Elements are released into water bodies, affecting the environment and human health. To address this problem, the adsorption-desorption capacity of untreated rice husk (URH) and rice husk treated with alkali (RHTA) for Cu(II), Pb(II), Fe(II), Cd(II), and Zn(II) was investigated. Analyses during the process were performed by X-ray diffraction (XRD), scanning electron microscopy, and elemental analysis by energy dispersive X-ray spectroscopy (SEM-EDS), as well as Fourier transform infrared spectroscopy (FTIR). Adsorption-desorption kinetics and isotherms were carried out. The FTIR analysis of RHTA revealed a lowering of intensity of the bonding signals (OH, C-O, CH₂, CH₃, SiO₂, Si-OH) and loss of some signals due to the adsorbent-elements interaction. The adsorption on RHTA presented higher adsorption of Fe, followed by Pb, Zn, Cu, and Cd. Meanwhile, in URH, the adsorption was Fe > Pb > Cu > Zn and Cd. On the other hand, the desorption values for RHTA were Zn > Cd > Pb > Cu > and Fe and Zn > Cd > Cu > Pb and Fe for URH. The adsorption kinetics showed that data fit (R² ≥ 0.89) to pseudo-second-order kinetics and Freundlich isotherms (R² ≥ 0.84) for both ATRH and URH, indicating that the process occurs in the multilayer form and is controlled by chemisorption, where the adsorption depends on the active sites of the adsorbent surface.

The global environmental issue of arsenic (As) contamination in drinking water is a significant problem that requires attention. Therefore, the aim of this research was to address the application of a sustainable methodology for arsenic removal through mycoremediation aerated with micro-nanobubbles (MNBs), leading to bioscorodite (FeAsO₄·2H₂O) generation. To achieve this, the fungus Trichoderma atroviride was cultivated in a medium amended with 1 g/L of As(III) and 8.5 g/L of Fe(II) salts at 28 °C for 5 days in a tubular reactor equipped with an air MNBs diffuser (TR-MNBs). A control was performed using shaking flasks (SF) at 120 rpm. A reaction was conducted at 92 °C for 32 h for bioscorodite synthesis, followed by further characterization of crystals through Fourier–Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and X-ray diffraction (XRD) analyses. At the end of the fungal growth in the TR-MNBs, the pH decreased to 2.7–3.0, and the oxidation-reduction potential (ORP) reached a value of 306 mV at 5 days. Arsenic decreased by 70%, attributed to possible adsorption through rapid complexation of oxidized As(V) with the exchangeable ferrihydrite ((Fe(III))_4-5(OH,O)₁₂), sites, and the fungal biomass. This mineral might be produced under oxidizing and acidic conditions, with a high iron concentration (As:Fe molar ratio = 0.14). The crystals produced in the reaction using the TR-MNBs culture broth and characterized by SEM, XRD, and FTIR revealed the morphology, pattern, and As-O-Fe vibration bands typical of bioscorodite and römerite (Fe(II)(Fe(III))₂(SO₄)₄·14H₂O). Arsenic reduction in SF was 30%, with slight characteristics of bioscorodite. Consequently, further research should include integrating the TR-MNBs system into a pilot plant for arsenic removal from contaminated water.

Taxco de Alarcón (Mexico) has been affected by mining activities and the presence of potentially toxic elements (PTEs). In this study, water samples from the Acamixtla, Taxco, and San Juan rivers were analyzed using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) to determine PTE concentrations. Statistical analyses included principal component analysis, Pearson’s correlation, the Pollution Index, and a Health Risk Assessment. Additionally, solid samples from the San Juan River with leachate from the “La Guadalupana” Mine (RSJMG S2.3) were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Identified PTEs included As, Cr, Ni, Zn, Fe, Mn, Cu, Cd, Pb, Se, and Li. Principal component analysis explained 94.8% of the data variance, and Pearson’s correlation revealed significant associations (p < 0.05) among Fe, As, Cu, Cd, Pb, and Zn. The RSJMG S2.3 site exhibited the highest Pollution Index value (8491.56) and the highest health exposure risks. Lower contamination levels at other sites may be attributed to the complexation of PTEs with ferrihydrite, which was identified in the RSJMG S2.3 site through microscopy and infrared analyses. These findings suggest that the in situ formation of ferrihydrite may enhance the adsorption of PTEs, thereby mitigating environmental contamination and potential health risks.

Background. Chili pepper (Capsicum spp.) cultivation extends throughout Mexico, hosting a wide variety worldwide. However, crop health is reduced by the incidence of pathogenic microorganisms such as those of the Fusarium genus, which is one of the main agents causing vascular wilt and mortality of plant species. The use of molecular tools allows for rapid and reliable identification of organisms at the species level and help characterize the symptoms and pathogenicity they cause in hosts, which is important for field management and control. Objective. To identify at the molecular level fungal strains isolated from Siete Caldos chili (C. frutescens) using ITS and evaluate their pathogenicity in C. frutescens and C. chinense. Methodology. Strains of Fusarium from chile Siete Caldos plants (C. frutescens L.) were isolated and identified using traditional techniques (humid chamber and isolation in specific culture media) and molecular techniques (ITS1 and ITS4), and their pathogenicity in C. chinense Jacq. and C. frutescens was evaluated. Results. Seven strains were identified using taxonomic keys denoted as: 44hp, 45ta, 46ta, 46hp, 47hp, 45hpssc and 45hpmcsc. From the amplified regions, the phylogenetic tree was obtained using the maximum-likelihood method based on the comparison of ITS sequences. The fungal isolates were identified and grouped, which corresponded to F. oxysporum strains reported in the NCBI database. The pathogenicity test showed the presence of symptoms in C. frutescens, with strain 45ta being the most virulent (80 % incidence in inoculated plants). However, under the evaluation techniques used, C. chinense plants did not present wilting symptoms. Implications. The higher incidence of strain 45ta in C. frutescens could be due to the affinity of F. oxysporum for its host (Siete Caldos chili), while the absence of symptoms in C. chinense could be due to an asymptomatic infection. Conclusions. The isolated strains showed no variability in their molecular identification, but not all showed the same infective capacity in the pathogenicity test. Therefore, it is necessary to perform tests with greater specificity to determine whether subspecies of the studied isolates exist.