Preparation of coated slow-release oxidants and evaluation of their slow-release performance
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 KMnO4 as the core material.Results showed that KMnO4 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.
in-situ chemical oxidationsustained-releaseKMnO4low permeability soil
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