| Atrazine is a herbicide widely used in agricultural production and has good control effects on annual grasses and broad-leaved weeds.However,atrazine usually remains in the soil and groundwater,which in turn poses a threat to environmental quality and biological health.Therefore,it is particularly necessary to quickly reduce the residual atrazine in the environment.The advanced oxidation technology of persulfate shows great advantages in the degradation of organic pollutants.Therefore,this study successfully prepared a new zero-valent iron/biochar composites?ZVI/BC?using biochar?BC?as raw material.On this basis,the research focused on the effect and mechanism of ZVI/BC activated persulfate?PS?oxidative removal of atrazine,and investigated the effects of ZVI/BC-PS system on soil p H,soil enzyme activities and bacterial community diversity during the restoration of atrazine contaminated soil.The main findings are summarized as follows:?1?The characterization and analysis of ZVI/BC by SEM-EDS,TEM,BET,XPS and FTIR.The results showed that the loading treatment could make the zero-valent iron?ZVI?particles uniformly dispersed on the surface of the BC.The mass percentage of C element and Fe element in the ZVI/BC was 2:1.The specific surface area and pore volume of the ZVI/BC were 68.075m2/g and 0.043 cm3/g,respectively,and the pore size was mainly distributed in the size range of<4 nm.In addition,-COOH and-OH oxygen-containing functional groups existed on the surface of ZVI/BC,and the ZVI in ZVI/BC after the reaction disappeared.?2?The atrazine removal experiment in water phase:compared with ZVI,when ZVI/BC was used as an activator,the ZVI/BC-PS system showed a higher removal capacity of 25 mg/L atrazine with a removal rate as high as 73.47%?15 min?.Response surface method?RSM?was used to determine the optimal reaction conditions for removing atrazine:ZVI/BC addition amount was 175 mg/L,PS concentration was 2.0 m M,and initial p H was 3.0.Under the optimal conditions,the actual removal rate of atrazine in 15 minutes was 89.68%?pre dicted value:85.23%?,and the RSD was 4.45%.?3?The free radicals in the atrazine oxidation removal experiment were identified by free radical quenching experiment and electron spin resonance?ESR?technology.The results showed that sulfate radicals?SO4-·?and hydroxyl radicals?OH·?were the major free radical for the degradation of atrazine in the ZVI/BC-PS system.As the activation process progressed,the concentrations of Fe???and Fe???in the ZVI/BC-PS system reached 13.24 mg/L and 11.19mg/L in 30 min,respectively.The results showed that during the oxidation process of atrazine,ZVI in the system participated in the reaction to produce Fe???and also promoted the formation of Fe???.According to the results of GC-MS and LC-MS,it was speculated that the degradation pathways of atrazine in ZVI/BC-PS system mainly included three processes:dealkylation,alkyl oxidation and dechlorination-hydroxylation.?4?The results of the atrazine removal experiment in soil showed that there were significant differences in the deceleration rate of atrazine?20 mg/kg?in simulated polluted soil under different levels of ZVI/BC and PS?P<0.05?,of which T7?0.1%ZVI/BC+1.0%PS?treatment showed the highest removal effect on atrazine,the removal reached 45.4%within 3 d.In the same reaction process,the removal rate of atrazine by T4?0.1%ZVI/BC+0.5%PS?treatment was 27.0%.?5?The ZVI/BC-PS system significantly reduced the soil p H.The soil p H values of the T4,T7 and T8?0.25%ZVI/BC+1.0%PS?treatments were 6.8,5.7 and 6.1,respectively,indicated that T4 treatment had the smallestt effect on soil p H.Under the effect of different ZVI/BC and PS dosage levels,the urease activity in CK,T4,T7,and T8 treatments were 0.0326 mg·g·-1h-1,0.0269mg·g·-1h-1,0.0184 mg·g·-1h-1 and 0.0194 mg·g·-1h-1 respectively.The results showed that ZVI/BC-PS system significantly inhibited soil urease activity,while T4 treatment had the lowest inhibitory effect on urease activity.The activities of alkaline phosphatase in CK,T4,T7 and T8 treatments were 523.64?g·g·-1h-1,470.93?g·g·-1h-1,454.11?g·g·-1h-1 and 464.36?g·g·-1h-1.The results showed that the ZVI/BC-PS system had a significant inhibitory effect on alkaline phosphatase,and the inhibition by T4 treatment was the smallest.The?-glucosidase activity in the above treatments were 222.64?g·g·-1h-1,237.18?g·g·-1h-1,248.89?g·g·-1h-1and 260.71?g·g·-1h-1.The results showed that the ZVI/BC-PS system could promote?-glucosidase activity in soil,and T4 treatment had the least effect on?-glucosidase.?6?The results of this study showed that the ZVI/BC-PS system could affect the diversity of bacterial communities in the soil,and the different dosing levels of ZVI/BC and PS had different effects on the richness of the bacterial community.T7 treatment could increase the richness of bacterial communities in soil,while T8 and T4 treatments had an inhibitory effect on the bacterial community richness.In addition,the ZVI/BC-PS system could change the structure and composition of the bacterial community.The addition of ZVI/BC and PS increased the relative abundance of Actinomycota and Planctomycetes,and inhibited the relative abundance of Proteobacteria,Acidobacteria and Bacteroides.At the same time,the ZVI/BC-PS system could inhibit the relative abundance of Sphingomonas and Gp4 in the soil,and promoted Gp6 and Gemmatimonas. |
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