The search for new natural sources of hydrocolloids with stabilizing, thickening, and good binding capacity, from raw materials that are environmentally friendly and that contribute to the circular economy is a challenge for the food industry. The aim of the study was the preliminary characterization of a spray-dried hydrocolloid from high Andean algae Nostoc sphaericum. Four ecotypes of algae from Peruvian high Andean lagoons located above 4000 m were considered. The samples were collected in the period March–April 2021 and were subjected to a spray drying process in an aqueous medium. The characterization showed that the dehydrated nostoc ecotypes presented high protein and carbohydrate content, making it a potential material for direct use as a functional food for humans. The spray-dried product presented good stability for its use as a hydrocolloid, with zeta potential values (ζ), around 30 mV, evidencing the presence of -CO-, -OH, -COO-, and -CH groups, characteristic of polysaccharides, representing 40% of total organic carbon on average, giving it low water activity values and particle size at the nanometric level. Major minerals such as Ca (>277 mg/100 g), Mg (>19.7 mg/100 g), and Fe (>7.7 mg/100 g) were reported. Spray-dried nostoc is a hydrocolloid material with high potential for the food industry, with good nutritional content and techno-functional behavior.

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.

Adsorption isotherms provide insight into the thermodynamic properties governed by food storage conditions. Adsorption isotherms of purple corn of the Canteño variety were evaluated at 18, 25, and 30 °C, for the equilibrium relative humidity (ERH) range between 0.065 and 0.95. The equilibrium moisture (X_e) was determined by the continuous weight-change method. Seven mathematical models of isotherms were modeled, using the coefficient of determination R², mean absolute error (MAE), and estimated standard error (ESE) as the convergence criterion. Thermodynamic parameters such as isosteric heat (q_st), Gibbs Free Energy (ΔG), differential entropy (ΔS), activation energy (E_a), and compliance with the isokinetic law were evaluated. It was observed that the adsorption isotherms presented cross-linking around 75% ERH and 17% X_e, suggesting adequate storage conditions at these values. The GAB and Halsey models reported better fit (R² > 97%, MAE < 10%, ESE < 0.014 and random residual dispersion). The reduction of X_e from 17 to 7%, increases q_st, from 7.7022 to 0.0165 kJ/g, while ΔG decreases considerably with the increase in X_e, presenting non-spontaneous endergonic behavior, and linear relationship with ΔS, evidencing compliance with the isokinetic theory, governed by q_st. E_a showed that more energy is required to remove water molecules from the upper layers bound to the monolayer, evaluated using C_GAB. The models predicted the storage conditions, and the thermodynamic parameters show the structural stability of the purple corn grains of the Canteño variety during storage.

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.

Anthropogenic activities generate waste that negatively impacts the environment, especially water resources, due to the accumulation of heavy metal ions. Several adsorption methods have been developed, including the use of natural materials such as algae and activated clay. This study aimed to evaluate the effect of pH on batch adsorption of heavy metal ions using Nostoc sphaericum hydrocolloid (HA)/activated nanoclay (NR) composites. The NR/HMB-HA and NR/HUT-HA composites were prepared with a 2:8 mass ratio of HA and NR, using types of clay with code HMB and HUT, previously activated with 1 M NaCl and acid treatment. The adsorption capacity was evaluated using batch tests at pH 4.5 and 5.5, analyzing the removal percentage, adsorption kinetics, adsorption isotherms, and regeneration cycles for unimetal and multimetal systems. The composites present a load point close to 5.1. The FTIR analysis showed changes in the intensity of functional groups following adsorption, confirming the interaction with metallic ions. Both composites showed high affinity in multimetallic systems, especially at pH 5.5, with high selectivity for Pb²⁺ (≈99% removal), followed by As, Cd, and Zn, from an initial concentration of 10 ppm for each metal ion. Equilibrium is reached in approximately 90 min, allowing adsorption of up to 69.9% after five regeneration cycles in a multimetal system. The kinetic study showed that multimetal absorption at equilibrium is governed by chemisorption processes in the order Pb > As > Zn > Cd, with q_e values between 0.392 and 0.058 mmol/g and diffusivity from 15.506 × 10¹¹ to 1.692 × 10¹¹ m²/s. Likewise, the isotherms study indicated a favorable process with maximum adsorption (q_max) between 16.696 and 5.223 mmol/g at pH 5.5. Altogether, the developed composites show high potential for the removal of heavy metals in contaminated waters, in addition to their high reuse capacity.