Surface modification of ferrous sulfide nanosheets for in-situ remediation of cadmium-contaminated groundwater.

Ferrous sulfide (FeS) nanomaterials exhibit promising remediation activities for heavy metals via adsorption, precipitation, reduction, etc. However, traditional chemical reduction or biosynthesis-prepared FeS nanomaterials tend to be agglomerated and oxidized easily, which reduces their reactivity, influence radius, and long-term performance for in-situ reaction zone technology to remediate contaminant plumes in a low permeability aquifer. Here, we proposed a one-step pyrolysis method to prepare scalable FeS nanosheets with carbon composites and ultrathin features. After modification with the surfactant sodium dodecyl benzene sulfonate (SDBS), the resulting FeS-SDBS slurry exhibited high reactivity toward Cd(II), achieving a removal capacity of 163.3 mg/g, along with excellent suspension stability and enhanced oxidation resistance. Moreover, the incorporated surfactant modification of FeS nanosheets to form the inorganic-organic complex was found to tune the surface electrostatic potentials and charge densities as well as increase the elastic deformation, resulting in the enhanced influence radius of 2.1 times compared to bare FeS nanosheets, and the efficient immobilization of Cd(II) in the clay column. Furthermore, X-ray micro-computed tomography revealed the spatial distribution of FeS nanosheets during injection, accompanied by an 18.2 % reduction in the original total porosity. This study demonstrates the potential of FeS nanosheets as an efficient slurry for in-situ remediation of groundwater in low-permeability aquifers.