Remoção de metais pesados de efluente de galvanoplastia por meio de precipitação e membranas líquidas emulsionadas

Abstract

The increase in the amount of industrial and domestic wastewater has caused a growing concern in the world. Waste from the electroplating industry has a high polluting load, as it comes from procedures that use large amounts of toxic products, such as heavy metals. These metallic residues directly impact the environment due to the substances present, which can cause imbalance to animals and human health, besides not being biodegradable, they need compatible and viable techniques to reduce them. Some of today's heavy metal treatment methods have several disadvantages, such as the use of potentially polluting chemical species, the generation of waste by its own methods, the high cost of implementation, and the inefficiency of reducing pollutant levels until compliance with legislation. Based on the principle of liquid-liquid extractions, the emulsified liquid membrane (ELM) treatment process is a technical and economic advantage. These characteristics are due to the low cost of the reagents and equipment used, as well as the efficiency in removing small concentrations of heavy metals and the low generation of process residues. The chemical precipitation method was also evaluated in this study as a step prior to application to the ELM method, resulting in an approximately 100% reduction in nickel (Ni), lead (Pb), chromium (Cr), zinc (Zn), cadmium (Cd) and copper (Cu). The ability to reduce residual metal concentrations of precipitation was also evaluated by the emulsified liquid membranes method, which obtained removal efficiency of 100% for Pb, 95.7% for Cd, 85.97% for Zn, 85, 88% for Ni and 69.46% for Cu by formulating 6% v/v n-octyl alcohol as carrier and 4% v/v SPAN 80® as surfactant. The use of soybean lecithin biosurfactant in the membrane composition proved inviable because of the properties acquired by the compound due to external exposure. Besides, due to the results obtained, the influence of the complexity of the galvanic effluent in the ELM system is indispensable, demonstrated by the destabilization of the membranes by the swelling, coalescence and demulsification phenomena observed during the process.