A superhydrophobic nZVI/Chitin/PDMS porous composite for removal of trichloroethylene and nitrobenzene from groundwater.

Aiming to improve the affinity between nano-zero-valent iron (nZVI) and hydrophobic organic contaminants and avoid its unexpected corrosion in water, a superhydrophobic nZVI porous composite was fabricated in the present study. This composite was prepared using a chitin nanofiber/polydimethylsiloxane matrix via an emulsion-template method, and systematic optimization of the emulsion composition, the nZVI loading strategy and content was conducted. The optimized composite nZVI(PSE)@ChP achieved homogeneous superhydrophobicity (water contact angle as high as 155.9°), robust mechanical resilience and high porosity. This composite could selectively remove non-aqueous phase liquid trichloroethylene (TCE) and nitrobenzene (NB) from water with adsorption capacity of 1315 wt% and 721.8 wt%, respectively. It could be reused for at least 20 times via simple mechanical squeezing. It also demonstrated significantly higher removal efficiency towards aqueous-phase pollutants than bare nZVI, achieving 88.44% for TCE and 100% for NB. The removal kinetics under various environmental factors were then investigated. nZVI(PSE)@ChP also showed enhanced anti-aging performance in oxic water, maintaining 78.59% TCE removal after 30 days of aging. The removal mechanisms were revealed as contaminant specific: NB underwent direct electron transfer reduction by nZVI, whereas TCE removal involved adsorption followed by sequential β-elimination and hydrogenolysis pathways. Column experiments further demonstrated the potential of nZVI(PSE)@ChP as a permeable reactive barrier filler for groundwater remediation. This study provides novel insights for the design of highly reactive nanomaterials and the targeted remediation of organic pollutants in groundwater.