RESUMO
Artisanal mining is the main source of mercury emissions in South America, which generates a serious environmental impact due to this toxic metal, recent research is directed to minimize the impact, therefore this study focuses on the green synthesis of nanoparticles for the absorption of mercury in water. For the synthesis of iron nanoparticles, an extract of Eucalyptus grandis was used with iron chloride salts using water as solvent. The synthesized nanoparticles showed a specific surface area of 131.90 m2/g, determined by Brunauer-Emmett-Teller isotherm (BET). Nanoparticles were characterized by Fourier transformed infrared spectroscopy (FTIR) and transmission electron microscopy (MET). The behavior of nanoparticles synthesized during Hg (II) retention was evaluated measuring pH, temperature, nanoparticle dosing, presence of other ions and comparing with other adsorbents. All analyses measured by atomic absorption spectroscopy by the cold vapor technique (CVAAS), presenting a retention percentage for Hg (II) between 75.05 and 79.59% with pH between 4 and 7. The adsorption isothermal was adjusted to the Freundlich model and the percentage of retention of Hg by the synthesized nanoparticle was 79.26%. This work shows a method for obtaining an environmentally friendly mercury adsorbent from iron and E. grandis with a mercury retention capacity comparable to commercial adsorbents.
RESUMO
Gold mining is one of the major problems of contamination of hydric resources in Colombia, this practice generates a high impact on water quality due to the accumulation of waste during its process. In this study water quality was evaluated in five natural stream beds corresponding to four streams with gold mining operations and one in the Cauca River, taking samples before the water inlet and after the outlet in each operation in the streams of Dios Te Dé, Tamboral, Piedra Imán, and Lorenzo affected by artisanal gold mining labor, which drain into the Salvajina Reservoir on the Cauca River in the municipality of Suárez Cauca, Colombia. Characterization of water bodies in the streams was carried out applying contamination indices of Colombia. The IDEAM protocol was used as guide to monitor the water currents. Samples were taken in 15 stations in the natural stream beds with operations and a sampling station on the Cauca River after the reservoir in these lotic ecosystems, during three periods; two from 2018 and one from 2019. The range of the contamination indices according to the environmental variables were considered. Results show that the contaminants associated with TSS, TUR, and Hg are high in the sampling stations in the output of the operations and the sampling stations of the streams with influence on the operations (T3, T4, I2, I3, D2, and D5). The water quality score according to the ICA IDEAM index varied between acceptable and regular in the different sampling stations. However the Hg concentration in sampling station C1 of the Cauca River is due to contributions from the operations in the amalgamation process. This requires strategic interventions by the communities, miners, operation owners, and control organisms as the Regional Autonomous Corporation of Cauca (CRC) and the Ministry of Environment and Sustainable Development (MADS) to minimize the negative impacts on the hydric resource and ecosystemic services associated with this resource.