Efficient novel amphiphilic double shells layer coupled with nanoscale zero-valent composite for the degradation of trichloroethylene.

An efficient novel amphiphilic material composed of core-double shells nanocomposite (CDSN) with nanoscale zero-valent iron (NZVI) as the core and PS-b-PAA as inner shell and chitosan as outmost shell has been synthesized successfully. Its application to remove the trichloroethylene (TCE) in stimulated TCE solution with 7.3 ± 0.3 mg/L dissolved oxygen was investigated. The results showed that CDSN after exposure to air for a month could still remove 92.6% of TCE as compared to 61.5% removal rate of NZVI in 360 min (the gram ratio of material: TCE equals to 10:1), exhibiting the great oxidation resistance performance. Specifically, dynamic research of the total removal divided into adsorption by shell layer and degradation by reducibility of NZVI at a predetermined interval was engaged to understand the complete mass transfer process of TCE. The results revealed that CDSN adsorbed 1.5 to 2 folds time TCE as compared to NZVI in the same initial pH = 8.5 aqueous solution. Importantly, CDSN could sustain fixed reactivity to remove about 94.8% of TCE from the start to end. NZVI exhibited greater removal capacity in first 180 min, but later it lost the reducibility and finial removal rate was 89%. The selective adsorption to protonated CDSN was strengthened to increase the removal of TCE at pH 3.5 while NZVI had a worse removal in pH 3.5 performance than pH 8.5.