Study On Degradation Of Dispersant Sodium Lignosulfonate By Persulfate Activated With Zero Valiant Iron

Sodium lignosulfonate is a polymeric surfactant with dispersing function,which can improve the suspension rate of dyes,enhance the water solubility of dyes and thus improve the printing and dyeing effect,so it is widely used in printing and dyeing industries.A large amount of sodium lignin sulfonate enters the natural environment with the printing and dyeing wastewater,which is likely to cause large ecological impact and potential risks.In this thesis,the degradation effect of zero-valent iron（Fe⁰）system alone,peroxynitrite（PS）system alone and Fe⁰/PS on sodium lignosulfonate was investigated,and a quasi-level reaction kinetic model was used to fit the degradation courses of targeted pollutant,and to provide an opportunity to study the degradation effect of zero-valent iron（Fe⁰）on the dispersant sodium lignosulfonate through the activation of PS by electron transfer.The elements influencing the degradation of sodium lignosulfonate（containing p H,initial mass concentration of sodium lignosulfonate,PS concentration,Fe⁰ dosing,and dominant free radical）and the degradation mechanism were explored,and the practical application of the system for treating actual wastewater was also verified,and the results of the study are as follows:（1）The reduction of sodium lignosulfonate by Fe⁰ itself was studied,and the degradation of sodium lignosulfonate by Fe⁰ could reach 10.2%in180 min of reaction without the participation of PS.Compared with the single Fe⁰ system and the single PS system,the degradation rate of sodium lignosulfonate in Fe⁰ PS system was significantly increased,reaching75.9%;the single PS system and the single Fe⁰ system were insignificant,26.3%and 10.2%,respectively.The hydrolysis reaction occurred in the single PS system to generate S₂O₈^2-redox potential of 2.01 V,which has a certain oxidation capacity（can oxidatively degrade a small amount of SL）.The degradation of sodium lignosulfonate by single Fe⁰ system was caused by the reduction of sodium lignosulfonate.The degradation rate of SL in Fe⁰-PS system was significantly improved compared with single Fe⁰ and single PS system.Fe⁰ can activate through electron transfer PS produces SO₄^-·,SO₄^-·can effectively degrade sodium lignosulfonate.（2）By quenching free radicals,the important active substances in the reaction system are SO₄^-·and·OH,In order to clarify the specific degradation pathway of sodium lignosulfonate through the system reaction,the lignin sulfonate was compared with the reaction products by infrared absorption spectroscopy,and it was assumed that the benzene ring structure of sodium lignosulfonate was broken under the oxidation of Fe⁰-PS system,and part of the sulfonic acid group was oxidized to SO₄^-.The water sample at 90 min of the reaction was detected by GC-MS after repeated tests under the explored optimal reaction conditions,and glycolic acid,phthalic acid and 2-methoxy were detected.The presence of low molecular acids indicates that the system disrupts the benzene ring structure of sodium lignosulfonate and can effectively degrade sodium lignosulfonate under certain conditions.（3）Fe⁰ can effectively activate PS to generate SO₄^-·,which in turn oxidatively degrades sodium lignosulfonate.The degradation rate is inversely proportional to p H,and it is first proportional and then inversely proportional to the amount of PS,and inversely proportional to the initial concentration of sodium lignosulfonate.And it reached 75.9%at p H 2,0.3g/L mass concentration of Fe⁰,PS 4 mmol/L,and 0.5 g/L initial sodium lignosulfonate for 180 minutes.（4）For the sake of apply the research results to the actual treatment of actual disperse dye wastewater,a textile factory in Xuzhou City was selected as the research object to produce disperse dye wastewater,and the Fe⁰/PS system was used for the deep treatment of actual disperse dye wastewater of the factory,and influences of Fe⁰ dosage,PS concentration,p H and other elements on the oxidation of sodium lignosulfonate in the system were researched,and the study showed that under the action of Fe⁰-PS system The degradation efficiency of sodium lignosulfonate in the actual disperse dye wastewater was 70.9%,which was basically in accordance with the pattern found in the laboratory self-formulated wastewater study.