydroxide, both mixed together with an aqueous solution (0.15 M) of phosphoric acid. Plate-shaped dicalcium phosphate dihydrate (brushite) particles were obtained and identified at a lower concentration of the solution of the reactants. The Ca/P ratio deduced by EDS was ~1, as expected. The nanoscale dimension of carbonate apatite and amorphous calcium phosphate, with variable Ca/P ratios, were revealed by X-ray diffraction (XRD) and scanning electron microscopy and energy dispersive X-ray spectroscopy analysis (SEM-EDS). They were characterized in medium and high concentrations of calcium hydroxide (0.15 M and 0.20 M). The equilibria involved in all the reactions in aqueous solution were determined. The thermodynamic calculations showed a decrease in the amount of chelate complexes with an increase in pH, being the opposite of [CaPO4-] and [CaHG+]. This fluctuation showed an evident influence on the morphology and polymorphism of CaP particles obtained under the present experimental conditions, with potential use as a biomaterial.

New Types and Dosages for the Manufacture of Low-Energy Cements from Raw Materials and Industrial Waste under the Principles of the Circular Economy and Low-Carbon Economy.

The cement manufacturing industry is one of the main greenhouse gas emission producers and also consumes a large quantity of raw materials. It is essential to reduce these emissions in order to comply with the Paris Agreement and the principles of the circular economy. The objective of this research was to develop different types of cement clinker blends using industrial waste and innovative design to produce low-energy cement. Several types of waste have been studied as alternative raw materials. Their main characteristics have been analyzed via X-ray fluorescence (XRF), X-ray diffraction (XRD), Attenuated total reflectance Fourier trans-form infrared spectroscopy (ATR-FTIR), thermal analysis (TG-DTG-DSC) and scanning electron microscopy and energy dispersive X-ray spectroscopy analysis (SEM-EDS). The results obtained from the experimental work carried out in this research focused on the study of crude blends for low-energy cement created from industrial waste. The effect of the addition of different industrial waste types, as a substitution for raw materials, in the production of low-energy cement with high dicalcium silicate content has been investigated. Thus, the dosage design has been performed using modified Bogue equations and quality indexes (LSF, AM, and SM). The calculations of both the modified Bogue equations and quality indexes necessitate knowledge of the weight percentages of CaO, SiO2, Al2O3, and Fe2O3, determined via XRF. In this theoretical design of the different blends, it has been established that a dicalcium silicate ratio of 60-65 wt % and an LSF of 78-83% as the limit are values common to all of them. The calculation basis for the crude blends has been based on calcined materials. Therefore, the chemical composition was established, following this premise. Thus, it was possible to develop cement clinker blends with compositions of 50 wt % and 100 wt % using industrial wastes. This research has shown that the clinkerization process is one of the main options for the valorization of waste and its consideration for inclusion as a raw material within the circularity of the cement industry's production process. Thus, waste is used as a raw material for the production of a more useful substance, taking into account the fundamental principles of the circular economy.

Study of a Waste Kaolin as Raw Material for Mullite Ceramics and Mullite Refractories by Reaction Sintering.

A deposit of raw kaolin, located in West Andalusia (Spain), was studied in this work using a representative sample. The methods of characterization were X-ray diffraction (XRD), X-ray fluorescence (XRF), particle size analysis by sieving and sedimentation, and thermal analysis. The ceramic properties were determined. A sample of commercial kaolin from Burela (Lugo, Spain), with applications in the ceramic industry, was used in some determinations for comparison purposes. The kaolin deposit has been produced by alteration of feldspar-rich rocks. This raw kaolin was applied as an additive in local manufactures of ceramics and refractories. However, there is not previous studies concerning its characteristics and firing properties. Thus, the meaning of this investigation was to conduct a scientific study on this subject and to evaluate the possibilities of application. The raw kaolin was washed for the beneficiation of the rock using water to increase the kaolinite content of the resultant material. The results indicated that the kaolinite content of the raw material was 20 wt % as determined by XRD, showing ~23 wt % of particles lower than 63 µm. The kaolinite content of the fraction lower than 63 µm was 50 wt %. Thus, an improvement of the kaolinite content of this raw kaolin was produced by wet separation. However, the kaolin was considered as a waste kaolin, with microcline, muscovite and quartz identified by XRD. Thermal analyses by Thermo-Dilatometry (TD), Differential Thermal Analysis (DTA) and Thermo-Gravimetry (TG) allowed observe kaolinite thermal decomposition, quartz phase transition and sintering effects. Pressed samples of this raw kaolin, the fraction lower than 63 µm obtained by water washing and the raw kaolin ground using a hammer mill were fired at several temperatures in the range 1000-1500 °C for 2 h. The ceramic properties of all these samples were determined and compared. The results showed the progressive linear firing shrinkage by sintering in these samples, with a maximum value of ~9% in the fraction lower than 63 µm. In general, water absorption capacity of the fired samples showed a decrease from ~18-20% at 1050 °C up to almost zero after firing at 1300 °C, followed by an increase of the experimental values. The open porosity was almost zero after firing at 1350 °C for 2 h and the bulk density reached a maximum value of 2.40 g/cm3 as observed in the ground raw kaolin sample. The XRD examination of fired samples indicated that they are composed by mullite, from kaolinite thermal decomposition, and quartz, present in the raw sample, as main crystalline phases besides a vitreous phase. Fully-densified or vitrified materials were obtained by firing at 1300-1350 °C for 2 h. In a second step of this research, it was examined the promising application of the previous study to increase the amount of mullite by incorporation of alumina (α-alumina) to this kaolin sample. Firing of mixtures, prepared using this kaolin and α-alumina under wet processing conditions, produced the increase of mullite in relative proportion by reaction sintering at temperatures higher than 1500 °C for 2 h. Consequently, a mullite refractory can be prepared using this kaolin. This processing of high-alumina refractories is favoured by a previous size separation, which increases the kaolinite content, or better a grinding treatment of the raw kaolin.

On the industrial symbiosis of alumina and iron/steel production: Suitability of ferroalumina as raw material in iron and steel making.

The biggest challenge for our society, in order to foster the sustainable circular economy, is the efficient recycling of wastes from industrial, commercial, domestic and other streams. The transition to a circular economy is the goal of the European Commission's Circular Economy Action, which was first launched in 2015. In 2020 the above action plan announced initiatives along the entire life cycle of the product, with the aim to make sustainable products the norm in the EU. Therefore, it is anticipated that the above action will result in an increase in Europe's economic competitiveness, sustainability, resource efficiency and resource security. Within this context, the suitability of ferroalumina as a raw material in the blast furnace is investigated. Ferroalumina is the product of the high-pressure filter press dewatering process of the Greek red mud generated during the production of alumina by means of the Bayer cycle. Ferroalumina is a low-cost raw material and its possible charging in the blast furnace and/or steelmaking aggregates is a step towards industrial symbiosis, where the wastes, namely by-products, of an industry or an industrial process, become the raw materials for another. In the present work the effect of ferroalumina addition as a raw material was examined by smelting ferroalumina, blast furnace-slag, lime and scrap at 1550°C in a graphite crucible and a constant slag basicity. The increase of the alumina content in the slag improves the desulfurization capacity. Moreover, the silicon exchange between slag and metal was examined. The results indicate that the alkalis' capacity of the slag increases with the addition of ferroalumina. The analysis of the finally obtained slag suggests that it could be suitable for utilization in slag-cement production.

Effect of Olive-Pine Bottom Ash on Properties of Geopolymers Based on Metakaolin.

In this research, the feasibility of using bottom ashes generated by the combustion of biomass (olive pruning and pine pruning) as a source of aluminosilicates (OPBA) has been studied, replacing the metakaolin precursor (MK) in different proportions (0, 25, 50, 75, and 100 wt.% substitution) for the synthesis of geopolymers. As alkaline activator an 8 M NaOH solution and a Na2SiO3 have been used. The geopolymers were cured 24 h in a climatic chamber at 60 °C in a water-saturated atmosphere, subsequently demoulded and cured at room temperature for 28 days. The results indicated that the incorporation of OPBA waste, which have 19.7 wt.% of Ca, modifies the characteristics of the products formed after alkaline activation. In general terms, the incorporation of increasing amounts of calcium-rich ashes results in geopolymers with higher bulk density. The compressive strength increases with the addition of up to 50 wt.% of OPBA with respect to the control geopolymers, contributing the composition of the residue to the acquisition of better mechanical behavior. The results indicate the potential use of these OPBA waste as raw material to produce unconventional cements with 28-day curing strengths greater than 10 MPa, and thermal conductivities less than 0.35 W/mK.

Wood Bottom Ash and GeoSilex: A By-Product of the Acetylene Industry as Alternative Raw Materials in Calcium Silicate Units.

The main objective of this research was to obtain calcium silicate units from alternative raw materials, such as the bottom ashes from the combustion of wooden boards (WBA), as a source of silica, and GeoSilex (G), a by-product with low energy and environmental costs generated in the manufacture of acetylene, as a source of lime. Once the raw materials were physically, mineralogically and chemically characterized, calcium silicate units were obtained by mixing different amounts of WBA residue (90-20 wt%) and G by-product (10-80 wt%). The mixtures were compressed at 10 MPa and cured in water for 28 days. The calcium silicate units were subjected to a wide experimental program that included the determination of physical properties (bulk density, apparent porosity and water absorption), mechanical properties (compressive strength), and thermal properties (thermal conductivity). Optimum values are obtained for calcium silicate units that contain a 1/1 WBA/G weight ratio, which have an optimal amount of SiO2 and CaO for the cementation reaction. The 50WBA-50g units have compressive strength values of 46.9 MPa and a thermal conductivity value of 0.40 W/mK. However, all calcium silicate units obtained comply with the European Standard EN 771-2: 2011 to be used as structural building materials.

Manufacture of Sustainable Clay Bricks Using Waste from Secondary Aluminum Recycling as Raw Material.

The aluminum recycling industry produces aluminum filter dust (AFD), a waste byproduct of the aluminum recycling process composed mainly of aluminum oxide in a percentage between 60⁻70%, 8% calcium oxide, almost 15% sodium chloride, and between 5⁻10% potassium chloride. Due to its aluminum content, this waste can be used as a raw material in the manufacture of ceramic bricks, at the same time reducing the environmental impact produced in landfill. In this work, the partial substitution of a clay mixture (40% black, 30% red, and 30% yellow clay) by different proportions of AFD in the range 0⁻25 wt % for the production of fired clay brick was studied. The raw materials, clays, and waste were characterized by XRF and XRD. The brick specimens were fired at 950 °C and their physical and mechanical properties, such as water absorption, water suction, loss of ignition, linear shrinkage, bulk density, and compressive strength, were analyzed. The more relevant results were obtained with the addition of up to 20 wt % AFD, obtaining bricks with physical properties comparable to pure clay-based bricks used as a reference and better compressive strength and thermal conductivity due to the balance between the melting and pore-forming effects of the waste. These sustainable bricks also comply with the regulations of heavy metals leached to the environment, as indicated by the leaching test.

Determination of oil and water content in olive pomace using near infrared and Raman spectrometry. A comparative study.

Near infrared (NIR) reflectance and Raman spectrometry were compared for determination of the oil and water content of olive pomace, a by-product in olive oil production. To enable comparison of the spectral techniques the same sample sets were used for calibration (1.74-3.93% oil, 48.3-67.0% water) and for validation (1.77-3.74% oil, 50.0-64.5% water). Several partial least squares (PLS) regression models were optimized by cross-validation with cancellation groups, including different spectral pretreatments for each technique. Best models were achieved with first-derivative spectra for both oil and water content. Prediction results for an independent validation set were similar for both techniques. The values of root mean square error of prediction (RMSEP) were 0.19 and 0.20-0.21 for oil content and 2.0 and 1.8 for water content, using Raman and NIR, respectively. The possibility of improving these results by combining the information of both techniques was also tested. The best models constructed using the appended spectra resulted in slightly better performance for oil content (RMSEP 0.17) but no improvement for water content.