Zn(II) adsorption from synthetic solution and kaolin wastewater onto vermicompost.

The adsorption of Zn(II) from both synthetic solution and kaolin industry wastewater by cattle manure vermicompost was studied. The adsorption process was dependent on the various operating variables, viz., solution pH, particle size of the vermicompost, mass of vermicompost/volume of the Zn(II) solution ratio, contact time and temperature. The optimum conditions for Zn adsorption were pH 6.0, particle size of < or = 250 microm, 1 g per 10 mL adsorbent dose, contact time of 4h and temperature of 25 degrees C. Langmuir and Freundlich adsorption isotherms fit well in the experimental data and their constants were evaluated, with R(2) values from 0.95 to 0.99. In synthetic solution, the maximum adsorption capacity of the vermicompost for Zn(2+) ions was 20.48 mg g(-1) at 25 degrees C when the vermicompost dose was 1 g 10 mL(-1) and the initial adjusted pH was 2. The batch adsorption studies of Zn(II) on vermicompost using kaolin wastewater have shown the maximum adsorption capacity was 2.49 mg g(-1) at pH 2 (natural pH of the wastewater). The small values of the constant related to the energy of adsorption (from 0.07 to 0.163 L mg(-1)) indicated that Zn(2+) ions were binded strongly to vermicompost. The values of the separation factor, R(L), which has been used to predict affinity between adsorbate and adsorbent were between 0 and 1, indicating that sorption was very favorable for Zn(II) in synthetic solution and kaolin wastewater. The thermodynamic parameter, the Gibbs free energy, was calculated for each system and the negative values obtained confirm that the adsorption processes are spontaneous. The DeltaG degrees values were -19.656 kJ mol(-1) and -16.849 kJ mol(-1) for Zn(II) adsorption on vermicompost in synthetic solution at pH 6 and 2, respectively, and -13.275 kJ mol(-1) in kaolin wastewater at pH 2.

Removal of Cu, Cr, Ni, Zn, and Cd from electroplating wastes and synthetic solutions by vermicompost of cattle manure.

This study was undertaken to evaluate the retention of Cu, Cr, Ni, Zn, and Cd under laboratory conditions from synthetic solution and electroplating wastes by vermicompost. A glass column was loaded with vermicompost, and metal solutions were passed through it. Metal concentrations were then measured in the eluate in order to evaluate the amounts retained by the vermicompost. Measurements of pH, metal concentrations, moistness, organic matter and ash contents, and infrared and XRD spectroscopy were used for vermicompost characterisation. Vermicompost residues obtained from this process were used for plant nutrition in eroded soil collected from a talus near a highway. Metal retention (in g of metal/kg of vermicompost) from effluents ranged from 2 for Cr and Zn to 4 in the case of Ni. In synthetic solutions, the values for metal retention were 4 for Cd and Zn, 6 for Cu and Ni, and 9 for Cr. The results also showed that metal concentrations in the purified effluents were below the maximum values established for waste discharges into rivers by the Brazilian Environmental Standards. The relatively high available Cd concentration of the vermicompost residue resulted in plant damage. This effect was attributed to the presence of Cd in the synthetic solution passed through the vermicompost. The data obtained do not give a complete picture of using vermicompost in cultivated lands, but such values as are determined do show that it can be suitable to remove heavy metals from industrial effluents.

[Selenium concentration in food consumed in Brazil]. / Concentrações de selênio em alimentos consumidos no Brasil.

OBJECTIVE: To determine the selenium content of foods consumed in Brazil. METHODS: The project was carried out between 1993 and 1999. The food samples were collected in stores in several Brazilian states. The levels of selenium were determined by hydride generation atomic absorption spectrophotometry and by wet oxidation. RESULTS: The highest levels of selenium were found in animal products, especially fish, and in wheat products. We found that plant products generally had selenium levels of less than 5.0 micrograms/100 g. CONCLUSIONS: In Brazil a diet rich in animal products, especially fish, is important in ensuring consumption of the recommended levels of selenium.

Concentracoes de selenio em alimentos consumidos no Brasil / Selenium content of Brazilian foods

Objective. To determine the selenium content of foods consumed in Brazil. Methods. The project was carried out between 1993 and 1999. The food samples were collected in stores in several Brazilian states. The levels of selenium were determined by hydride generation atomic absorption spectrophotometry and by wet oxidation. Results. The highest levels of selenium were found in animal products, especially fish, and in wheat products. We found that plant products generally had selenium levels of less than 5.0 µg/100 g. Conclusions. In Brazil a diet rich in animal products, especially fish, is ensuring consumption of the recommended levels of selenium

Objetivo. Determinar os teores de selênio em alimentos consumidos no Brasil. Métodos. O trabalho foi desenvolvido de 1993 a 1999. As amostras de alimentos foram coletadas no comércio varejista em vários estados do Brasil. Os teores de selênio foram determinados por meio de espectrofotometria de absorção atômica, utilizando-se a técnica de geração de hidretos, e oxidação da matéria orgânica por via úmida. Resultados. Os teores mais elevados de selênio foram encontrados nos produtos de origem animal, sobretudo nos pescados, e nos produtos derivados do trigo. Observou-se que os teores de selênio nos alimentos de origem vegetal foram, de modo geral, inferiores a 5,0 µg/100g. Conclusões. No Brasil, a presença de pescados, principalmente, e de outros produtos de origem animal é importante na dieta para garantir o consumo dos teores recomendados de selênio.

Cloraminas orgânicas, uma soluçäo para evitar a formaçäo de trihalometanos no processo de desinfecçäo de águas para abastecimento público / Organic chloramines a solution to avoid trihalomethanes in process of water desinfection for public water consumption

Avaliou-se a formaçäo de trihalometanos (THM), após três processos de desinfecçäo da água conduzidos na estaçäo de tratamento de água (ETA) de Poços D'Antas, em Juiz de Fora: pré-cloraçäo com hipoclorito de sódio (HPCS), pós-cloraçäo com HPCS e dicloroisocianurato de sódio (DCIS). As amostras foram coletadas na caixa de partida da ETA e num ponto da rede (Panificadora/IA). As concentraçöes de THM foram determinadas por cromatografia de fase gasosa em coluna capilar, com procedimento de microextraçäo em fase sólida (MEFS). Ocorreu a formaçäo de THM na pré e na pós cloraçäo com o HPCS, em níveis considerados relevantes nos dois pontos de amostragem. Na desinfecçäo da água com DCIS detectaram-se apenas traços de THM tanto na ETA como na IA, e o TCM näo foi encontrado. Confirma a viabilidade do uso do DCIS no processo de desinfecçäo na ETA e na IA, mas ressalta a necessidade da utilizaçäo de um produto com maior grau de pureza, já que foram detectadas substâncias desconhecidas.