Sergio Gómez-Salazar

Silica gel polymer material with imprinted phosphate cavities was successfully obtained using one-pot sol–gel reaction. Differences in the textural properties concerning the reduction in specific area and pore size between functionalized and pristine silica gel demonstrated the presence of the phosphate moieties in the cavities. The chemical and structural characterization of the functionalized material before and after copper adsorption was performed by Fourier-transform infrared spectroscopy (FTIR) and solid-state ²⁹Si and ³¹P nuclear magnetic resonance (NMR) spectroscopy. All these measures proposed a phosphate non-covalently bound in the cavities of the silica gel and stabilized by silanol groups on the surface of the matrix. The phosphate–copper complex is removed after the metal desorption process, and the free cavities in the silica matrix can be replenished with phosphoric acid without affecting its adsorption capacity. The entire process of phosphate incorporation, copper adsorption, and metal-ligand desorption was repeated in three cycles, showing a similar metal adsorption capacity. Energy-dispersive X-ray spectroscopy (SEM-EDX) experiments were performed to monitor the presence and proportion of phosphorus and copper at each step of the phosphate loading and copper adsorption processes. These results demonstrate the feasibility of synthesizing a rechargeable polymer material with functional molded cavities with phosphate groups capable of adsorbing copper ions. Finally, this investigation represents the first approach to new materials with a rechargeable ligand system for the adsorption of heavy metals.

Reframing solid–solution interactions beyond classical site-density descriptions requires an interpretation integrating surface energetics, polarizability, and vibrational response. In this work, an energetic framework is developed to rationalize the interaction of As(V) with CNTsG0.5, a PAMAM-functionalized carbon nanotube hybrid selected after comparative evaluation of generation-dependent energetic responses. CNTs were synthesized by chemical vapor deposition, partially oxidized to introduce oxygenated anchoring groups, and covalently grafted with PAMAM, producing a chemically integrated solid phase with tunable dipole density and conformational flexibility. Comparative analysis identified CNTsG0.5 as the most suitable configuration, exhibiting a balanced distribution of accessible high- and low-energy regions enabling polarization-driven interactions with As(V). Time- and concentration-dependent responses were analyzed to resolve energetic accessibility and polarization strength. Results reveal rapid establishment of electronic coupling together with an energetically heterogeneous response associated with domains of distinct interaction strength. Spectroscopic evidence (FTIR, Raman, and XPS) confirms that As(V) interaction induces localized electronic rearrangements involving amide, amine, and oxygenated functionalities, consistent with charge redistribution and vibrational coupling at the CNT–PAMAM hybrid interface. DFT-derived surface-energy distributions, f(E), obtained from N₂ physisorption, correlate with these spectroscopic signatures. The combined experimental strategy provides design principles for hybrid solids governed by cooperative electronic response and surface-energy matching.

The development of oxidation-resistant and regenerable materials remains a major challenge for mercury removal from contaminated waters and industrial effluents. In this study, a zwitterionic mesoporous silica gel functionalized with L-cysteine (SG-3PS-Cys) was synthesized, where the thiol group is covalently anchored to the silica framework, preventing oxidative degradation while preserving –NH₃⁺ and –COO⁻ groups for Hg(II) coordination. Spectroscopic analyses (FTIR, XPS, and ¹³C NMR) confirmed the formation of a stable, thiol-free binding environment in which mercury interacts through carboxylate oxygen atoms, electrostatically stabilized by neighboring ammonium groups. The material exhibited a high surface area (134 m² g⁻¹) and uniform mesoporosity (9.8 nm), achieving a maximum Hg(II) uptake of 82.7 mg g⁻¹ at pH 3 with rapid kinetics and cooperative S-type isotherms. The adsorbent retained 72% of its capacity after five regeneration cycles and maintained 38.7% selectivity toward Hg(II) in multicomponent solutions. DFT-based surface energy distribution analysis supported the zwitterionic coordination mechanism, revealing energetically homogeneous and high-affinity binding domains. Beyond its chemical stability, the material introduces a sustainable route for mercury remediation, linking surface energy, electrostatic effects, and porosity to achieve durable performance under acidic and complex aqueous conditions. These findings provide a mechanistic and design framework for the next generation of non-thiol adsorbents capable of selective and reusable Hg(II) removal in environmentally relevant scenarios.

Pesticide contamination in drinking water poses serious risks due to their toxicity, persistence, and poor degradability. In Mexico, the absence of specific regulations creates exposure risks for non-occupational populations. This study assessed pesticide occurrence and chronic exposure risk in the Guadalajara Metropolitan Area (GMA). A total of 39 household tap water samples and 40 commercial purified water samples were analyzed by HPLC–MS/MS. Commercially purified water samples were obtained from local purification establishments unaffiliated with national or transnational brands. Five pesticides were detected in tap water, with molinate and malathion showing the highest exposure frequencies (43.6% and 38.5%). In purified water, only malathion was found, present in 95% of samples, with a maximum of 1.57 mg/L in a single case. Risk levels were classified using Acceptable Daily Intake (ADI) thresholds. Spatial patterns revealed higher risk in areas supplied by Lake Chapala. Multivariate statistics identified atrazine and picloram as key contributors to exposure variance. Levene’s and Kruskal–Wallis tests confirmed significant differences in malathion levels between municipalities. The results show contrasting contamination profiles and treatment limitations in both water sources. This is the first study in Mexico to jointly evaluate pesticide contamination and human exposure risk in public and commercial water using a spatial-statistical framework.

The demand to alleviate climate change produced by greenhouse gases, such as CO₂, is a fact at present. The use of porous adsorbents such as Prussian blue analogues (PBAs) possessing fast removal velocities and improved uptake capacity properties has shown promise as an alternative in the solution to this problem. In this work, the structural characterization and CO₂ adsorption data of a potassium cobalt hexacyanoferrate (CoHCFM11) are presented. FTIR demonstrates the presence of a mixture of two chains, Fe³⁺-CN-Co²⁺ and Fe²⁺-CN-Co³⁺, produced during the synthesis procedure. XRD reveals a face-centered cubic crystal, spatial group Fm3̅m, and corroborates the presence of cavities ideal to capture CO₂ molecules. XPS shows the existence of two oxidation states of Co and Fe in PBA. TEM measurements confirm the cubic shape nature of CoHCFM11 with an average size of 80-130 nm. A deep understanding of the CO₂ adsorption mechanism by CoHCFM11 is obtained by mathematical models. The validation of models in predicting experimental isotherm and kinetic adsorption data sets is presented. The goodness of fit is collated through the residual and normal probability plots to discriminate the appropriate model. Normal probability plots confirm the best stability of the 2-S Langmuir model in agreement between the measurements and model. Kinetic data are fitted using five models. Goodness-of-fit statistics confirm that Avrami's model better explains the data. Isosteric heats of adsorption are obtained through the Clausius-Clapeyron equation using the isosteres approach to which the heats obtained via the different isotherm model predictions are compared. The 2-S Langmuir model predicts closely the results obtained via the isosteres approach. The results of this study demonstrate the need to use goodness-of-fit statistics when selecting a model to recommend as the most appropriate in CO₂ adsorption data.

Water Quality Indices (WQIs) are used to evaluate the environmental conditions of a body of water and are mathematical combinations that integrate physical, physicochemical and biological parameters that describe the state of health or the degree of contamination of an aquatic system as a whole. Currently, there are many models which must be used depending on the required quality of the body of water. This is the case of the Chignahuapan lagoon in the municipality of Almoloya del Río EDOMEX, which is the source of the Lerma River and for its evaluation five ICAS models were used: NSF, León-Dinius, Montoya et al., OQWI and ATI, of which, the last four, in which 11 parameters were used, indicated that, The lagoon has sites with poor, very bad, polluted or highly polluted quality. In the case of the NSF AQI that only uses 7 parameters, the results were not reliable.

Tequila vinasses are organic wastes generated during ethanol fermentation at elevated temperatures (≥90 °C) and pH ≤ 4.0, making them hazardous to the environment. This paper describes a new, simplified UV–vis spectroscopy-based procedure for monitoring the adsorption of color compounds in tequila vinasses onto silica-based adsorbents, along with an optimized synthesis method to produce the most efficient sol–gel synthesized thiol-functionalized adsorbent. Under optimized conditions, the uptake capacity of this adsorbent reaches 0.8 g g⁻¹ in 90 min. Experimental results demonstrate that the adsorbent has a specific affinity for melanoidin-type molecules. The adsorbent demonstrates excellent thermal stability (~316 °C). The results of this work indicate that the adsorbent possesses potential in the treatment of tequila vinasses from wastewater discharges.

The stoichiometry of the components of hexacyanoferrate materials affecting their final porosity properties and applications in CO₂ capture is an issue that is rarely studied. In this work, the effect that stoichiometry of all element components and oxidation states of transition metals has on the structures of mesoporous K or Na-cobalt hexacyanoferrates (CoHCFs) and CO₂ removal is reported. A series of CoHCFs model systems are synthesized using the co-precipitation method with varying amounts of Co ions. CoHCFs are characterized by N₂ adsorption, TGA, FTIR-ATR, XRD, and XPS. N₂ adsorption results reveal a more developed external surface area (72.69–172.18 m²/g) generated in samples containing mixtures of K⁺/Fe²⁺/Fe³⁺ ions (system III) compared to samples with Na⁺/Fe²⁺ ions (systems I, II). TGA results show that the porous structure of CoHCFs is affected by Fe and Co ions oxidation states, the number of water molecules, and alkali ions. The formation of two crystalline cells (FCC and triclinic) is confirmed by XRD results. Fe and Co oxidation states are authenticated by XPS and allow for the confirmation of charges involved in the stabilization of CoCHFs. CO₂ removal capacities (3.04 mmol/g) are comparable with other materials reported. CO₂ adsorption kinetics is fast (3–6 s), making CoHCFs attractive for continuous operations. Q_st (24.3 kJ/mol) reveals a physical adsorption process. Regeneration effectiveness for adsorption/desorption cycles indicates ~1.6% loss and selectivity (~47) for gas mixtures (CO₂:N₂ = 15:85). The results of this study demonstrate that the CoHCFs have practical implications in the potential use of CO₂ capture and flue gas separations.

An L-glutathione-functionalized silica adsorbent was applied in this study to remove malathion from aqueous media. This adsorbent has demonstrated an improved adsorption efficiency of malathion. The maximum uptake achieved was 130 mg g⁻¹ at pH 8. Equilibrium was reached after about 90 min. A pseudo-second-order model best described the adsorption kinetics. The adsorption isotherms were best simulated by the Freundlich model. The functional groups are thermally stable up to about 150 °C. The elemental analysis results indicated high glutathione ligand densities. The results of this study show that the environmentally friendly L-glutathione functionalized silica is a promising candidate for the removal of malathion from water at the industrial level.