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Design and operation of pilot scale anaerobic compost wetland for the treatment of acidic drainage from the Stratoni mixed sulphide mines, Chalkidiki, Northern Greece
Published in Gülhan Özbayoğlu, Çetin Hoşten, M. Ümit Atalay, Cahit Hiçyılmaz, A. İhsan Arol, Mineral Processing on the Verge of the 21st Century, 2017
To monitor the anaerobic laboratory cells performance, effluent water samples were periodically collected and measured for: pH, EMF, dissolved oxygen (DO), acidity/alkalinity and metal levels. Alkalinity and acidity were measured with an automatic titrator, Greenberg et al. (1985), whereas net alkalinity expressed in CaCO3 mg/l was calculated by subtracting the measured acidity from alkalinity. Ferrous iron concentrations were determined spectrophotometrically with the phenathroline method. Fe, Zn and Mn analyses were carried out with AAS (Perkin Elmer model 2100), while SO4= was measured gravimetrically.
Leaching of ferrous iron after drainage of pyrite-rich soils and means of preventing pollution of streams
Published in A.L.M.Van Wijk, J. Wesseling, Agricultural Water Management, 2020
Ferrous iron is toxic at very low concentrations. Some invertebrates are sensitive to concentrations as low as 0.2 mg/1, e.g. larvae of some beetles, and streams with concentrations of more than 0.5 mg/1 will not contain invertebrate species normally found in otherwise clean waters (Skriver, 1984).
The Direct Leaching of Nickel Sulfide Flotation Concentrates – A Historic and State-of-the-Art Review Part I: Piloted Processes and Commercial Operations
Published in Mineral Processing and Extractive Metallurgy Review, 2023
Nebeal Faris, Mark I. Pownceby, Warren J. Bruckard, Miao Chen
Metallic Ni powder is produced via hydrogen reduction of the copper-free solution in an autoclave at elevated temperature and pressure and the resultant powder is briquetted (Forward 1953; Forward and Mackiw 1955). The solution from Ni reduction is treated with H2S to precipitate Ni and Co as a mixed sulfide precipitate (MSP) and the barren solution is then processed further to recover ammonium sulfate as a by-product (Forward 1953; Forward and Mackiw 1955; Mackiw et al. 1958). The MSP product is further processed in a cobalt refinery, the main process steps of which are depicted in Figure 4; leaching is carried out via sulfuric acid pressure oxidation in an autoclave at 121°C and pressure of 790 kPa (absolute) using air as an oxidant (Mackiw et al. 1958). The leach solution is purified to remove dissolved iron by adjusting the pH to 4.9–5.1 using ammonia and sparging air to oxidize any ferrous iron to the ferric state (Mackiw et al. 1958). After iron removal, solid ammonium sulfate is added to increase the concentration of (NH4)2SO4 in solution to the level required for cobalt reduction, and to remove Ni from solution as nickel ammonium sulfate which is recycled to the nickel reduction circuit (Forward 1953; Mackiw et al. 1958). Cobalt is recovered from solution by hydrogen reduction at elevated temperature and pressure in an autoclave to form cobalt powder (Mackiw et al. 1958).
Bromate removal from water by acid activated and surfactant enriched Red Mud – the case of cooling water
Published in Environmental Technology, 2020
Fivos A. Megalopoulos, Maria T. Ochsenkuehn-Petropoulou
All dilutions were carried out with ultra-pure water (18.2 MΩ resistance) coming from a Barnstead Easy-Pure device. All solutions’ pH values were measured and adjusted with the use of a Metrohm 716 DMS Titrino pH adjuster. The electric conductivity was measured with a Metrohm 660 Conductometer. Ferrous iron was measured spectrophotometrically with the help of a Hach-Lange DR 4000 Spectrophotometer using the 1,10 Phenanthroline method. Bromate was measured on a Dionex BioLC Ion Chromatography system using a set of AS9-HC/AG9-HC columns (EPA Method 300.1). Residual CTAC in water was measured by titration with tetrabromophenolophthalein ethyl ester as an indicator [19]. The difference in weight between initial CTAC addition and residual amount in solution after the treatment of AARM represents the amount loaded onto AARM particles. A Jesco 4200 spectrometer with a resolution of 4.0 cm−1 was employed for the Fourier Transform Infrared Analysis; samples were pelletised using KBr. The pH of point zero charge (pHpcz) for the adsorber was determined with the ‘pH drift method’ [44].
Role of multiple substrates (spent mushroom compost, ochre, steel slag, and limestone) in passive remediation of metal-containing acid mine drainage
Published in Environmental Technology, 2019
Verma Loretta M. Molahid, Faradiella Mohd Kusin, Zafira Madzin
Oxidation of iron pyrite (FeS2) forms insoluble ferrous iron (Fe2+) (Equation (1)). Ferrous iron is later oxidised to ferric iron (Fe3+) in the presence of oxygen (Equation (2)). This process is slow and usually catalysed by the Thiobacillus and Ferroplasma bacteria. The ferric iron (Fe3+) produced reacts in the two different reactions. First reaction depends on the solubility of iron hydroxides and oxyhydroxides. In this reaction, Fe3+ reacts with water (hydrolysed) and forms Fe(OH)3 and hydrogen ion (H+) (Equation (3)). The remaining Fe3+ further oxidises iron pyrite (FeS2) (Equation (4)); therefore, this is the major producer of both acidity and sulphate. Other sulphide minerals experiencing similar weathering reactions, such as chalcopyrite (CuFeS2), chalcocite (Cu2S), millerite (NiS), pyrrhotite (FeS), and galena (PbS) are also responsible for releasing heavy metals into surface and ground water bodies [2].