包覆型缓释氧化剂的制备及其缓释性能评价

Preparation of coated slow-release oxidants and evaluation of their slowrelease performance

在低渗层非水相液体污染物的原位化学氧化修复过程中,土壤有机质会消耗氧化剂,导致氧化剂的有效浓度难以长期维持,从而使污染物浓度容易反弹。为了解决该问题采用硬脂酸作为壳材,通过相分离法包覆高锰酸钾制备缓释氧化材料。结果表明,硬脂酸包覆型高锰酸钾(PP@SA)具有良好的缓释性能,可以持续缓释120 h以上。正交实验结果显示,当芯壳比为1∶3,超声时间为15 min,搅拌速度为300 r·min^(-1),粒径为1.12~4.00 mm时缓释效果最佳。并且,随着PP@SA的粒径和硬脂酸用量的增大,MnO4-的缓释机制从Fickian扩散模式向骨架溶蚀和Fickian扩散混合释放机制转变,其中骨架溶蚀释放机制逐渐起主导作用。此外,土相缓释柱实验结果表明,PP@SA在淤泥质粘土和粉质粘土两种低渗土壤中可以保持高锰酸根离子的扩散浓度在0.25 g·L^(-1)以上的时间分别为7和9d,其缓释寿命远超过原高锰酸钾。

During the in-situ chemical oxidation remediation process of low-permeability non-aqueous phase liquid,the consumption of oxidants by soil organic matter is inevitable.This makes it difficult to maintain the effective concentration of oxidants in the long term,and the concentration of pollutants is prone to rebound.This study managed to prepare sustained-release oxidation materials using the phase separation method,with stearic acid as the wall material and KMnO_(4) as the core material.Results showed that KMnO_(4) coated with stearic acid(PP@SA)had good sustained-release performance,which could last for more than 120 h.The orthogonal experimental results indicated that the optimal sustained-release lifespan was achieved when the core-shell ratio was 1∶3,ultrasound time was 15 min,stirring speed was 300 r∙min^(-1),and the particle size ranged from 1.12 to 4.00 mm.As the particle size of PP@SA and the amount of stearic acid increased,the sustained-release mechanism shifted from the Fickian diffusion to a mixed release mechanism involving both skeleton dissolution and Fickian diffusion.Moreover,in two low permeability soils,chalky clay and silty clay,PP@SA maintained a diffusion concentration of MnO4-above 0.25 g∙L^(-1) for 7 and 9 d,respectively.Its sustained release lifetime was significantly longer than that of the original potassium permanganate.