【摘要】：我國(guó)由于工業(yè)化和城市化進(jìn)程的加快,污染物大量排放,造成了嚴(yán)重的土壤污染,其中土壤場(chǎng)地的有機(jī)污染是除重金屬污染之外的另一種土壤污染的主要形式。針對(duì)有機(jī)污染土壤,尤其是高濃度有機(jī)污染土壤,傳統(tǒng)的物理、化學(xué)、生物及植物土壤修復(fù)技術(shù)由于其分別具有產(chǎn)生二次污染、需要投加化學(xué)藥劑、處理有機(jī)物種類有限及修復(fù)周期長(zhǎng)等局限性而難以滿足綠色、高效、快速的土壤修復(fù)目的。低溫等離子體(Non-thermal plasma,NTP)技術(shù)被越來(lái)越多地應(yīng)用到環(huán)境領(lǐng)域并被認(rèn)為是一種有前途的污染物治理技術(shù)。低溫等離子體又被稱為非平衡等離子體,是指在由氣體或液體放電產(chǎn)生的含有電子、帶正電的重離子、UV、O3、強(qiáng)電場(chǎng)、沖擊波及各種自由基(·O、·O2、·OH等)的等離子體系中,溫度高的電子密度較低,與重粒子碰撞機(jī)會(huì)較少,使對(duì)系統(tǒng)溫度起決定作用的重粒子動(dòng)能與高溫電子差別較大,整個(gè)體系溫度較低。這種技術(shù)因不需要另外投加化學(xué)藥劑即可原位產(chǎn)生各種活性粒子而被稱為“綠色處理技術(shù)”,并逐漸成為污染物治理領(lǐng)域研究的熱點(diǎn)。本文采用介質(zhì)阻擋放電(Dielectric Barrier Discharge,DBD)和脈沖電暈放電(Pulsed Corona Discharge,PCD)等離子體對(duì)PNP(P-nitrophenol,PNP)和菲(Phenanthrene,PHE)污染土壤進(jìn)行了修復(fù),探討了降解過(guò)程中土壤特性對(duì)降解效率的影響,分析了污染物的降解機(jī)理,并對(duì)比了 DBD和PCD放電方式對(duì)污染土壤的處理效能差異,以考察低溫等離子體技術(shù)在難降解、重污染土壤修復(fù)方面的可行性。主要研究?jī)?nèi)容和結(jié)果如下:(1)以PNP為目標(biāo)污染物,系統(tǒng)地考察了 DBD體系的電壓、土壤污染的初始濃度、土壤pH值、氣體流速等實(shí)驗(yàn)參數(shù)對(duì)DBD等離子體降解PNP效果的影響。結(jié)果表明,DBD等離子體能夠有效去除土壤中的PNP,在50 min內(nèi)污染物的去除率為63.6%,能量效率為0.0067 mg/kJ。DBD等離子體反應(yīng)系統(tǒng)可以礦化20%的PNP。通過(guò)對(duì)比等離子體法和臭氧法發(fā)現(xiàn),臭氧在PNP降解過(guò)程中起到的作用約為25%。此外,對(duì)處理前后的土壤進(jìn)行了 FTIR、GC-MS、IC和HPLC分析,檢測(cè)到了鄰苯二酚、對(duì)苯二酚、富馬酸、馬來(lái)酸、草酸,甲酸、乙酸、硝酸根等產(chǎn)物,推測(cè)出了PNP在降解過(guò)程中發(fā)生了脫氮反應(yīng)、羥基化反應(yīng)、替代反應(yīng)和苯環(huán)破裂等反應(yīng),并對(duì)其降解途徑進(jìn)行了推導(dǎo)。(2)以典型的多環(huán)芳烴(Polycyclic Aromatic Hydrocarbons,PAHs)PHE 為目標(biāo)污染物,考察該DBD反應(yīng)器對(duì)其降解效果和機(jī)理。結(jié)果表明,在頻率為150 Hz,電壓為110 V,放電間隙為1.5 cm,占空比為20%,空氣流速為0.6 L/min時(shí),系統(tǒng)的輸入功率為64 W,PHE的去除率為98%。采用DBD等離子體技術(shù)修復(fù)PHE污染土壤取得了良好的效果,證明了該技術(shù)對(duì)不同結(jié)構(gòu)的有機(jī)污染均有理想的處理效果。通過(guò)GC-MS、FTIR、IC的色譜分析檢測(cè)到了 9,10-菲醌和2,2'-聯(lián)苯甲酸等主要降解產(chǎn)物。利用密度泛函理論(Density Functional Theory,DFT)對(duì)PHE的分子軌道進(jìn)行了計(jì)算和結(jié)構(gòu)優(yōu)化。通過(guò)實(shí)際檢測(cè)與模擬計(jì)算對(duì)PHE的降解途徑進(jìn)行推導(dǎo)與驗(yàn)證。采用光學(xué)發(fā)射光譜(Optical Emission Spectra,OES)鑒定了含氧活性粒子、含氮活性粒子以及羥基自由基,并推導(dǎo)了其產(chǎn)生方式。(3)采用PCD等離子反應(yīng)器對(duì)PHE污染土壤進(jìn)行修復(fù)研究。結(jié)果表明,PCD等離子體反應(yīng)系統(tǒng)對(duì)PHE污染土壤有良好的降解效果,在初始濃度160 mg/kg,放電電壓30 kV、脈沖頻率50 Hz、放電間隙20 cm、放電氣氛空氣的條件下,PHE的去除率能達(dá)到93%,反應(yīng)遵循一級(jí)反應(yīng)動(dòng)力學(xué),反應(yīng)速率常數(shù)為0.032 min-1。此外,通過(guò)脈沖波形、處理效果、降解產(chǎn)物等多方面對(duì)比分析了正脈沖電暈放電、負(fù)脈沖電暈放電和雙脈沖電暈放電。通過(guò)對(duì)比處理前后的FTIR光譜圖可知PHE的分子結(jié)構(gòu)遭到破壞并生成了帶有C=O、N-H、羧基和羥基等基團(tuán)的中間產(chǎn)物。最后,通過(guò)DBD等離子體和PCD等離子體處理PHE污染土壤的對(duì)比研究可知,兩種不同的等離子技術(shù)均對(duì)PHE污染土壤產(chǎn)生了很好的修復(fù)效果。然而,兩者對(duì)PHE污染土壤的修復(fù)也存在一定的差異,主要體現(xiàn)在放電波形、能源效率、動(dòng)力學(xué)反應(yīng)系數(shù)以及主要降解中間產(chǎn)物等方面。DBD等離子體反應(yīng)快,污染物的去除率高。然而,PCD等離子體的能源效率高。
[Abstract]:As a result of the accelerated industrialization and the process of urbanization, the large amount of pollutant is discharged, which causes serious soil pollution, in which the organic pollution of the soil site is the main form of another kind of soil pollution other than the heavy metal pollution. in the light of the organic pollution soil, in particular the high-concentration organic pollution soil, the traditional physical, chemical, biological and plant soil remediation technology has the advantages of secondary pollution generation, It is difficult to meet the needs of green, high-efficiency and fast soil remediation by the limitation of limited organic species and long repair cycle. Low-temperature plasma (NTP) technology is increasingly applied in the field of environment and is considered a promising pollutant treatment technology. the low-temperature plasma is also referred to as a non-equilibrium plasma, which means that in a plasma system containing electrons, positively charged heavy ions, uv, o3, strong electric fields, shock waves, and various free radicals (路 o, 路 o2,. oh, etc.) generated by gas or liquid discharge, the electron density with high temperature is lower, and the collision chance of the heavy particles is less, so that the kinetic energy of the heavy particles acting on the temperature of the system and the high-temperature electronic difference are large, and the temperature of the whole system is lower. This technique is known as a 鈥済reen treatment technology鈥，

本文編號(hào)：2340431