This work presents the scale up and technoeconomic evaluation for waste management towards the recovery of aluminum and its use to produce a valuable adsorbent and catalyst. Experimental data for the performance of various stages, including lixiviation, basic extraction and zeolite synthesis are used for process design and scale up and a detailed process synthesis and technoeconomic evaluation is performed. The yield to product reaches 0.185kg/kgrawmaterial and a valuable by-product, ammonia, is also obtained. For a production capacity of 212kg/h, the investment required is 9.4M€ and the production costs for the zeolite add up to 5.22 €/kg. To make it competitive, a waste management fee of 0.64 €/kg is required. The effect of the scale on waste management shows an important reduction in the production costs. As a result, the process may be feasible both technically and economically if it is considered as part of the waste management strategy.

Aluminum is the most used non-ferrous metal, with a well-established recycling procedure, but this process also produces new residues. We recently proposed an integrated laboratory practice based on the recovery of aluminum from the slag generated during its recycling. Now, we expand upon this research by proposing the preparation of a layered material, namely hydrocalumite, from recovered Al3+. The synthesis of this solid, its characterization, and the use of the mixed oxides produced after its calcination for the photocatalytic removal of ibuprofen from aqueous solutions are structured as a laboratory practice for students in the last years of Chemistry, Chemical Engineering, Environmental Engineering, Materials Engineering, and related university or masters degrees. In this way, the work integrates material synthesis and characterization procedures with a practical introduction to catalysis photodegradation, incorporating key concepts of the Circular Economy and Sustainable Development Goals, and educating students with respect to the environment.

The present work reports a facile, eco-friendly synthesis of an Ag-sepiolite nanocomposite utilizing Mentha aquatica leaf extract, serving simultaneously as a reducing and stabilizing agent. The pristine sepiolite and the resulting nanocomposite were comprehensively characterized via XRD, FT-IR, SEM, EDX, TEM, and XPS, confirming the successful loading of silver nanoparticles (AgNPs) onto the fibrous sepiolite matrix with uniform dispersion and evidence of metal-support interaction. The catalytic activity of Ag-sepiolite was evaluated for the reduction of methylene blue (MB) in the presence of NaBH4, revealing rapid pseudo-first-order kinetics with an apparent rate constant of 0.60 min-1 and over 98% degradation within 4 min under optimized conditions. The catalyst exhibited excellent reusability, maintaining an efficiency of over 88% across five cycles. In addition, the Ag-sepiolite nanocomposite demonstrated significant antibacterial activity against Gram-positive (Staphylococcus aureus, Bacillus subtilis) and Gram-negative (Escherichia coli, Salmonella typhi) bacteria, as well as potent antifungal activity against Candida albicans. Its antioxidant potential was confirmed through 2.2-Diphenyl-1-picrylhydrazyl (DPPH) and Ferric Reducing Antioxidant Power (FRAP) assays, with significantly higher radical scavenging and ferric-reducing capacity than sepiolite or plant extract alone. Furthermore, machine learning approaches were utilized to predict electronic characteristics, including energy per atom and optical band gap, using structural descriptors derived from X-ray diffraction data, providing insights into the enhanced reactivity and catalytic efficiency of Ag-sepiolite. The work highlights the synergistic effect of AgNPs and sepiolite, establishing a sustainable approach for environmental remediation and catalytic applications.

This study presents the synthesis of CAU23 and MIL53 MOFs using saline slags as an aluminum source and evaluates the effect of microwave treatment on the preparation process. The saline slags underwent chemical treatment with HCl or NaOH to produce Al3+ or AlO2-solutions, which were used for MOF synthesis while simultaneously reducing the hazardous nature of the waste. The MOF were characterized using several techniques as powder X-ray diffraction, FT-infrared spectroscopy, thermal analysis, N 2 adsorption-desorption isotherms at-196 degrees C, laser diffraction, and electron microscopy. The results demonstrate that these MOF types can be successfully synthesized from saline slags and that microwave treatment significantly reduces synthesis times; specifically, CAU23 was obtained after 90 min of microwave treatment (compared to 3 or 6 h under reflux), while MIL53 required only 5 min. Finally, the CO2 adsorption capacity was evaluated at several temperatures from 50 to 200 degrees C and up to 80 kPa, with the CAU23 series showing the highest results, ranging from 0.80 to 1.08 mmolCO2 /g.

Hydrotalcite-like solids are commonly subjected to thermal aging treatments in order to modify and homogenise their crystal and particle sizes; however, the samples can still show a large heterogeneity in their particle sizes. Mechanical milling is an alternative treatment that has been used to achieve the desired homogeneity in particle size. In this work, the effect of the application of a mechanical milling treatment on the morphological and textural properties of hydrotalcite-like solids synthesized in the presence of amines as precipitating agents was studied. The application of a mechanical milling treatment over the samples subjected to hydrothermal treatment was also studied, analysing the effect of both post-treatments on the final properties of these compounds. Once the samples were synthesized and characterised, a mechanical treatment was carried out in a ball mill with planetary geometry, where the solids were ground at a speed of 600 rpm for 30 min. The milled samples were studied attending to their morphological and textural properties, and non-agglomerated solids with smaller crystallite sizes were obtained. These results highlighted mechanical milling as an effective post-synthetic strategy to tailor the microstructural properties of layered double hydroxides (LDH), which may enhance their suitability for future catalytic and adsorptive applications.

Novel materials based on Na2S2O4-modified griffithite and griffithite-katoite-hydrocalumite hybrid composites have been prepared to be applied as catalysts in Fenton-type processes for biodigested distillery wastewater (BDW) purification using salt cake as aluminum source. The catalysts were thus based on a natural Fe-rich clay and on Ca-Al synthetic cheap materials, all with layered structure. The characterization of these materials showed the presence of phases with catalytic activity in heterogeneous Fenton processes such as Fe2O3 and Fe3O4. The sample Griffithite-2 mu m-750 and the hybrid material Griffithite@HC-750 were the most effective in removing the total organic carbon (TOC) and chemical oxygen demand (COD) from BDW. The best reaction conditions were determined using Griffithite-2 mu m-750 as heterogeneous Fenton catalyst and considering pH, [H2O2]:COD ratio and catalyst dosage as key parameters. In addition, the Griffithite-2 mu m-750 sample was subjected to a cyclic (5 cycles) and long-term (similar to 200 h of time-on-stream) study, showing excellent stability. Scavenger experiments confirmed that the process proceeds predominantly via a radical mechanism, with hydroxyl radicals (OH center dot) playing the main role.

In this study, a conductive and magnetic nanocomposite, PANI@PVP-Fe3O4, was successfully synthesized. The nanocomposite was thoroughly characterized to determine its crystallographic structure, chemical composition, and morphological features using XRD, FTIR, SEM-EDS, TEM, zeta potential, and DLS analyses. The PVP@Fe3O4 was obtained as nanosized particles ranging from 8 to 15 nm, while the PANI@PVP-Fe3O4 exhibited an average particle size between 20 and 45 nm. The nanocomposite demonstrated excellent catalytic activity, achieving complete reduction of MB in 8 min and OG in 4 min. Reusability tests demonstrated that the catalyst could be reused more than five times without a significant loss of efficiency, confirming its stability. Furthermore, the material displayed strong antibacterial activity, with inhibition zones of 31 mm, 25 mm, and 23 mm against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, respectively. The PANI@PVP-Fe3O4 was also evaluated for its water disinfection potential, including the effect of nanocomposite mass and initial bacterial concentration. In these tests, it achieved a 94 % removal rate of E. coli within 30 min at an initial concentration of 106 CFU/mL. Finally, DFT studies were done to understand how Fe3O4 interacts with the PVP/PANI polymer matrix, providing a molecular-level insight into the composite's multifunctional behavior in environmental applications.

In present research, small-sized Sep-NiO nanocomposites were synthesized using Mentha aquatica leaf extract as a reducing and capping agent. The nanocomposites were systematically characterized to determine their crystallographic structure, chemical composition, morphological features, thermal stability, and luminescence properties. X-ray diffraction (XRD) was employed to assess the crystal structure and phase purity, while FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS) provided insights into the chemical bonding and surface states. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX) were used to examine the nanoscale morphology and bulk elemental distribution. Atomic force microscopy (AFM) offered additional topographical information, and thermogravimetric analysis (TGA) evaluated the thermal stability. Zetasizer Nano and zeta potential measurements were conducted to assess particle size distribution and colloidal stability, respectively. Photoluminescence (PL) studies were performed to explore the optical and electronic properties of the nanocomposites. The nanocomposite was applied to the catalytic reduction of methylene blue, with a deep neural network model predicting degradation efficiency based on variables including catalyst mass, NaBH4 concentration, MB concentration, and reaction time. The model demonstrated excellent predictive accuracy (R 2 = 0.99), with RMSE, MAE, and MSE values of 1.95, 1.71, and 3.83, respectively. Kinetic studies showed that methylene blue degradation increased with catalyst mass and NaBH4 concentration but decreased at higher MB concentrations. Thermodynamic analysis indicated that the process was endothermic, involving physical adsorption on the catalyst surface, and led to increased system order.

Preparation of CaAlGa and ZnAlTi mixed metal oxides (MMO) synthesized via CaAlGa-hydrocalumites and ZnAl-hydrotalcite impregnated with TiO2 using saline slags as aluminum source, is reported for the first time. The solids obtained by calcination at 750 degrees C are highly crystalline and the photocatalytically active crystalline phases Ca12Al14-xGaxO33, ZnO, ZnAl2O4 and Zn2TiO4 have been identified. The MMO were used for the catalytic degradation of paracetamol under UV irradiation, obtaining good results for the removal of this emerging pollutant, reaching a removal above 90 % for the sample containing 25 % Ga3 +, under the optimum photodegradation conditions ([Paracetamol]0 = 40 mg/L and catalyst dose = 1 g/L), showing better results than the commercial photocatalyst TiO2-P25 from Degussa and other more complex catalysts based on MMO. In addition, this photocatalyst was submitted to a cyclic process study, finding that it maintained its performance after at least two cycles.

Due to the abundance of lignin, its valorisation for the synthesis of various materials may be important from an environmental perspective. This work proposes the synthesis of porous carbon materials using sodium lignosulphonate and a polysaccharide with thermal transitions (kappa-carrageenan), assessing how the precursor's viscoelasticity and the drying process (supercritical CO2 or freeze-drying) can tune the properties of the obtained material. Rheological and infrared results indicate the formation of a network based on electrostatic interactions, leading to strong gels (G' over 100,000 Pa). Furthermore, the use of supercritical CO2 promotes the obtention of materials with a nanofibrous mesoporous structure, as opposed to the chaotic macroporous structure obtained through freeze drying. The nanofibrous network reduces the pore size compared to the macroporous structure by three orders of magnitude (10 nm vs 30 μm). The nanofibrous network also improves the surface area of the material (values between 60 and 90 m2·g-1) compared to the null area of the macroporous solid. Furthermore, thermogravimetric results indicated that lignin can be removed from the network before drying with supercritical CO2 due to the solvent exchange step. Finally, materials dried with supercritical CO2 have the highest swelling ratio (ranging from 400 % to 1000 % depending on the lignin ratio), following pseudo-second-order kinetics. This phenomenon is numerically studied using computational fluid dynamics (volume of fluid method), which determines the material's permeability and observes how the fluid replaces the air inside the pores of the dried material with supercritical CO2 in <1 s.

Herein, we report the first example of MOF synthesis employing aluminum slags as a waste resource. This synthesis was exclusively carried out from waste materials, under ambient conditions in water, thus aligning with the guiding principles of Green Chemistry. The resulting MIL-53(Al) material was further functionalized with SnO2 nanoparticles and tested as catalyst for the dehydration of glucose to 5-hydroxymethylfurfural (5-HMF), showing a tenfold increase in catalytic efficiency compared to unsupported SnO2.

Aluminum is the most used non–ferrous metal. It can be recycled saving several natural resources, but generates large amounts of residues with a complex composition—still containing a valuable amount of aluminum, although also including contaminant compounds. The laboratory-scale valorization of an industrial aluminum residue is here used as a powerful didactic resource in Inorganic and Analytical Chemistry and related fields such as Chemistry, Chemical Engineering, Environmental Engineering, Materials Engineering, and related university degrees, since concepts like acid-base properties (particularly amphoterism), redox reactions, speciation diagrams, or solubility–precipitation concepts are applied. The students are encouraged to look for information on the topic, to teamwork, and to elaborate a well-written laboratory report. At the same time, this laboratory work introduces them to advanced laboratory techniques and to incorporate concepts of Circular Economy and various Sustainable Development Goals, educating the students with respect to the environment. Although focused on University studies, this manuscript also contains excellent ideas for secondary teachers to motivate STEM vocations, particularly for Chemistry and Chemical and Environmental Engineering, and is also ideal for being included in the preparation of future Secondary School teachers.

Fe-rich saponite clay mineral solids have been tested as heterogeneous catalysts for organic synthesis. The major aim was the synthesis of substituted imidazoles under solvent free conditions. Saponite was used in the natural rock form, purified by dispersion-decantation (<2 mu m fraction), and calcined at 750 degrees C. The catalysts were characterized by X-ray diffraction, FT-IR spectroscopy, thermal analyses, N-2 adsorption-desorption and electron microscopy. The calcined solid showed the best catalytic performance (86 %), and the purified uncalcined solid also gave good yield (78 %). The temperature and time of the reaction, and the catalyst doses were optimized, 120 degrees C, 3 h and 30 mg being the optimal conditions. The reaction was also carried out using different substrates, finding that electron-withdrawing groups from aldehydes tended to increase electrophilicity, while slightly electron-withdrawing groups from amines improved reactivity. The best catalyst was reusable over four cycles without appreciable loss in activity. The prepared solids are environment friendly catalysts for this reaction under solvent-free conditions.

Synthesis of hydrocalumite–TiO2 hybrid systems and their use in photodegradation of ibuprofen is reported for the first time. Hydrocalumite was prepared with Al3+ recovered from an aluminum slag (circular economy), TiO2 was deposited on hydrocalumite by hydrolysis of titanium(IV) isopropoxide, and the solids thus obtained were calcined at 400 and 750 ºC. The solid calcined at 400 ºC was essentially amorphous, showing the presence of calcite due to the fixation of atmospheric CO2, while the solid calcined at 750 ºC was composed of mayenite, perovskite and rutile. The calcined solids were used for catalytic degradation of ibuprofen (50 ppm in aqueous solutions) under UV irradiation, obtaining better results than when using commercial TiO2–P25 from Degussa. Under the specific conditions used, the degradation took place in the initial steps of the process, mainly giving rise to species with higher molecular mass than initial ibuprofen.

Solids with potential application in tyrosol (Ty) removal by photo–Fenton processes have been synthesized using aluminum salt cake as a source. Two series of hydrocalumite layered double hydroxides (LDH) were synthesized: one containing structural Fe3+ (occupying octahedral positions in the LDH) and another containing surface impregnated Fe3+; all solids were calcined in air at 750 ºC. The solids were characterized by powder X–ray diffraction, FT–infrared spectroscopy, thermal analysis, N2 adsorption–desorption isotherms at –196 °C, particle size distribution and electron microscopy. One of the main differences between the two series was that Fe3+ impregnation by the incipient wetness method and subsequent calcination at 750 °C did not lead to the formation of CaAlFe mixed oxides. The calcined solids were evaluated as photocatalysts in the photo–Fenton process for Ty removal (a typical compound found in olive oil mill wastewater), the samples containing surface Fe3+ showing better results. The solid prepared by impregnation of hydrocalumite with 20% iron and subsequently calcined at 750ºC, under the optimum reaction conditions (catalyst dose = 0.5g/L, [H2O2] = 0.468g/L and [Ty]0 = 100mg/L, in the presence of UV light), reached complete Ty removal with contaminant mineralization of 95% after only 60min reaction. The cyclic study showed that this sample maintained its stability after 3 cycles of reuse without iron leaching, and a better performance than other materials reported in the literature.

Three heavy metals (Cu2+, Cd2+ and Pb2+) were removed from aqueous solutions using zeolites prepared from saline slags, a very important waste generated during aluminum recycling. Zeolites were characterized by powder X-ray diffraction, thermal analysis, Fourier transform infrared spectroscopy, X-ray microfluorescence, element chemical analysis, nitrogen adsorption at -196 degrees C and electron microscopy. The textural and structural properties of X-type faujasite zeolite convert it in a promising adsorbent in aqueous streams. Removal of the heavy metals was evaluated in batch mode, studying the adsorbent dose, the initial concentration of the heavy metal, the selectivity of the solid in case of mixtures with various metal cations and the recyclability of the solid. The kinetic and equilibrium results were evaluated using both pseudo-first- and pseudo-second-order kinetics, and Langmuir, Freundlich and Toth equation isotherms for the equilibrium. The time needed to reach equilibrium was between 10 and 20 min. Faujasite was highly effective in removing Cu2+, Cd2+ and Pb2+ from aqueous solutions, much higher than analcime and pollucite, other two zeolites recently synthesized by us from aluminum slags, and used in this work for comparison purposes. The maximum adsorption capacity was 591 mg/g for Pb2+, 304 mg/g for Cu2+ and 279 mg/g for Cd2+.

Several Al3+-based 3+ -based LDHs with different divalent cations have been synthesized by coprecipitation from aluminum salt slag and have been impregnated with Pd. After their characterization by PXRD, FT-IR, thermal analysis, N2 2 adsorption-desorption isotherms at -196 degrees C and electron microscopy (SEM and TEM), they were used as heterogeneous catalysts in the A3-coupling 3 -coupling reaction (benzaldehyde + morpholine + phenylacetylene) to produce propargylamines. The catalyst that showed the best results was NiAl-Pd and the optimal reaction conditions were: catalyst dose 30 mg, temperature 80 degrees C and reaction time 6 h. In addition, this catalyst showed a good cyclic behavior, retaining a catalytic activity higher than 80 % after 4 cycles.

Solids with photocatalytic properties have been prepared by calcination of hydrocalumite (a sort of layered double hydroxide, LDH) at 750 degrees C, which had been prepared using an aluminum salt cake as a source. The characterization of the obtained solids was performed by powder X-ray diffraction, FT-infrared spectroscopy, thermal analysis, N2 adsorption-desorption isotherms at -196 degrees C and electron microscopy. Different crystalline phases were identified depending on the amount of Fe3+ incorporated. The Fe-free photocatalyst showed the best performance under UV light for the photodegradation of ibuprofen.

Potentially-CO2 adsorbing solids at moderate temperature have been prepared by calcination at 400 degrees C and 750 degrees C of CaAlFe hydrocalumites (a sort of Ca2+-layered double hydroxide), which had been prepared using a salt cake as aluminum source. The characterization of the obtained solids was carried out by powder X-ray diffraction, FT-infrared spectroscopy, thermal analysis, N2 adsorption-desorption isotherms at -196 degrees C and electron microscopy. After calcination, different crystalline phases were identified as a function of the amount of Fe3+ incorporated. Static sorption equilibrium experiments were performed at 300 degrees C and pCO2 = 0.3 bar. The CO2 sorption capacity was affected by the presence of different phases in the CaAlFe-mixed oxides (MMOs), being maximum when the amount of Fe3+ was 40 mol % of the trivalent positions. No differences in CO2 sorption capacities were observed between CaAlFe-MMOs-400 and CaAlFe-MMOs-750 (materials calcined respectively at 400 and 750 degrees C), suggesting that CO2 sorption capacity was not related to SBET. Experiments under dynamic conditions at 400 degrees C and pCO2 = 0.15 bar showed good behaviors for CaAl-400, CaAl0.60Fe0.40-400 and CaFe-400. In addition, CaAl0.60Fe0.40-400 was evaluated in several CO2 sorption-desorption cycles in the presence of water vapor, finding that the steam presence enhanced the CO2 capture.