Remoção de Chumbo e Bário de um efluente aquoso via flotação por ar dissolvido

Abstract

The removal of metals present in aqueous solutions at concentrations (in the range of 10-7 to 10-4 mols.dm-3) is not satisfactory because of traditional methods that do not achieve adequate results for the effluent guidelines on the parameters of emission of wastewater. The technique of removing heavy metals from solution by ion flotation has been studied as an alternative that has a feasible capacity to treat large volumes of effluent in relatively small areas and accepting combinations with other techniques such as coagulation. The use of dissolved air flotation (DAF) adds advantages to flotation, especially with the use of lower concentrations of coagulants/flocculants and the diminutive size of the bubbles formed after depressurization in flotation cell, thus obviating the generation of small bubbles air by passing through a needle valve and differential pressure that the system has undergone. This study aimed to investigate some important variables that influence the ion flotation process via DAF and the influence of combined utilization of dissolved air flotation and coagulation using ferric chloride as coagulant agent in the removal of lead and barium contained in synthetic solutions within 15 mgL-1 of metal, and the application of anionic collector sodium dodecyl sulfate (SDS) in molar ratios. The choice of the metals lead and barium was based on real effluent from the soil washing contaminated by drilling fluids from oil wells. As a complement for the tests of ion flotation for the removal of lead and barium was developed the study of the flotation of colloidal sorbent and based on this technique it was investigated the ideal conditions for the flotation of a synthetic wastewater containing lead and barium. The influence of various parameters: pH, concentration of surfactant (SDS), recycle ratio, saturation pressure, flotation time. The introduction of clotting agent with and without agitation during the process of dissolved air flotation was also observed. The results showed that the equipment used is capable of producing satisfactory results for the removal of lead and barium in the range of values investigated. In the presence of SDS at a one to three ratio, recycle 10%, and pH of the entry about 10 and 50 mgL-1 ferric chloride, obtained the best results when it was recorded up to 97% removal.