背景水质对过流式VUV/UV反应器降解水中阿特拉津的影响

Effect of water matrices on atrazine degradation in a flow-through VUV/UV reactor

为探究连续流进水模式下水中复杂的背景物质对真空紫外/紫外(VUV/UV)高级氧化工艺效率的影响,采用过流式VUV/UV反应器,考察了水中不同浓度的氯离子(Cl^(–))、碱度(HCO_(3)^(–))、硝酸盐(NO_(3)^(–))和溶解性有机物(DOM)对微量污染物阿特拉津(ATZ)降解的影响。结果表明,上述背景组分对ATZ的VUV/UV降解均表现出一定的抑制作用,辐照时间为30 s时,ATZ去除率从空白组中的57%分别最多下降至33%、29%、40%和35%,且过流式条件下的抑制程度与文献中序批式反应器中的略有不同。污染物去除率下降的原因在于,一方面,三种无机阴离子都对VUV辐射有一定的蔽光效应,NO_(3)^(–)强于Cl^(–)强于HCO_(3)^(–);另一方面,VUV辐照下Cl^(–)产生的Cl·和Cl_(2)·–、NO_(3)^(–)产生的NO_(2)·和HO·都能补充水中氧化性自由基浓度,使得VUV贡献的ATZ降解速率常数的抑制程度低于VUV光子被阴离子竞争吸收的比例,但HCO_(3)^(–)对HO·较强的清除作用则导致了ATZ的降解速率常数的快速下降。低浓度DOM在VUV/UV辐照下可能产生的活性物种抵消了其对VUV/UV辐射的蔽光效应,但高浓度DOM对HO·的清除作用仍使其对ATZ降解产生了显著的抑制。在所有考察的水质条件下,ATZ降解所需的单位能耗EEO介于0.61~1.56 kWh·m^(-3)。

In order to explore the impact of complex water matrices on VUV/UV advanced oxidation efficiency under continuous flow mode,the degradation of atrazine (ATZ) in water with additional chloride (Cl^(–)) bicarbonate (HCO_(3)^(–)),nitrate (NO_(3)^(–)) and dissolved organic matter (DOM) at different concentrations were investigated in a flow-through VUV/UV reactor.The results showed that all these water constituents had some inhibition effects on ATZ degradation.The ATZ removal decreased from 57% in deionized water to 33%,29%40% and 35% under the largest investigated matrix concentrations at an irradiation time of 30 s.These inhibition extents were somewhat different from those reported in batch reactors in literatures.The reduction of ATZ removal could be ascribed to following reasons.On the one hand,all the three anions have a certain shielding effect on VUV irradiation,following the order:NO_(3)^(–)>Cl^(–)>HCO_(3)^(–).On the other hand,reactive species under VUV irradiation,such as Cl·and Cl_(2)·–produced from chloride,NO_(2)·and HO·formed by nitrate,could supplement the concentration of oxidative radicals in water and contribute to ATZ degradation,which resulted in a lower reduction of ATZ degradation contributed by VUV than the proportion of VUV photons absorbed by the anions.In contrast,the strong scavenging of HO·by HCO_(3)^(–)led to a significant reduction of ATZ degradation The reactive species generated from DOM at low contents could counteract the shielding effect,while DOM a high concentration still had a prominent inhibition on ATZ degradation due to its remarkable scavenging of HO·.The specific energy consumption under the investigated water matrices ranged between 0.61~1.56kWh·m^(-3).