Extração de metais pesados por membranas líquidas emulsionadas: uma revisão de literatura da performance e modelos de transferência de massa

Abstract

With the constant industrial development, the generation of liquid effluents increases each day. Linked to this fact, there is great concern about the disposal of these effluents, since many of them are contaminated by substances that are harmful to the environment and human beings; therefore, they need appropriate treatments before being released into bodies of water. Among the substances present in effluents from industries are heavy metals. These are compounds of high toxicity and accumulative nature in organisms and therefore, need special attention. There are several methods for extracting heavy metals, but most of them have high cost of implantation, low efficiency in the removal of pollutants and also, generation of residues. In that regard, the use of emulsion liquid membranes (ELM) has been shown to be a method very advantageous, since it allows the efficient separation of small concentrations of heavy metals and also needs a small amount of organic solvent for the process. However, parameters such as properties of the surfactant, extractant, internal and membrane phases, as well as the preparation of the emulsion, should be studied to enable greater extraction efficiency. In this way, a critical literature review was performed based on the ProKnow-C methodology, which consisted of selecting the research database through a portfolio bibliographic analysis, followed by a bibliometric and systematic analysis of the portfolio and, finally, the evaluation of the results obtained regarding the performance and models of mass transfer of heavy metals extraction through ELM. In relation to performance, the main factors that affect the extraction of these compounds and also, the models of facilitated diffusion type I and II for mass transfer analysis. Among the works selected for study, it was possible to conclude that factors such as surfactant concentration, extractant, droplet diameter of emulsion and stirring speed affect the extraction efficiency, requiring new studies in this field in order to verify the best experimental conditions for each heavy metal.