Efficient removal of triclosan from water through activated carbon adsorption and photodegradation processes

This study investigated the application of adsorption with activated carbons (ACs) and photodegradation to reduce the concentration of triclosan (TCS) in aqueous solutions. Concerning adsorption, ACs (Darco, Norit, and F400) were characterised and batch experiments were performed to elucidate the effect of pH on equilibrium. The results showed that at pH = 7, the maximum adsorption capacity of TCS onto the ACs was 18.5 mg g-1 for Darco, 16.0 mg g-1 for Norit, and 15.5 mg g-1 for F400. The diffusional kinetic model allowed an adequate interpretation of the experimental data. The effective diffusivity varied and increased with the amount of TCS adsorbed, from 1.06 to 1.68 × 10-8 cm2 s-1. In the case of photodegradation, it was possible to ensure that the triclosan molecule was sensitive to UV light of 254 nm because the removal was over 80 % using UV light. The removal of TCS increased in the presence of sulfate radicals. It was possible to identify 2,4-dichlorophenol as one of the photolytic degradation products of triclosan, which does not represent an environmental hazard at low concentrations of triclosan in water. These results confirm that the use of AC Darco, Norit, and F400 and that photodegradation processes with UV light and persulfate radicals are effective in removing TCS from water, reaching concentration levels that do not constitute a risk to human health or environmental hazard. Both methods effectively eliminate pollutants with relatively easy techniques to implement.

Sustainable Zeolite-Silver Nanocomposites via Green Methods for Water Contaminant Mitigation and Modeling Approaches

This study explores cutting-edge and sustainable green methodologies and technologies for the synthesis of functional nanomaterials, with a specific focus on the removal of water contaminants and the application of kinetic adsorption models. Our research adopts a conscientious approach to environmental stewardship by synergistically employing eco-friendly silver nanoparticles, synthesized using Justicia spicigera extract as a biogenic reducing agent, in conjunction with Mexican zeolite to enhance contaminant remediation, particularly targeting Cu2+ ions. Structural analysis, utilizing X-ray diffraction (XRD) and high-resolution scanning and transmission electron microscopy (TEM and SEM), yields crucial insights into nanocomposite structure and morphology. Rigorous linear and non-linear kinetic models, encompassing pseudo-first order, pseudo-second order, Freundlich, and Langmuir, are employed to elucidate the kinetics and equilibrium behaviors of adsorption. The results underscore the remarkable efficiency of the Zeolite-Ag composite in Cu2+ ion removal, surpassing traditional materials and achieving an impressive adsorption rate of 98% for Cu. Furthermore, the Zeolite-Ag composite exhibits maximum adsorption times of 480 min. In the computational analysis, an initial mechanism for Cu2+ adsorption on zeolites is identified. The process involves rapid adsorption onto the surface of the Zeolite-Ag NP composite, followed by a gradual diffusion of ions into the cavities within the zeolite structure. Upon reaching equilibrium, a substantial reduction in copper ion concentration in the solution signifies successful removal. This research represents a noteworthy stride in sustainable contaminant removal, aligning with eco-friendly practices and supporting the potential integration of this technology into environmental applications. Consequently, it presents a promising solution for eco-conscious contaminant remediation, emphasizing the utilization of green methodologies and sustainable technologies in the development of functional nanomaterials.

Detection and mapping of the seasonal distribution of water hyacinth (Eichhornia crassipes) and valorization as a biosorbent of Pb(II) in water

In the present research, the presence of water hyacinth (Eichhornia crassipes) on the surface of the San Jose Dam located in the city of San Luis Potosi, S.L.P, Mexico, was monitored and mapped. The monitoring was conducted for 2 years (2018-2020) with remote sensing data from OLI Landsat 8 sensors, based on the normalized difference vegetation index (NDVI). The results demonstrated the capability and accuracy of this method, where it was observed that the aboveground cover area, proliferation, and distribution of water hyacinth are influenced by climatic and anthropogenic factors during the four seasons of the year. As part of a sustainable environmental control of this invasive species, the use of water hyacinth (WH) root (RO), stem (ST), and leaf (LE) components as adsorbent material for Pb(II) present in aqueous solution was proposed. The maximum adsorption capacity was observed at pH 5 and 25 °C and was 107.3, 136.8, and 120.8 mg g-1 for RO, ST, and LE, respectively. The physicochemical characterization of WH consisted of scanning electron microscopy (SEM), N2 physisorption, infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), charge distribution, and zero charge point (pHPZC). Due to the chemical nature of WH, several Pb(II) adsorption mechanisms were proposed such as electrostatic attractions, ion exchange, microprecipitation, and π-cation.

Synthesis and Characterization of α-Al2O3/Ba-β-Al2O3 Spheres for Cadmium Ions Removal from Aqueous Solutions

The search for adsorbent materials with a certain chemical inertness, mechanical resistance, and high adsorption capacity, as is the case with alumina, is carried out with structural or surface modifications with the addition of additives or metallic salts. This research shows the synthesis, characterization, phase evolution and Cd(II) adsorbent capacity of α-Al₂O₃/Ba-β-Al₂O₃ spheres obtained from α-Al₂O₃ nanopowders by the ion encapsulation method. The formation of the Ba-β-Al₂O₃ phase is manifested at 1500 °C according to the infrared spectrum by the appearance of bands corresponding to AlO₄ bonds and the appearance of peaks corresponding to Ba-O bonds in Raman spectroscopy. XRD determined the presence of BaO·Al₂O₃ at 1000 °C and the formation of Ba-β-Al₂O₃ at 1600 °C. Scanning electron microscopy revealed the presence of spherical grains corresponding to α-Al₂O₃ and hexagonal plates corresponding to β-Al₂O₃ in the spheres treated at 1600 °C. The spheres obtained have dimensions of 4.65 ± 0.30 mm in diameter, weight of 43 ± 2 mg and a surface area of 0.66 m²/g. According to the curve of pH vs. zeta potential, the spheres have an acid character and a negative surface charge of -30 mV at pH 5. Through adsorption studies, an adsorbent capacity of Cd(II) of 59.97 mg/g (87 ppm Cd(II)) was determined at pH 5, and the data were fitted to the pseudo first order, pseudo second order and Freundlich models, with correlation factors of 0.993, 0.987 and 0.998, respectively.

Relationship of thorium, uranium isotopes and uranium isotopic ratios with physicochemical parameters in cenote water from the Yucatán Peninsula

Uranium (U) and Thorium (Th) concentrations are normally low in the water (<30 and 5 ng mL^-1, respectively). However, we performed a direct analysis of ²³²Th, ²³⁴U, ²³⁵U and ²³⁸U in cenote water from the Yucatán Peninsula using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) as a rapid response technique to perform environmental radioactivity monitoring. Water samples were collected in 2021 from the cenotes and these were certificated by zones (PYNO, PYNE and PYSE) and monitoring depth [surface water (n = 52) and depth water (n = 48)]. Moreover, physicochemical parameters such as pH, electrical conductivity (EC), total dissolved solids (TDS), and temperature were measured in situ. Results obtained were total U and Th levels below permissible for human consumption. However, physicochemical parameters must be considered before use because it is outside the permissible limits in most cenotes. The median concentration value for ²³⁴U, ²³⁵U, ²³⁸U and ²³²Th in surface + depth water were 0.0001 ng mL^-1, 0.0130 ng mL^-1, 1.76 ng mL^-1, and 0.062 ng mL^-1, respectively. In addition, isotopic ratio of ²³⁵U/²³⁸U in surface + depth water was 0.00730. In addition, the PYNO zone showed a correlation between ²³²Th with EC and TDS. The PYSE zone showed a correlation between ²³²Th and temperature, and ²³⁵U/²³⁴U with pH, while PYEN did not show correlations. In conclusion, the first time evaluated U isotope concentrations and isotopic ratios of U and ²³²Th in cenote water from the Yucatán Peninsula, where U and Th concentrations were found below the permissible limits mentioned by guidelines for drinking-water quality. The average of ²³⁵U/²³⁸U is similar to isotopic ratios in "natural" water.

Formaldehyde and tripolyphosphate crosslinked chitosan hydrogels: Synthesis, characterization and modeling

In this work, the synthesis of crosslinked chitosan hydrogels was performed by ionic and covalent interactions using tripolyphosphate (TPP) and formaldehyde (CH₂O), respectively. The hydrogels synthesis was performed using a D-Optimal combined experiment design with two mixing variables, A and B representing the TPP weight fraction (slack variable) and CH₂O weight fraction, respectively, and three (3) process variables C-chitosan concentration, D-cross-linker concentration, and E-Contact time. The response variables studied were the point of zero charge (pH_PZC), the swelling ratio (SW), and the equilibrium water content (EWC), which are relevant physicochemical properties in applications such as the pollutant removal from water. According to the ANOVA results, the model obtained was significant; this means it can be adequately used to predicting pH_PZC, SW, and EWC from the mixing and process variables, obtaining coefficients of determination R² of 0.9572, 0.8900, and 0.8447, respectively. The pH_PZC is affected by chitosan concentration, while the crosslinker concentration influences the SW, and the contact time most significantly affected the EWC. Morphology and hardness tests, thermal stability, infrared spectroscopy, and scanning electron microscopy, allowed verifying the types of crosslinking of chitosan with TPP and CH₂O.

Medicinal plants used in the Huasteca Potosina, México

ETHNOPHARMACOLOGICAL IMPORTANCE

Medicinal plants have been a source of medicinal compounds since ancient times. This study documented the use of plant species in traditional medicine in the municipality of Aquismón, San Luis Potosí, México.

MATERIALS AND METHODS

Direct interviews were performed with inhabitants from Aquismón. The interviews were analyzed with two quantitative tools: (a) the informant consensus factor (ICF) that estimates the level of agreement about which medicinal plants may be used for each category and (b) the relative importance (RI) that determines the extent of potential utilization of each species.

RESULTS

A total of 73 plant species with medicinal purposes, belonging to 37 families and used to treat 52 illnesses and 2 cultural filiations were reported by interviewees. Nineteen mixtures with medicinal plants were reported by the interviewers. Matricaria recutita was the most used plant for combinations (five mixtures). The results of the ICF showed that diseases of the digestive and respiratory systems had the greatest agreement. The most versatile species according to their RI are Ruta graveolens, Tagetes erecta, Ocimum basilicum and Erigeron karwinskianus.

CONCLUSION

This study demonstrates that plant species play an important role in healing practices and magical-religious rituals among inhabitants from Huasteca Potosina. Further studies with medicinal flora, including mixtures, from Aquismón are required for the experimental validation of their traditional uses.