零价铁活化过硫酸盐降解分散剂木质素磺酸钠研究

On the dispersant degradation of zero-valiant iron activated by the persulfate sodium lignosulfonate

为研究零价铁(Fe^(0))通过电子转移对过硫酸盐(PS)降解分散剂木质素磺酸钠(SL)能力的影响,以SL作为目标污染物对影响SL降解的因素(初始pH值、SL初始质量浓度、PS浓度、Fe^(0)投加量)及降解机理进行探讨。结果表明,1)当pH值小于2时,SL降解率随pH值升高而升高;当pH值在2~5时,SL降解率随pH值升高而降低。当PS浓度在2~4 mmol/L时,SL的降解率随PS浓度的增大而增大;当PS浓度超过4 mmol/L后降解率呈现下降趋势。当固定其他反应条件时,SL的降解率随SL初始质量浓度的升高而降低。2)相比于单一 Fe^(0)体系和单一 PS体系,Fe^(0)-PS体系对SL的降解率有显著提高,对含SL废水可生化性有所改善。在最佳反应条件下(pH值为2,Fe^(0)投加后质量浓度为0.3 g/L,SL初始质量浓度0.5 g/L ,PS浓度为4 mmol/L),180 min内SL的降解率能达到75.9%。3)Fe^(0)活化PS产生SO_(4)^(-)·,通过自由基淬灭剂进行淬灭试验,确定降解过程中的SO_(4)^(-)·与·OH为体系活性物质。4)通过红外吸收光谱扫描,比较SL与反应产物的FTIR图谱,推测在氧化作用下,SL的苯环结构断裂,部分磺酸基团被氧化为SO_(4)^(-)。研究表明,Fe^(0)-PS体系与单-Fe^(0)体系和单一 PS体系相比,Fe^(0)能有效活化PS产生SO_(4)^(-)·,进而对SL有更好的降解效果。

The present paper has chosen the zero-valiant iron(Fe^(0)) activated persulfate(PS) as the sampling pollutant to examine the degrading ability of the sodium lignosulfonate on the sodium lignosulfonate through the electronic transfer.For the said purpose,we have investigated the effect of the initial pH value,the initial mass concentration of sodium lignosulfonate,the PS concentration,and Fe^(0) dosage on the degradation of the sodium lignosulfonate.The results of our investigation indicate that:(1) When the pH value is greater than 2(i.e.pH <2),the sodium lignosulfonate degradation rate may tend to increase with the increase of the pH value.But,when the pH value of 2 is inclined to increase to 5,the sodium lignosulfonate degradation rate may tend to decrease with the increase of its value.Rather,the sodium lignosulfonate degradation rate may tend to be negatively correlated with the initial mass concentration rate of the sodium aforementioned.And,when the 2 mmol/L <PS <4 mmol/L,the sodium lignosulfonate degradation rate tends to get improved with the increase of the PS concentration rate.However,when PS>4 mmol/L,the degradation rate of the sodium lignosulfonate would appear in a downward trend;And,(2) as compared with the single Fe^(0) or PS system,the activation of Fe^(0) can even help to enhance the degradation rate of the sodium lignosulfonate by the Fe^(0)/PS system and in turn enhance the biodegradability of the sodium lignosulfonate sewage effectively.Furthermore,at the optimal reaction conditions,say,pH=2,and Fe^(0)=0.2 g/L,the initial mass concentration rate of the sodium lignosulfonate can even be made equal to 0.5 g/L,with PS being equal to 4 mmol/L.In such a case,the sodium lignosulfonate degradation rate can even be made to go up to 75.9% during a period of 180 min.And,then,(3),Fe^(0) can help to activate and promote SO4 by producing PS through electronic transfer and adding a certain amount of free radical quenchers to the system to perform the quenching experiment,for instance,by adding the tert-butanol,isopropanol and methanol to it to ensure the production of SO_(4)^(-)· and OH,which can be transformed into active substances in the degrading process.And,next,(4),the FTIR spectrum of sodium lignosulfonate can also be made to compare with the reaction products by scanning through the infrared absorption spectrum.It can also be speculated that the benzene ring of the sodium lignosulfonate would like to be destroyed by oxidation,with some sulfonic acid groups oxidized to SO_(4)^(-)·And,so,it is just for such a reason that this paper believes that Fe^(0) can help to activate PS to produce SO_(4)^(-)· effectively,whereas,since the Fe^(0)-PS system has a higher degree of activation of PS than the single Fe^(0) or PS system,it can be expected that it would also help to improve the degrading rate of the sodium lignosulfonate.