Abstract
The main element of PbRS (passive (bio)remediation systems) are sorbents, which act as natural filters retaining heavy metals and carriers of microorganisms involved in water treatment. Thus, the effectiveness of PbRS is determined by the quality of the (ad)sorbents, which should be stable under various environmental conditions, have a wide range of applications and be non-toxic to (micro)organisms used in these systems. Our previous studies showed that bog iron ores (BIOs) meet these requirements. However, further investigation of the physical and chemical parameters of BIOs under environmental conditions is required before their large-scale application in PbRS. The aim of this study was (i) to investigate the ability of granulated BIOs (gBIOs) to remove arsenic from various types of contaminated waters, and (ii) to estimate the application potential of gBIOs in technologies dedicated to water treatment. These studies were conducted on synthetic solutions of arsenic and environmental samples of arsenic contaminated water using a set of adsorption columns filled with gBIOs. The experiments performed in a static system revealed that gBIOs are appropriate arsenic and zinc adsorbent. Dynamic adsorption studies confirmed these results and showed, that the actual sorption efficiency of gBIOs depends on the adsorbate concentration and is directly proportional to them. Desorption analysis showed that As-loaded gBIOs are characterized by high chemical stability and they may be reused for the (ad)sorption of other elements, i.e., zinc. It was also shown that gBIOs may be used for remediation of both highly oxygenated waters and groundwater or settling ponds, where the oxygen level is low, as both forms of inorganic arsenic (arsenate and arsenite) were effectively removed. Arsenic concentration after treatment was <100 μg/L, which is below the limit for industrial water.
Highlights
Passiveremediation systems (PbRS) are low-cost and environmentally-friendly technological solutions for the treatment of metal-polluted water, which passes through a semi-permeable barrier while the contaminants are retained by means of biogeochemical reactions (Groudev et al, 2008; Obiri-Nyarko et al, 2014)
This study presents the results of an investigation of the capabilities of arsenic-loaded adsorbent, including three-step chemical desorption experiments and studies of the re-use of Asloaded bog iron ores (BIOs) for the sorption of other heavy metals, in which zinc was used as an example
Water samples used in this study were collected in the Zloty Stok area (SW Poland), from the following reservoirs polluted with arsenic: (i) a settling pond of an old paint and varnish factory, (ii) a dewatering system of an ancient gold mine, and (iii) a 30 m deep mine pit filled with water flowing through arsenic deposits
Summary
Passive (bio)remediation systems (PbRS) are low-cost and environmentally-friendly technological solutions for the treatment of metal-polluted water, which passes through a semi-permeable barrier while the contaminants are retained by means of biogeochemical reactions (Groudev et al, 2008; Obiri-Nyarko et al, 2014). Adsorbents that are used in passive (bio)remediation systems (e.g., constructed wetlands or permeable reactive barriers) act as: (i) natural filters (barriers) retaining heavy metals by physicochemical sorption, and (ii) carriers for microorganisms involved in water treatment (Li et al, 2013; Meng et al, 2014; Hua et al, 2015). The use of an adsorbent with fast adsorption kinetics but with low sorption capacity is inconvenient, as to ensure high efficiency, a large amount of the material is required. An adsorbent used in systems based on both physico-chemical and microbiological remediation technologies should be non-toxic to bacteria
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