环氧化季铵盐改性颗粒活性炭去除溴酸根的效能与机理研究

Bromate removal has drawn great concerns in both water treatment plants in coastal areas and scientific community, since it has been classified as a possible carcinogen by the International Agency for Research on Cancer, and it is not easily removed using conventional technologies. Granular Activated Carbon is the most widely used adsorbents for removing bromate among the current technologies. However, the major challenges for GAC technologies include: (a) some of the functional groups that had been preloaded onto GAC would leach during water treatment operations, resulting in secondary pollution; (b) the fresh GAC has a potential to transfer to Bio-activated carbon (BAC) under long term operation, which decreases the bromate removal efficiency dramatically. To overcome the above barriers, we propose a novel approach of anchoring Quaternary Ammonium/epoxide-forming (QAE) compounds into the activated carbon by an epoxide-induced reaction between the epoxide-forming functionality within the QAE molecule, as linked to the oxygen-containing functional groups of GAC (or of other.QAE molecules). By anchoring this functionality rather than preloading surfactants, the authors anticipated that the subsequent leaching of the.surfactants would be mitigated, while maintaining a good bromate removal performance. In addition, this technique will reduce the possibility of conversion from fresh GAC to BAC. The proposed work will focus on (a) fundamentally understanding the effects of length of QAE, type of GAC, dose of QAE, reaction time, temperature and pH on the QAE loading efficiency and bromate adsorption capacity, and further explaining the mechanism of QAE anchoring on the GAC by studying the relationships between the composition, textural peoperties, chemical characteristics of the QAE-anchored GAC and the bromate removal efficiency; (b) technically developing a novel and highly-efficient QAE-anchored GAC technology for removing bromate from drinking water, and investigating the optimum conditions for developing this novel adsorbents, in such manner, bromate in drinking water can be treated down to 10 ppb with this novel, clean and highly-efficient technology. Moreover, it will enrich the adsorption theories and generate new interdisciplinary adsorption-based science for bromate removal with tailored.granular activated carbon.

针对现有活性炭去除溴酸根技术中易产生二次污染和新鲜活性炭向生物活性炭转化的两大关键性难题，本项目首次提出将环氧化季铵盐通过化学键固定负载在颗粒活性炭(GAC)表面，这不仅有助于提高GAC对溴酸根的吸附活性，又可解决因负载官能基团从GAC上脱落而造成水体二次污染的问题，同时季铵盐改性GAC的表面碱性官能团和等电点值增加，降低了新鲜活性炭向生物活性炭转化的可能性。本项目将从理论层面上，研究季铵盐链长、GAC类型、季铵盐改性GAC的制备条件及其表面物化特性对季铵盐负载率和溴酸根吸附效能的影响规律，阐明环氧化季铵盐改性GAC的表面化学负载和溴酸根去除机理；从技术层面上，研制出新型高效去除饮用水中溴酸根的吸附剂-季铵盐改性GAC，获得吸附剂制备的最优条件，研究基于该吸附剂的饮用水厂深度处理溴酸根的动态活性炭床技术，提出最佳运行条件。该研究成果将为溴酸根深度处理技术提供新的思路，具有良好的应用前景。

针对现有改性活性炭技术在去除水中潜在致癌物溴酸根时容易产生二次污染的问题，本项目开展了环氧化季铵盐改性颗粒活性炭去除溴酸根的效能与机理研究，首次提出将环氧化季铵盐通过化学键固定负载在颗粒活性炭(GAC )表面，这不仅有助于提高GAC对溴酸根的吸附活性，又可避免负载官能基团从GAC上脱落而造成水体二次污染。本项目首先制备了新型高效去除饮用水中溴酸根的吸附剂-环氧化季铵盐改性GAC，并探讨了其对溴酸根去除效能的影响规律；其次通过表面物化特性表征，阐明了环氧化季铵盐在GAC表面的化学负载机理与溴酸根去除机理；最后研究了基于该吸附剂的饮用水厂深度处理溴酸根的动态活性炭床技术，提出最佳运行条件。研究结果表明：1）采用阳离子化反应可成功研制出环氧化季铵盐改性GAC，通过曲面响应优化方法获得了季铵盐改性GAC的最佳制备条件为：QUAB/GAC的质量比R为0.6 g /g，溶液pH为10，反应温度为30 ℃，其最大溴酸根吸附量可达到51.546 mg/g，比优化改性前增加了30.041 mg/g。2）QUAB342通过与GAC表面的含氧官能基团-COOH和-OH发生化学反应进而负载到GAC表面微孔内。CB-Q342-O吸附去除水中溴酸根，一方面是由于QUAB342带正电荷的含氮官能团对带负电荷的溴酸根产生静电吸引力和较强的离子交换活性；另一方面，CB-Q342-O对溴酸根有还原作用。3）当溴酸根初始浓度为100 ppb时，基于CB-Q342-O的小型动态GAC柱吸附去除水中溴酸根时的初始突破床体积为54855 BV，且不同竞争离子对溴酸根的去除均有影响，影响次序为： NO3-> Cl->SO42-，最终发现采用NaHCO3再生季铵盐改性GAC床的效果（4800 BV）优于NaCl（4100 BV）。综合上述结果，本研究为探讨改性GAC去除水中溴酸根的影响规律奠定了坚实的工作基础，同时也为水厂溴酸根深度处理技术提供新的思路，具有良好的应用前景。项目资助共发表论文5篇（SCI2篇），待发表2篇。培养硕士生3名，其中1名已经取得硕士学位，2名在读。项目投入经费20万元，支出16.1819万元，各项支出基本与预算相符。剩余经费3.8181万元，剩余经费计划用于本项目研究后续支出。