在氧化材料领域,目前常用的材料有Fenton试剂、过碳酸钠、高锰酸钾、臭氧、活化过硫酸钠等。其中,过硫酸钠凭借氧化还原电位(E0=2.01V)高、性质比过氧化氢稳定、可以在土壤中传输更长距离、便宜等优势,近年来稳坐有机污染土壤修复应用的“头把交椅”。
In the field of oxidizing materials, the commonly used materials include Fenton reagent, sodium percarbonate, potassium permanganate, ozone, activated sodium persulfate, etc. Among them, sodium persulfate, with its high redox potential (E0 = 2.01v), more stable properties than hydrogen peroxide, longer transmission distance in soil and low price, has been firmly in the "top position" in the remediation and application of organic polluted soil in recent years.
过硫酸钠在常温条件下反应速率低,对有机污染物的降解效果不显著。然而,在热、过渡金属离子(Fe2+、Fe3+等)、OH-等条件的激发下,会活化分解为·SO4-(E0=2.6V),反应速率大幅度提升。
The reaction rate of sodium persulfate is low at room temperature, and the degradation effect of organic pollutants is not significant. However, under the excitation of heat, transition metal ions (Fe2 +, Fe3 +, etc.) and oh -, it will be activated and decomposed into · SO4 - (E0 = 2.6V), and the reaction rate will be greatly improved.
既然过硫酸钠在多种条件下均可被,那么,过硫酸钠在不同条件下被的机理特征及作用效果又如何呢?带着以上疑问,高能环境修复技术研发团队针对不同方式过硫酸钠进行了实验研究。
Since sodium persulfate can be activated under various conditions, what are the mechanism characteristics and effect of sodium persulfate activated under different conditions? With the above questions, the R & D team of high-energy environmental remediation technology conducted experimental research on different ways to activate sodium persulfate.
▲红外测油仪-有机污染物检测
▲ infrared oil detector - organic pollutant detection
▲GCMS-有机污染物检测
▲ GCMS organic pollutant detection
▲项目现场小试
▲ project site pilot test
▲项目现场中试
▲ project site pilot test
通过实验室检测及在多个项目现场试验,结合文献调研资料,对不同方式过硫酸钠的机理及特征总结如下:
The mechanism and characteristics of different ways to activate sodium persulfate are summarized as follows through laboratory testing and field tests in multiple projects, combined with literature research data:
(1)热
(1) Thermal activation
升温30°以上,过硫酸钠被产生硫酸根自由基:
When the temperature rises above 30 °, sodium persulfate is activated to produce sulfate radical:
体系温度大于50℃,反应1周左右,过硫酸钠对TPH的降解效率大于90%。
The degradation efficiency of TPH by sodium persulfate was more than 90% when the system temperature was more than 50 ℃ for about 1 week.
(2)金属离子
(2) Metal ion activation
过硫酸钠被Fe(II)或Fe(III)发生系列反应:
Sodium persulfate is activated by Fe (II) or Fe (III) to produce a series of activation reactions:
Fe(II)过硫酸钠效率高、反应剧烈、现象明显,体系升温明显,反应1周左右,过硫酸钠对TPH降解率大于90%,对PAHs也有良好的降解效果。
Fe (II) activated sodium persulfate has high efficiency, violent reaction and obvious phenomenon. The temperature rise of the system is obvious. The degradation rate of TPH is more than 90% and PAHs is also good.
(3)过氧化氢
(3) Hydrogen peroxide activation
过硫酸钠被过氧化氢或过碳酸钠产生硫酸根自由基:
Sodium persulfate is activated by hydrogen peroxide or sodium percarbonate to produce sulfate radical:
该反应体系为双氧化系统(由一种氧化剂另一种氧化剂),反应剧烈,升温明显,反应1周左右,过硫酸钠对TPH降解效率大于90%,对PAHs也有良好的降解效果,对有机氯农药类污染物也有一定的降解能力。
The reaction system is a double oxidation system (one oxidant activates another oxidant). The reaction is intense and the temperature rises obviously. After reaction for about 1 week, sodium persulfate has a degradation efficiency of more than 90% for TPH, a good degradation effect for PAHs, and a certain degradation capacity for organochlorine pesticide pollutants.
(4)碱
(4) Alkali activation
控制体系pH>11时,过硫酸钠被碱产生羟基自由基:
When the pH of the control system is > 11, sodium persulfate is activated by alkali to produce hydroxyl radical:
碱反应体系对pH要求较高,随pH升高反应速率有升高趋势,pH升13~14时,反应速率升高幅度渐缓。但采用这种方式后期需要投加酸性物质中和强碱性,对土壤体系理化性质影响较大。
The alkali activated reaction system has high requirements for pH, and the reaction rate tends to increase with the increase of pH. when the pH rises to 13 ~ 14, the increase of reaction rate slows down. However, this activation method needs to add acidic substances to neutralize strong alkalinity in the later stage, which has a great impact on the physical and chemical properties of the soil system.
相对了解机理来说,大家更关注不同方式过硫酸钠的性能以及对有机污染物的降解能力。
Compared with understanding the mechanism, people pay more attention to the performance of sodium persulfate activated by different activation modes and the degradation ability of organic pollutants.
分别将热、Fe(II)、过氧化氢、碱4种方式的过硫酸钠作用于总石油烃(TPH)、多环芳烃(PAHs)、有机氯农药3种典型有机污染土壤中进行实验,得出以下结论:
Sodium persulfate activated by heat, Fe (II), hydrogen peroxide and alkali was applied to three typical organic contaminated soils: total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides. The following conclusions were obtained:
热、Fe(II)、过氧化氢、碱4种方式对土壤中TPH的降解效果良好,降解效率均可达90%以上。
Heat, Fe (II), hydrogen peroxide and alkali have good degradation effects on TPH in soil, and the degradation efficiency can reach more than 90%.
热、碱2种方式对土壤中多环芳烃、有机氯农药的降解能力相对Fe(II)、过氧化氢2种方式较弱。
The degradation ability of heat and alkali activation methods to polycyclic aromatic hydrocarbons and organochlorine pesticides in soil is weaker than that of Fe (II) and hydrogen peroxide.
4种方式对土壤中有机氯农药的降解效果均不理想。
The degradation effects of four activation methods on organochlorine pesticides in soil were not ideal.
过氧化氢过硫酸盐虽然效率高、污染物降解效果好,但对过氧化氢的消耗量较大,过氧化氢的少量多次添加有利于维持氧化能力的同时节约氧化剂。
Although hydrogen peroxide activated persulfate has high efficiency and good pollutant degradation effect, it consumes a large amount of hydrogen peroxide. A small amount of hydrogen peroxide added for many times is conducive to maintaining oxidation capacity and saving oxidant.