OPTIMIZATION OF VOLCANIC ASH LEACHING METHODOLOGIES

NICOLAS KARIN VALLEJO AZAR; RAÚL GIL; PAUL EMIR HASUOKA; SABRINA PERMIGIANI; LUIS ESCUDERO

Mendoza

Congreso; 15th Rio Symposium Actomic spectrometry; 2019

Universidad Nacional de Cuyo

The potential impact of volcanic ash deposition on the environment is usually established and predicted through laboratory scale leaching studies. However, reproducing environmental conditions in the laboratory is usually a very difficult task. So far, different ash leaching methodologies have been proposed, and it is necessary to seek a consensus on these methodologies to establish a standard protocol that provides a better environmental impact assessment [1].Since there are different variables that can influence the leaching process such as: ash grain size, contact time, acidity of the system, solid / liquid ratio, stirring speed, temperature, among others [2], in the present study was used a two-level fractional factorial design, which allowed to study the influence and possible interactions between the variables that affect the leaching process. Volcanic ashes collected in the town of San Carlos de Bariloche, corresponding to the eruption of Puyehue Volcano in 2011, were studied.In this work, 20 experiences were carried out (in duplicate), in which the variables studied were: I- the contact time (between 1 and 8 h); II- the acidity of the system (pH between 3 and 10); III- Solid / Liquid / (S / L) ratio between 1: 100 and 1:20); IV- the particle size (fraction smaller than 74 µm and larger than 74 µm); V- speed agitation in leaching (120 and 480 rpm). All design trials were performed in batch, using 10 mL of ultrapure water as a leach and the amount of ash was varied to modify the S / L ratio. The solutions obtained from the leaching of volcanic ash were analyzed by ICP-MS.According to the optimization of the experimental design (Desirability Function D), we found that the optimal release conditions can be grouped into two groups, the first consisting of Cu, Pb, Tl, V, Na, K, Ca, Si, and P with optimal conditions of pH 8, rapid agitation, S / L ratio of 1:20, the smallest particle size and the highest agitation speed (480 rpm). The other group consists of Cd, Cr, Hg, Fe and Sr, differing with the first group that the optimal conditions are in larger ash size and the slower agitation speed (120 rpm).The main differences in the results obtained in this work with respect to the protocols established above are related to the solid / liquid ratio factors and the contact time. In this way, the findings obtained in the present study provide optimal leaching conditions, based on an exhaustive statistical analysis and contribute to the establishment of a standard protocol for leaching volcanic ash.