Avaliação da reação foto-fenton na decomposição de resíduos de carrapaticida

Experimental procedures based on factorial design and surface response methodology were applied to establishe experimental conditions for the decomposition of a 1:400 (v/v) Supocade® (chlorfenvinphos 13.8% and cypermethrin 2.6%) solution, used to control cattle ticks. Experiments exploring photo-oxidative reactions were performed with and without UV radiation, fixing exposition time and pesticide volume, and varying the oxidant mixture. The use of 3.6 mmol L-1 Fe2+ plus 1.9 mol L-1 H2O2 plus UV radiation provided destruction of 94% of the original carbon content and reduction of aromatic, aliphatic and carbinolic compounds, evaluated by determination of residual carbon content by ICP OES and NMR analysis.

Synthesis, characterization and thermal behaviour of solid-state compounds of benzoates with some bivalent transition metal ions

Solid-state MBz compounds, where M stands for bivalent Mn, Fe, Co, Ni, Cu and Zn and Bz is benzoate, have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), infrared spectroscopy and complexometry were used to characterize and to study the thermal behaviour of these compounds. The procedure used in the preparation of the compounds via reaction of basic carbonates with benzoic acid is not efficient in eliminating excess acid. However the TG-DTA curves permitted to verify that the binary compounds can be obtained by thermosynthesis, because the benzoic acid can be eliminated before the thermal decomposition of these compounds. The results led to information about the composition, dehydration, thermal stability, thermal decomposition and structure of the isolated compounds. On heating, these compounds decompose in two (Mn, Co, Ni, Zn) or three (Fe, Cu) steps with formation of the respective oxide (Mn3O4, Fe2O3, Co3O4, NiO, CuO and ZnO) as final residue. The theoretical and experimental spectroscopic studies suggest a covalent bidentate bond between ligand and metallic center.

Parâmetros operacionais no processamento de zeólitas desativadas por fusão com KHSO4

This work presents a study on the determination of the optimal experimental conditions for processing spent commercial zeolites in order to recover lanthanide elements and eventually other elements. The process is based on the fusion of the sample with potassium hydrogenosulfate (KHSO4). Three experimental parameters were studied: temperature, reaction time and catalyst/flux mass ratio. After fusion the solid was dissolved in water and the amount of insoluble matter was used to determine the efficiency of the process. The optimized experimental parameters depend on the composition of the sample processed. Under such conditions the insoluble residue corresponds to SiO2. Lanthanide elements and aluminum present in solution were isolated by conventional precipitation techniques; the yields were at least 75 wt%. The final generated wastes correspond to neutral colorless solutions containing alkali chlorides/sulfates and solids that can be disposed of in industrial dumps.

Caracterização dos produtos líquidos e do carvão da pirólise de serragem de eucalipto

This study proposes the low temperature pyrolysis as an alternative conversion process for residual biomass and for obtaining gaseous, liquid and solid chemical feedstocks. Using a bench electrical pyrolysis oven, four product fractions from eucalyptus sawdust were obtained: a gaseous one, two liquid (aqueous and oily), and a solid residue (char). These products were characterized by different analytical methods. The liquid fractions showed themselves as potential sources for input chemicals. The residual char revealed appreciable adsorption capability. The process demonstrated good efficiency, generating at least two fractions of great industrial interest: bio oil and char.

Decomposição térmica de espumas de poliuretano para fabricação de vitrocerâmica celular de Li2O-ZrO2-SiO2-Al2O3 (LZSA)

Characterization of the thermal decomposition of polyurethane (PUR) foams was performed by Fourier-transformed infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). Three main weight loss paths were observed by TGA, the residue being lower than 3 wt.% for 3 different PUR foams analyzed. FT-IR spectra indicated CO2, CO, NH3 and isocyanides as main decomposition products. PUR foams of different cell sizes were immersed in a slurry of the parent glass ceramic of composition Li2O-ZrO2-SiO2-Al 2O3 (LZSA) and submitted to heat treatment. The LZSA cellular glass ceramics obtained after sintering and crystallization resembled the original morphology of the PUR foams.

Composição química de um resíduo alcalino da indústria de papel e celulose (DREGS)

Dregs is an alkaline solid by-product generated in the cellulose manufacturing industry that could be used to correct soil acidity. The present study aimed to evaluate the chemical composition of this product and some of its properties. The dregs presented 354 g kg-1 of calcium, neutralization capacity of 80.3%, and pH 10.7, besides low concentration of sodium (10.2 g kg-1), lead (62.9 mg kg-1) and cadmium (5.6 mg kg-1). Thus, it is a product that can safely be used to increase the soil pH.

De resíduo a insumo: a construção do caminho para uma química mais limpa através de um projeto de ensino

The discussion among teachers, students, and technicians about the destination of residues from chemistry laboratories led to a research project whose results were incorporated into a course in its daily practices. The treatment of the residues from argentimetric practices allowed us to establish cognitive relations of technological basis and of those related to the rising of the level of awareness about environmental aspects and social responsibility of chemistry professionals. The techniques and the results, from the economic point of view, namely that of value aggregation (metallic silver) and the conversion of the residue into input (potassium chromate solution) are shown.

Isolation of compounds attractive to the leaf-cutting ant Atta sexdens rubropilosa forel (hymenoptera: Formicidae) from Mabea fistulifera elaiosome

Mabea fistulifera (Euphorbiaceae)is a pioneer plant species with seeds dispersed by the ant Atta sexdens rubropilosa. Since the ants are attracted to the seeds to use its elaiosome as a source of energy, we investigated its composition. The elaiosomes from 13,000 seeds were extracted with a methanol:chloroform mixture (2:1 v/v) and yielded 22% of a residue. This residue was fractionated by column chromatography and its composition determined by infrared spectroscopy and chromatography/mass spectrometry (GC-MS). The elaiosome lipids are constituted mainly by free fatty acids, triacylglycerols and minor quantities of monoacylglycerols or diacylglycerols.

Estudo sobre a utilização da lama vermelha para a remoção de corantes em efluentes têxteis

Red mud is the principal residue of the alumina (Al2O3) industry. Generated during the Bayer process, it is characterized by strong alkalinity and ion exchange. Iron oxides are the principal component (30 to 60%). Annually millions of tons of red mud are generated in the world. Red mud disposal is responsible for a large part of the cost of alumina production. On the other hand, textile industry wastewaters containing dyes have a great impact on the environment and on human health. In this paper the possibility of applying red mud for the removal of dyes was investigated by two processes: adsorption and degradation by the Fenton reagent.

Caracterização de bauxita ativada antes e depois da saturação com óleo mineral isolante

A characterization of activated bauxite and of activated bauxite impregnated with insulating mineral oil was made. The activated bauxite is used as adsorbent material in percolators during the regeneration of insulating mineral oil. After regeneration an insulating mineral oil is obtained with physical and chemical characteristics similar to those of the new oil. Moreover, saturated activated bauxite impregnated with insulating mineral oil is also produced. It is a dangerous residue according to NBR 10004 (Class I) and, thus, harmful to the environment. An alternative use of this waste in the ceramic industry is discussed.

Resíduos de agrotóxicos em alimentos: uma preocupação ambiental global - Um enfoque às maçãs

This paper describes the use of pesticides in agriculture. Research has shown that significant quantities of pesticide residues have been found in many types of foods. Thus, an overview is given of pesticide residue determinations in fruits and vegetables, with special attention to apples. The toxicity and the adverse effects possibly caused by the exposure of these compounds are alerting the scientific community to develop studies about the validation of analytical methods for multiresidue pesticide determination in these samples. This review shows that pesticide-residue determination in apples is becoming a very important and challenging issue.

Degradação de espécies nitroaromáticas e remediação de efluentes da indústria de explosivos, utilizando-se processos redutivos-oxidativos fundamentados no uso de ferro metálico

In this work the potentiality of reductive-oxidative processes based on zero-valent iron was studied aiming the degradation of nitroaromatic compounds and the remediation of residues from the explosive industry. The reductive process was applied as a continuous treatment system, using steel-wool as zero-valent iron source. The process permitted an almost total degradation of nitrobenzene, nitrophenol, nitrotoluene, dinitrotoluene and trinitrotoluene, probably with generation of the respective amine-derivative. The yellow-water residue, containing soluble trinitrotoluene, was notably modified by the reductive process, a fact that permitted a substantial enhancement of its biodegradability. Furthermore, the subsequent photo-Fenton process allowed TOC removal of about 80%.

Avaliação de biocombustível derivado do bio-óleo obtido por pirólise rápida de biomassa lignocelulósica como aditivo para gasolina

A biofuel was prepared from acid aqueous fraction (pH = 2) of bio-oil produced by fast pyrolysis (Bioware Technology) of lignocellulosic biomass (sugar cane residue) and tested in blends (2, 5, 10 e 20% v/v) with gasoline type C (common) marketed in Brazil. The specification tests made in the Refinery President Getúlio Vargas (PETROBRAS) showed increasing in the octane number (MON) and antiknock index (AKI) with reduction in the residue generation during the combustion. The physicochemical characteristics of the biofuel were similar that combustible alcohol allowing its use as gasoline additive.

Reciclagem do crômio de resíduos químicos provenientes da determinação de carbono oxidável em fertilizantes orgânicos

This work proposes a separation, recovery and reuse procedure of chemical residues with chromium. This residue was generated by the determination of oxidizable carbon in organic fertilizers samples. The Cr(VI) of the residue was reduced with ethanol and precipitated with NaOH. The Cr(OH)3 precipitate was separated and oxidized to dichromate ions with hydrogen peroxide. This solution was used another time in organic carbon determination. The uses of recycled dichromate solution were appropriated in four successive recycling. The accuracy was proven using potassium hydrogen phthalate and ten organic fertilizer samples. The organic carbon results, determined with recycled solutions, were similar the conventional solution.

Planejamento experimental na otimização da extração dos frutos de Syzygium cumini (L.) skeels

The aim of this study was to standardize the extractive solution of Syzygium cumini. The extractive solution was selected through a full factorial design, considering the extraction method (maceration-5-days, turbo extraction, percolation), extractor solvent (ethanol 50, 70, 96%) and plant material particle size 0.302 mm into a plant:solvent ratio (1:10), using the dried residue and antimicrobial activity determination as evaluation criteria. The tests were performed in triplicate. It appeared that the percolation is the best procedure extractive, and ethanol mixture: water (50:50) the best solvent. ANOVA analysis showed the importance of these parameters.