In this work, the degradation of sulfamethoxazole (SMX) and trimethoprim (TMP) via Fenton and Fenton-like processes was evaluated using Mn²⁺ as supporting catalyst in the Fenton reaction. The optimum conditions of degradation were also evaluated. Besides that, the effect of independent factors pH, [H₂O₂], [Fe²⁺], [Mn²⁺] and reaction time (t) on the efficiency of the SMX and TMP degradation were assessed. Box–Behnken was the experimental design adopted, delineating the relative concentration (C/Co) of antibiotics after treatments as response variable. The inferences were conducted using variance analysis, Pareto chart, response surface methodology, and desirability function. Due to the lack of adjustment of the SMX degradation model, there are no more inferences about it. The significant variables (p ≤ 0.05) on TMP degradation were: reaction time quadratic and linear effect, [Fe²⁺] linear effect, [Mn²⁺] linear effect, interaction pH vs. [Mn²⁺]. The Mn²⁺ addition aided TMP degradation in environments with lower pH values. However, the addition may harm the efficiency of the antibiotic degradation at higher pH. The optimum condition for TMP degradation in the conventional process (without the addition of Mn²⁺) is: pH 5, [H₂O₂] equal to 4.41 mmol L⁻¹, [Fe²⁺] equal to 0.81 mmol L⁻¹ and 90 min reaction time.

RESUMO: A caracterização das chuvas intensas para utilização em projetos de engenharia é fundamental, especificadamente no que tange à obras hidráulicas. O estudo das chuvas intensas é feito por meio da relação entre a intensidade, a duração e a frequência das mesmas. Este artigo trata da determinação de tais relações para o município de Ipameri, Goiás, devido à falta de estudos relacionados a esta localidade. Foi feito o ajustamento à distribuição estatística de Gumbel de forma a obter os valores de precipitação máxima para os períodos de retorno de 2, 5, 10, 15, 20, 25, 50 e 100 anos. Para verificação do ajuste dos dados observados a distribuição de Gumbel, realizou-se os testes de aderência de Kolmogorov-Smirnov, Anderson-Darling e Qui-Quadrado, ao nível de significância de 1%. A desagregação dos valores de precipitação máxima em durações menores que 24 horas foi feita utilizando o método das Relações de Durações. Os parâmetros K (881,7487), a (0,1333), b (10,5332) e c (0,7519) da equação de chuvas intensas foram obtidos utilizando o método do Gradiente Reduzido Generalizado. Para avaliação da equação obtida foi utilizado o coeficiente de determinação (R²), o índice de concordância de Willmott (d) e índice de confiança (Ic), com resultados respectivos de 0,9986, 0,9997 e 0,9990. Assim esta pesquisa contribuiu para a determinação da equação de chuvas intensas, permitindo seu uso no dimensionamento de estruturas hidráulicas do local. Heavy rains characterization for use in engineering design projects is essential, specifically with regard to the hydrological researches and structures. In this way the study of heavy rains is done relating the intensity, duration and frequency of the events. This paper deals with the determination of such relations for the city of Ipameri, Goiás - Brazil, due to lack of studies related to the municipality. Adjusting the statistical Gumbel distribution in order to obtain maximum precipitation values for return periods of 2, 5, 10, 15, 20, 25, 50 and 100 years is made. To check the adjustment of the data observed distribution of Gumbel, we held the adherence tests (Kolmogorov-Smirnov, Anderson-Darling and Chi-Square) at a significance level of 1%. The disaggregation of the maximum precipitation values in smaller duration than 24 hours were made using the method of durations relations. The parameters K (881.7487), a (0.1333), b (10.5332) and c (0.7519) of equation heavy rains were obtained using the Generalized Reduced Gradient method. To validate the obtained equation was used the coefficient of determination (R²), the concordance index of Willmott (d) and confidence index (Ic) with the results of 0.9986, 0.9997 and 0.9990. Thus, this research contributes to the determination of the intense rainfall equation, allowing its use in the design of local hydraulic structures.

This study investigates the Humic Acid (HA) degradation in aqueous solution by a Fenton-Like process using Fe2+ and Mn4+ as a catalyst. The effect of the independent factors: pH, [H2O2], [Fe2+], [Mn4+] and t (reaction time) at the efficiency of HA degradation were evaluated, aiming at obtaining the optimum conditions. The statistic arrangement adopted was the Central Composite Design, and the response variable was the HA relative concentration after the treatments. The inferences were made using variance analysis, the Pareto chart, the response surface method and the desirability function. The variables which were more significant at the HA degradation were: [Fe2+] (linear and square effects), pH (square effect) and the interactions between [Fe2+] vs [H2O2] and [Fe2+] vs t. The addition of Mn4+ did not provide a significant improvement to the efficiency of HA degradation. Nevertheless, it was observed that the conventional Fenton process proved to be an efficient alternative for the HA degradation. The optimal and most economical condition is pH 5, [H2O2] of 6.17 mmol L-1, [Fe2+] of 0.54 mmol L-1, reaction time of 120 min and no added Mn4+.

Análise da viabilidade da utilização da cinza de bagaço de cana-de-açúcar como substituição parcial do cimento Portland (doi.:10.5216/reec.V9i3.32023)