Natural Antioxidants and Their Reducing Power Against Silver Ions: Alternative in the Recovery of Metals

Abstract

The contamination of the waters of rivers and seas due to the presence of metals is a worldwide problem mainly due to the impact of mining tailings. It has been scientifically proven that, in addition to causing some of the most serious environmental problems, exposure to metals in certain circumstances is the cause of the degradation and death of vegetation, rivers, animals and even of direct damage to humans, by what is essential look for ways to eliminate them, or at least reduce their impact. This work shows the results obtained from the reducing behavior of plant extracts against silver ions, a process where the extracts are chemicals used as reagents in the recovery of a metal instead of using synthetic reagents, simple and economical method. Extracts containing antioxidant substances such as flavonoids, tannins and phenolic compounds, which are secondary metabolites of many plants, and their antioxidant activity play a fundamental role in the reduction processes. The plant extracts studied were: Dandelion (Taraxacun officianale), Parsley (Petroselinum crispum) and Hierbabuena (Camellia sinensis). Analytical tests of the qualitative identification of the presence in the aqueous extracts of the flavonoids, phenolic acids responsible for their reducing power, were carried out. The reducing power of the extracts was tested through the formation of silver nanoparticles, monitoring the UV-Vis spectra with the appearance of the plasmon band characteristic of metallic nanoparticles, as well as through the recovery of silver in the form of clean and bright solid with good yields, the yield of the silver obtained with each of the plant extracts used was quantified. From the results obtained it can be concluded that it is feasible to use plant extracts for the reduction of metals and in this way recover metals in metallic form.