In the present work, we analyzed the linear and nonlinear model suitabilities for adsorption data from aqueous As(III) removal by manganese ferrite nanoparticles (NPs). Hence, As(III) adsorption onto ferrite NPs was formerly analyzed by the intraparticle diffusion model (IPD). Then, adsorption kinetics was described by the pseudo-first-order (PFO), pseudosecond-order (PSO), and Elovich models, while equilibrium adsorption was fitted to the Freundlich and Langmuir isotherms. Linear and nonlinear kinetic and isotherm models were solved and compared. The nonlinear data fitting was applied through the lsqcurvefit user-defined function (Matlab ver. 7.10.0). The initial adsorption rate was influenced by intraparticle diffusion and surface or film diffusion from the arsenic bulk solution to ferrite NPs, according to the IPD model. Adsorption kinetics of As(III) on manganese ferrite NPs was better described by the PSO model, followed by the Elovich model and then the PFO model. Equilibrium adsorption data were only worthily described by the Freundlich isotherm model. While the PSO, Elovich and Freundlich linear models showed even better fit than the nonlinear models, determinant bias was depicted for the PFO and Langmuir linear models. Thus, to use nonlinear adsorption models is highly advisable, having the Matlab lsqcurvefit function been proven very useful to face such task.

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Pollution from oil spills affects the soil and crops, so this study evaluated the effect of soil contaminated with diesel at different concentrations on the development of Creole corn (Zea mays). Creole corn seeds were placed in soil contaminated with diesel at different concentrations: 0%, 0.5%, 1%, 2%, 4% and 8%, each treatment had four replicates, the experimental units were kept under controlled laboratory conditions. Variables such as germination percentage, plant height, leaf area, mortality rate, aerial and root biomass were evaluated at 7, 10, 14, 21 and 28 days after sowing. The results indicate that germination was delayed and a delay in the appearance of the sprout was also observed at higher concentrations. Plant height, root area, biomass, and taproot were affected at higher concentrations (p < 0.05). Presence of chlorosis and malformations in the leaves were observed on the ninth day after planting, causing the onset of wilting of the leaves in the 4% and 8% treatments. Exposure to diesel significantly reduces the growth of native corn in its early stages of development.

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