دانلود مقاله ترجمه شده از بین بردن یون های فلزات سنگین از پساب – مجله الزویر

فهرست مطالب:

چکیده
۱ مقدمه
۲ فنون نصفیه پسماند فلزات سنگین
۲ ۱ رسوب شیمیایی
۲ ۱ ۱ رسوب هیدروکسید
۲ ۱ ۲ رسوب سولفید
۲ ۱ ۳ رسوب شیمیایی همراه با روش های دیگر
۲ ۱ ۴ رسوب و کلاته شدن فلزات سنگین
۲ ۲ تبادل یونی
۲ ۳ جذب سطحی
۲ ۳ ۱ جاذب های کربن فعال
۲ ۳ ۲ جاذب های نانولوله کربن
۲ ۳ ۳ جاذب های کم هزینه
۴ ۳ ۲ جاذب های زیستی
۲ ۴ فیلتراسیون غشا
۲ ۴ ۱ الترافیلتراسیون
۲ ۴ ۲ اسمزیس معکوس
۳ ۴ ۲ نانوفیلتراسیون
۴ ۴ ۲ الکترودیالیز
۵ ۲ انعقاد و فلوکوله شدن
۶ ۲ فلوتاسیون
۷ ۲ تصفیه الکتروشیمیایی
۳ ملاحظاتی در خصوص روش های تصفیه فلزات سنگین
۴ نتیجه گیری

بخشی از ترجمه:

آلودگی فلزات سنگین یکی از جدی ترین مسائل زیست محیطی در حال حاضر به شمار می رود. تصفیه و تیمار فلزات سنگین به دلیل پایداری و ماندگاری زیاد در محیط زیست موسوم به یکی از مسائل اصلی می باشد. در سال های اخیر، روش های مختلف برای حذف فلزات سنگین از فاضلاب به طور گسترده ای مورد مطالعه قرار گرفته اند. این مقاله به مرور روش های فعلی می پردازد که برای تصفیه فاضلاب دارای فلز سنگین و ارزیابی این فنون مورد استفاده قرار گرفته است. این تکنولوژی ها شامل رسوب شیمیایی ، تبادل یونی، جذب سطحی، فیلتراسیون غشا، فلکوله شدن و لخته شدن، فلوتاسیون، و روش های الکتروشیمیایی می باشد.حدود ۱۸۵ مطالعه منتشر شده از سال ۱۹۸۸ تا ۲۰۱۰ در این مقاله مرور شده است. عمده مقاله های موجود در منابع حاکی از آن هستند که تبادل یونی، جذب سطحی و فیلتراسیون غشا از رایج ترین روش های مورد استفاده برای تصفیه پسماند ها و فلزات سنگین می باشند.

۱ مقدمه

فلزات سنگین عناصری هستند که دارای وزن اتمی بین ۶۳.۵ و ۲۰۰.۶ و وزن مخصوص بیش از ۵ می باشند(سریواستاوا و مجمتند۲۰۰۸). با توسعه روزافزون و سریع صنایعی نظیر کارخانجات پوشش دهی فلزی، عملیات استخراج معادن و آفات کش ها ، صنایع تولید کود شیمیایی، پیل های سوختی، صنایع تولید کاغذ و غیره، فاضلاب و پسماند های فلزات سنگین به طور مستقیم و غیر مستقیم به درون محییط به خصوص در کشورهای در حال توسعه تخلیه می شوند.برخلاف آلاینده های آلی، فلزات سنگین تجزیه پذیر زیستی نمی باشند و در بدن و بافت های موجودات زنده انباشته شده و بسیاری از یون های فلزات سنگین سمی و سرطان زا می باشند. فلزات سنگین سمی که در تیمار فاضلاب از نگرانی های اصلی محسوب می شوند شامل روی، مس، نیکل، اورانیوم، کادمیوم، سرب و کروم می باشند.

بخشی از مقاله انگلیسی:

abstract Heavy metal pollution has become one of the most serious environmental problems today. The treatment of heavy metals is of special concern due to their recalcitrance and persistence in the environment. In recent years, various methods for heavy metal removal from wastewater have been extensively studied. This paper reviews the current methods that have been used to treat heavy metal wastewater and evaluates these techniques. These technologies include chemical precipitation, ion-exchange, adsorption, membrane filtration, coagulationeflocculation, flotation and electrochemical methods. About 185 published studies (1988e2010) are reviewed in this paper. It is evident from the literature survey articles that ion-exchange, adsorption and membrane filtration are the most frequently studied for the treatment of heavy metal wastewater.
۲۰۱۰ Elsevier Ltd. All rights reserved. 1. Introduction Heavy metals are elements having atomic weights between 63.5 and 200.6, and a specific gravity greater than 5.0 (Srivastava and Majumder, 2008). With the rapid development of industries such as metal plating facilities, mining operations, fertilizer industries, tanneries, batteries, paper industries and pesticides, etc., heavy metals wastewaters are directly or indirectly discharged into the environment increasingly, especially in developing countries. Unlike organic contaminants, heavy metals are not biodegradable and tend to accumulate in living organisms and many heavy metal ions are known to be toxic or carcinogenic. Toxic heavy metals of particular concern in treatment of industrial wastewaters include zinc, copper, nickel, mercury, cadmium, lead and chromium. Zinc is a trace element that is essential for human health. It is important for the physiological functions of living tissue and regulates many biochemical processes. However, too much zinc can cause eminent health problems, such as stomach cramps, skin irritations, vomiting, nausea and anemia (Oyaro et al., 2007). Copper does essential work in animal metabolism. But the excessive ingestion of copper brings about serious toxicological concerns, such as vomiting, cramps, convulsions, or even death (Paulino et al., 2006). Nickel exceeding its critical level might bring about serious lung and kidney problems aside from gastrointestinal distress, pulmonary fibrosis and skin dermatitis (Borba et al., 2006). And it is known that nickel is human carcinogen. Mercury is a neurotoxin that can cause damage to the central nervous system. High concentrations of mercury cause impairment of pulmonary and kidney function, chest pain and dyspnoea (Namasivayam and Kadirvelu, 1999). The classic example of mercury poisoning is Minamata Bay. Cadmium has been classified by U.S. Environmental Protection Agency as a probable human carcinogen. Cadmium exposes human health to severe risks. Chronic exposure of cadmium results in kidney dysfunction and high levels of exposure will result in death. Lead can cause central nervous system damage. Lead can also damage the kidney, liver and reproductive system, basic cellular processes and brain functions. The toxic symptoms are anemia, insomnia, headache, dizziness, irritability, weakness of muscles, hallucination and renal damages (Naseem and Tahir, 2001). Chromium exits in the aquatic environment mainly in two states: Cr(III) and Cr(VI). In general, Cr(VI) is more toxic than Cr(III). Cr(VI) affects human physiology, accumulates in the food chain and causes severe health problems ranging from simple skin irritation to lung carcinoma (Khezami and Capart, 2005). Faced with more and more stringent regulations, nowadays heavy metals are the environmental priority pollutants and are becoming one of the most serious environmental problems. So these toxic heavy metals should be removed from the wastewater to protect the people and the environment. Many methods that are being used to remove heavy metal ions include chemical precipitation, ion-exchange, adsorption, membrane filtration, electrochemical treatment technologies, etc. The present review article deals with the current techniques for the removal of heavy metal ions from wastewater. Their advantages and limitations in application are also evaluated. ۲٫ Heavy metal wastewater treatment techniques 2.1. Chemical precipitation Chemical precipitation is effective and by far the most widely used process in industry (Ku and Jung, 2001) because it is relatively simple and inexpensive to operate. In precipitation processes, chemicals react with heavy metal ions to form insoluble precipitates. The forming precipitates can be separated from the water by sedimentation or filtration. And the treated water is then decanted and appropriately discharged or reused. The conventional chemical precipitation processes include hydroxide precipitation and sulfide precipitation. 2.1.1. Hydroxide precipitation The most widely used chemical precipitation technique is hydroxide precipitation due to its relative simplicity, low cost and ease of pH control (Huisman et al., 2006). The solubilities of the various metal hydroxides are minimized in the pH range of 8.0e11.0. The metal hydroxides can be removed by flocculation and sedimentation. A variety of hydroxides has been used to precipitate metals from wastewater, based on the low cost and ease of handling, lime is the preferred choice of base used in hydroxide precipitation at industrial settings (Baltpurvins et al., 1997) (Table 1). Hydroxide precipitation process using Ca(OH)2 and NaOH in removing Cu(II) and Cr(VI) ions from wastewater was evaluated by Mirbagheri and Hosseini (2005). The Cr(VI) was converted to Cr(III) using ferrous sulfate. Maximum precipitation of Cr(III) occurred at pH 8.7 with the addition of Ca(OH)2 and the concentration of chromate was reduced from 30 mg/L to 0.01 mg/L. The cuproammonia was reduced by aeration and the optimum pH for maximum copper precipitation was about 12.0 for both Ca(OH)2 and NaOH and the concentration of copper was reduced from 48.51 mg/L to 0.694 mg/L. To enhance lime precipitation, fly ash was used as a seed material (Chen et al., 2009b). The fly ashelimecarbonation treatment increased the particle size of the precipitate and significantly improved the efficiency of heavy metal removal. The concentrations of chromium, copper, lead and zinc in effluents can be reduced from initial concentration of 100.0 mg/L to 0.08, 0.14, 0.03 and 0.45 mg/L, respectively. In hydroxide precipitation process, the addition of coagulants such as alum, iron salts, and organic polymers can enhance the removal of heavy metals from wastewater. Charerntanyarak (1999) employed chemical coagulation and precipitation by lime to treat synthetic wastewater consisting of Zn, Cd, Mn and Mg at the concentration of 450, 150, 1085 and 3154 mg/L, respectively. He found that the optimum pH was more than 9.5 and the treated wastewater could meet the Wastewater Standard of the Ministry of Industry. Moreover, if coagulant was added, the residual concentration of heavy metal can be decreased further. Although widely used, hydroxide precipitation also has some limitations. Firstly, hydroxide precipitation generates large volumes of relatively low density sludge, which can present dewatering and disposal problems (Kongsricharoern and Polprasert, 1995). Secondly, some metal hydroxides are amphoteric, and the mixed metals create a problem using hydroxide precipitation since the ideal pH for one metal may put another metal back into solution. Thirdly, when complexing agents are in the wastewater, they will inhibit metal hydroxide precipitation. 2.1.2. Sulfide precipitation Sulfide precipitation is also an effective process for the treatment of toxic heavy metals ions. One of the primary advantages of using sulfides is that the solubilities of the metal sulfide precipitates are dramatically lower than hydroxide precipitates and sulfide precipitates are not amphoteric. And hence, the sulfide precipitation process can achieve a high degree of metal removal over a broad pH range compared with hydroxide precipitation. Metal sulfide sludges also exhibit better thickening and dewatering characteristics than the corresponding metal hydroxide sludges.

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