硫化矿浮选废水中巯基捕收剂真空紫外/臭氧联合降解研究

A large amount of thiol collectors and degradation intermediates are remained in sulfide flotation wastewaters. These compounds may disturb sulfide flotation processes while reusing flotation wastewaters in mineral processing, and cause severe environmental pollution if discharged into rivers. Ozone oxidation is proved to be suitable to treat sulfide flotation wastewaters due to special quality of flotation wastewaters such as high alkalinity and various metal ions. The thiol collectors can be effectively decomposed in the O3 oxidation process. However, this method shows low mineralization rate of collectors and releases various intermediates due to the low production of hydroxyl radicals. Therefore, the water quality of treated flotation wastewater can not reach the requirements of the reuse in mineral flotation or of the discharge into rivers. . In this study, the vacuum ultraviolet (VUV) photochemistry and ozone oxidation are integrated to generate a powerful oxidizing system which includes UV/O3, VUV photochemistry and O3 oxidation. The novel combined VUV/O3 process can enhance the degradation of thiol collectors in sulfide flotation wastewaters and simultaneously reduce the process energy consumption. The mechanism of enhanced degradation of thiol collectors should be revealed in the VUV/O3 process, and its energy consumption and degradation performance will be provided. The generation and transformation of intermediates will be present in the degradation process. The change of water qualities (e.g., pH value and biodegradability) of wastewaters should be also provided. Additionally, the effects of intermediates and water qualities on the flotation separation of lead/zinc sulfide minerals should be exhibited while the VUV/O3 process is used to decompose thiol collectors. . The results can provide a novel sulfide flotation wastewater treatment method with higher efficiency in removing thiol collectors and degradation intermediates than the O3 oxidation. At the same time, the degradation efficiency and mechanism of the combined VUV/O3 process will be presented for advanced treatment of sulfide flotation wastewaters.

硫化矿浮选废水中残留有大量巯基捕收剂及降解产物，回用于选矿生产会恶化浮选指标，直接排放会引起严重环境污染，故巯基捕收剂的高效去除已引起矿业界高度重视。臭氧氧化法适合于浮选废水呈碱性和多金属离子的水质，巯基捕收剂去除效率高，但羟基自由基产率低，氧化不彻底，降解产物多，处理后水质难以满足生产回用或排放要求。本项目将真空紫外(VUV)光化学与臭氧氧化结合，构建出能同时包括UV/O3、VUV光化学和O3氧化功能的强氧化体系，形成真空紫外/臭氧(VUV/O3)联合新工艺，强化捕收剂降解，降低工艺能耗。通过研究，揭示VUV/O3工艺降解巯基捕收剂的强化机理，明确工艺能耗和巯基捕收剂降解特性；弄清降解产物的生成和转化规律及水质指标(如pH值、可生化性)变化过程；揭示降解产物和水质指标对铅锌硫化矿浮选分离的影响机理。研究结果能为硫化矿浮选废水处理提供一种效率高于臭氧氧化的净化方法及其工艺技术原理和参数。

金属硫化矿浮选废水残留有多种有机药剂，返回浮选流程会恶化矿物分选，与重金属结合能形成重金属‒有机复合污染，引起严重环境污染，如何高效去除浮选废水中残留有机药剂已引起高度重视。本项目以真空紫外/臭氧(VUV/O3)联合工艺强化巯基捕收剂的降解和矿化，研究捕收剂降解的动力学、矿化过程和工艺能耗，确定降解关键工艺参数；揭示VUV/O3降解巯基捕收剂的强化机理，弄清降解产物的生成和转化规律，提出捕收剂降解历程和抑制有毒中间产物生成的方法；明确降解过程水质参数（pH、ORP和电导率）和可生化性的变化规律；研究浮选废水共存矿物和共存离子对臭氧氧化捕收剂的影响，提示其影响机理。. 结果表明，O3和VUV/O3降解捕收剂均符合准一级反应动力学，与O3相比，VUV/O3降解捕收剂的动力学常数提高了2.23~6.01倍，VUV/O3体系将O3氧化、VUV光化学和UV254nm/O3氧化耦合，促进羟基自由基的生成，强化捕收剂降解。同时，VUV/O3强化捕收剂的矿化过程，与O3相比，分子中有机碳、硫、氮和磷的矿化率能提高15%~80%，生成更多CO2、SO42‒、PO43‒ 和NO3‒最终产物。诸多工艺因素中，pH值和臭氧投加量对降解效率影响较大，碱性介质有利于捕收剂降解，表明VUV/O3工艺合适于碱性浮选废水处理。捕收剂以VUV/O3降解后残留的有机中间产物较少，特别延长降解时间后，促进有毒中间产物的再氧化，控制其残留浓度、降低降解液的毒性。因降解时通入气体，挥发性CS2和H2S会逸出反应器，但释放的CS2和H2S占总硫的量<2%，绝大部分被氧化成SO42‒离子。臭氧氧化巯基捕收剂的能耗值(EE/O值)均属于可接受的能耗水平，其值与捕收剂的可降解性和溶液pH有关，易降解捕收剂的能耗低，pH值高降解能耗也低。捕收剂降解后pH降低和ORP升高，废水的可生化性大幅提高，但乙硫胺酯除外。浮选废水中共存硫化物和非金属矿均对臭氧氧化捕收剂有促进作用，以高岭土、方铅矿的强化最为明显，共存阴离子多对降解有抑制作用，但共存金属阳离子可催化臭氧氧化捕收剂。本项目的研究可为VUV/O3处理硫化矿浮选废水提供技术原理、关键参数和有机浮选药剂的降解特性。