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不同种类活性炭对CX3R型消毒副产物的吸附探讨
论文作者:童鞋论文网  论文来源:www.txlunwenw.com  发布时间:2020/11/18 14:43:41  

摘要:饮用水水质安全是关乎千家万户的重大民生问题,消毒是保障饮用水安全不可或缺的重要措施。然而,应用广泛的氯消毒工艺在杀死细菌病毒的同时,也会产生对人体有害的消毒副产物(disinfection by-products,DBPs),我国现行《生活饮用水卫生标准》对三卤甲烷(trihalomethanes,THMs)等传统含碳消毒副产物(carbon-containing disinfection by-products,C-DBPs)进行了管控,然而,水源水质遭受破坏,水源水中含氮物质(即前体物)不易被水厂净水工艺去除,从而在水厂消毒环节与含氯消毒剂生成含氮消毒副产物(nitrogen-containing disinfection by-products,N-DBPs)。这些新型DBPs的毒性远高于传统C-DBPs,严重影响饮用水安全和人体健康,是全球环境、市政和公共卫生领域的国际热点问题。卤代乙酰胺(haloacetamides,HAMs)和卤乙腈(haloacetonitriles,HANs)是含氮消毒副产物中典型代表,其在饮用水(自来水)中的含量较高且具有较高的细胞毒性和遗传毒性,同时其去除难度也较大。此外,除THMs之外,传统C-DBPs中卤代醛(haloacetaldehydes,HALs)因其去除工艺要求更高,近年也得到较多关注。随着人们对供水系统最末端-龙头水水质的关注,DBPs的末端去除技术开始得到重视。活性炭是较好的水处理吸附材料,在水厂得到了大量应用,然而有关活性炭及其改性材料用于去除多种传统C-DBPs和新型N-DBPs的研究较少,亟待探究活性炭及其改性材料对各类DBPs的去除效能,以期为保障供水“最后一公里”水质安全提供理论与技术支撑。

本文选用6种不同种类活性炭为吸附材料,以21种DBPs为目标污染物,探究活性炭吸附技术对多种DBPs的吸附效果和综合毒性降低率;选出其中经济性及广谱性较强、实用性较高的活性炭,进一步研究实验条件对其吸附效果的影响,此外,对其进行表面改性,考察改性活性炭对三类典型DBPs的吸附情况及其动力学模型。

研究表明:(1)GAC对溴代消毒副产物(Br-DBPs)的被吸附量明显高于相对应氯代(Cl-DBPs)同系物,6种GAC对HANs、HAMs和HALs的吸附量表现为HANs > HAMs > HALs;对综合毒性降低率表现为HANs > HAMs > HALs。6种GAC对21种DBPs吸附实验发现:6种GAC中GAC-F碘值最大、强度最小,其对21种DBPs吸附量最大,而GAC-E碘值次之、堆重最小,对DBPs的吸附量最低。综合毒性降低率与吸附量正相关,吸附量越大,综合毒性降低率就越高,故GAC-F综合毒性降低率最高而GAC-E综合毒性降低率最低。GAC-F对TBAN的吸附量最大为122.2 μg/g。Br-DBPs水溶性较Cl-DBPs更大,其达到吸附平衡时间延长,但因Br电负性小于Cl,因此GAC对Br-DBPs吸附去除和毒性降低效果优于Cl-DBPs。

(2)温度对于实验影响因素不大,吸附剂质量浓度是最直接影响因素。在多元体系中,GAC对各物质的静态吸附不会互相干扰且改性后活性炭与原GAC吸附规律基本相似,实验进行300 min时接近吸附平衡,480 min基本到达吸附平衡。

(3)SAC(氧化改性)因改变GAC表面的含氧官能团,活性炭表面极性增加,对CH的吸附能力也显著增加,较原GAC对CH吸附量提高了30.45 μg/g,而NAC(还原改性)较原GAC吸附量增加最低,仅增加13.94 μg/g。SAC和NAC对DBPs的吸附更符合Freundlich吸附等温线的拟合效果,SAC对TCAN、TCAM、CH的吸附等温方程R2为0.94-0.99。SAC和NAC吸附TCAN、TCAM和CH的反应过程符合准二级吸附动力学规律,R2均高于0.94。

关键词:消毒副产物;吸附技术;吸附量;动力学;综合毒性快捷检索

Abstract: Halocetamides (HAMs) and halocetonitriles (HANs) are typical by-products of nitrogen-containing disinfection. They have high content in drinking water (tap water) and have high cytotoxicity and genotoxicity. At the same time, it is difficult to remove them. In addition to THMs, halogenated aldehydes (HALs) in traditional C-DBPs have been paid more attention in recent years due to their higher requirements for removal process. With people's attention to the water quality of the tap water, the terminal removal technology of DBPs has been paid more attention. Activated carbon is a good adsorption material for water treatment, which has been widely used in waterworks. However, there are few studies on the use of activated carbon and its modified materials to remove a variety of traditional C-DBPs and new type N-DBPs. It is urgent to explore the removal efficiency of activated carbon and its modified materials for all kinds of DBPs, so as to provide theoretical and technical support for ensuring the "last mile" water quality safety of water supply.

In this paper, six kinds of activated carbon were selected as adsorption materials and 21 kinds of DBPs were taken as target pollutants to explore the adsorption effect and comprehensive toxicity reduction rate of activated carbon adsorption technology for a variety of DBPs. Among them, the activated carbon with strong economy and wide spectrum and high practicability was selected to further study the influence of experimental conditions on its adsorption effect. In addition, the surface modification was carried out to investigate the modification The adsorption of three typical DBPs on activated carbon and its kinetic model were studied.

(1)The adsorption amount of brominated disinfection by-products (Br-DBPs) by GAC was significantly higher than that of Cl-DBPs. The adsorption capacity of six kinds GAC to HANs, HAMs and HALs was HANs > HAMs > HALs; the reduction rate of comprehensive toxicity was HANs > HAMs > HALs. The results showed that GAC-F had the largest iodine value and the lowest strength, and the adsorption capacity of 21 DBPs was the largest, followed by GAC-E iodine value and heap weight. The higher the adsorption capacity, the higher the comprehensive toxicity reduction rate. Therefore, GAC-F had the highest comprehensive toxicity reduction rate, while GAC-E had the lowest comprehensive toxicity reduction rate. The maximum adsorption capacity of GAC-F for tban was 122.2 μg/g. The water solubility of Br-DBPs was higher than that of Cl-DBPs, and the adsorption equilibrium time of Br-DBPs was prolonged. However, because the electronegativity of Br-DBPs was less than that of Cl, GAC was better than Cl-DBPs in the removal and toxicity reduction of Br-DBPs. The comprehensive toxicity of various HALs was higher than that of Cl-DBPs, and the adsorption equilibrium time of Br-DBPs was prolonged. However, because the electronegativity of Br-DBPs was less than that of Cl, GAC was better than Cl-DBPs in the removal and toxicity reduction of Br-DBPs. The comprehensive toxicity of various HALs was higher than that of HANs and HAMs. Due to the close adsorption capacity, the six kinds GAC had higher comprehensive toxicity removal rate for HALs.

(2)Temperature has little effect on the experiment, and the

concentration of adsorbent is the most direct factor. In the

V multicomponent system, the static adsorption of GAC on various

substances will not interfere with each other, and the adsorption law of modified activated carbon is basically similar to that of the original GAC.The adsorption equilibrium is close to the adsorption equilibrium at 300 min and reaches the adsorption equilibrium at 480 min.

(3)It was found that the surface polarity of activated carbon was

increased and the adsorption capacity of CH was significantly increased by 30.45 μg/g compared with the original GAC, while the adsorption capacity of NAC (reduction modification) was the lowest, only 13.

Key words: disinfection by-products; adsorption technology; adsorption capacity; kinetics; comprehensive toxicity

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