This study reports the synthesis of mesoporous nano-fibrillar alumina prepared by hydrolysis-precipitation route from aqueous solution of aluminum sulfate analytical reagent (AR) compared to aluminum sulfate technical grade (TG) of low purity under similar conditions using ammonia as the precipitating agent. The phisicochemical properties of these samples was studied with the assistance of characterization techniques such as Thermogravimetric and differential thermal analysis (TG/DTGA–DTA), X-ray diffraction (XRD), N2 adsorption-desorption isotherms, Fourier transform infrared (FTIR) spectroscopy, particles size and Transmission electron microscopy with energy-dispersive X-ray analysis (TEM/EDAX). The TG-DTA and XRD results show greater stability and a slightly greater crystallinity in Al2O3-TG sample than Al2O3-AR. N2 adsorption-desorption results show for both materials greatly surface area of 311 m2/g for Al2O3-TG and 272 m2/g for Al2O3-AR exhibiting characteristics of mesoporous materials. The FTIR results show a lower percentage of surface OH groups for Al2O3-TG showing a lower acidity due to the lower concentration of Al-OH species (AlIV). TEM measurements confirmed fibers size ranged from 20 to 100 nm for Al2O3-TG and 20-80 nm for Al2O3-AR. EDAX shows the presence of 0.20 % atomic of Mg as an impurity in Al2O3-TG, is attributed that this amount is sufficient to generate structural defects and decrease slightly acidity, likewise, extended the fibrillar chain of the alumina.

The present research reports the synthesis of ZrO₂-doped TiO₂ photocatalysts at different ZrO₂ contents (1, 3 and 5% wt.) synthesized by the sol–gel method. The samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction, attenuated total reflectance-Fourier transform infrared, ultraviolet–visible, X-ray photoelectron spectroscopy and N₂ adsorption–desorption analysis. The photocatalytic activity of the ZrO₂-doped TiO₂ was investigated against the dyes methyl orange and rhodamine B through mineralization studies. The ZrO₂-doped TiO₂ samples presented a semiglobular-ovoid agglomerate shape around 500–800 nm. The samples presented high crystallinity of the TiO₂ anatase phase, XPS suggested the formation of Zr–O–Ti bonds and the samples were classified as mesoporous materials with slight changes in the optical features in comparison with pure TiO₂. Our study shows that the ZrO₂-doped TiO₂ composites exhibited a higher photocatalytic activity than just utilizing the synthetized TiO₂ and a commercial P25. The different degradation behaviors are attributed to differences in the textural properties, and to the different optical absorptions of the samples due to structural defects created by the level of doping of Zr⁴⁺ ions into the TiO₂ lattice. Reaction kinetics parameters were calculated by the Langmuir–Hinshelwood model, and a third run cycle of the ZrO₂-doped TiO₂ at 1% wt. achieved a photocatalytic degradation of 78.1 and 75.5% for RhB and MO, respectively.

This study describes the preparation of TiO₂-modified Bi₂O₃ photocatalysts with different TiO₂ contents, synthesized via an in situ hydrothermal method. The powder samples were characterized by XRD, SEM, TEM, FTIR–ATR, UV–Vis, XPS, and N₂ physisorption analysis. The photocatalytic activity of the TiO₂-modified Bi₂O₃ was studied for the removal of methyl orange (MO) and methylene blue (MB) under different reaction conditions. The TiO₂-modified Bi₂O₃ photocatalysts exhibited superior photocatalytic activity compared to the pristine samples of TiO₂ and Bi₂O₃. The BiT16 sample achieved degradation rates of approximately 93.9% and 98.2% for MO and MB, respectively, within 120 min of reaction at 30 ppm. These results are attributed to the band gap values, differences in textural features, TiO₂ content, and the reduction in the recombination process of e⁻/h⁺ pairs in the Bi₂O₃–TiO₂ composites. Reaction kinetics were determined using the Langmuir–Hinshelwood mechanism, and during the third photoreaction cycle, the TiO₂-modified Bi₂O₃ (BiT16) achieved photocatalytic degradation rates of 65.6% for MO and 70.5% for MB.

Arsenic is a toxic element for human health. It persists in the environment as a result of natural and anthropic contamination, generating nocive effects for consumers. Some of them can be cancer, cardiovascular disorders, hypotension, metabolic disease and peripheral neuropathy. Adsorption is considered to be one of the most effective technologies widely used in global environmental protection areas. The objective of this study was to generate a low cost agglomerated alumina adsorbent (A-1) for the effective removal of arsenic (V) from water and its comparison with a commercial agglomerated alumina (A-2). Both of them of 5 mm of diameter. The physicochemical properties of the adsorbents were characterized by various techniques, such as: XRF, zeta potential, XRD, adsorption-desorption of N2 and FE-SEM/EDS. Batch experiments were performed to evaluate the efficiency of removal of As (V) from water by A-1 and A-2. The point of zero charge of A-1 and A-2 was at pH 8.5 and 8.1, respectively. The experimental results in batches indicated that agglomerate A-1 has a higher adsorption capacity than A-2 (1.212 mg∙g-1; 1.058 mg∙g-1) in similar conditions, concentration of 15 mg∙L-1 of As (V), temperature (20± 2 °C) and pH 7. The adsorption processes of As (V) in A-1 and A-2 followed the kinetics of Pseudo-first order kinetic and the Freundlich isotherm. The results showed that the agglomerate A-1 is an attractive adsorbent for the effective removal of As (V) from water.

A spheroidal agglomerate γ-Al2O3 adsorbent obtained from pseudoboehmite for effective removal of fluoride from aqueous medium was investigated in the present study. The surface properties were characterized by several techniques: XRD, physisorption of N2, FE-SEM/EDS, 27Al NMR, FT-IR Pyridine adsorption, PZ and particle size. Batch experiments were conducted and they were compared with a commercial activated alumina (AA). The process was carried out at pH 5, 7, and 9, then at 25 and 35 ºC. Batch experimental results indicated that the spheroidal agglomerates of γ-Al2O3 remove up to 15 mg/g with a higher adsorption capacity than AA of 13 mg/g, at pH 5, studied at 25 and 35 °C. The F− adsorption processes in γ-Al2O3 and AA followed the pseudo-first-order kinetics and the Langmuir isotherm. The results showed an adsorbent effective for removal of F−.