Arsenic Retention on Technosols Prepared with Nanoparticles and Ferric Soil from Mine Drainage Water

Abstract

Mining activities generate a large amount of solid waste and acid drains that contain heavy metals in high concentrations. In wastewater of gold mines from Southern Ecuador (Portovelo), arsenic concentrations between 4.8 and 27.5 μg/L have been detected. In this context, the objective of this study is to prepare a technosol, which was used in the capture of arsenic dissolved in the acid drains. Technosol was elaborated using a clay-silty soil (iron-rich soil), collected in the mining area, and iron nanoparticles synthetized with the extract of orange peel. e technosol was experimentally characterized using adsorption isotherms and uptake kinetics. Besides, a mathematical model was developed using Vensim ® to scale the process and predict the dynamic behavior of the adsorbent. Results indicate that adsorption behavior of technosol can be fitted to Langmuir isotherms (R 2 > 0.9), with 95% of adsorption of As from an input of 4.5 mg/L. e model will be useful to predict the time needed to remedy contaminated water and the duration of the adsorbent (until its saturation).

Low-Quality Irrigation Water Treated Using Waste Biofilters

“…The experiment was conducted over twenty weeks. Water was collected weekly (Figure 1 quality in mining areas, urban stormwater and wastewater [7,32,33,[43][44][45][46][47]. However, their ability to treat irrigation water has not been studied as much, especially when macrophytes are not involved [27].…”

“…Several authors consider that technosols can be designed to provide ecosystem services like a natural soil does and to recover a degraded ecosystem, including aquatic ones [35][36][37][38][39][40][41][42]. Technosols, have been successfully used to improve the surface runoff water quality in mining areas, urban stormwater and wastewater [7,32,33,[43][44][45][46][47]. However, their ability to treat irrigation water has not been studied as much, especially when macrophytes are not involved [27].…”

Design and Construction of a Prototype for Arsenic Retention in Mining-Contaminated Waters by Application of Nanoparticles-Based Technosols

“…In response to the encountered mining pollution problems, this current study proposes the use of Technosol combined with nanoparticles in order to recover polluted soil and water [9][10][11]. In previous studies, the uptake of heavy metals by Technosols prepared in Ecuador has been evaluated mainly at the laboratory level [12][13][14][15]. Moreover, iron-based nanoparticles prepared by green or conventional synthesis have been used to remove toxic metals from polluted water and soils under laboratory experimental conditions, such as the multicomponent nanoparticles biosynthesized with orange peel (Citrus sinensis) extract [16].…”

“…This chemical composition gives the nanoparticles enhanced sorption properties to selectively capture heavy metals. Particularly, the active groups of the zero-valent iron and ferrous sulfide chemically retain arsenic through the formation of Fe-oxide-As 3+ complexes, complexation with iron hydroxides, reduction to As 0 or As 3+ in the presence of Fe 0 [17] and surface complexation by FeS [18] The capability of nanoparticles to immobilize heavy metals dissolved in water was over 80%, reaching even 99% for arsenic, allowing the design and elaboration of Technosol mixed with nanoparticles [13,14]. A silty clay extracted from a mining area was used as Technosol.…”

“…A fast removal of metals was observed within 5 min with the best dose of 99.75% soil + 0.25% nanoparticles, and an immobilization higher than 90% was achieved. On the other hand, it was analyzed the retention of arsenic with the use of Technosol prepared with ferric soil and nanoparticles [13]. Using Vensim software, a model was developed capable of scaling and predicting the behavior of the adsorbent.…”