Degradation of Malachite Green by Using Ozone/Persulfate/Micron-iron Process

ZHANG Zhen; LIU Rupeng; SUN Cuizhen; QIAO Yimu; YANG Lubing; CHEN Yongkai

doi:10.19672/j.cnki.1003-6504.0777.23.338

Abstract：This paper reported on a bench-scale experiment for purpose of degradation of malachite green in aqueous solu-tionn by means of the ozone/persulfate/micron-iron process,emphasizing the investigation of the effect of operating condition on the degradation of malachite green,and the optimizaation of operating parameters by the response surface method of central composite design(CCD),besides to characterize the micron iron before and after the reactionIn instruments including SEM,Raman and FT-IR were used.The results of the experiment presented as the following:the degradation rate of malachite green was accelerated with the increases of ozone flux,persulfate concentration and micron iron concentration,and the degradation rate could attain more than 93％in a rather wide pH range(3～11);the confidence of CCD model was at 95％significant level(P-value＜0.000 1,R2=0.990 4);the operational parameters in terms of signifigance couldl be ranked in order of decreaing magnitude:sulfate concentration＞reaction time＞ozone flow rate＞micron iron concentration;as to the degrada-tion of malachite,green ozone flow rate had interaction with persulfate concentration,persulfate concentration and the reaction time;according to the prediction by CCD model,the optimized condition was ozone flow rate of 1.188 L/min,persulfate concentration of 1.169 mmol/L,micron iron concentration of 0.110 g/L,and the reaction time of 19.040 min.In general,the predicted values were in line with the experimental ones.Furthermore,after the reaction,the weight percentage of micron-iron increased from 16.09％to 29.40％in terms of oxygen element,and decreased from 78.39％to 66.00％in terms of iron element.It was also noted that the micron-iron was intensively corroded so that its surface turned into a flake-like structure with loosened flaws,resulting in a number of γ-Fe2O3 和 α-Fe2O3.In addition,the changes of the intensity of hydrox-yl group and FeOOH species peak before and after the reaction suggested that the surface hydroxyl group may be the main active site in the catalytic process.