Dye residues from the textile industry constitute a critical wastewater problem. This study aimed to evaluate the removal capacity of methylene blue (MB) in aqueous media, using an adsorbent formulated from activated and sonicated nanoclay (NC) and microatomized Nostoc sphaericum (ANS). NC was obtained by acid treatment, followed by activation with 1 M NaCl and sonication, while ANS was obtained by microatomization in an aqueous medium. NC/ANS was mixed in a 4:1 weight ratio. The NC/ANS synergistic adsorbent was characterized by the point of zero charge (PZC), zeta potential (ζ), particle size, FTIR spectroscopy, and scanning electron microscopy (SEM). NC/ANS exhibited good colloidal stability, as determined by pH_PZC, particle size in the nanometer range, and heterogeneous morphology with functional groups (hydroxyl, carboxyl, and amide), removing between 72.59 and 97.98% from an initial concentration of 10 ppm of MB, for doses of 20 to 30 mg/L of NC/ANS and pH of 5 to 8. Optimal adsorption conditions are achieved at pH 6.8 and 32.9 mg/L of adsorbent NC/ANS. It was observed that the pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models best described the adsorption kinetics, indicating a predominance of the physisorption process, with adsorption capacity around 20 mg/g. Isotherm models and thermodynamic parameters of adsorption, ΔS, ΔH, and ΔG, revealed that the adsorption process is spontaneous, favorable, thermodynamically stable, and occurs at the monolayer level, with a regeneration capacity of 90.35 to 37.54% at the fifth cycle. The application of physical activation methods, such as sonication of the clay and microatomization of the algae, allows proposing a novel and alternative synergistic material from organic and inorganic sources that is environmentally friendly and promotes sustainability, with a high capacity to remove cationic dyes in wastewater.

Cultural customs often condition solid waste management, especially in developing countries. The decomposition of solid waste depends on climatic conditions and is related to geomorphology and anthropogenic practices. Leachate generated in landfills can migrate superficially and underground, contaminating soils and aquifers. Knowing the level of contaminant load in leachate is important for proper solid waste management. However, in the Andean regions of Peru, there is scarce data on the polluting potential of leachates. This research aimed to determine the Leachate Pollution Index (LPI) according to the sub-indexes of organic, inorganic, and heavy metals from landfills in the high Andean regions of Peru. Physical, chemical, and microbiological parameters were evaluated in fresh and retained leachate samples, in both dry and rainy seasons, from two landfills located at around 3000 m of altitude. The results showed high contamination levels, particularly in BOD₅, COD, NH₃-N, and total coliforms, with high organic and inorganic sub-indexes that affect the LPI, indicating high levels of contamination and posing a potential risk to surrounding ecosystems. It was also found that the high Andean landfills studied have a good-to-high biodegradability. This research contributes essential baseline information for environmental monitoring and supports the need for improved leachate management in high-altitude landfills in Peru and similar Andean contexts.

There is a growing emphasis on seeking stabilizing agents with minimal transformation, prioritizing environmentally friendly alternatives, and actively contributing to the principles of the circular economy. This research aimed to assess the stability of a novel spray-dried hydrocolloid from high Andean algae when introduced into an aqueous solution. Nostoc sphaericum freshwater algae were subject to atomization, resulting in the production of spray-dried hydrocolloid (SDH). Subsequently, suspension solutions of SDH were meticulously prepared at varying pH levels and gelling temperatures. These solutions were then stored for 20 days to facilitate a comprehensive evaluation of their stability in suspension. The assessment involved a multifaceted approach, encompassing rheological analysis, scrutiny of turbidity, sedimentation assessment, ζ-potential, and measurement of particle size. The findings from these observations revealed that SDH exhibits a dilatant behavior when in solution, signifying an increase in with higher shear rate. Furthermore, it demonstrates commendable stability when stored under ambient conditions. SDH is emerging as a potential alternative stabilizer for use in aqueous solutions due to its easy extraction and application.

The aim of this study was to evaluate the removal of Pb and As from an aqueous solution using corn residue cellulose nanocrystals (NCCs). The corn husk was subjected to alkaline digestion, followed by bleaching and esterification with 3% citric acid to obtain NCCs. A 10 ppm multimetal solution of Pb and As was prepared. The adsorption process was evaluated by adjusting the pH and NCC dosage, optimized through the nonlinear regression of empirical mathematical models. Based on the optimal parameters, the kinetics were evaluated using the PFO and PSO models. The NCCs displayed nanometer-level characteristics with a particle size less than 383.7 nm, a ζ potential in the range of −28–70 mV, pH_ZCP with an acidic tendency, a porous crystal structure as evaluated through SEM images, and the presence of functional groups with a high chelating capacity, as identified via FTIR. Optimum values of pH 8.0 and 20 mg/L of the NCC dose were found, from which it was observed that the PFO, PSO, and Elovich kinetics showed R² > 0.974, with an adsorption capacity in the order Pb > As. The adsorbent-formulated NCCs presented a good capacity to remove heavy metals from aqueous media.

Lentic ecosystems are highly vulnerable to anthropogenic disturbances, which can lead to ecological imbalances with the loss of native biodiversity. This research evaluated the impact of anthropogenic activities on water quality and the trophic status of the Pacucha Lagoon, Andahuaylas, Apurimac. Seasonal sampling was conducted at six strategic points on the surface and bottom of the lake, following standardized protocols, during both the dry and rainy seasons. Physical and chemical parameters, metal ions, chlorophyll-a, and trophic status were determined using the Carlson indices, and water quality was assessed through the WQI-PE. The quantification of anthropogenic impacts was performed using the Leopold matrix. Statistical analysis included descriptive methods, ANOVA, Pearson correlation, and PCA at 5% significance. The results classify the lake as having “Regular” water quality according to WQI-PE. Physical and chemical parameters remain within the Environmental Quality Standards (ECA-Peru), while heavy metal ions exceed the limits in both seasons. The system exhibits mesotrophic conditions that tend to become eutrophic during the rainy season, suggesting a favorable nutrient balance for biological productivity. Activities with the most significant adverse impacts include agricultural practices that involve the intensive use of agrochemicals, morphological alterations to the surrounding area, and unregulated aquaculture. The lack of effective regulatory mechanisms and a lack of commitment to conservation suggest a high risk of irreversible degradation of the Pacucha Lagoon ecosystem.