Marco Aurélio Kondracki de Alcântara

Movimentação de nitrato em horizonte superficial e subsuperficial de Latossolo e Nitossolo com cargas variáveis

The objective of this work was to evaluate nitrate movement on soil columns considering mainly, total amount recovered, fit among experimental and model‑predicted transposition curves, and model‑obtained retardation factors. Samples of A and B horizons of Udox and Udult soils were used. A leaching experiment was carried out considering the miscible displacement theory, using 100 mL of a 10-mmol L -1 KNO3 solution as pulse. The amounts of nitrate leached and recovered in the columns for Udox and Udult soils in horizons A and B varied from 0.405 to 1.432 mmol L -1 . There was significant (p<0.05) correlation between experimental and model-predicted curves for columns Udult-A, Udult-B and Udox-B. The mathematical model used is suitable for predicting nitrate lixiviation in B-horizon columns in Udox and Udult soils. The retardation factor was greater than 1.0 in the soil columns with good fit among experimental and predicted data, which indicates that the nitrate movement is delayed in comparison to the advance of the soil wetting front.

Evaluation of sample preparation methods and optimization of nickel determination in vegetable tissues

Nickel, although essential to plants, may be toxic to plants and animals. It is mainly assimilated by food ingestion. However, information about the average levels of elements (including Ni) in edible vegetables from different regions is still scarce in Brazil. The objectives of this study were to: (a) evaluate and optimize a method for preparation of vegetable tissue samples for Ni determination; (b) optimize the analytical procedures for determination by Flame Atomic Absorption Spectrometry (FAAS) and by Electrothermal Atomic Absorption (ETAAS) in vegetable samples and (c) determine the Ni concentration in vegetables consumed in the cities of Lorena and Taubate in the Vale do Paraiba, State of Sao Paulo, Brazil. By means of the analytical technique for determination by ETAAS or FAAS, the results were validated by the test of analyte addition and recovery. The most viable method tested for quantification of this element was HClO4-HNO3 wet digestion. All samples but carrot tissue collected in Lorena contained Ni levels above the permitted by the Brazilian Ministry of Health. The most disturbing results, requiring more detailed studies, were the Ni concentrations measured in carrot samples from Taubate, where levels were five times higher than permitted by Brazilian regulations.

Manipulação de carga e movimento de nitrato em horizontes B de um Latossolo Vermelho

The objective of this work was to evaluate the influence of pH and of the addition of carbonates, phosphates and sulphates on nitrate movement in columns composed by a subsuperficial horizon of an Udox soil. The experiments were carried out according to the miscible displacement technique. A 10 or 40-mmol L -1 KNO3 solution was used as nitrate pulse. Nitrate breaktrough curves were obtained for all columns. The net charge varied from -24.0 to +35.0 mmolc L -1 in the different treatments. In the treatments that received additions of hydrochloric acid, hydrochloric acid + phosphate, carbonate + phosphate and sulphate nitrate, recovery was greater than the total amount applied as pulse. Carbonate, phosphate and sulphate additions favored nitrate leaching, displacing nitrate breaktrough curves to the left. Soil acidification delayed nitrate movement, displacing breaktrough curves to the right. Soil nitrate movement was more influenced by the pH of the environment and by the presence of carbonates, phosphates and sulphates than by the ionic strength of the pulse.

Catalytic Ozonation Using Fe 2+ in the Treatment of Dairy Effluent in a Semi-Batch Process with Recycle

This work describes the treatment of dairy industry effluent using catalytic ozonation with Fe2+ as its catalyst in a semi-batch process with recycle. A fractional factorial design 24-1 was used with a reduction percentage of total organic carbon (TOCred) as response. Optimal conditions were obtained by the reaction time of 30 min, ozonator power of 35 W, O2 flow rate of 0.125 L min-1, Fe2+ concentration of 1.0 g L-1 and pH 4.0 for a 2 L raw effluent. TOCred of 64.03% represents a decrease in concentration from 473.0 to 170.1 mg L-1, with an estimate cost of US

Deslocamento miscível de um efluente de indústria de explosivo em colunas de solo

0.03 L-1effluent. The treatment performed was not sufficient to discharge it directly on surface water; however, significant reduction of TOCred, among physical and chemical characteristics makes a better product to be proceeded into a biological treatment.

Carbonaceous decomposition of a recalcitrant effluent treated by the photo-Fenton process: a kinetic approach

Este estudo teve como objetivo avaliar alguns impactos decorrentes do deslocamento miscivel de efluente de nitracao de uma industria de explosivos aplicado em colunas de um Latossolo Amarelo, horizonte B (LA-B), submetido aos tratamentos: adicao de carbonatos (BASE), acidos (ACID), fosfato (FOSF), carbonatos e fosfato (BASE-FOSF) e acidos e fosfatos (ACID-FOSF). A recuperacao de nitrogenio em relacao ao total aplicado varia entre 10,1 (ACID) e 65,5% (BASE). Ha correlacao significativa entre as curvas de transposicao de N obtidas experimentalmente e as simuladas pelo aplicativo STANMOD para a maioria das colunas (p<0,001). A excecao ocorreu para ACID-FOSF (p=0,202). Nao ha correlacao entre carga eletrostatica liquida (CEL) e as variaveis de ajuste do modelo: fator de retardamento (FR), coeficiente de dispersao-difusao (D) e taxa de decaimento de primeira ordem (µ). A adicao de fosfato (FOSF) favorece a movimentacao do nitrogenio, pois diminui FR (2,35±0,05) e µ (0,498±0,050 h-1) e aumenta D (41,8±5,5 cm2 h-1) em relacao ao observado na coluna LA-B (2,51±0,03; 1,697±0,084 h-1 e 2,8±1,3 cm2 h-1 respectivamente). A adicao de carbonatos e/ou fosfatos (BASE, BASE/FOSF e FOSF) resultou nos maiores valores maximos de demanda quimica de oxigenio (DQOMAX). A pequena quantidade de DNA extraida das celulas bacterianas nos solos sugere que, possivelmente, os processos que governam a adsorcao e movimentacao de N sejam de natureza nao biologica ou que a elevada DQO do liquido percolado prejudica os microrganismos do solo.

State-of-the-Art and Trends in Atomic Absorption Spectrometry

ABSTRACT Natural effluents with marked variation in their chemical composition over decomposition time in the matrix from which they are generated have a complex composition and are not totally known in most cases. Landfill leachate can be considered an effluent with complex composition, requiring imminent and more comprehensive studies on organic load degradation. Such complexity of numerous organic compounds (most of them recalcitrant humic and fulvic substances) demands a large number of kinetic equations to satisfactorily describe the temporal evolution of such conversion. Thereby, this work aims to study a kinetic approach grounded on previously consolidated chemical reactions of radical generation through the photo-Fenton mechanism. A molar balance was developed for each species in a batch photo-Fenton process and the resulting ordinary differential equations were numerically solved in MATLABTM. The kinetic model satisfactorily described an organic load conversion of the effluent under the various experimental conditions studied herein. Experimental trends could be represented by a free-radical mechanism and a degradation rate equation of first order for organic carbon, hydroxyl radical and H+. The model fittings revealed a hydroxyl radical/organic carbon stoichiometric ratio of 2:1. The kinetic study has confirmed the importance of pH levels for the reaction medium, and indicated that degradation rate depends on the medium organic composition, which provided an exponential function of conversion for the degradation rate coefficient. The model simulations corroborated the positive effect of sunlight on the radical generation through decomposition reaction with a rate coefficient in the range 4 × 10−3–2 × 10−1 s−1. GRAPHICAL ABSTRACT

Advanced Oxidative Degradation Processes: Fundamentals and Applications

Atomic Absorption Spectrometry, or AAS, is an analytical technique commonly used for the quantitative and qualitative determination of elements in samples such as aqueous solutions, waters, sea-waters, metals and alloys, glass, drugs, food, environmental samples, industrial wastes, biological samples among others. This technique is based on measuring the amount of electromagnetic energy of a particular wavelength (ultraviolet or visible region), which is absorbed as it passes through a cloud of atoms of a particular chemical element (the analyte) coming from samples and standards. An appropriate mathematical treatment allows relating the amount of absorbed energy to the number of absorbed atoms by providing a measurement of the element concentration in the sample. This technique is established, relatively quickly, economically affordable and allows to determine more than 60 chemical elements from a huge type of samples. It is used by most of research laboratories and industry quality control around the world. The aim of this text is to present concisely this powerful technique providing basic information about fundamental concepts, instrumentation and application. Relevant and effective techniques will be shown including flame atomization, hydride generation, cold vapor and electrothermic atomization or graphite furnace. Fundamental and theoretical details will not be presented on mechanical components, electronic, software and data processing. They are deeply discussed in specific literature.