Methylene Blue (MB) is a dye widely used in the industrial sector and in human and veterinary pharmacology. This dye, if improperly disposed of, can cause a significant environmental impact due to its low biodegradability, as it is a stable and complex substance. Additionally, it may affect human health and generate highly toxic byproducts. Hence, the purpose of this work is to assess the removal efficiency of MB from a synthetic effluent using a ionic flocculation process. Such a process consists of the dissolution of a biodegradable anionic surfactant (obtained from soybean oil used for frying food) in the synthetic effluent and the subsequent addition of calcium to the system. The addition of Ca leads to the formation of insoluble surfactant flocs with a high capacity to adsorb organic pollutants. The FTIR testing showed the presence of OH⁻ and C=O groups in the surfactant flocs, which favor the removal of MB by an adsorption process. The maximum adsorption capacity of MB was 101.38 mg g⁻¹. The process is in fact a chemisorption and has an exothermic nature. Desorption studies showed a desorption efficiency of up to 47.81% using an ethanol 1:2 solution. An MB removal efficiency of up to 93.71% was attained in just 0.5 min for an initial MB concentration of 100 mg L⁻¹, showing that ionic flocculation is a very fast and effective process for the treatment of effluents.

The use of ionic flocculation is proposed to remove malachite green (MG), in this case, from water. A surfactant with the polluted solution and calcium is added. The surfactant-calcium reaction forms a precipitate, which aggregates into flocs on agitation. The flocs adsorb MG, which can then be removed by centrifugation. Ionic flocculation was assessed by varying parameters including: surfactant and MG concentrations, electrolyte content, pH, contact time, etc. The isotherm and adsorption kinetic models that best fit this process are the Langmuir and pseudo-second-order models, respectively. MG removal efficiency of 96% was obtained at pH 9, with surfactant concentration 1,400 mg L−1, MG concentration 10 mg L−1 and contact time 10 minutes. The process has potential for pollutant removal.

This study aimed to evaluate the methyl red (MR) removal efficiency from aqueous matrices using an eco-friendly anionic surfactant (a calcium surfactant, or CaSF), obtained from frying oil residue. Data obtained by infrared spectroscopy revealed several functional groups that favor the capture of the dye by chemisorption by forming hydrogen bonds and covalent interactions. The kinetic testing results fit the pseudo-second order model, reaching equilibrium in 30 min. Adsorption was greatly influenced by temperature. The Langmuir isotherm was the one best fitting the process at 20 °C, while the Dubinin–Radushkevich isotherm fitted it better at higher temperatures. Under optimized conditions, the maximal MR adsorption capacity of CaSF reached 53.59 mg·g⁻¹ (a removal rate of 95.15%), proving that the adsorbent at hand can be an excellent alternative for the removal of undesirable levels of MR present in aqueous matrices.

The contamination of surface and groundwater by nutrients due to the discharge of untreated effluents is a serious environmental issue, as it can promote eutrophication and compromise water quality. This study aimed to optimize the synthesis of Fe–Ca (oxy)­hydroxide (CaFe) and evaluate its adsorptive capacity for phosphate ions. The coprecipitation route was chosen for the material synthesis. Structural characterizations revealed that the material exhibits high roughness, a large number of active sites, thermal stability, and a predominance of the amorphous phase, all of which favor its efficiency in phosphate adsorption. Optimization using response surface methodology (RSM) yielded a high adjusted coefficient of determination (R _adj ² = 0.97), indicating excellent fit to the experimental data. The adsorption process followed the pseudo-second-order kinetic model (R _adj ² > 0.99) and was best described by the Sips isotherm (R _adj ² > 0.99), suggesting multilayer adsorption in a heterogeneous system. The maximum adsorption capacity (q _m = 41 mg/g) was achieved when the process temperature was adjusted to 30 °C. Thermodynamic parameters confirmed that the adsorption is spontaneous and endothermic (ΔH° = 17.38 kJ/mol). CaFe exhibits a high capacity for phosphate adsorption, even in the presence of other anions, demonstrating excellent selectivity and robustness in complex aqueous matrices. Moreover, CaFe was capable of removing up to 84.86% of phosphate from a real effluent sample by simply applying a dosage of 1.5 g/L and adjusting the effluent pH (pH = 4). In conclusion, the results demonstrated that CaFe is a promising material for phosphate removal, showing high potential for application in the treatment of water bodies susceptible to eutrophication. The findings indicated that CaFe exhibits excellent performance as an adsorbent, with high adsorption capacity, strong selectivity in the presence of competing anions, and satisfactory regeneration efficiency. Additionally, the development of sustainable materials such as CaFe is essential for achieving the Sustainable Development Goals (SDGs), particularly SDG 6, SDG 9, SDG 12, and SDG 14.

The present study aimed to evaluate the removal efficiency of two types of cationic dyes of different classes – methylene blue (MB) and malachite green (MG) – from a synthetic effluent using a calcium surfactant (CaSF) originated from used frying soybean oil. The Fourier Transform Infrared Spectroscopy (FTIR) spectra showed that the functional groups present on the surface of CaSF can form surface complexes or bonds with the dye molecules and, consequently, promote their adsorption. The adsorption kinetics studies indicated that the equilibrium point of the process is reached in 90 min for both dyes. Equilibrium studies indicated that the adsorption isotherm models that best fit MB and MG were the Langmuir and the Dubinin–Radushkevich models, respectively. The maximum adsorption capacities of MB and MG, according to the Langmuir model, were 199 and 123 mg·g−1, respectively. In the sight of the high MB and MG removal efficiency (84 and 100%, respectively), the use of CaSF is an excellent alternative for the treatment of effluents contaminated by cationic dyes. The adsorption–desorption cycle studies showed that CaSF maintains a good dye removal efficiency for up to three cycles.

O clima de uma região impõe características que a definem. Compreender o comportamento do clima é essencial para o planejamento de uma série de atividades, como gestão dos recursos hídricos, agricultura e potencial energético, entre outros. Objetivou-se com esse trabalho estudar o balanço hídrico e a classificação climática para a região do Cariri. Compreender os fenômenos climáticos como precipitação, temperatura, evapotranspiração é essencial para o desenvolvimento sustentável desta e de outras regiões circunvizinhas. Especificamente, recorreu-se à estação meteorológica de Barbalha-CE (INMET 82784), com raio de abrangência de 150 km. Seus dados representam a tendência do clima para toda região do Cariri. Para o balanço hídrico e classificação climática utilizou-se o método de Thornthwaite & Mather (1948, 1955). A partir dos resultados alcançados verificou-se que o clima da região está classificado como C1dB'4b'1 (seco subúmido, com pequeno ou nenhum excesso de água do tipo climático mesotérmico e subtipo mesotérmico), com precipitação média anual de 1037 mm e temperatura média anual de 26,7 °C, com chuvas concentrando-se de janeiro a abril. Os testes de Shapiro-Wilk e Kolmogorov Smirnov demonstraram que as precipitações mensais não seguem uma distribuição normal, com coeficientes de variação variando de 60 a 253% ao mês. Os dados da frequência de chuvas ao mês, temperatura e evapotranspiração permitiram a promoção de modelos de predição com coeficiente de determinação de 0,91 e 0,89 respectivamente.Palavras-chaves: Clima. Precipitação. Evapotranspiração. Temperatura. Modelagem. Predição. Water Balance and Climate Classification for Barbalha Weather Station, Ce A B S T R A C TThe climate of a region imposes characteristics that define it. Understanding the behavior of the climate is essential for planning a series of activities, such as water resources management, agriculture, and energy potential, among others. The objective of this work was to carry out the water balance and climatic classification for the Cariri region. Understanding climate phenomena such as precipitation, temperature, and evapotranspiration is essential for the sustainable development of this and other surrounding regions. Specifically, the meteorological station of Barbalha-CE (INMET 82784) has been taken into account. With a radius of coverage of 150 km, its data represents the climate trend for the entire Cariri region. For the water balance and climatic classification, the method of Thornthwaite & Mather (1948, 1955) was used. From the results achieved, it was found that the climate of the region is classified as C1dB'4b'1 (sub-humid dry, with little or no excess water of the mesothermal climate type and mesothermal subtype) with average annual precipitation of 1037 mm and average temperature annual rate of 26.7 °C, with rainfall concentrated from January to April. The Shapiro-Wilk and Kolmogorov Smirnov tests showed that monthly rainfall does not follow a normal distribution, with coefficients of variation ranging from 60 to 253% per month. The monthly rainfall frequency, temperature and evapotranspiration data lead to prediction models with coefficient of determination of 0.91 and 0.89 respectively.Keywords: Climate. Precipitation. Evapotranspiration. Temperature. Modeling. Prediction.