Comparing three stabilizers for stabilizing FeS nanoparticles: Performance and effects on immobilization of cadmium in water and soil

In this study, we evaluated effectiveness of three polysaccharide stabilizers (sodium carboxymethyl cellulose (CMC), sodium carboxymethyl starch (CMS), and a water-soluble starch) for stabilizing FeS nanoparticles, and tested the stabilized nanoparticles for immobilization of Cd²⁺ in water and soil. Fully stabilized FeS nanoparticles (100 mg/L FeS) were obtained using 0.010 wt% CMC, 0.025 wt% CMS, or 0.065 wt% starch. CMC-FeS showed a highly negative zeta potential, starch-FeS remained neutral, whereas CMS-FeS displayed a moderately negative potential. CMC-FeS showed the fastest sorption rate and highest sorption capacity for Cd²⁺. When a Cd-laden soil (58.3 mg/kg Cd) was amended with 100 mg/L CMC-FeS or CMS-FeS, the TCLP-leachable Cd was reduced by 88.4% and 68.0%, respectively. Both CMC-FeS and CMS-FeS were transportable through a model soil and showed high potential for in-situ immobilization of Cd²⁺ in soil. Nearly complete breakthrough occurred at 4.5 pore volumes (PVs) for CMC-FeS and about 25 PVs for CMS-FeS. When the Cd-laden soil was treated with 55 PVs of CMC-FeS and CMS-FeS suspensions (100 mg/L), the water-leachable soluble Cd was reduced by 98.2% and 98.0%, respectively. The three stabilizers may find their best uses in soil remediation according to the target contaminants, transport properties in soil, and material cost.