دانلود رایگان مقاله انگلیسی بازیابی منیزیم از شورابه های Uyunisalar به صورت منیزیم کربنات هیدراته به همراه ترجمه فارسی
| عنوان فارسی مقاله: | بازیابی منیزیم از شورابه های Uyunisalar به صورت منیزیم کربنات هیدراته |
| عنوان انگلیسی مقاله: | Recovery of magnesium from Uyuni salar brine as hydrated magnesium carbonate |
| رشته های مرتبط: | محیط زیست، شیمی، مهندسی بهداشت محیط، شیمی محیط زیست و شیمی تجزیه |
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| نشریه | الزویر – Elsevier |
| کد محصول | f155 |
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بخشی از ترجمه فارسی مقاله: چکیده : تولید ترکیبات منیزیم از منابع شورابه ها در ابعاد صنعتی طی چند دهه آزمایش شده است .به وسیله واکنش دولومیت (Cao.Mgo) تولید می شود از طریق حرارت دادن دولومیت یا منیزیت با منیزیم موجود در آب دریا.در نتیجه منیزیم هیدروکسید بیشتر تکلیس می شود تا تولید اکسید منیزیم با خلوص 98 تا 99 درصد کند . استفاده از NaoH کاربرد وسیع یدر بازیابی منیزیم محلول های غنی از منیزیم دارد .Lartey ( 1997 ) منیزیم هیدروکسید را از تلخ آبها (4.24 Mg) را می توان با استفاده از NaoH رسوب داد که NaoH باعث تولید NaoH می شود بعد از خاکستر کردن .ساختار ذرات Mg(oH)2 در ابعاد نانو از کریستال های ضعیفی تشکیل شده که باعث به وجود آمدن مشکلاتی در بازیابی می شود در زمانی که از NaoH برای ته نشینی استفاده می شود . مقدار NaoH اندازه گیری شده است در بسیاری از مطالعات آزمایشگاهی .پیشنهاد شده است یک روش جدید در بازیابی Mg(oH)2 از اسمز معکوس شورابه های حاوی 2.6 g/lمنیزیم بر اساس تحقیق این مولف فرآیند بر مبنای ته نشینی Mg(oH)2 بر روی سطح ترکیبات مگنتیکی ( Fe3O6) در ابعاد میکرو و جدایش مغناطیسی مگنتیک در جهت بازیابی محصول است پس از آن اسید برای انحلال مجدد Mg(oH)2 در PH >4 ( برای جلوگیری از انحلال مگنتیک ) استفاده می شود که در نتیجه بازیابی منیزیم به میزان بیش از 97 درصد انجام می شود. با اضافه کردن Na2Hpo4 در دمای 20 درجه و کنترل PH در PH = 8Mg موجود در آب دریا ته نشین شده و منیزیم بازیابی می شود استخراج با حلال و تبادل یونی کاربرد وسیعی در تولید منیزیم از شورابه ها دارد. lee و joclcsn فرآیندی را به ثبت رساندند که طی آن برای جداسازی از شورابه های حاوی 1 g/lit منیزیم از سولفات ها و سولفونات های قلیایی استفاده کردند.پس از اختلاط منیزیم جداسازی می شود از مخلوط با استفاده از مواد انحلال پذیر در آب مانند Nacl |
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بخشی از مقاله انگلیسی: ABSTRACT Uyuni Salar (Bolivia), the largest resource of lithium (Li) in the world not only contains a high level of Li but also ~1.3% w/w magnesium (Mg) in strong NaCl brines. The recovery of Mg is therefore essential as the resources represent high value of Mg by-products if recovered. High purity hydrated magnesium carbonate (HMC as dypingite or hydromagnesite) could be recovered from the Uyuni salar brines as an easy-saleable product. The precipitation process used for this recovery relies on the selective removal of Ca by adding excess oxalic acid at an oxalate/Ca molar ratio of 6.6:1. The excess oxalate has to be subsequently removed as Mg oxalate by adjusting the pH to pH 4 – 7. HMC products of 97.3 – 99.6% purity could be produced as a result (equivalent to 25.3 – 25.9% Mg in the product compared to a theoretical value of 25.99% Mg for hydromagnesite). Without removing Mg oxalate, products could only reach 23.3- 24.3% Mg. The light HMC (hydromagnesite) product could be precipitated at ambient conditions as long as the drying was set at >65 oC. Precipitation at >55 oC also yields more crystalline hydromagnesite compared to those obtained at lower temperatures. The light HMC product has a heat adsorbing capacity (endothermic) of 1123-1196 J/g dry product. The product has a sheetlike structure and is easily filtered, compared to magnesium hydroxide. 1. Introduction Magnesium (Mg), an alkaline earth metal, is the 8th most abundant element in the Earth‟s crust. Since its discovery in 1808, Mg has been used in a number of applications such as in the production of magnesium metal used in alloys, aircraft, automobiles, electronics, and in chemical, pharmaceutical and agricultural industries. Due to its highly reactive nature, Mg is rarely found in the pure metallic form in nature. Mg thus is found in natural liquors such as seawater, geothermal water, brines or bitterns and in minerals such as dolomite, magnesite, brucite, carnalite, talc, olivine, etc [Wikipedia-Magnesium, 2014]. A total of 12 billion tonnes of Mg ores (mainly magnesite) is identified in various mineral resources while the Mg in seawater is unlimited [USGS, 2014]. The world production of Mg metal is estimated to have increased from 499,000 tonnes in 2002 to 905,000 tonnes in 2012 [Roskill, 2012]. Industrial Mineral (2015) reported that the global production of magnesia from magnesite is ~8.5 Mtpa (China produces 49% of the total world market, Russia 12% and Australia 3%). Additionally, the global manufacture of synthetic MgO and other Mg chemicals from brines is also estimated to be about 925,000 tpa, mainly from Japan, Brazil, Mexico, Holland, Norway, Russia and USA. Together with the production of refractory magnesia from minerals, synthetic magnesium products such as Mg chloride, hydroxide, carbonate, etc. can also be produced from brines and bitterns. Located in the highland of Bolivia, Salar de Uyuni contains over 40% of the global lithium and is known to have the richest Li salar brines in the world. Moreover, the Uyuni salar brines also contain a high level of Mg (~13.3 g/L or 1.3 %w/w Mg) compared to other brine sources as shown in Table 1 (Boryta et al., 2011; An et al., 2012; Wikipedia-Sea water, 2015). The manufacture of Mg products from brines has been in practice on an industrial scale for several decades (Robinson et al., 1943; Panda and Mahapatra, 1983; Dave and Ghost, 2005; CMI Group, 2013; Nakai, 2014) by reacting dolime (CaO.MgO) produced from roasting dolomite or magnesite with the Mg contained in seawater. The resultant Mg hydroxide was then further calcined to produce MgO of 98-99% purity. The use of NaOH has also been extensively applied for the recovery of magnesium from magnesium-rich liquors. Lartey (1997) precipitated magnesium hydroxide from a bittern (4.24% Mg) using NaOH to produce MgO after sintering. The formation of nano-sized Mg(OH)2 particles of poor cystallinity, which caused difficulty for its recovery when NaOH was used for precipitation, was dealt with in many laboratory studies (Baird et al., 1988; Henrist et al., 2003; Alamdari et al., 2008). Lehmann et al. (2014) proposed a new approach to recover Mg(OH)2 from reverse osmosis brines bearing 2.6 g/L Mg. According to these authors, the process used was based on Mg(OH)2 precipitation on the surface of synthesised magnetite (Fe3O4) micro-particles and magnetic separation to recover the product. Thereafter, acid was used to redissolve Mg(OH)2 at pH >4 (to avoid dissolution of magnetite), recovering a high purity (>97% Mg) solution. The recovery of magnesium by adding Na2HPO4 at 20 oC and controlling pH at pH 8 was conducted to precipitate Mg from seawater (Golubev et al., 1999) or Ca-free seawater (Golubev et al., 2001) as (Ca,Mg)4H(PO4)3.xH2O or Mg3(PO4)2.8H2O, respectively. Solvent extraction and ion-exchange were also applied to produce magnesium from brines. Lee and Jackson (1970) patented a process to extract magnesium from a brine containing 1 g/L Mg using alkyl sulphates and sulphonates. After loading, Mg was stripped from the mixture by a water-soluble strippant such as NaCl. Mackay (1977) used 1-dodecylphenyl-3- triflouromethyl-1,3-propanedione to selectively recover Mg from synthetic seawater bearing 1.4 g/L Mg and other elements at pH 6-9. Later, Muraviev et al. (1995) proposed a process to separate calcium and magnesium from artificial and natural seawater, which contained 0.11 g/L Mg and 0.02 g/L Ca, respectively, by carboxylic ion-exchange resins of acrylic and methacrylic types. For several years, many methods have been studied to synthesise different magnesium carbonate compounds such as nesquehonite (MgCO3.3H2O), dypingite ((MgCO3)4.Mg(OH)2.5H2O or (MgCO3)4.Mg(OH)2.8H2O) and hydromagnesite ((MgCO3)4.Mg(OH)2.4H2O). As stated by Canterford and Tsambourakis (1984), dypingite (or heavy hydrated magnesium carbonate, HMC as commonly known commercially) was found in materials yielded during the production of high purity magnesia from crude magnesite by a calcination/CO2-leaching process. Caceres and Attiogbe (1997) suggested a technique to produce hydromagnesite (or Light HMC) from dolomite which was first roasted in a CO2 atmosphere at 750 oC to obtain semi-calcined dolime (MgO.CaCO3). The semi-calcined dolime was then wet ground at 30-90 oC to completely ensure the hydration of MgO. Further re-carbonation of Mg(OH)2 by reacting with CO2 under pressure formed an aqueous Mg(HCO3)2 solution. Hydromagnesite was yielded by heating Mg(HCO3)2 to 100 oC to remove all water and then drying the solid at 120 oC. The precipitation of hydromagnesite and dypingite via the formation of magnesium hydroxide slurry and sparging CO2 gas or reacting with sodium carbonate were also mentioned in several other studies as summarised in Table 2. In a previous study, Botha & Strydom (2001) showed that different Mg carbonate products were formed depending on (a) precipitation temperature, (b) drying temperature and (c) drying time. Wang et al. (2008) confirmed that the reaction between Mg2+ and carbonate will form nesquehonite at a low temperature (30-50 oC) whereas hydromagnesite was formed at 60 oC. Cheng et al. (2009) produced nesquehonite at 0-40 oC, whereas dypingite was formed at 50 oC and hydromagnesite at 60-90 oC, but no information was given on drying time. The conclusions reached from these studies indicate that (a) at room temperature and low drying temperature and short drying time nesquehonite is preferentially formed, (b) however when the temperature of either precipitation and drying is raised to 65oC or higher dypingite or a transitional species is formed and (c) hydromagnesite is formed at high temperature (65oC or higher) of precipitation and (d) drying at 120 oC will produce dypingite (3 h drying time) or hydromagnesite (6-24 h) from nesquehonite. In our previous studies on the Uyuni salar brines, Mg was first recovered as a low grade Mg hydroxide using lime (An et al., 2012) or high purity Mg oxalate after first selectively removing Ca (Tran et al., 2013) before lithium is recovered. The processes proposed in these studies, although effectively removed Mg, did not produce conventional products ready for sale. They have to be further purified (as in the case of low grade Mg hydroxide) or roasted to produce standard commercial MgO products. The present study therefore aims to recover Mg from the Uyuni salar brine (containing ~13 g/kg Mg) as marketable magnesium carbonate compounds. During the process, Ca was first removed selectively as Ca oxalate by adding oxalic acid, followed by removal of the excess oxalate in the form of Mg oxalate. The Ca and oxalate free brine obtained was subsequently added with sodium carbonate to precipitate Mg as a mixed carbonate product containing nesquehonite and/or dypingite. This precursor was then heat treated at different temperatures to produce hydromagnesite, having superior properties (calorific value, purity and higher MgO content) compared to the original precipitate. |