RESUMO
Durante as análises de Demanda Química de Oxigênio (DQO) é gerado um efluente líquido que se caracteriza pela presença de elevadas concentrações de metais pesados (Hg, Ag, Cr e Fe). Visando à remoção seletiva destes metais, possibilitando suas reutilizações, foram avaliados diferentes agentes precipitantes (Cl-, Br-, I- e S= para a Ag e o Hg e NaOH, NH4OH e NaHCO3 para o Cr e o Fe). Para a Ag e o Hg os melhores resultados em termos de remoção e recuperação seletiva foram obtidos quando do emprego seqüencial dos íons cloreto e sulfeto. Devido à presença de Hg(I), se fez necessário o emprego de NH4OH para separar seletivamente a Ag, presente na forma de AgCl, precipitada concomitantemente com Hg(I) como Hg2Cl2. Para o Cr e o Fe foram obtidas remoções que satisfazem à legislação (FEPAM) para ambos os elementos, somente quando do emprego do NaOH como agente precipitante.
In the analysis of Chemical Oxygen Demand (COD) a liquid residue rich in heavy metals (Hg, Ag, Cr, Fe) is obtained. This work aimed to remove, in a selective way, such metals from the residue using chemical precipitation, also creating a possibility to recover and reuse the heavy metals,. Different precipitants were evaluated (Cl-, Br-, I- and S= for Ag and Hg, and NaOH, NH4OH and NaHCO3 for Cr and Fe). The best results for selective recovery of Ag and Hg were obtained using chloride followed by sulphide. Due to the presence of Hg(I) it is necessary the use of NH4OH to separate Ag and Hg(I) that are both precipitated as AgCl and Hg2Cl2. Removal of Cr and Fe that attends the local limits set by the official control agency (FEPAM) was only obtained when NaOH was used as precipitating agent.
RESUMO
Objective: To investigate the effect of four kinds of inactivation methods on the activity of soybean agglutinin (SBA). Methods: Dry-heat, humid-heat, acid-alkali and metal ion were employed to evaluate their effects on the activity of SBA, which were quantified by hemagglutination. Results: Dry-heat below 120℃ did not obviously decrease the activity of SBA, while humid-heat (95℃ for 30 min,100℃ for 20 min or 105℃ for 10 min) completely inactivated the SBA. The activity of SBA significantly decreased when soybean protein was extracted under pH 1.0-4.5 or pH 9-13. Quadrivalent and trivalent metal ions markedly inhibited the activity of SBA. Conclusion: SBA can be inactivated effectively by humid-heat, acid-alkali or metal ion. Further study is needed to clarify whether there are synergistic effects between these treatments.