摘要
持久性污染物六六六（BHC）是一种广谱、长效、耐热、耐酸、脂溶性强、成本低的有机氯杀虫剂，在农业生产上曾起到过一定的积极作用。20世纪40～80年代世界各国曾普遍大量地使用BHC防治农业虫害，在20世纪50-80年代，BHC占我国农药生产总量的60%。由于其化学性质稳定，残留时间长，脂溶性强，给整个生态环境造成严重的污染，先后被世界各国禁止生产和使用。我国停止生产和使用BHC已二十多年了，但受各种环境条件的制约，其降解速度很慢，在各地区的环境监测报告中BHC依然普遍存在，有些地区甚至还有较高浓度BHC的检出。BHC已被确定为全球生态系统广泛存在的POPs。
有机氯农药BHC的残留对农业环境、水环境、农产品和水产品的质量、以及人体健康都产生潜在的危害。BHC各异构体均是可疑致癌物，γ-BHC可刺激中枢神经系统，α-BHC、δ-BHC被认为是中枢神经系统的抑制剂，γ-BHC、β-BHC均被确认为内分泌干扰激素，对生殖系统有不良影响；受BHC影响的生理系统还包括肾脏、肝脏、血液及生化稳态。研究表明，水系中的BHC即使存在量极少，也会通过动、植物的富集、食物链的积累，危害人类健康。
随着社会的发展和人类的进步，人们对食品安全和环境保护愈加重视。由于农产品和水产品中BHC超标而影响出口的事件时有发生，带来了一定的经济损失。为提高农产品和水产品的质量，改善环境，有效地去除BHC对环境和人类的危害仍是我们在一定时期内急待解决的重要问题。
长期以来，对BHC的分布及浓度监测一直没有间断。但对BHC在环境中去除方法的研究却较少，而且主要集中在生物降解的研究上。生物降解和光降解一样，在BHC污染的环境修复中起着一定的积极作用。但是受环境因素的影响，降解能力受到限制，尤其是微生物作用在高污染富集区、低温等条件下，微生物生长受到抑制，降解速率不高，常常伴有副反应发生，降解产物不彻底，有时还会产生新的环境污染物。而非生物降解法则可以有效地克服生物降解的滞后性，不会因为营养盐的引入而带入新的污染。所以，寻找一种可行的非生物降解方法去除水体中的BHC是非常重要
的。
自从1997年加拿大学者Gillham与O’Hannesin提出金属铁屑可以用于地下水的原位修复以来，价廉、简单、高效的处理方法--零价铁金属促进含氯有机物还原性脱氯就成为国外的一个研究热点。目前Fe0-PRB技术处理水体中污染物日益受到人们的重视，在含氯直链烃的处理中有较好的效果，但该技术应用于处理水体中高氯高饱和结构的BHC污染还没有相关报道。
本文以废物利用为宗旨，去除水中BHC为目的，在吸取了PRB技术成功经验（PRB技术能够有效的脱去直链卤代有机物中的卤素，使毒性大大降低）的基础上，针对这一技术也有很多缺陷，如反应中容易产生副反应及单质铁腐蚀生成的沉淀附着在Fe0的表面，降低了铁的反应活性，及铁屑在使用过程中，局部易结块使系统堵塞等现象，致使该系统有效使用周期短的缺点。分别以煤渣、铁屑、煤渣和铁屑为反应介质设计了不同的反应墙，用于去除污染水中的BHC。
分别对煤渣和铁屑去除水体中BHC进行条件实验，结果表明，二者对水体中BHC去除的最佳条件类似，在弱酸性条件下去除效果较好；同时二者粒径的减小、用量的增加、接触时间的延长均对BHC去除有利。煤渣在最佳条件下对水体中的BHC吸容量能达到354.22μg/g ，相当于每吨煤渣能处理70.8～35.4kgBHC；铁屑对水中BHC的反应动力学符合准一级反应动力学方程，根据铁屑降解BHC时检测到的过渡产物，推断了BHC的可能脱氯过程。在应用煤渣处理被BHC污染的安图水库水样，效果较为理想。
反应墙实验结果表明，三种反应墙对BHC的去除均有较好的效果。但煤渣吸附反应墙的吸附容量有限，铁屑反应墙则易局部结块，使系统发生堵塞现象，二者的使用寿命均不足40天。以煤渣为吸附材料、铁屑为降解材料，将铁屑和煤渣按一定配比制成高效低耗的吸附-氧化还原化学反应墙，集渗透、吸附、降解反应于一体，使水体在流过该反应墙时BHC能够在煤渣中充分富集。因为铁屑与煤渣的良好接触，铁屑能够与被煤渣吸附的BHC充分接触而发生氧化还原反应，从而被BHC占据的煤渣吸附点位及时空出，以便进行新的吸附，这样吸附介质总是处于动态吸附过程中。同时煤渣的多孔结构和一定比例砂子的存在，使铁腐蚀产生的沉淀物在水
力的冲刷下，不会附着在Fe0的表面造成铁屑的反应活性降低，有效地克服铁屑局部产生板结，阻塞水体流动现象的发生。此反应墙解决了PRB存在的难以解决的系统容易产生堵塞、使用周期短的缺点。应用该反应墙在室温下运行到第94天，出水中BHC的去除率仍在92.5%以上。且在反应墙运行期间出水流量稳定，未发生堵塞现象。
综上所述，利用吸附-氧化还原化学反应墙处理被BHC污染的水体具有较好的效果。该处理方法简单、材料易得、应用范围宽，既适应高氧化态脱毒，也适用于低氧化态去除，是一种以废治废、科学环保的新方法。该反应墙使用方便，既可以作为地表水处理反应装置，也可以作为地下水处理反应装置。吸附-氧化还原化学反应墙是对BHC污染的水源水净化较有前景的创新技术之一，也是一种经济效益和环境效益兼俱的解决水环境
BHC is an extensive, lasting, fatty soluble and low cost organic chlorine pesticide, it is resistant to high temperature and acid, which has once improved the agricultural production. In the 40~80years last century, almost every country in the world used BHC to protect the agriculture from pest hazard. And in the 50~80years last century, the production amount of BHC is 60% of that of total pesticides. BHC have seriously contaminated the ecological environment due to its long remnant and stability, and because of that our country has banned its production and use in early 80years last century. But restricted by kinds of environment conditions, the degradation speed is very slow. In the environment superintend reports of some area proved that the residue of BHC still can be detected even in high concentration, and it is confirmed one of those widely used POPs.
BHC residue has latent danger to the agricultural environment, agricultural and water products, and also the human health. The different framework of BHC is doubted to cancer inducement. γ-BHC can incentive central nerve system, α-BHC、δ-BHC is believed to depress on the central nerve system. γ-BHC、β-BHC are all proved to be endocrine-disrupting hermaphroditism , and can result in dysgenesis or effect on kidney, liver, blood etc. It has reported that BHC can endanger the human health even its concentration is low in water by accumulated through animals and plants or transported by food chains.
With the development of society and human science, people pay more and more attention on food safety and environment protection. The BHC pollution case in agricultural and water products occasionally affect the export transaction, resulting in economic loss. In order to enhance the quality of agricultural and water products and ameliorate environment, effective removal of BHC is one of our urgent issue waiting for solve in a period.
There is long superintend on the distribution and concentration of BHC. But the removal method study of BHC is comparatively scarce. The current study mostly focuses on biodegradation. Biodegradation, the same as photodegradation, has an active effect on environment remediation. But its degradation ability is limited by the environmental
factors, especially in the area with heavy pollution and low temperature. That will result in the low degradation rate and degree, the new pollutants produced with side reaction accompanied by. According to that, it is obvious that we should find a non-biological degradation method.
It was expounded by Gillham and O’Hannesin(Cannada) that the metal iron could be used in the in situ remediation of the groundwater. From then, study on the low cost, simple, high effect disposal method-zerovalent metal used to improve the dechlorination of organic chlorine became a research issue. The Fe0-PRB used to remove the water pollutants has gained more and more attention from researchers. Although it was improved a high effect on line chlorineaceous hydrocarbon, there is no report on using in BHC removal.
In order to remove the BHC from water and using the discard, this paper refer to the success experience of the PRB technology (it can dechlorine and detoxity on the line hydrocarbon). Considering the defects of it, such as the side reaction and the erosion of the iron and the precipitation produced coated on the surface of the zero valent iron, which may reduce the activity of the iron or result blocking in the barrier, result in the short using period. Different barriers were set up using the cinder, iron, cinder and iron as the reaction material to remove the BHC in water.
The conditional experiments were done on the adsorption by cinder and degradation by zerovalent iron on BHC. The results suggest that both the above two have the similar optimal condition in BHC removal. The removal effect is preferably on the asourish, When the diameter diminished or the using amount and reaction time increased, the removal rate enhanced with it. Under the optimal conditions, the cinder’s adsorption on BHC can rea
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