重金屬一般是指密度大于4.5 g/cm3的金屬，主要包括汞、鎘、鉛、鉻、釩、錳、銅、鋅及鎳等有毒重金屬元素。重金屬是地殼的重要構(gòu)成元素，廣泛地分布于自然界中，并在自然環(huán)境中遷移、轉(zhuǎn)化、循環(huán)。水體中的重金屬主要來(lái)自兩部分：自然源和人為源。通過(guò)自然循環(huán)進(jìn)入水體中的重金屬濃度一般較低，不會(huì)影響人體健康，人為源是造成水體重金屬污染的主要原因。由于一些人為因素，大量的重金屬向環(huán)境中排放并不斷累積，使其遠(yuǎn)遠(yuǎn)超過(guò)了環(huán)境的本底含量，從而造成了嚴(yán)重的重金屬污染。采礦、冶金、石油化工、電子生產(chǎn)、制革等工業(yè)生產(chǎn)過(guò)程中均會(huì)產(chǎn)生含重金屬離子的廢水和廢渣，其中冶金和采礦是最重要的重金屬污染源。水體流經(jīng)被重金屬污染的土壤及含重金屬的大氣沉降物排入水中，也能使水中重金屬含量急劇升高，進(jìn)一步加劇水體重金屬污染。
Heavy metals generally refer to metals with a density greater than 4.5 g / cm3, mainly including mercury, cadmium, lead, chromium, vanadium, manganese, copper, zinc and nickel. Heavy metals are important elements in the earth's crust. They are widely distributed in nature and migrate, transform and circulate in the natural environment. Heavy metals in water mainly come from two parts: natural source and man-made source. The concentration of heavy metals entering the water body through natural circulation is generally low, which will not affect human health. Anthropogenic source is the main cause of heavy metal pollution in water body. Due to some human factors, a large number of heavy metals are discharged into the environment and accumulated continuously, which makes them far beyond the background content of the environment, thus causing serious heavy metal pollution. Waste water and waste residue containing heavy metal ions will be produced in the process of mining, metallurgy, petrochemical, electronic production, tanning and other industrial production processes. Metallurgy and mining are the most important sources of heavy metal pollution. Water flowing through the soil polluted by heavy metals and atmospheric deposition containing heavy metals into the water, can also make the content of heavy metals in the water increase sharply, and further aggravate the heavy metal pollution of water body.
重金屬在水中不斷的遷移轉(zhuǎn)化，形態(tài)也可能發(fā)生變化，并有可能被水中膠體物質(zhì)等吸附，濃度隨著pH和水溫的變化不斷變化。但是重金屬不能被生物降解，因此水中重金屬的總量不會(huì)減少。進(jìn)入水中的重金屬部分被水生生物所攝取，并在食物鏈中放大，而且有可能轉(zhuǎn)化成毒性更大的形態(tài)，最后富集在人體內(nèi);直接飲用含重金屬的水或者食用含重金屬的水澆灌的農(nóng)作物也會(huì)使重金屬進(jìn)入人體內(nèi)。重金屬能夠使蛋白質(zhì)結(jié)構(gòu)發(fā)生不可逆轉(zhuǎn)的改變，蛋白質(zhì)的功能也隨之喪失，從而影響人體的正常代謝活動(dòng)，導(dǎo)致各種疾病的發(fā)生和機(jī)體紊亂。世界八大公害事件中的水俁病和骨痛病都是由于重金屬中毒引起的。其中，水俁病是工廠排放廢水中汞所引起的，汞被水生生物食用后在體內(nèi)轉(zhuǎn)化成甲基汞，甲基汞的毒性是汞毒性的100倍，而且甲基汞更容易溶于脂肪，主要侵犯中樞神經(jīng)系統(tǒng)。
With the continuous migration and transformation of heavy metals in water, their forms may change, and they may be adsorbed by colloidal substances in water. The concentration of heavy metals changes with the change of pH and water temperature. However, heavy metals can not be biodegraded, so the total amount of heavy metals in water will not be reduced. Some of the heavy metals in the water are absorbed by aquatic organisms and amplified in the food chain, and may be transformed into more toxic forms and finally enriched in the human body; drinking water containing heavy metals directly or eating crops irrigated with water containing heavy metals will also cause heavy metals to enter the human body. Heavy metals can cause irreversible changes in protein structure and protein function, thus affecting the normal metabolic activities of human body, leading to the occurrence of various diseases and disorders of the body. Minamata disease and osteodynia disease are all caused by heavy metal poisoning. Among them, Minamata disease is caused by mercury in wastewater discharged from factories. Mercury is converted into methyl mercury in vivo after being eaten by aquatic organisms. The toxicity of methyl mercury is 100 times that of mercury. Moreover, methylmercury is more easily soluble in fat and mainly invades the central nervous system.
3.重金屬?gòu)U水常見(jiàn)的處理方法
3. Common treatment methods of heavy metal wastewater
處理含重金屬?gòu)U水的傳統(tǒng)方法有：化學(xué)沉淀法、離子交換法、膜分離法、吸附法、生物法等。
The traditional methods of treating wastewater containing heavy metals include chemical precipitation, ion exchange, membrane separation, adsorption and biological methods.
3.1化學(xué)沉淀法
3.1 chemical precipitation method
化學(xué)沉淀法是向廢水中加入與作用機(jī)理相適應(yīng)的反應(yīng)劑，使水中溶解狀態(tài)的重金屬離子轉(zhuǎn)化成不溶于水的金屬化合物，再將其從水中分離出去的方法。該方法技術(shù)成熟、操作簡(jiǎn)單、處理成本低等優(yōu)點(diǎn)，但容易造成二次污染，其最主要的影響因素是pH。難溶鹽沉淀法又包括硫化物沉淀法、碳酸鹽沉淀法、鋇鹽沉淀法，其主要優(yōu)點(diǎn)是處理后的廢水pH大約是7~9，不用再進(jìn)行中和處理，而且還可以回收廢水中的重金屬，具有一定的經(jīng)濟(jì)效益。鐵氧體法主要是在含有重金屬離子廢水中加入鐵鹽或亞鐵鹽，形成鐵氧體，通過(guò)吸附、包裹和夾帶作用使重金屬離子形成復(fù)合鐵氧體沉淀析出。該方法處理?xiàng)l件溫和、處理量大、處理效果明顯、能回收磁性材料，在工業(yè)上得到了廣泛的應(yīng)用。

Chemical precipitation method is to add the reaction agent suitable for the mechanism of action to the wastewater, so that the dissolved heavy metal ions in water can be transformed into insoluble metal compounds, and then separated from the water. This method has the advantages of mature technology, simple operation and low treatment cost, but it is easy to cause secondary pollution, and the main influencing factor is pH. The insoluble salt precipitation method includes sulfide precipitation method, carbonate precipitation method and barium salt precipitation method. Its main advantage is that the pH value of the treated wastewater is about 7 ~ 9, and there is no need for neutralization treatment. Moreover, the heavy metals in the wastewater can be recovered, which has certain economic benefits. The ferrite method is mainly to add iron salt or ferrous salt to the wastewater containing heavy metal ions to form ferrite. Through adsorption, encapsulation and entrainment, the heavy metal ions form composite ferrite precipitation. This method has been widely used in industry due to its mild treatment conditions, large amount of treatment, obvious treatment effect and recovery of magnetic materials.
3.2離子交換法
3.2 ion exchange method
離子交換法是利用離子交換劑中的可交換基因與廢水中的重金屬離子交換能力的不同來(lái)分離的方法。常用的離子交換劑有陽(yáng)離子交換樹(shù)脂、陰離子交換樹(shù)脂、螯合樹(shù)脂、腐殖酸樹(shù)脂等。離子交換法可對(duì)廢水中的重金屬離子選擇性的分離，通過(guò)再生回收再生液，可實(shí)現(xiàn)重金屬離子的回收，還具有交換容量大、吸附-再生可逆性好等優(yōu)點(diǎn)，但適用范圍有限，且容易造成二次污染。
Ion exchange method is a method to separate the exchangeable genes in ion exchanger and heavy metal ion exchange ability in wastewater. The commonly used ion exchangers are cation exchange resin, anion exchange resin, chelating resin, humic acid resin, etc. Ion exchange method can selectively separate heavy metal ions from wastewater, and the recovery of heavy metal ions can be realized through regeneration and recovery of regeneration solution. It also has the advantages of large exchange capacity and good reversibility of adsorption regeneration, but its application scope is limited and it is easy to cause secondary pollution.
3.3膜分離法
3.3 membrane separation method
膜分離法是利用一種特殊的半透膜，在外界壓力作用下，不改變?nèi)芤旱幕瘜W(xué)形態(tài)使溶質(zhì)和溶劑進(jìn)行分離和濃縮的方法。根據(jù)膜的不同可以分為擴(kuò)散滲析、電滲析、反滲透、液膜、納濾、超濾等。膜分離技術(shù)具有能耗低、無(wú)相變、操作簡(jiǎn)單、無(wú)二次污染、分離產(chǎn)物易回收等優(yōu)點(diǎn)，目前已在國(guó)內(nèi)外重金屬?gòu)U水處理中得到了廣泛的應(yīng)用。Hafez等利用反滲透膜對(duì)廢水中的鉻進(jìn)行的回收處理試驗(yàn)中對(duì)鉻的平均回收量高達(dá)99.8%。但是膜分離法存在膜組件價(jià)格貴、膜污染等問(wèn)題亟待解決。
Membrane separation is a method that uses a special semi permeable membrane to separate and concentrate solute and solvent without changing the chemical form of solution under external pressure. According to the different membrane can be divided into diffusion dialysis, electrodialysis, reverse osmosis, liquid membrane, nanofiltration, ultrafiltration and so on. Membrane separation technology has the advantages of low energy consumption, no phase change, simple operation, no secondary pollution and easy recovery of separation products. At present, it has been widely used in the treatment of heavy metal wastewater at home and abroad. Hafez et al. Used reverse osmosis membrane to recover chromium from wastewater. The average recovery of chromium was up to 99.8%. However, there are some problems in membrane separation, such as high price of membrane module and membrane pollution.
3.4吸附法
3.4 adsorption method
吸附法是利用多孔性吸附劑表面的各種活性基團(tuán)與廢水的重金屬離子形成離子鍵或共價(jià)鍵將重金屬離子吸附于吸附劑表面，從而達(dá)到吸附金屬離子的目的。活性炭是傳統(tǒng)常用的吸附劑，具有巨大的比表面積，對(duì)重金屬的吸附能力強(qiáng)、去除率高。姜玉娟[8]在利用活性炭吸附處理絡(luò)合鎳重金屬?gòu)U水的試驗(yàn)中，鎳離子的去除率達(dá)到95.65%。近年來(lái)，對(duì)吸附法的研究主要是尋找更加廉價(jià)、高效的吸附劑。國(guó)內(nèi)外許多研究發(fā)現(xiàn)生物材料對(duì)重金屬也有很好的吸附能力，如香蕉皮、木桔葉、花生殼、褐
Adsorption method is to use various active groups on the surface of porous adsorbent to form ionic bond or covalent bond with heavy metal ions in wastewater to adsorb heavy metal ions on the surface of adsorbent, so as to achieve the purpose of adsorption of metal ions. Activated carbon is a traditional adsorbent, which has a large specific surface area, strong adsorption capacity and high removal rate of heavy metals. Jiang Yujuan [8] in the experiment of using activated carbon to treat the wastewater containing heavy metal complex nickel, the removal rate of nickel ion reached 95.65%. In recent years, the research of adsorption method is mainly to find more cheap and efficient adsorbents. Many studies at home and abroad have found that biomaterials have good adsorption capacity for heavy metals, such as banana peel, kumquat leaf, peanut shell, brown