LEANDRO GOULART DE ARAUJO
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Artigo IPEN-doc 29048 Uranium biosorption by hydroxyapatite and bone meal2022 - WATANABE, TAMIRES; GUILHEN, SABINE N.; MARUMO, JULIO T.; SOUZA, RODRIGO P. de; ARAUJO, LEANDRO G. deBiosorption has been examined for the treatment of aqueous solutions containing uranium, a radiotoxic pollutant. Nevertheless, the evaluation of the role of process variables by experimental design on the use of hydroxyapatite and bone meal as biosorbents for uranium has not yet been previously addressed. In this study, the effects of adsorbent dosage (M), initial uranium concentrations ([U]0), and solution pH were investigated, using a two-level factorial design and response surface analysis. The experiments were performed in batch, with [U]0 of 100 and 500 mg L−1, pH 3 and 5, and adsorbent/uranium solution ratios of 5 and 15 g L−1. Contact time was fixed at 24 h. Removal rates were higher than 88%, with a maximum of 99% in optimized conditions. [U]0 and M were found to be the most influential variables in U removal in terms of adsorption capacity (q). The experiments revealed that bone meal holds higher adsorption capacity (49.87 mg g−1) and achieved the highest uranium removal (~ 100%) when compared to hydroxyapatite (q = 49.20 mg g−1, removal = 98.5%). The highest value of q for both biomaterials was obtained for [U]0 = 500 mg L−1, pH 3, and M = 5 g L−1. Concerning the removal percentage, bone meal achieved the best performance for [U]0 = 500 mg L−1, pH 3, and M = 15 g L−1. Further experiments were made with real radioactive waste, resulting in a high uranium adsorption capacity for both materials, with 22.11 mg g−1 for hydroxyapatite and 22.08 mg g−1 for bone meal, achieving uranium removal efficiencies higher than 99%.Artigo IPEN-doc 27702 Uranium removal from aqueous solution using macauba endocarp-derived biochar2021 - GUILHEN, SABINE N.; ROVANI, SUZIMARA; ARAUJO, LEANDRO G. de; TENORIO, JORGE A.S.; MASEK, ONDREJThe main aim of this study was to evaluate options for addressing two pressing challenges related to environmental quality and circular economy stemming from wastage or underutilization of abundant biomass residue resources and contamination of water by industrial effluents. In this study we focused on residues (endocarp) from Macaúba palm (Acrocomia aculeata) used for oil production, its conversion to activated biochar, and its potential use in uranium (U) removal from aqueous solutions. Batch adsorption experiments showed a much higher uranyl ions (U(VI)) removal efficiency of activated biochar compared to untreated biochar. As a result of activation, an increase in removal efficiency from 80.5% (untreated biochar) to 99.2% (after activation) was observed for a 5 mg L 1 initial U(VI) concentration solution adjusted to pH 3 using a 10 g L 1 adsorbent dosage. The BET surface area increased from 0.83 to 643 m2 g 1 with activation. Surface topography of the activated biochar showed a very characteristic morphology with high porosity. Activation significantly affected chemical surface of the biochar. FTIR analysis indicated that U(VI) was removed by physisorption from the aqueous solution. The adsorbed U(VI) was detected by micro X-ray fluorescence technique. Adsorption isotherms were employed to represent the results of the U adsorption onto the activated biochar. An estimation of the best fit was performed by calculating different deviation equations, also called error functions. The Redlich-Peterson isotherm model was the most appropriate for fitting the experimental data, suggesting heterogeneity of adsorption sites with different affinities for uranium setting up as a hybrid adsorption. These results demonstrated that physical activation significantly increases the adsorption capacity of macauba endocarp-derived biochar for uranium in aqueous solutions, and therefore open up a potential new application for this type of waste-derived biochar.Artigo IPEN-doc 27250 Synthesis and physicochemical characterization of a novel adsorbent based on yttrium silicate2020 - MEDEIROS, VINICIUS L.; ARAUJO, LEANDRO G. de; RATERO, DAVI R.; PAULA, ALEX S.; MOLINA, EDUARDO F.; JAEGER, CHRISTIAN; MARUMO, JULIO T.; NERY, JOSE G.A new metallosilicate based on yttrium was synthesized and characterized by XRD, FT-IR, 29Si MAS-NMR, and 89Y MAS-NMR. The mixed framework of the material was confirmed by the detection of distinct chemical shift groups using 29Si MAS-NMR (at -82 to -87 ppm, -91 to -94 ppm, -96 to -102 ppm, and -105 to -108 ppm), as well as four distinct chemical shifts in the 89Y MAS-NMR spectrum (at -89, -142, -160, and -220 ppm). Adsorption and kinetic analyses indicated the potential of the new material for the removal of lead and cadmium from aqueous media. The adsorption results for lead indicated that dynamic equilibrium was reached after five hours, with total lead removal of around 94 %, while for cadmium it was reached in the first hour, with total cadmium removal of around 74 %. The adsorptions of lead and cadmium were modeled using pseudo-first order (PFO) and pseudo-second order (PSO) kinetic models. Although both models provided high R2 values (0.9903 and 0.9980, respectively), the PSO model presented a much lower χ2 red value (4.41×10−4), compared to the PFO model (2.12×10−3), which indicated that the rate-limiting step was probably due to the chemisorption of lead from the solution onto the yttrium-based metallosilicate.