Abstract
The adsorption of biosurfactants and polysaccharides changes the surface properties of solid particles, which is important for controlling the release of arsenic compounds from the solid phase and preventing undesirable bioleaching. Microbial leaching and scorodite adhesion experiments, including pure and modified mineral material, were conducted in a glass column with a mineral bed (0.8–1.2 mm particle size) to test how rhamnolipids (Rh) and lipopolysaccharides (LPS) affect surface properties of mineral waste from Złoty Stok (Poland) and secondary bio-extraction products (scorodite). Adsorption tests were conducted for both solid materials. The adsorption of Rh and LPS on the solids was shown to modify its surface charge, affecting bioleaching. The highest bio-extraction efficiency was achieved for arsenic waste with adsorbed rhamnolipids, while the lowest, for the LPS-modified mineral. Under acidic circumstances (pH~2.5), the strongly negative zeta potential of arsenic-bearing waste in the presence of Rh creates conditions for bacteria adhesion, leading to the intensification of metal extraction. The presence of a biopolymer on the As waste surface decreases leaching efficiency and favours the scorodite’s adhesion.
Highlights
Environmental contamination by heavy metals is problematic in former mining areas [1,2]
In the case of heap leaching or in a column where the suspension of bacteria and circulates in a closed circuit, both secondary minerals and bacteria cells adhere to the surface secondary minerals circulates in a closed circuit, both secondary minerals and bacteria of the primary mineral
This study was conducted to explain the bacteria–mineral interactions that might occur during the bioleaching of As-bearing minerals, which occurs through (i) cell adhesion and biofilm formation or (ii) reaction of microorganisms and their metabolites with ore
Summary
Environmental contamination by heavy metals is problematic in former mining areas [1,2]. Natural bioleaching forms acid rock (mine) drainage. As-bearing deposits are excavated, mine water becomes rich in arsenic. It encourages the growth of arsenophilic bacteria [3,4] and enriches bottom sediments with arsenites and arsenates [5,6]. In Poland, one of the old gold mining and processing centres is Złoty Stok (southwest), which, from the 17th century until 1962, was one of Europe’s arsenic industry centres. Ore mining and processing, which took place in this area, produced large quantities of waste materials rich in As, such as mine waste rock, slag, and tailings [7]. Ore smelting carried out in small facilities that produced gold was the primary source of As released into the atmosphere and deposited on the earth’s surface. Other than Poland, there are regions where this problem is significant (Chile, Bangladesh)
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