https://ri.ufs.br/jspui/handle/riufs/2422 2026-05-04T14:29:00Z 2026-05-04T14:29:00Z Lima, Lucas dos Santos https://ri.ufs.br/jspui/handle/riufs/24753 2026-03-12T17:38:42Z 2026-01-27T00:00:00Z

Título: Materiais adsorventes obtidos da biomassa de Ingá-cipó (Inga edulis): remoção de metais pesados e avaliação ecotoxicológica Autor(es): Lima, Lucas dos Santos Abstract: Water contamination by toxic metals, especially hexavalent chromium Cr(VI) and divalent lead Pb(II), represents a significant environmental challenge due to their persistence and harmful effects on aquatic organisms. In this study, two adsorbent materials derived from the biomass of Inga edulis bark were developed and evaluated: raw biomass (BMIG) and sulfuric acid–activated biomass (BMIGA). The materials were characterized using physicochemical techniques, which confirmed structural modifications and the presence of functional groups capable of interacting with the studied metals. Batch adsorption experiments enabled the identification of favorable operational conditions and showed that BMIGA exhibited maximum adsorption capacities of 356.6 and 222.1 mg g-1 for Cr(VI) and Pb(II) ions, respectively, compared to BMIG, which presented an adsorption capacity of 46.0 mg g-1 for Cr(VI) and showed no removal of Pb(II) ions. Chemical activation resulted in an increase in surface area and the introduction of oxygenated functional groups, which enhanced the adsorption of both metal ions. Kinetic models indicated that Cr(VI) adsorption by BMIG and BMIGA followed the Elovich model, characterizing a chemisorption process on a heterogeneous surface. For BMIGA and Pb(II), the best fit was obtained with the pseudo-second-order model, suggesting interaction with oxygenated functional groups. In isotherm studies, Cr(VI) adsorption fitted both the Langmuir and Freundlich models, whereas Pb(II) showed a better fit to the Freundlich model. Thermodynamic analyses demonstrated that Cr(VI) adsorption by BMIG was non-spontaneous, while BMIGA promoted spontaneous adsorption for both metals. Under continuous-flow conditions, fixed-bed columns exhibited stable performance, with breakthrough times of 200.0 min and 281.7 min for Cr(VI) adsorption and 554.8 min for Pb(II) adsorption at low concentrations, which were compatible with practical applications and showed good agreement with the Thomas, Yoon–Nelson, and Clark models. The ecotoxicological assessment performed with Daphnia similis confirmed the high toxicity of solutions containing Cr(VI) and Pb(II) ions prior to treatment. After adsorption, no acute effects were observed on the organisms, demonstrating that the materials were able to significantly reduce toxicity. Finally, the saturated adsorbents were applied in electrochemical tests for green hydrogen and oxygen production, revealing potential for reuse and value addition after environmental application. Overall, the results demonstrate that Inga edulis bark is a promising biomass for the production of sustainable and efficient adsorbents with multifunctional potential, contributing to pollution mitigation strategies and technologies associated with the circular economy.

2026-01-27T00:00:00Z Santos, Marcos Vinícius Quirino dos https://ri.ufs.br/jspui/handle/riufs/24224 2026-01-14T19:29:06Z 2025-08-14T00:00:00Z

Título: Eletrocatalisador bifuncional baseado em material carbonáceo para geração de hidrogênio e oxigênio de baixo carbono Autor(es): Santos, Marcos Vinícius Quirino dos Abstract: The high cost, scarcity, and limited durability of noble-metal-based electrocatalysts, such as platinum, iridium, and rhodium, have driven the search for alternative materials that are abundant, sustainable, and economically viable for use as catalysts in water electrolysis. In this context, biochar derived from plant residues has emerged as a promising carbon-based material for the development of efficient and environmentally friendly electrocatalysts. This dissertation reports the development of an electrocatalyst based on biochar derived from the aquatic plant Marsilea minuta (BMQ), applied to the hydrogen evolution reaction (HER) in acidic medium and to the oxygen evolution reaction (OER) in alkaline medium. The biochar was prepared by pyrolysis at 500 °C under an inert nitrogen atmosphere and characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results revealed an amorphous structure with a porous surface and the presence of oxygen- and nitrogen-containing functional groups, which act as active sites for electrocatalytic reactions. Electrochemical tests using a glassy carbon electrode modified with the material demonstrated significant activity for both HER and OER, exhibiting low overpotentials required to reach a current density of 10 mA cm⁻² and Tafel slopes consistent with favorable reaction kinetics. Electrochemical stability was confirmed by chronopotentiometry, highlighting the potential of BMQ as a bifunctional electrocatalyst with low carbon emissions. These results indicate that biochar derived from Marsilea minuta is a promising and sustainable alternative for application in water electrolysis systems, contributing to the advancement of low carbon hydrogen and oxygen production technologies.

2025-08-14T00:00:00Z Almeida, Yslaine Andrade de https://ri.ufs.br/jspui/handle/riufs/24203 2026-01-13T17:51:41Z 2025-12-16T00:00:00Z

Título: Síntese e caracterização de biocarvões a partir do coco verde (Cocos nucifera L.) para potencialidade eletroanalítica Autor(es): Almeida, Yslaine Andrade de Abstract: The growth of the agro-industry has intensified the generation of lignocellulosic waste, whose improper disposal represents an environmental and economic challenge, while also highlighting the need for sustainable strategies for its valorization. In this context, the conversion of this waste into functional materials emerges as a promising alternative. Given this problem, this research proposed the sustainable use of agro-industrial waste using green coconut mesocarp to produce cbiochars via pyrolysis and chemical activation, with the aim of developing carbonaceous materials with high porosity and electrical conductivity applicable in electrochemical sensors. Different activation methods (pre- and post-pyrolysis) using phosphoric acid and potassium hydroxide were evaluated, resulting in porous and thermally stable structures. Morphological and structural characterizations were performed using elemental analysis, FT-IR, TG, EDX, XPS, SEM/EDS, TEM/EDS, and N2 adsorption, with statistical processing through Principal Component Analysis. The synthesized biochars exhibited high thermal stability, significant modifications in lignocellulosic structure, and adsorption properties directly related to surface area and pore distribution, highlighting their potential as functional platforms. The produced biochars were applied to modify electrodes for the detection of heavy metals and emerging contaminants. In the first application, the electrode modified with activated biochar with orthophosphoric acid showed excellent performance in the simultaneous detection of Cd2+, Pb2+, and Hg2+ by differential pulse voltammetry, with sensitivities of 42.75 µA L µmol-1 (Cd2+), 38.96 µA L µmol-1 (Pb2+), and 8.07 µA L µmol-1 (Hg2+), as well as very low detection limits, particularly for Cd2+ (1,4 nmol L-1 ). The sensor showed satisfactory selectivity and reproducibility, with recovery values between 89% and 106% in real samples (sewage, tap water, and cosmetics), confirming its practical feasibility, low cost, and sustainable nature. In a second application, the activated biochar with potassium hydroxide was functionalized with bimetallic Au@Pd nanoparticles, yielding the CMB500-Au@Pd electrode, which was used for the determination of the synthetic hormone 17α-ethinylestradiol (EE2). The sensor displayed a linear response in the range of 0.05-5.0 µM (R2= 0.9993), a detection limit of 2.53 nmol L -1 , and a quantification limit of 8.43 nmol L-1 , approximately 2,000 times lower than those obtained by HPLC. Reproducibility tests showed intra-day and inter-day RSDs of 5.77% and 8.14%, respectively. Selectivity studies indicated significant interference only for structurally related compounds (17β-estradiol and ascorbic acid), while urea, NaCl, and caffeine produced negligible effects. The method was successfully validated in real and simulated samples (groundwater, artificial breast milk, synthetic urine, saline solution, and contraceptive tablets), with recoveries ranging from 58.20% to 133.65%. Overall, the results prove the high potential of biochars derived from green coconut mesocarp as functional materials for sustainable electrochemical sensors. The developed electrodes combine high sensitivity, selectivity, and stability, representing cost-effective and environmentally responsible alternatives for monitoring toxic metals and hormonal contaminants in diverse matrices.

2025-12-16T00:00:00Z Silva, Wenes Ramos da https://ri.ufs.br/jspui/handle/riufs/24073 2025-12-15T17:40:11Z 2025-07-18T00:00:00Z

Título: Termoconversão do sistema caulinar da mandioca para a obtenção de bioprodutos de valor agregado Autor(es): Silva, Wenes Ramos da Abstract: There is increasing interest in the use of residual lignocellulosic biomass to produce biomaterials, biofuels, and renewable chemicals due to its high availability and low cost. In this context, the residual biomass from cassava harvesting has been proposed as a potential source of raw material for environmentally and economically valuable products. This study evaluated the pyrolysis of biomass from the cassava shoot system (SCM), which includes the aerial parts of the plant and the rhizome, at temperatures of 400, 500, and 600 °C, and characterized the thermoconversion products. The highest yields of biooil (12.6%) and pyrolytic gas (34.1%) were achieved at 600 °C, while biochar reached a maximum yield of 38.9% at 400 °C. Immediate and elemental analyses revealed an increase in the degree of carbonization, aromaticity, and calorific value of the biochar produced at higher temperatures, associated with a decrease in organic functionalization observed by FTIR. De-functionalization, together with an increase in the inorganic content of the biochar, raised the pH from 5.6 to 9.17 and, when applied to soil, BC600C most effectively improved field capacity and water retention at the application rate of 50 tons ha−1. From the biochar granulation process, a soil fertilizer with up to 12.2% urea was produced, which benefited the initial development of corn plants by providing the necessary nutrition and stimulating growth when applied at the appropriate rate, equivalent to 100 kg of N ha−1. The pyrolysis temperature also affected the composition of the liquid products, resulting in the de-functionalization of BO600C as observed by FTIR analysis, which was reflected in the lower total acidity index of this biooil (68 mg KOH g−1). BO400C and BO500C had the highest carbon and lowest oxygen contents, with BO500C having the highest total phenolic content, ~41% EAG, confirmed by GC/MS analysis (33.8% of the total area), followed by carboxylic acids (15.5%) and alcohols (9.9%). The chemical characterization by (−)FT-Orbitrap MS highlighted the presence of classes O2‒7, mainly phenolic compounds. In the positive mode, the predominant constituents were from the Ny and OxNy classes, mainly from the thermal degradation of proteins. Among the pyrolysis products, SCM bio-oils, especially BO500C and BO600C, proved to be promising sources of renewable phenolic compounds, which can be integrated into the chemical industry to replace fossil derivatives. As for the biochar, among iv its many technological applications, it can be used to condition the soil and improve its hydrological characteristics. Additionally, biochar serves as an effective method for carbon sequestration and is also potentially valuable raw material for the production of controlled-release fertilizers.

2025-07-18T00:00:00Z