石墨烯电极电活化过硫酸盐降解含酚废水研究

以苯酚为目标污染物,利用石墨烯电极自身性质及电活化共同作用下活化过硫酸盐(PDS)产生氧化性自由基降解苯酚,对影响苯酚降解的因素(包括电流密度、初始pH值、PDS浓度及影响反应的主导自由基)进行探讨。通过系统中加入一定量的甲醇和叔丁醇作为自由基猝灭剂的猝灭试验确定降解过程中的主导自由基。结果表明,在未通电情况下石墨烯电极对苯酚也具有去除作用,可以吸附苯酚。在通电情况下,由于电活化和石墨烯活化的双重作用,相比于单一石墨烯体系和单一PDS体系,石墨烯/PDS体系对苯酚的降解率显著提高,在n(PDS)∶n (phenol)为50∶1、苯酚初始质量浓度为25mg/L、pH值为11、电流密度为30 mA/cm²的条件下,在90 min内苯酚的降解率可达98.91%。通过淬灭试验确定在石墨烯/PDS降解苯酚体系中以硫酸根自由基为主(SO₄^-·)、羟基自由基(·OH)为辅。综上所述,在未通电情况下,石墨烯可以利用自身吸附作用去除苯酚,在通电情况下,石墨烯电极利用自身性质以及电活化活化过硫酸盐,与单一PDS体系和单一石墨烯体系相比,有效提高了过硫酸盐的活化程度,提高了苯酚的降解率。

Degrading phenolic sewage via the graphene electrodes through the electrically activated persulfate

The present paper intends to discuss the influential factors of the phenol degradation,including the volume current density,the initial p H value,the PDS concentration rate and the dominant volatile radicals. As is well known,with phenol as the target pollutant,the activation of the persulfate( PDS) by the graphene electrode and electric activation can help to result in oxidative free degraded radical of phenol. On the other hand,the graphene electrode can also have a removal effect on the phenol with no need to be energized due to the honeycomb hexagonal structure of the grapheme electrode. This is because the surface of this kind of structured material is rich in PI electrons and enjoys a strong electronic conjugation effect on the aromatic organism,which makes it adsorptive on the phenol. And,so,in the electro-supporting conditions,with the dual action of the electroactivation and graphene activation,the removal rate of the phenol by the system of graphene/PDS can be made improved significantly as compared with that of a single graphene or a single PDS system. Furthermore,in case of n( PDS),when n( phenol) is equal to 50: 1,the initial concentration of the phenol should be 25 mg/L,with the pH value being 11 and the current density being 30 m A/cm²,the degradation rate of the phenol can be made to reach so high as to a percentage of 98. 91% during a period of 90 min. Besides,if a certain amount of methanol and tert-butanol were added to the system as a free radical quenching agent,the added alcohol can help to quench out the free radicals to heighten the degraded rate of phenol so as to clarify and identify the dominant free radicals. Due to the different reaction constant rates of the methanol and tert-butanol to S0₄^-· and ·OH,the inhibitory effects can also be made different. Therefore,experiments can help us to determine that the phenol system degradation of the graphene/PDS of the sulfate radical(S0₄^-·) should be taken as the dominant one,whereas the hydroxyl radical(·OH) serves as the auxiliary one. To sum up,in the unpowered case,graphene can be used to adsorb and remove the phenol content. However,in current situation,the graphene electrode itself and the dual action of the electro-activation persulfate can also be used to promote the activation of the persulfate and the removal rate of the phenol in comparison with the single PDS system and the single graphene system.