过硫酸钠缓释材料的释放性能及其对2,4-二硝基甲苯的降解效果

Sustained-Release of Sodium Persulfate Composite and Degradation of 2,4-Dinitrotoluene

针对原位化学氧化技术修复土壤和地下水时氧化剂因释放过快而导致的利用率低等问题,通过熔化成型法制备过硫酸钠缓释材料,分析石蜡、硅砂和过硫酸钠不同配比对材料成型度和释放性能的影响,研究缓释过程中溶液pH的变化,探讨其在水溶液中的缓释行为及其对2,4-二硝基甲苯(2,4-DNT)的降解效果.结果表明:当固定过硫酸钠质量为6 g、硅砂质量为18 g、蜡砂比(石蜡、硅砂质量之比)为1:4~1:8时,过硫酸钠缓释材料成型度适中,且过硫酸钠的累积缓释量随着时间的延长而逐渐增大,第31天时过硫酸钠累积释放百分比为74.67%~88.40%,可实现过硫酸钠的持续可控释放.当硅砂质量为18 g、蜡砂比为1:1~1:6时,过硫酸钠累积释放百分比随着过硫酸钠质量的增加而增大,且溶液中的pH呈先降低后上升的变化规律.缓释材料缓释前后实物图和显微镜分析结果显示,过硫酸钠缓释材料的释放是一个由外到内、速率由快变慢最终趋于平稳的过程.过硫酸钠质量为12 g、硅砂质量为18 g、蜡砂比为1:4的缓释材料对2,4-DNT具有较好的降解效果,第16次置换浓度为0.2 mg/L的2,4-DNT水溶液时,2,4-DNT的降解率为56.38%.研究显示,改变制备材料的配比可有效实现缓释材料中过硫酸钠的缓慢释放及对污染物的有效降解,可为原位化学氧化修复土壤和地下水提供理论支撑.

Due to the low oxidant utilization of implementing in-situ chemical oxidation in soil and groundwater remediation,a method for preparing sustained-release of sodium persulfate composite by melting and cooling method was studied.The effects of different ratios of paraffin,silica sand and sodium persulfate on the formability and sustained release properties of the sustained release composite were analyzed.Release performance,degradation of 2,4-dinitrotoluene(2,4-DNT)and the change of pH in solution during the sustained release process were investigated.The results showed that when the quality of sodium persulfate silica sand were 6 g and 18 g respectively,the sustained-release of sodium persulfate composite with the paraffin-to-silica sand mass ratios of 1:4 to 1:8 had a good shape and excellent releasing performance.The accumulated release of Na2S2O8 varied from 74.67%to 88.40%after 31 d.When silica sand was 18 g and the paraffin-to-silica sand had a mass ratio of 1:1 to 1:6,the sustained-release of sodium persulfate composite increased with the increasing of persulfate content,and the pH value in the solution decreased first and then increased.Microscopic analysis showed that the release of Na2S2O8 from sustained-release sodium persulfate was a process from outside to inside,and the releasing rate gradually decreased and maintained stable finally.The sustained-release material with a sodium persulfate of 12 g,a silica sand content of 18 g and a wax-sand ratio of 1:4 had a good degradation effect on 2,4-DNT,and the degradation rate of 2,4-DNT was 56.38%after 16th replacement of 0.2 mg/L 2,4-DNT aqueous solution.Therefore,the sustained releasing performance and effective degradation of contaminants can be obtained through changing the ratios of paraffin,silica sand and sodium persulfate.The results obtained in this study will provide a technique that can be applied in the soil and groundwater remediation.