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Oxpemul is an archaeological site with pre‐Hispanic legacy located in the Calakmul biosphere reserve in Mexico. The stelae in this site have important epigraphic records of the Mayan culture. However, this information can be lost due to weathering processes that these structures undergo. In this work, ion chromatography analysis of ions extracted from samples obtained in situ using cotton poultices was used to discuss the weathering processes involved in four stelae located in Oxpemul. The plots of Ca2+vs SO42−, (Ca2+ + Mg2+) vs HCO3− and Ca2+vs HCO3− and the mineral phases found by x‐ray diffraction (XRD) revealed that the dissolution of carbonates from the limestone and the recrystallization processes of these phases are the main weathering processes that occur in the stelae. Furthermore, it was found that the hydrolysis of silicates by cation exchange reactions to form montmorillonite contributes to the weathering process. The presence of oxalate crystals found by XRD and electron microscopy revealed that biodeterioration reactions also contribute to the weathering of the stelae. This is the first study carried out to identify and understand the weathering processes that occur in these stelae. This information could be useful to establish strategies for preserving, conserving, and restoring these vestiges. [ABSTRACT FROM AUTHOR]

The use of guava seeds (GS) and acid-modified guava seeds (MGS) for the removal of Cr(VI) from aqueous solutions was investigated. Batch-type experiments were performed with Cr(VI) aqueous solutions and biosorbents to determine the kinetic and equilibrium sorption parameters. Results indicated that GS and MGS were capable of reducing and remove Cr(VI) from solutions, but the reduction was only observed at some experimental conditions. Infrared analysis showed that several functional groups were involved in the reduction, and biosorption of Cr(VI), particularly alcohol, phenolic, carboxylic, and methoxymethyl structures. The mechanisms of reduction and biosorption depended upon the type of biosorbent, pH, and temperature of the system. The pseudo-second-order kinetic model describes the kinetic sorption data, and the Langmuir-Freundlich (L-F) model describes the isotherm data in most cases. Significantly high total chromium biosorption capacities were obtained. Acid modification of guava seeds improves chromium biosorption performance.

The adsorption of fluoride and arsenic ions by modified natural materials may have an impact on the removal of F−and As(V) from waters. In this work, a zeolitic material and pozzolan (commonly known as pumicite) were modified with aluminium an iron by an electrochemical method and chemical precipitation, respectively. The adsorbents were characterized by X-ray diffraction, scanning electron microscopy with energy X-ray disperse spectroscopy analysis and the point of zero charge (pHzpc). F−and As(V) adsorption properties of both materials were investigated. Adsorption kinetic data were best fitted to pseudo-second-order model and equilibrium data to the Langmuir isotherm model. The highest F−and As(V) sorption capacities were obtained for modified zeolitic (0.866 mg/g) and pozzolan (3.35 mg/g) materials, respectively, with initial F−or As(V) concentrations of 10 mg/L. It was found that the unmodified materials did not show either adsorption of F−ions or As(V), which indicated that Al and Fe in the adsorbents are responsible for the adsorption of these ions. In general, both modified materials show similar capacities for the adsorption of F−and As(V). [ABSTRACT FROM AUTHOR]

The removal of fluoride from water by aluminum modified iron oxides (CP-Al) using a fixed-bed column adsorption system was investigated. Fixed-bed column experiments were carried out at different bed depths, and flow rate of 2 mL/min. The Bohart–Adams model and the Thomas model were applied to the experimental results. The adsorption efficiency decreases as the bed depth increases. The adsorption capacity for fluoride ions by CP-Al is higher for fluoride aqueous solutions than well water. The regeneration was accomplished by eluting a 0.1 M NaOH through the fluoride-loaded CP-Al bed. Scale-up and kinetic approach methods were used to calculate the design parameters from the breakthrough curves of fixed-bed column experiments. The parameters calculated from both methods indicated that they were suitable for fixed-bed column design. [ABSTRACT FROM PUBLISHER]

Dexamethasone (DXM) was the first drug used to treat COVID-19, only a small part is metabolized and has been identified in wastewater and surface water, conventional treatments do not remove these compounds, therefore new technologies must be developed. A commercially injectable solution containing dexamethasone (DXM) was removed by heterogeneous sono/photo-Fenton (SPF) process using clinoptilolite zeolite (CZ) modified with Fe (CZ-Fe) by an electrodeposition method. The effect of initial concentration (1.2, 3, 5.5, 8, 9.7 mg/L), H 2 O 2 dose (9.8, 15, 22.5, 30, 35.1 mg/L) and hydraulic retention time (HRT, 39.5, 60, 90, 120, 140 min) were evaluated through central composite design (CCD). The frequency of the ultrasound was 140 kHz. The optimal conditions were 5.5 mg/L DXM, 22.5 mg/L H 2 O 2 and 140 min obtaining an 85.4% DXM by UV-Vis, 99% by high-performance liquid chromatography (HPLC) and 76% by chemical oxygen demand (COD) removal. The systems generated 12, 25, 40.5 and 45.5 mg/L of total oxidant at 20, 60, 100 and 140 kHz, respectively. In individual effects, UV radiation removed 23.6%, ultrasound 18.1% and H 2 O 2 14% of DXM. In kinetic studies, the best fit was obtained for the Behnajady-Modirshahla-Ghanbery (BMG) model. SPF improved the mass transfer within the reaction media, the oxidation rate and the consumption of H 2 O 2, and no sludge was generated. Finally, another oxidant formed during the process (H • , HO 2 • , O 2 -• ) contributed to DXM removal.

Objective: To analyzes the gender gap among residents enrolled in the medical specialization program of the Graduate Division at the Universidad Nacional Autónoma de México (UNAM), Facultad de Medicina., Materials and Methods: We conducted a descriptive observational study of students registered in all 78 medical specialties offered by UNAM over a period of 7 years (2015-2022) at approximately 161 hospitals in Mexico., Results: A total of 79 175 students were studied, we observed a predominance of women 51.69%, compared to 48.30% men. In medical specialties, we found a predominance of women of 57.33%, in contrast to surgical specialties with 44.76% women. The specialties with the most women enrolled were dermatology, neonatology, pediatrics, gynecology, and psychiatry. In men, the specialties with the most enrollment were general surgery, cardiology, neurosurgery, plastic surgery among others., Conclusion: Women predominance is observed in some medical specialties, especially those that require caregiving tasks. However, a gap remains between men and women, particularly in surgical specialties and in higher decision-making positions. We suggest extending support networks to include men as well as women.

Microbially induced carbonate precipitation (MICP) immobilizes toxic metals and reduces their bioavailability in aqueous systems. However, its application in the treatment of acid mine drainage (AMD) is poorly understood. In this study, the genomes of Sporosarcina sp. UB5 and UB10 were sequenced. Urease, carbonic anhydrases, and metal resistance genes were identified and enzymatic assays were performed for their validation. The geochemical mechanism of precipitation in AMD was elucidated through geo-mineralogical analysis. Sporosarcina sp. UB5 was shown to be a new genomospecies, with an average nucleotide identity < 95 % (ANI) and DNA-DNA hybridization < 70 % (DDH) whereas UB10 is close to S. pasteurii. UB5 contained two urease operons, whereas only one was identified in UB10. The ureolytic activities of UB5 and UB10 were 122.67 ± 15.74 and 131.70 ± 14.35 mM NH 4 + min -1 , respectively. Both strains feature several carbonic anhydrases of the α, β, or γ families, which catalyzed the precipitation of CaCO 3 . Only Sporosarcina sp. UB5 was able to immobilize metals and neutralize AMD. Geo-mineralogical analyses revealed that UB5 directly immobilized Fe (1-23 %), Mn (0.65-1.33 %) and Zn (0.8-3 %) in AMD via MICP and indirectly through adsorption to calcite and binding to bacterial cell walls. The MICP-treated AMD exhibited high removal rates (>67 %) for Ag, Al, As, Ca, Cd, Co, Cu, Fe, Mn, Pb, and Zn, and a removal rate of 15 % for Mg. This study provides new insights into the MICP process and its applications to AMD treatment using autochthonous strains., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Rainwater Electro-Galvanic Alkalization (EGA) was performed using copper and magnesium (1:1) electrode. Efficiently removal of pollutants without external energy consumption was carried out, in addition essential ions were dosed for alkalization of rainwater. The optimal system conditions were obtained using response surface methodology (RSM) by considering the following operating variables: flow rate and concentration of the supporting electrolyte (NaCl and CaCl 2 ). Furthermore, the maximum efficiency of nitrate, ammoniacal nitrogen, colour, and turbidity removal was evaluated. The results showed that the response variables were mainly sensitive to the type of supporting electrolyte used and the flow rate. Under experimental conditions of 0.009 M (NaCl) and 20 mL min -1 , the removal rate was 74.19%, 72.49%, and 81.43% for nitrates, colour, and turbidity, respectively, and the lowest concentration of ammoniacal nitrogen ( 0.99 mg L - 1 ) was obtained. The kinetic models for nitrate and colour were fitted to zero-order models with k = 0.33 mg L - 1 mi n - 1 and k = 0.933 Pt - Co , respectively. In addition, turbidity was fitted to a first-order model ( k = 0.1661 mi n - 1 ) , and ammoniacal nitrogen was fitted to a second-order model ( k = 0.0217 L m g - 1 mi n - 1 ) . The concentration increases of minerals such as Ca and Mg, which rises the rainwater alkalinity after treatment (pH shift from 6.1 to 8.91), was determined by inductively coupled plasma (ICP) analysis.

The textile industry is an important economic sector; however, its wastewater generates a great impact on the environment. A heterogeneous solar Fenton (HSF) process was evaluated for denim wastewater treatment. The catalyst was obtained through ultrasonic modification of recycled polyethylene terephthalate (PET) with Fe nanoparticles (PET/NPs- Fe 3 O 4 ). The SFH process was optimized using surface response methodology with a face-centered central composite design considering the effects of the hydraulic retention time (10, 25, and 40 min), hydrogen peroxide dosage (500, 1000, and 1500 mg/L), and mass of the packed catalyst (4, 6 and 8 g) on the color, COD, and turbidity removal efficiencies. The operating conditions for maximum COD removal were H 2 O 2 541.7 mg/L, HRT 33.9 min, and PET/NPs- Fe 3 O 4 dose 7.9 g with solar radiation. The removal of 91.2% COD, 86.2% color, 90.4% turbidity, and 81.9% TOC was obtained at 14.2 kJ/L QUva. PET modification yielded 1.6 mg Fe/g PET, and the modification method does not allow Fe leaching. The effluent obtained from the SFH process complies with the maximum permissible limits in Mexican legislation in terms of COD, TOC, turbidity, and color and allows the reuse of PET., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Acid mine drainage was evaluated using a galvanic (GV) electrochemical system, Al-Cu (anode/cathode), based on a 3 2 factorial design. The factors analyzed were anodic area/volume ratios (A/V) of 0.037, 0.072, and 0.112 cm 2 /cm 3 , and treatment time from 0.25-8 h, and analyses were performed in duplicate with 11 degrees of freedom. The response variables were the total dissolved solids and concentrations of As, Cu, Co, Cr, Pb, Fe, Ni, and S O 4 2 - . The pH, electrical conductivity, and temperature were monitored during the process. Significant differences between treatments were determined by analysis of variance with Tukey's test ( p  < 0.05) using Statgraphics Centurion XVI.I software. The results showed that a greater electrode surface, A/V ratio, and treatment time improved pollutant removal. The spontaneous reactions generated by the galvanic cell, through the current that flows owing to the potential difference between the Al and Cu electrodes, allows the removal of heavy metals, arsenic, and S O 4 2 - by coagulation and precipitation mechanisms. The removal efficiencies achieved were Cu (99.1%), As (76.6%), Ni (80.2%), Pb (83.6%), Cr (100%), Fe (93.71%), and 92.9% for sulfates. The X-ray diffraction and Raman analyses of the solid fraction indicated that cuprite was formed with a purity of 96%, and the recovery of Cu by the GV system may be a viable option for mining companies.

Biological treatments have become insufficient to treat municipal wastewater with greater toxicity and excess nitrogen and phosphate species, thus affecting the organisms that consume the water. In this work, a process was implemented for the removal of nutrients through three stages: stage A, complete aeration (24 h, 43 months); stage B, decreased aeration (12 h, 17 months); and stage C, decreased aeration with biocalcium (12 h, 19 months). The addition of biocalcium from eggshell promoted the formation of flocks, which resulted in the removal of nitrites (61 %), nitrates (84 %), total nitrogen (57 %), total phosphorus (8.3 %), sedimentable solids (50 %), total suspended solids (69 %), BOD 5 (76 %), helminth eggs (50 %) and fecal coliforms (54 %). The statistical analyses in the three stages indicated that there is a strong correlation between the concentration of fats and oils and the removal of sedimentable solids and total suspended solids, since these parameters were correlated by 97 and 89 %, respectively. Sedimentable solids were correlated with total suspended solids by 94 %, while nitrates and total nitrogen were correlated 92 %, which favors the removal of nutrients in wastewater . The increase in the concentration of nitrogen in the sludge in stage C generated a C:N ratio of 7.98. This ratio shows that the sludge is feasible for use as a mediator of soils and a biofertilizer because of the high contents of calcium, phosphorus and nitrogen. In addition, biocalcium promoted the precipitation of hydroxyapatite, struvite, calcite and quartz. In general, the three stages of the treatment contributed to the stabilization of the wastewater treatment plant (WWTP) in an efficient, economical, and safe way., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors. Published by Elsevier Ltd.)

H 2 S is a gaseous compound that contributes to air pollution. In this work, the electrochemical oxidation treatment of gaseous streams polluted with H 2 S is evaluated using a jet mixer and electrochemical cell device, in which the performance of electrolytic and electro-Fenton assisted absorption processes are compared. Results demonstrate the feasibility of both processes to remove H 2 S, reaching coulombic efficiencies of nearly 100% in the electrolytic assisted absorption, and 70-80% in the electro-Fenton assisted absorption. Aqueous solutions containing phosphate salts as electrolyte were found to be suitable as absorbents for the process. Efficiency in the cathodic production of H 2 O 2 in these solutions using the experimental device was found to be as high as 32.8% (1.184 mgH 2 O 2 /min) at 12 °C and atmospheric pressure. Sequential formation of SO 2 and SO 3 is obtained by the oxidation of H 2 S contained in the gas. These species are hydrolysed, and a part remained in the absorbent as SO 3 2- and SO 4 2- , while the rest is dragged in the outlet gas. SO 3 production is promoted by electrolytic assisted absorption and polysulphides by the electro-Fenton technology. Low concentrations of elemental sulphur are detected in the solid suspensions formed during the process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The goal of this research is to apply an electrocoagulation process in continuous flow for the defluoridation of drinking water. Two sampling sites were studied, Temascalcingo (T), Mexico state and Jerecuaro (J), Guanajuato, with fluoride (F - ) concentrations above the norms (2.3 mg L -1 and 4.5 mg L -1 , respectively). In addition, a second Temascalcingo sample was enriched (T E ) to 9.2 mg L -1 F - to study the effect of the F - concentration. A response surface design was proposed through a Box-Behnken model, and the variables studied were electrode system, flow-rate and current intensity. 51 experiments were performed with T-site to determine the best operating conditions for the system. These conditions were applied to the J-site. The experiments for T, Al/Al system achieves an F - concentration within permissible limits (0.72 mg L -1 F - ) at 10 min of treatment, 0.2 A (Current density j 48.78 A m -2 ) and 10 mL min -1 with a removal efficiency of 68.69%, and after 160 min, the removal increased to 99.56%. AlMg/AlMg needs 10 min to achieve a concentration of 0.75 mg L -1 F - at 0.2 A ( j 25 A m -2 ), 16 mL min -1 with a removal efficiency of 67.39%, and after 100 min, the removal is increased to 92.17%. An important and novel advantage is the use of AlMg allows an acceptable removal of F - (<1.5 mg L -1 ) at high and low concentrations in short periods of time; this also allows save energy costs and the effluent is free of residual aluminum, avoiding side effects.

This review summarizes research data on the pharmaceutical drugs used to treat the novel SARS-CoV-2 virus, their characteristics, environmental impacts, and the advanced oxidation processes (AOP) applied to remove them. A literature survey was conducted using the electronic databases Science Direct, Scopus, Taylor & Francis, Google Scholar, PubMed, and Springer. This complete research includes and discusses relevant studies that involve the introduction, pharmaceutical drugs used in the SARS-CoV-2 pandemic: chemical characteristics and environmental impact, advanced oxidation process (AOP), future trends and discussion, and conclusions. The results show a full approach in the versatility of AOPs as a promising solution to minimize the environmental impact associated with these compounds by the fact that they offer different ways for hydroxyl radical production. Moreover, this article focuses on introducing the fundamentals of each AOP, the main parameters involved, and the concomitance with other sources and modifications over the years. Photocatalysis, sonochemical technologies, electro-oxidation, photolysis, Fenton reaction, ozone, and sulfate radical AOP have been used to mineralize SARS-CoV-2 pharmaceutical compounds, and the efficiencies are greater than 65%. According to the results, photocatalysis is the main technology currently applied to remove these pharmaceuticals. This process has garnered attention because solar energy can be directly utilized; however, low photocatalytic efficiencies and high costs in large-scale practical applications limit its use. Furthermore, pharmaceuticals in the environment are diverse and complex. Finally, the review also provides ideas for further research needs and major concerns., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Drinking water contaminated with As and [Formula: see text] is increasingly prevalent worldwide. Their coexistence can have negative effects due to antagonistic or synergistic mechanisms, ranging from cosmetic problems, such as skin lesions and teeth staining, to more severe abnormalities, such as cancer and neurotoxicity. Available technologies for concurrent removal include electrocoagulation ~ adsorption > membranes > chemical coagulation > , and among others, all of which have limitations despite their advantages. Nevertheless, the existence of competing ions such as silicon > phosphate > calcium ~ magnesium > sulfate > and nitrate affects the elimination efficiency. Mexico is one of the countries that is affected by As and [Formula: see text] contamination. Because only 10 of the 32 states have adequate removal technologies, more than 65% of the country is impacted by co-presence problems. Numerous reviews have been published concerning the elimination of As or [Formula: see text]. However, only a few studies have focused on the simultaneous removal. This critical review analyzes the new sources of contamination, simultaneous physicochemical behaviors, available technologies for the elimination of both species, and future trends. This highlights the need to implement technologies that work with actual contaminated water instead of aqueous solutions (55% of the works reviewed correspond to aqueous solutions). Similarly, it is necessary to migrate to the creation of pilot, pre-pilot, or prototype scale projects, because 77% of the existing studies correspond to lab-scale research., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In this study, acetaminophen (ACT) in aqueous solution was treated with electrooxidation and photo-electrooxidation processes (PEO). An electrochemical cell was used for the treatment of different concentrations of ACT (10, 50 and 80 mg L -1 ). A 2 3 factorial design was proposed, and the variables studied were current intensity 0.5 A (45.45 mA cm -2 ) and 1.0 A (90.91 mA cm -2 ), electrode configuration (anode:BDD, cathode:Fe or Cu) and presence/absence of UV light; NaCl 0.043 M (2.5 g L -1 ) was used as supporting electrolyte, the initial pH was 5.5, and the treatment time was 3 h. The aqueous solutions were characterized before and after the treatment using infrared spectroscopy (FT-IR), Ultraviolet-visible spectroscopy (UV-Vis), chemical oxygen demand (COD), total organic carbon (TOC), total carbon (TC), and fluorescence spectroscopy. The optimal operating conditions using an initial ACT concentration of 80 mg L -1 were 1.0 A, BDD-Fe configuration and UV light (254 nm). The removal efficiencies were 100% of ACT and 82.75% of TOC after 15 min of treatment. At concentrations of 50 and 10 mg L -1 , 77.16% and 50.29% of TOC were removed after 10 and 5 min of treatment, respectively. Finally, the kinetic study showed an increase in the rate constants when the UV light was applied.

Organochlorine pesticides have generated public concern worldwide because of their toxicity to human health and the environment, even at low concentrations, and their persistence, being mostly nonbiodegradable. The use of 2,4-dichlorophenoxyacetic acid (2,4-D) has increased in recent decades, causing severe water contamination. Several treatments have been developed to degrade 2,4-D. This manuscript presents an overview of the physicochemical characteristics, uses, regulations, environmental and human health impacts of 2,4-D, and different advanced oxidation processes (AOPs) to degrade this organic compound, evaluating and comparing operation conditions, efficiencies, and intermediaries. Based on this review, 2,4-D degradation is highly efficient in ozonation (system O 3 /plasma, 99.8% in 30 min). Photocatalytic, photo-Fenton, and electrochemical processes have the optimal efficiencies of degradation and mineralization: 97%/79.67% (blue TiO 2 nanotube arrays//UV), 100%/98% (Fe 2+ /H 2 O 2 /UV), and 100%/84.3% (MI-meso SnO 2 ), respectively. The ozonation and electrochemical processes show high degradation efficiencies, but energy costs are also high, and photocatalysis is more expensive with a separation treatment used to recover the catalyst in the solution. The Fenton process is a viable economic-environmental option, but degradation efficiencies are often low (50-70%); however, they are increased when solar UV radiation is used (90-100%). AOPs are promising technologies for the degradation of organic pollutants in real wastewater, so evaluating their strengths and weaknesses is expected to help select viable operational conditions and obtain optimal efficiencies.

This work focuses on the development of electro-absorption and photoelectro-absorption technologies to treat gases produced by a synthetic waste containing the highly volatile perchloroethylene (PCE). To do this, a packed absorption column coupled with a UV lamp and an undivided electrooxidation cell was used. Firstly, it was confirmed that the absorption in a packed column is a viable method to achieve retention of PCE into an absorbent-electrolyte liquid. It was observed that PCE does not only absorb but it was also transformed into phosgene and other by-products. Later, it was confirmed that the electro-absorption process influenced the PCE degradation, favoring the transformation of phosgene into final products. Opposite to what is expected, carbon dioxide is not the main product obtained, but carbon tetrachloride and trichloroacetic acid. Both species are also hazardous but their higher solubility in water opens possibilities for a successful and more environmental-friendly removal. The coupling with UV-irradiation has a negative impact on the degradation of phosgene. Finally, a reaction mechanism was proposed for the degradation of PCE based on the experimental observations. Results were not as expected during the planning of the experimental work but it is important to take in mind that PCE decomposition occurs in wet conditions, regardless of the applied technology, and this work is a first approach to try to solve the treatment problems associated to PCE gaseous waste flows in a realistic way.