The aim of this work was to study the adsorption and removal of chromium (VI) ions contained in aqueous solutions using a chitosan-based hydrogel synthesized via chemical crosslinking of radical chitosan, polyacrylic acid, and N,N'-methylenebisacrylamide. Fourier-transform infrared spectroscopy confirmed the hydrogel synthesis and presence of reactive functional groups for the adsorption of chromium (VI) ions. The chromium (VI) adsorption mechanism was evaluated using non-linear Langmuir, Freundlich, Redlich-Peterson, and Sips isotherms, with the best fit found by the non-linear Redlich-Peterson isotherm. The maximum chromium (VI) adsorption capacities of the chitosan-based hydrogel were 73.14 and 93.03 mg metal per g dried hydrogel, according to the non-linear Langmuir and Sips isotherm models, respectively. The best kinetic fit was found with the pseudo-nth order kinetic model. The chromium (VI) removal percentage at pH 4.5 and 100 mg L initial metal concentration was 94.72%. The results obtained in this contribution can be useful for future works involving scale-up of a water and wastewater treatment method from a pilot plant to full-scale plant.

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Gamma spectrometric measurements were obtained for the agricultural soils aiming at characterizing the spatial distribution of radionuclide concentrations (K, eU and eTh), as well for the samples of phosphatic fertilizers and agricultural gypsum. In the study areas, three types of soils occured: Eutrophic Red Nitosol (Alfisoil), Eutroferric Red Latosol of clayey texture (Oxisoil) and Dystrophic Red Latosol of medium texture (Oxisoil

ABSTRACT. Gamma-ray spectrometry, electrical resistivity, and magnetic susceptibility measurements were taken from agricultural areas near the City of Maringá, in the Northwest region of the Paraná state, south Brazil, in order to characterize the spatial distribution of radionuclides (K, eU, and eTh), the apparent resistivity, and the magnetic susceptibility determined for soils. Three different types of soils are present in this agricultural area: Alfisoil, clayey texture Oxisoil, both deriving from Lower Cretaceous basalts of the Serra Geral Formation; and medium texture Oxisoil from reworked Serra Geral and Goio-Erê formations, the latter deriving from sandstones of the Upper Cretaceous Caiuá Group. It could be observed that in more clayey soils both concentration of radionuclides and susceptibility values are higher than in more sandy soils, especially due to the higher adsorption in the former and to the higher availability of magnetic minerals in the latter. The average ppm and Bq Kg −1 grades for K, eU, and eTh in the areas under anthropic activity are of 1766-54.75, 0.83-10.22, and 1.78-7.27, respectively. These grades are significantly higher than those of non-occupied or non-fertilized areas (1101-34.15 K, 0.14-1.69 eU, and 1.31-5.36 eTh in ppm and Bq Kg −1 , respectively.) Correlations were observed between uranium and clay, uranium and magnetic susceptibility, uranium and organic matter, and between electric resistivity and clay grades. Varied concentrations of radionuclides were also observed in different fertilizer formulations applied to soy and wheat cultures. Apparent electric resistivity values between 25 and 647 Ohm.m and magnectic susceptibility values between 0.28 e 1.10 × 10 −3 SI due to clay and magnetic minerals represented important soil discrimination factors in the study area that can be incorporated as easy, low-cost soil mapping tools.Keywords: Gamma-ray spectrometry, electrical resistivity, magnetic susceptibility, agriculture, soils, fertilizers. RESUMO. Medições gamaespectrométricas, de resistividade elétrica e de susceptibilidade magnética foram tomadas em solos agrícolas situados próximos a cidade deMaringá, noroeste do estado do Paraná, sul do Brasil, objetivando caracterizar a distribuição espacial das concentrações de radionuclídeos (K, eU e eTh), da resistividade aparente e da susceptibilidade magnética. Naárea agrícola ocorrem três tipos de solos: Nitossolo Vermelho Eutrófico, Latossolo Vermelho Eutroférrico textura argilosa, ambos derivados da Formação Serra Geral (basaltos do Cretáceo Inferior) e Latossolo Vermelho Distrófico textura média, oriundo do retrabalhamento das formações Serra Geral e Goio-Erê, estaúltima composta por arenitos do Grupo Caiuá (Cretáceo Superior). Constatou-se que as concentrações de radionuclídeos e os valores de susceptibilidade magnética nos solos mais argilosos foram maiores do que nos solos mais arenosos, em função, principalmente, da maior adsorção dos primeiros e da maior disponibilidade de minerais magnéticos. Os teores médios em ppm e Bq...

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