This work evaluates phosphate and nitrate ion adsorption from aqueous solutions on calcined adsorbent substrates of variable charge, prepared from three granulometric fractions of an oxidic lithological material. The adsorbent material was chemically characterized, and N2 gas adsorption (BET), X-ray diffraction, and DTA techniques were applied. The experimental conditions included the protonation of the beds with HCl and H2SO4 and the study of adsorption isotherms and kinetics. The lithological material was moderately acidic (pH 5) with very little solubility (electrical conductivity 0.013 dS m−1) and a low cation exchange capacity (53.67 cmol (+) kg−1). The protonation reaction was more efficient with HCl averaging 0.745 mmol versus 0.306 mmol with H2SO4. Likewise, the HCl-treated bed showed a better adsorption of PO4−3 ions (3.296 mg/100 g bed) compared to the H2SO4-treated bed (2.579 mg/100 g bed). The isotherms showed great affinity of the PO4−3 ions with the oxide surface, and the data fit satisfactorily to the Freundlich model, suggesting a specific type of adsorption, confirmed by the pseudo-second-order kinetic model. In contrast, the nitrate ions showed no affinity for the substrate (89.7 µg/100 g for the HCl-treated bed and 29.3 µg/100 g bed for the H2SO4-treated bed). Amphoteric iron and aluminum oxides of variable charges present in the lithological material studied allow for their use as adsorbent beds as an alternative technique to eliminate phosphates and other ions dissolved in natural water.

One of the main challenges for environmental sciences today is the effective treatment of dye-laden industrial effluents. This work aimed to study the potential of an untreated (natural occurring clayey composite) red clay (RC) for the adsorption of a cationic dye Basic Navy Blue 2RN (CNB) and anionic dye Drimaren Yellow CL-2R (ADY). We evaluated the effect of pH, dye concentration, and adsorbent concentration on the removal effectiveness to study the absorption process. Also, we studied the adsorption process by analyzing the feasibility of several known adsorption isotherms and kinetic models. The results show that at a pH of less than 4, the CNB and ADY removal percentages were 97% and 96%, respectively. At a pH greater than 8, the CNB and ADY removals were 75% and 25%, respectively. The CNB adsorption happened by chemisorption of a monolayer on iron-containing particles (IPs). In congtrast, the ADY adsorption occurred by monolayer physisorption on kaolinite particles (KPs) and Na, K-rich Laumontite particles (LPs). The Langmuir isotherm model fits very well with CNB experimental data. The Temkin model shows the best fit between the isotherm function and the ADY dye-adsorption data. The pseudo-second-order kinetic model fits the CNB and ADY dye-adsorption data on RC particles. The heterogeneous composition of naturally occurring clay favors different adsorption mechanisms and opens an avenue for the separation process’s engineering.

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The páramo is home to a significant proportion of global biodiversity and provides essential services for the development of life for millions of people in Ecuador. However, land use/land cover (LULC) changes threaten biodiversity and modify its functioning. The objectives of this study were: (1) to evaluate the conservation status of the herbaceous páramo (HP) ecosystem by analyzing its LULC in Ecuador’s southern region. (2) to identify possible regions where the native páramo ecosystem is being restored. We analyzed Landsat 8 images using Object-Based Image Analysis (OBIA) and a Classifier Decision Tree (CDT) to achieve these objectives. The results show that the native herbaceous páramo (NHP) ecosystem is being transformed into an anthropogenic HP (AHP). The area covered by the NHP ecosystem (296,964 ha) has been reduced by 50% (149,834 ha). Nevertheless, we identified five regions where the NHP is upgrading. These regions are relevant for studying NHP regeneration in Ecuador’s southern region, where soils are mostly andosols. The LU of the páramo, with cycles of exploitation, abandonment, and regeneration in a secondary páramo, is transforming the NHP ecosystem. These exploitation practices, global climate change, and lack of knowledge about the NHP ecosystem’s regeneration and its soils’ recovery threaten to substantially reduce the NHP area, its functionality, and its ecosystem services.

Different types of tuned mass dampers (TMD) have been applied to reduce wind and seismic induces vibrations in buildings. We analyze a pendulum tuned mass damper (PTMD) to reduce vibrations of structures that exhibit elastoplastic behavior subjected to ground motion excitation. Using a simple dynamic model of the primary structure with and without the PTMD and a random process description of the ground acceleration, the performance improvement of the structure is assessed using statistical linearization. The Liapunov equation is used to estimate the mean-square response in the stationary condition of the random process and optimize PTMD parameters. The optimum values of the PTMD frequency and damping ratio are defined as PTMD design values for a specific maximum seismic intensity design criterion. The results show that: (1) The values of the PTMD effectiveness criterion and the optimal design values of the frequency ratio are higher when the damping ratio of the primary structure decreases. (2) The performance of the optimized PTMD is higher when the structure exhibits a linear hysteresis loop (low seismic intensity). (3) The optimized PTMD controls the development of structural plasticity reducing vulnerability. (4) There is a strong dependence of the optimum PTMD parameters on the dynamic soil properties of the building foundation. (5) The PTMD performance improves as its mass increases. The optimum frequency ratio decreases, and the damping ratio increases as the mass of the pendulum increases. The PTMD designed and optimized with the proposed methodology reduces vibrations, controls the development of plasticity, and protects the primary structure, particularly in low and medium-intensity earthquakes.