Gabriela Alejandra Vázquez Rodríguez

The arrangement of common filter materials can influence urban runoff treatment, but initial removal does not establish whether performance persists during repeated loading. This study evaluated a proposed stratification of soil, geotextile, coarse sand, gravel, and tezontle (volcanic scoria) through nutrient and metal breakthrough curves. Nine laboratory columns, comprising three independent replicates each of the stratified configuration, soil alone, and tezontle alone, received synthetic urban runoff during 16 eight-hour feeding cycles. Feeding occurred on weekdays, with overnight and weekend interruptions; the effluent from each feeding period and 30 min of subsequent drainage was combined for analysis. The curves represent ratios of mean effluent to mean influent concentrations for the three columns per configuration. In the stratified configuration, ammonium removal ranged from 74.53% to 91.60%, and mean nitrate removal was 68.29%. Phosphate and metal removal declined over successive cycles, and effluent lead concentrations exceeded influent concentrations during part of the experiment. Soil-only columns showed broadly similar nutrient trends, whereas tezontle provided limited, transient metal removal. These results identify pollutant-specific differences in the persistence of treatment within the proposed stratification. Their main design implication is that favorable initial removal by common materials must be considered together with subsequent breakthrough and possible release. The findings apply to the tested materials and loading sequence rather than establishing field service life.

This study evaluated recycled concrete aggregates (RCAs) as a filter medium and secondary mineral resource in bioretention cells treating synthetic urban runoff, with emphasis on pollutant retention, start-up, and stabilization dynamics. Four laboratory-scale columns containing RCAs were operated for 12 weekly cycles under unplanted and vetiver-planted configurations, with and without a 2 cm granular activated carbon layer. Ammonium, nitrate, total nitrogen, phosphate, Pb, Zn, pH, and electrical conductivity (EC) were monitored throughout the experiment. Ammonium was consistently retained, reaching removal efficiencies above 95% in all configurations by the final cycles, while Pb and Zn remained below detection in nearly all effluents. Nitrate, total nitrogen, and phosphate showed initial export and greater variability during start-up, followed by more consistent retention, particularly in the vegetated configurations. The GAC layer did not provide a consistent improvement in nutrient retention. EC generally decreased during operation, indicating progressive conditioning of the RCA media, whereas effluent pH remained persistently alkaline. Altogether, RCAs provided effective pollutant retention while exhibiting distinct conditioning and stabilization trajectories. Their use as the main mineral component of bioretention filter beds also offers a pathway for substituting virgin aggregates and valorizing construction and demolition waste, although long-term performance and life-cycle impacts require further evaluation.

La capacidad de las plantas del género Opuntia para crecer en suelos empobrecidos y soportar sequías prolongadas las convierte en un recurso estratégico frente al cambio climático, en torno al cual pueden articularse esquemas de economía circular en México. Este trabajo presenta experiencias de investigación sobre el aprovechamiento de Opuntia spp. no comestibles o sus residuos para la producción de (i) un medio de cultivo para gránulos fúngicos, (ii) pectina y mucílago, (iii) películas comestibles y (iv) biofertilizante y biogás. Estas aplicaciones se desarrollaron bajo un enfoque de biorrefinería, con bajo impacto ambiental y sin competir con el uso alimenta­rio tradicional de estas plantas. Los resultados respaldan el papel de Opuntia spp. como recurso clave para implementar modelos de economía circular en regiones áridas y semiáridas de México.

Es un hecho que la escasez de agua está aumentando día con día; el crecimiento poblacional, la producción masiva, el consumo desmedido y los efectos del cambio climático han incrementado la presión sobre este recurso vital. En 2021 la ONU-Hábitat publicó que el consumo promedio per cápita en México es de 366 litros al día, sin contar el agua virtual proveniente de los productos que consumimos, mientras que el consumo promedio en países desarrollados como Estados Unidos alcanza los 575 litros al día. Aun así, el consumo promedio de agua de los mexicanos se encuentra arriba del consumo recomendado, que es de 96 litros al día. Los hogares son uno de los espacios donde el agua es un recurso vital y donde la economía circular puede contribuir a un mejor uso y diseño de nuevas formas de reutilización y reciclaje del agua mediante la filtración, separación, biodigestión, entre otros procesos combinados, con el fin de darle un tratamiento para construir un modelo de economía circular del agua a nivel de vivienda. Este capítulo tiene como objetivo analizar la posibilidad de reciclar agua a nivel doméstico y tener una aproximación de la proporción de agua que se puede ahorrar mediante economía circular.

This paper presents the conceptual design of blue and green infrastructure (BGI) prototype focused on the decentralized stormwater collection, treatment, and storage in urban dwellings of semi-arid areas. The proposal emerges as an adaptation strategy to address water scarcity, taking into account the poor performance of conventional supply systems in such vulnerable contexts. The BGI system integrates two complementary strategies: direct collection from rooftops and collection of surface runoff generated on impervious sidewalks, which is conducted through permeable pavement to a bioretention cell composed of vegetation and recycled construction aggregates. This configuration allows runoff water to be collected, filtered, and stored for later use. Local climate data were used to estimate surface runoff, infiltration into the system layers, and potential storage in a preliminary water balance. The design was applied to a typical home with a roof area of 39.2 m² and a daily consumption of 724.9 liters (for five inhabitants, with water-saving devices). The results indicate that, during representative rainfall events, the volume captured partially covers this allocation for at least one day, demonstrating the hydraulic viability of the system in urban environments with limited space. It should be noted that the water balance did not consider losses due to evaporation or evapotranspiration, as the objective was to make a preliminary estimate for conceptual sizing. It is concluded that the BGI prototype represents a viable and sustainable alternative for harvesting rainwater in homes with limited space and access to conventional sources, thus contributing to the circular water economy.

The development of stable, recyclable solid-based catalysts remains a major challenge in heterogeneous biodiesel production, due to CaO leaching and limited durability. This study evaluates, for the first time, the use of a commercial Zr-doped alumina support (Sasol Puralox SCFa-190 Zr20) combined with eggshell-derived CaO as a potential strategy to enhance catalyst stabilization. CaO was calcined at 800 °C and impregnated onto the support at 40, 50, and 60 wt% loadings, yielding catalysts CaP40, CaP50, and CaP60. Structural characterization by XRD and SEM revealed the formation of portlandite and calcium aluminate phases with high crystallinity, along with progressive surface coverage of alumina particles by calcic agglomerates and flake-like structures. The supported catalysts exhibited strong basicity and a significant increase in basic site density compared to the bare support. Under reaction conditions (60 °C, methanol-to-oil molar ratio 10:1, 6 wt% catalyst, 1 h), CaP50 and CaP60 achieved biodiesel yields of 98% using soybean oil and waste palm olein. However, catalytic activity decreased upon reuse due to Ca leaching and surface blockage; thermal reactivation at 800 °C partially restored performance. These results indicate that the alumina-zirconia support promotes the dispersion of active Ca species and favors the formation of mixed oxide phases, thereby improving structural stability during reuse.

Zeolites, microporous crystalline materials composed mainly of silicon and aluminum, possess physicochemical properties that make them valuable in water treatment and catalysis applications. Using construction and demolition waste (CDW) as raw material for producing zeolites represents a sustainable strategy to reduce its environmental impact. Thus, the present work addresses the synthesis of zeolites from CDW within the framework of the circular economy. Crushed brick waste was used and subjected to a hydrothermal process in a stainless-steel reactor with 2 M KOH, at 160 °C, for 6, 8, 10, and 12 hours. After treatment, the products were characterized by powder X-ray diffraction to evaluate their crystallinity. The results showed a progressive evolution in the formation of crystalline phases: at 6 hours an amorphous material was obtained; at 8 hours the first signs of nucleation of ordered phases were identified; at 10 hours zeolitic structures were consolidated, including aluminosilicates typical of zeolites, such as phillipsite; and finally, at 12 hours secondary phases were observed. It is concluded that it is feasible to transform CDW into functional zeolites by hydrothermal synthesis, with an optimum reaction time of about 10 hours. This approach allows the valorization of solid waste and contributes to the production of high-value materials, promoting sustainable practices in the materials science field.

This study evaluates the catalytic performance of strontium-based materials combined with Sasol Puralox SCFa-190 Zr20-doped alumina for the transesterification of soybean and canola oil to produce biodiesel. Catalysts were synthesized by impregnating the support with 30, 40, and 50 wt% Sr using Sr(NO ₃ ) ₂ , followed by calcination at 750 °C. XRD analysis revealed the formation of well-crystallized strontium aluminates, primarily Sr ₃ Al ₂ O ₆ and SrAl ₂ O ₄ , with the structures observed by SEM. The catalyst surface exhibited progressive morphological changes, progressing from needle-like features to coral-like aggregates and finally to compact, cement-like structures. 40 % of Sr catalysts (40 SrPx) exhibited high catalytic performance due to the crystallinity of Sr ₃ Al ₂ O ₆ , which provided abundant and strong basic sites. Under enhanced conditions (55 °C, methanol:oil 10:1, 4 % catalyst, and 2 h), a maximum biodiesel yield of 97 % was achieved with canola oil. The catalyst demonstrated reasonable stability, yielding 76.5 % after four cycles. The combination of Sr and Puralox SCFa-190 Zr20 is an effective and reusable catalyst for biodiesel production.

En el presente trabajo se analizó la adsorción del ion fosfato sobre superficies de óxido de calcio (CaO) y óxido de aluminio en su fase gamma (γ-Al2O3), modeladas como cúmulos de tamaño finito y utilizando el nivel de teoría semiempírico PM6. Se calcularon las energías de adsorción, y se obtuvieron valores de ΔHads = -476.159 kJ/mol para la interacción entre el fosfato y la superficie de CaO, y de -2357.1 kJ/mol para la interacción con la γ-Al2O3. Los resultados indican que la interacción entre el ion fosfato y la superficie de CaO corresponde a un proceso de fisisorción, caracterizado por una energía de adsorción relativamente baja e interacciones débiles, predominantemente de tipo electrostático y de Van der Waals. En contraste, la fuerte interacción observada en el sistema fosfato–γ- Al2O3, junto con el alto valor estimado para la energía de adsorción, sugieren un proceso de quimisorción, en el cual se forman enlaces químicos entre el adsorbato y la superficie.