Nanoporous anodic aluminum oxide (AAO) films play an important role in nanotechnology due to their easily adjustable morphological properties and wide range of applications. Thus, a deep and systematic characterization of the morphological properties of these coatings is essential. The most important variables in the synthesis of nanoporous AAO films include the anodization voltage, nature, concentration and temperature of the electrolyte, which, combined, result in pores of different sizes and geometries. In the present work, AA 1050 alloy was used to synthesize AAO films, using 0.3 and 0.9 M oxalic acid as the electrolyte and combining different electrolyte temperatures (20, 30 and 40 °C) and anodizing voltages (30, 40 and 60 V), with the aim to correlate the morphological properties of the coatings with the synthesis parameters of a single anodization step. The coatings obtained were characterized by optical microscopy and scanning electron microscopy, determining pore diameter, interpore distance, pore density and coating thickness. The results showed that, by varying the anodic synthesis conditions, it is possible to obtain coatings with a pore diameter between 21 and 97 nm, an interpore distance between 59 and 138 nm, pore density between 2.8 × 10¹⁰ and 5.4 × 10⁹ pores/cm² and thicknesses between 15 and 145 µm. In this way, the right combination of synthesis variables allows synthesizing AAO coatings with morphological characteristics best suited to each particular application.

The anodic oxidation of aluminium is an electrochemical technique that allows obtaining nanostructures with easily adjustable morphology depending on the synthesis variables, for its application in medicine, engineering, biotechnology, electronics, etc. In this work, low-cost aluminium oxide nanostructured films were synthesized and morphologically characterized using two anodization steps in sulphuric acid, varying the concentration and temperature of the electrolyte and anodization voltage. The order of the porous matrix, pore diameter, interpore distance, pore density, thickness, and porosity were measured and statistically analyzed. The results showed that under the proposed conditions it is possible to synthesize low-cost nanoporous aluminium oxide films, with a short-range ordering, being the best ordering conditions 10 °C and 0.3 M sulphuric acid at 20 V and 5 °C and 2 M sulphuric acid at 15 V. Furthermore, it was determined that the pore diameter and the interpore distance vary proportionally with the voltage, that the pore density decreases with the voltage and increases with the concentration of the electrolyte, and that the thickness of the oxide film increases with electrolyte concentration, temperature, and anodization voltage.

The contamination of water bodies with toxic compounds from the agricultural, industrial, and domestic sectors is a serious environmental problem. Adsorption is one of the simplest, most functional, and economical methods for treating large volumes of water and removing its contaminant load. Thanks to its nanoporous structure, versatility, chemical inertness, and low-cost synthesis, anodic aluminum oxide (AAO) can be used as an adsorbent in a wide range of applications. In this work, nanostructured AAO coatings were successfully synthesized, and their performance as adsorbents was evaluated in decolorization tests of Eriochrome Black T (EBT) solutions. The adsorption process was found to be dependent on the initial dye concentration, agitation, temperature, and contact time. At 25 °C and 16 mg·L⁻¹ initial EBT concentration, a maximum removal efficiency (%R) of 78% was obtained after 4.5 h at 500 rpm and after 5.5 h at 100 rpm, while without agitation, after 8.3 h of treatment, the highest %R was 40%. Furthermore, the adsorption rate increased significantly with temperature, reaching a %R of 99% after 2.25 h at 60 °C and 500 rpm. Additionally, it was demonstrated that the adsorbent can be used up to four times with a removal efficiency greater than 50%.

The influence of the synthesis method on the properties of Zn₁₋ₓFeₓO nanoparticles with different Fe doping levels (x = 0, 0.01, 0.03, and 0.05) for Congo Red (CR) adsorption was investigated. Nanoparticles were prepared by sol-gel and coprecipitation, and characterized using XRD, SEM, and FTIR. Sol-gel synthesis produced smaller (~13 nm) particles, exhibiting high CR adsorption efficiency (~90%) at 10 ppm and room temperature. In contrast, coprecipitation generated larger (~35 nm) nanostructures, with lower adsorption capacity (~24%). Both the synthesis method and calcination temperature significantly influenced the nanocrystallite size. Fe doping enhanced adsorption in all cases, particularly by maintaining high adsorption percentages at elevated temperatures. Fe³⁺ incorporation into ZnO nanoparticles modifies the crystal structure, possibly creating defects and vacancies that serve as preferential adsorption sites for anionic dyes. Efficient removal of organic dyes such as Congo Red is critical due to their toxicity and environmental persistence in industrial wastewater. These findings suggest that careful selection of synthesis parameters can yield highly effective adsorbents, providing a promising strategy for environmental remediation and sustainable water treatment applications.

Industrial synthetic dyes represent a major source of water pollution because current treatment methods fail to remove them efficiently prior to discharge. Consequently, developing cost-effective and highly efficient technologies for wastewater systems is essential. Adsorption satisfies these demands and easily couples with other industrial effluent treatments. This study focuses on nanoporous anodic aluminum oxide (AAO), an outstanding adsorbent known for its versatility, high specific surface area, significant porosity, and thermal stability. Although the adsorption capacity of this nanoadsorbent has been recently studied, this work specifically evaluates the performance of AAO modified through different thermal and chemical treatments for the removal of Eriochrome Black T from aqueous solutions. Within a 1-h process, the applied treatments significantly enhanced AAO adsorption performance: standalone calcination and chemical etching led to a 10% increase in dye removal efficiency, while combining calcination with alkaline etching resulted in a 38% improvement. Furthermore, the combined treatment was demonstrated to enhance the adsorption process at alkaline pH levels (up to pH 10), and the modified AAO could be reused up to four times while maintaining a significantly high removal efficiency. Finally, this study provides key insights into the underlying phenomena governing the adsorption of anionic dyes onto AAO nanostructures.

Optimizing industrial wastewater treatment systems requires efficient, cost-effective, and easily adaptable technologies. In this context, adsorption emerges as a promising alternative through the use of advanced nanostructured materials that optimize contaminant removal and facilitate their separation from the treated medium. This work evaluates the use of nanoporous anodic aluminum oxide (AAO) as a nanoadsorbent for the removal of Eriochrome Black T (EBT) dye, analyzing the effect of thermal and chemical modifications on its performance. The results demonstrated that calcination and chemical etching with NaOH, applied individually, increased removal efficiency by 10% compared to untreated AAO. Notably, the combined treatment (calcination + alkaline etching) boosted removal efficiency by 38% after 1 h of contact. Furthermore, this synergistic modification extended the viability of the process to alkaline media (up to pH 10) and allowed the material to be reused for four consecutive cycles, maintaining an 85% removal rate. Finally, the kinetic analysis elucidated the influence of the structural and chemical modifications on the adsorption rate, obtaining satisfactory correlations with various theoretical models.