RESUMO Objetivou-se, neste trabalho, determinar o crescimento e o acúmulo de macronutrientes de duas cultivares de abacaxi submetido a diferentes concentrações de alumínio; para isto foi realizado um estudo com vasos de plástico contendo quatro litros de solução nutritiva e utilizado o delineamento em blocos casualizados em esquema fatorial 2 x 5 sendo duas cultivares de abacaxi (IAC Fantástico e Vitória) cinco concentrações de alumínio (0, 21,6; 43,2; 64,8 e 86,4 mg de Al planta-1) e quatro repetições. Foram avaliados o comprimento de raiz, a matéria seca da raiz, o talo e as folhas, diâmetro do talo, emissão de folhas, teor de clorofila e acúmulo de macronutrientes aos 60 dias após os tratamentos. A cv. Vitória apresentou decréscimo linear no teor de clorofila, matéria seca de raízes, comprimento da raiz e acúmulo de N, P, K, Ca e Mg, na maioria dos componentes da planta promovidos pelo aumento da concentração de Al na solução nutritiva. A cv. IAC Fantástico teve menor massa de matéria seca total, matéria seca do talo, diâmetro do talo e acúmulo de N, Ca e Mg; no entanto, as características avaliadas não foram influenciadas pelo aumento da concentração de Al indicando maior tolerância desta cultivar ao Al em solução nutritiva.

ABSTRACT The objective was to determine the growth and accumulation of macronutrients of two pineapple cultivars submitted to different concentrations of aluminum (Al). For this, a study was conducted in plastic pots containing 4 L of nutrient solution, in a randomized block design, in a 2 x 5 factorial scheme, corresponding to two pineapple cultivars (‘IAC Fantástico’ and ‘Vitória’) and five Al concentrations (0, 21.6, 43.2, 64.8 and 86.4 mg of Al plant-1), with four replicates. The following variables were evaluated: root length, dry matter of root, stem and leaf, stem diameter, number of leaves, chlorophyll content and accumulation of macronutrients at 60 days after treatment. The cv. ‘Vitória’ showed a linear decrease in chlorophyll content, root dry matter, root length and accumulation of N, P, K, Ca and Mg in most plant components promoted by the increase of Al concentration in the nutrient solution. The cv. ‘IAC Fantástico’ had lower total dry matter, stem dry matter, stem diameter and accumulation of N, Ca and Mg. However, the evaluated characteristics were not influenced by the increase of Al concentration, showing greater tolerance of this cultivar to Al in nutrient solution.

In this study, we evaluated the combination between an electrochemical process, occurring in the dark, and a heterogeneous photocatalytic process for dye degradation, using the azo dye tartrazine as model of oxidizable substrate. TiO2 P25 and an Ag-doped TiO2 were used as photocatalysts in suspensions containing 50 mg L–1 of tartrazine. The best result, 74% of dye mineralization in 120 min of reaction, was obtained using TiO2 P25 as photocatalyst and a current density of 10 mA cm–2 in the electrochemical cell, a value 30% higher than the sum of the results obtained by heterogeneous photocatalysis (44%) and electrochemical oxidation (13%). The use of Ag-doped TiO2 did not result in significant improvement on tartrazine mineralization, due to the aggregation of these nanoparticles. Our results suggest that this process can be an alternative for a complete treatment (discoloration and mineralization) of tartrazine and most likely other azo dyes.