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عنوان فارسی مقاله:
اثربخشی لایه های مختلف قلیایی پراکنده برای قبل از زهکشی معدن اسیدی آهن دار
عنوان انگلیسی مقاله:
Effectiveness of various dispersed alkaline substrates for the pretreatment of ferriferous acid mine drainage
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
Environmental impacts of acid mine drainage (AMD), which is characterized by low pH (3.6 < pH < 6) and high concentrations of dissolved metals, metalloids and sulfate (SO4 2) are largely documented (Neuman et al., 2014; Nordstrom et al., 2015). Improvement of technologies has been conducted over the last decade to limit and prevent AMD generation (Sahoo et al., 2013; Jennings and Jacobs, 2014). Several treatment technologies, including active and passive systems, have also been developed (USEPA, 2014). Passive treatment is preferred, principally for moderately contaminated water, because of its low cost, potential production of marketable sludge, and simple installation and operation (Hedin et al., 2013; Zipper and Skousen, 2014). Despite these advantages, efficiency of a single unit of passive treatment (e.g. oxic/anoxic limestone drains- OLD/ALD, passive biochemical reactor- PBR) is limited when used for the treatment of highly contaminated AMD, particularly ferriferous AMD (Fe > 500 mg/L) (Neculita et al., 2008; Genty et al., 2010). Hence, combinations of two or more units of passive treatment or so-called passive multi-step treatment system have been developed (Macías et al., 2012; Genty et al., 2012a). Nonetheless, coating/passivation (loss of reactivity) and clogging (loss of permeability) caused by precipitated minerals during treatment (e.g. gypsum, metal oxide-hydroxides) (Rotting et al., 2008a € ) are presently limiting the long term performance of such systems. Their longstanding efficiency is conditioned by removal, at an early stage, of acidogenic metallic elements, such as Fe and/or Al (Ayora et al., 2013). Indeed, during precipitation of ferric iron as hydroxide [Fe(OH)3] (Eq. (1)), which starts at pH around 3e3.5, depending on Fe total concentration, the pH decreases, and the removal of divalent metals (which precipitation requires pH > 8.5), is inhibited.Consequently, a pre-treatment unit for Fe removal in ferriferous AMD is a must before forwarding water into a second treatment unit for the removal of other metals and of SO4 2, if necessary. Various techniques have been developed for Fe pre-treatment, such as oxidation/precipitation (Champagne et al., 2008), oxic limestone drain (OLD) (Figueroa et al., 2007), natural Fe-oxidizing lagoon (NFOL) (Macías et al., 2012), and cascade aeration (USEPA, 2014). Most of these techniques gave promising results, but have been mostly used for Fe pre-treatment when AMD has low to moderate concentrations (40e1000 mg/L Fe). Regarding Fe concentration, the quality of water in this study is then considered as extremely contaminated (2500 mg/L Fe). Innovative approaches using reactive mixtures composed of a coarse, highly porous material (wood chips) and small grain size of neutralizing agents (e.g. MgO, CaCO3) known as dispersed alkaline substrate (DAS) have also been investigated with the aim of overcoming the coating-clogging general issues in passive treatment (Macías et al., 2012; Ayora et al., 2013). Two main types of DAS have been used to treat AMD, one comprised of MgO (MgO-DAS), for the removal of bivalent metals (e.g. Macìas et al., 2012; Ayora et al., 2013), and one of calcite (calcite-DAS), for the removal of trivalent metals (e.g. Rotting et al., 2008b; Caraballo et al., 2011 € ). In passive treatment, the use of economic, available and natural materials or substitute is recommended. Other selection criteria include the reaction rate of neutralizing agents, sludge production and costs (Potgieter-Vermaak et al., 2006). Hence, the dolomite DAS could be an economic replacement of the calcite/limestone DAS because it could reduce expenses up to 23% (Potgieter-Vermaak et al., 2006). Moreover, previous studies using dolomite as a neutralizing agent in the treatment of very acidic water have shown promising results (Potgieter-Vermaak et al., 2006; Huminicki and Rimstidt, 2008; Genty et al., 2012a). Depending on the grain size, some studies even presented comparable efficiency of calcite and dolomite when used for the treatment of moderately contaminated AMD under anoxic condition, with lower difference in alkalinity production (105e220 mg/L as CaCO3) for a hydraulic retention time of 15 h (Genty et al., 2012a). Additional benefits of dolomite-DAS include the delaying of the neoformed minerals (e.g. gypsum CaSO4$H2O) because of the belated release of Ca2þ. Another potential replacement of MgO in DAS systems could be wood ash, principally used for its high pH (up to 12), metal retention, and neutralization capacity. The wood ash, which is usually considered as a waste, has in fact a good potential of reuse. It showed efficiency in the pre-treatment of ferriferous AMD (Genty et al., 2012b). Moreover, it is an economic material, relative to MgO which cost is up to ten times higher than limestone (Rotting € et al., 2006). Then, wood ash-DAS (WA-DAS) could be advantageous and potentially give similar performance to MgO-DAS. Despite the satisfactory performance (in terms of Fe and SO4 2 removal, as well as of hydraulic conductivity stability) of the wood ash, its long term performance remains uncertain (Genty et al., 2012b). Moreover, additional treatment units for sulfate removal are necessary. The results of a very recent laboratory study, which compared the performance of calcite-DAS to witherite (BaCO3)-DAS, in terms of SO4 2 removal, showed that the last was more efficient, but became unreactive after only 40 days of operation, due to passivation (by coating with barite e BaSO4) (Lozano et al., 2015). Therefore, the objective of the present study is to evaluate the efficiency of WA-DAS, calcite-DAS and dolomite-DAS in batch testing, in the perspective of their use as pre-treatment units for Fe removal in a ferriferous AMD. The residual Fe concentration targeted for this pre-treatment is 500 mg/L. This concentration was reported as a threshold value based on the steady performance of a PBR, in a 15-month laboratory study (Neculita et al., 2008).
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کلمات کلیدی:
Applied Geochemistry | Vol 73, Pgs 1-178, (October 2016 ... www.sciencedirect.com/science/journal/08832927/73 The De values of ReO4− were almost unchanged at pH 3.0–10.0 ... various dispersed alkaline substrates for the pre-treatment of ferriferous acid mine drainage. Effectiveness of various dispersed alkaline substrates for the pre ... https://www.deepdyve.com/.../effectiveness-of-various-dispersed-alkaline-substrates-f... Read "Effectiveness of various dispersed alkaline substrates for the pre-treatment of ferriferous acid mine drainage, Applied Geochemistry" on DeepDyve, the ... Passive biochemical treatment of ferriferous mine drainage: Lorraine ... https://www.imwa.info/docs/imwa_2016/IMWA2016_Genty_10.pdf by T Genty - Related articles 2 Research Institute on Mines and Environment (RIME), University of ... Environmental impacts of acid mine drainage (AMD), characterized by low pH (-3.6 < pH ..... substrate for the pre-treatment of highly contaminated acid mine drainage. Carmen Mihaela Neculita - Publications www.carmenneculita.com/frpublications.html ... for the pre-treatment of ferriferous acid mine drainage" Applied Geochemistry 73: ... F (2016) "Biochemical passive reactors for treatment of acid mine drainage: ..... S, Neculita, CM (2015) "East Sullivan mine site restoration: Current success ... Publications | RIME UQAT-Polytechnique www.irme.ca/en/publications?p=240&page=10 Research Institute on Mines and the Environment UQAT-Polytechnique ... Effectiveness of various dispersed alkaline substrates for the pre-treatment of ferriferous acid mine drainage ... Yilmaz E., Belem T., Bussière B., Benzaazoua M. (2008) Publications - Directory of Expertises - Polytechnique Montréal www.polymtl.ca › Polytechnique › Research › Directory ... dispersed alkaline substrates for the pre-treatment of ferriferous acid mine drainage. ..... (Chaire industrielle CRSNG en assainissement et gestion des sites, ...
