دانلود رایگان مقاله لاتین انتشار عناصر شیمیایی از سایت الزویر
عنوان فارسی مقاله:
انتشار عناصر شیمیایی انتخاب شده از کنده های حفاری شیل به محلول های آبی با pH مختلف
عنوان انگلیسی مقاله:
Release of selected chemical elements from shale drill cuttings to aqueous solutions of different pH
سال انتشار : 2016
برای دانلود رایگان مقاله انتشار عناصر شیمیایی اینجا کلیک نمایید.
مقدمه انگلیسی مقاله:
1. Introduction
Drilling procedure during the unconventional hydrocarbon exploration and extraction generates various types of waste including drilling mud containing fine-grained rock fragments (cuttings). Drill cuttings are then separated from mud using vibrating screens, hydrocyclones and/or centrifuges. However, separation step does not remove drilling fluid entirely (Ifeadi, 2004). Diversity of produced wastes is related to the variable chemical composition of the rock reservoir, as well as drilling fluid, which has got significant effect on the determination of the potential environmental impacts. Drill cuttings from aquatic sedimentary shale formations are composed mainly of inorganic minerals, mainly clays interspersed with organic matter. Most commonly used drilling muds, in turn, may be based on water, oil orglycol enriched with additives such as bentonite, inorganic salts (barium/calcium sulfates, sodium/potassium/calcium chlorides, potassium hydroxide etc.), polysaccharides and certain specialized chemicals. According to the European waste catalogue and hazardous waste list drilling cuttings are classified as group no. 01 05 e drilling muds and other drilling wastes (Commission Decision, 2011). Release of the chemicals from rock waste materials is one of the main problems needed to be considered when designing storage, utilization and new management procedures of cuttings. To assess the range of release of the potentially dangerous components (PDCs) to the environment, leaching tests are commonly performed. Leaching is a process by which constituents migrate from a solid material into an interacting fluid under condition applied (Lavergren et al., 2009). As a consequence, this phenomenon may lead to formation of the liquids with properties depending on the chemical and physical composition of given wastes and the leach- * Corresponding author. ing operational conditions (pH, redox potential, composition of theinteracting fluid, contact time, pressure or temperature) (Heasman et al., 1997). Moreover, the release of the constituents arises from a confluence of mass transfer mechanisms and chemical reactions (Klein, 1989). The leaching experiments provide information on the factors that determine the release of variety of elements from secondary materials, in accordance to environmental concerns, rare/valuable metals recovery as well as specific field scenarios. Although this procedure is often used for characterisation and prediction of metal mobility from fly ash (Izquierdo and Querol, 2012) (Ugurlu, 2004) (Querol et al., 2001), contaminated soils (Dijkstra et al., 2004) (Sun et al., 2001) (Sahuquillo et al., 2003), sludges (Kazi et al., 2005) (Mantis et al., 2005) (Vijay and Sihorwala, 2003) or mining residues (Cappuyns and Swennen, 2008) (Concas et al., 2006) (Fallman and € Hartlen, 1994 ), shale drill cuttings are poorly studied. For example, Lavergren et al. presented abundance and mobility of main and trace elements in black shales (Sweden) determined by waterbased leaching and sequential chemical extraction to describe behavior of selected constituents in the mineral matrix. It was observed that shale is rich in many PDCs such as As, Cd, Mo, U, V, Zn, Ni and Cd. Water leaching experiments resulted in a considerable leaching of Mo from the unoxidized sample and Cd, Zn and Ni from acidic samples. Based on the pH-controlled experiments with addition of hydrogen peroxide it was concluded that Cd, Mo, Zn, Ni and U can be leached in considerable amounts from the shale material (Lavergren et al., 2009). Continuing research, the same group investigated leaching behavior of As, U and Ni from black shales in order to define mechanism of trace metals release and their behavior in pyritic acidic environment by means of a longterm humidity cell test combined with sequential chemical extraction. It was found that the degree of pyrite oxidation is a major factor controlling Ni release, being highly elevated in acidic conditions, as well as also related to the chalcophilic character of nickel. Leaching of the uranium was observed to be dependent on the redox potential of the system and controlled by the solubilization of carbonate U phases, whereas arsenic was removed by adsorption into the surface or coprecipitation with iron compounds (Yu et al., 2014). Moller and Giese determined the metal/element € migration in metamorphic rocks under batch leaching test at different pH (3, 6 and 8.5). Mobility patterns in pH relation of Mn, Zn, Mg, Sr and Na were observed to be analogous, whereas Ca, K and Ba at pH ¼ 3 was significantly higher, probably due to calcite dissolution and enhanced ion exchange in biotite. Moreover, the dissolution behavior of various minerals due to the contact time was also presented. For Al-bearing minerals, calcite and fluorite, the leached fractions of Al or Ca revealed minor percentage levels of dissolved material after 28 h of leaching. Chlorite and biotite, in turn, released nearly 60% Al content within 28 h. This behavior may explain strong influence of silicates on metals-based minerals (Moller and Giese, 1997 € ). Li and co-workers applied leaching procedure in acidic conditions and under pressure (1.2 MPa) to extract V2O5 from black shale (China) (Li et al., 2009). Leaching efficiency was investigated under different processing conditions (reaction time, temperature, concentration of sulfuric acid and iron (II) sulfate and liquid to solid ratio). Conditions for effective vanadium separation (90%) from black shales was proposed. Shale rock leaching tendency was also evaluated by our group as changes of given elements concentration in four samples of rock material before and after leaching procedure measured by XRF without pH dependence of the leaching fluid (Piszcz-Karas et al., 2014). Possibility of shale gas production in Poland (accompanied by drill cuttings formation), growing environmental and health awareness, concerns about effects of heavy metals exposure (even at trace levels) as well as insufficient data on cuttings leaching, lead us to undertake studies on the dissolution of elements from shale drill cuttings. Leaching tests at various pH conditions were performed because changes in pH are one of the main factors that control the leaching process. Moreover, these experiments provide information on pH conditions imposed by external influences, both natural as well as caused by treatment, and of acid/base neutralization capacity. The leaching results stand also basis for geochemical speciation modelling. In this regard, the effect of pH on leachability of light and heavy metals from shale drill cuttings generated from unconventional shale gas production was investigated. To establish migration levels as a function of pH changes in a range of 3e12 in static parallel batch testing mode was applied. Atomic absorption spectrometry, elemental analysis, conductometry and potentiometry techniques were used to analyse drill cuttings and determine the amount of released constituents and characterize physicochemical properties of the leachates.
برای دانلود رایگان مقاله انتشار عناصر شیمیایی اینجا کلیک نمایید.
کلمات کلیدی:
22222
