Removal of Nickel and Zinc Using Natural Zeolite Estilbita Through the Process of Ionic Exchange / RemoÃÃo de NÃquel e Zinco Utilizando ZeÃlita Natural Estilbita AtravÃs do Processo de Troca IÃnica

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

One of the most serious problems of the modern age in environmental pollution; water contamination by industrial wastes is of great international concern. Frequently contaminants are heavy metals with a concentration in excess of that established by Legislation. The health problems are associated with heavy metal pollutants such as mercury, lead, zinc, nickel and chromium are serious and well known. Therefore the research and development of processes that reduces or eliminates metals found in industrial effluents are an important topic for all environmentalists. This study evaluates the removal of zinc and nickel from laboratory prepared solutions using ion exchange techniques. A finite bath system using a previously characterized natural exchange material, stilbite zeolite, was employed. The solutions were prepared to simulate the actual zinc and nickel conditions of the effluents usually met in industrial situations. To maximise metals extraction a factorial experimental design was performed to determine the optimum operational conditions. It was established that at pH = 4.5, pretreated zeolite with 2M NaCl solution and a granulometry in the range of 100 to 150 mesh Tyler, 51% of zinc and 36% of nickel were removed from the solution. Based upon these data, kinetic and equilibrium experiments, in two steps were undertaken; firstly for each single component and than combined. In order to evaluate the preferential extraction of the metals equilibrium ion exchange isotherms for this system were analized. The obtained equilibrium constants were 9.78 mEqÂL-1 and 12.93 mEqÂL-1 for zinc and nickel respectively. The maximum removal values for zinc were 0.40 mEq of Zn2+/g of zeolite and for nickel 0.34 mEq of Ni2+/g of zeolite at pH = 4.5. The experimental kinetic data were evaluated using an ion exchange model; the kinetic constants were k1 = 3.26 (LÂmEq -1Âh-1) and k -1 = 0.25 (L2ÂmEq -2Âh-1) for nickel and k1 = 4.15 (LÂmEq -1Âh-1) and k -1 = 0.42 (L2ÂmEq -2Âh-1) for zinc. This system presented a higher efficiency for zinc removal than for nickel; indicating that stilbite zeolite is more selective for zinc. The natural stilbite zeolite indicated a potential to remove zinc and nickel from synthetic solutions, proving that it may be used to reduce zinc and nickel concentrations of industrial effluents.

ASSUNTO(S)

stilbite zeolite ion exchange zeÃlita estilbita metais pesados heavy metals troca iÃnica engenharia quimica nÃquel e zinco zinc and nickel

ACESSO AO ARTIGO

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