Shell biomass material supported nano-zero valent iron to remove Pb²⁺ and Cd²⁺ in water

Nanoscale zero-valent iron (NZVI) has a high adsorption capacity for heavy metals, but easily forms aggregates. Herein, preprocessed undulating venus shell (UVS) is used as support material to prevent NZVI from reuniting. The SEM and TEM results show that UVS had a porous layered structure and NZVI particles were evenly distributed on the UVS surface. A large number of adsorption sites on the surface of UVS-NZVI are confirmed by IR and XRD. UVS-NZVI is used for adsorption of Pb²⁺ and Cd²⁺ at pH = 6.00 in aqueous solution, and the experimental adsorption capacities are 29.91 and 38.99 mg g^-1 at optimal pH, respectively. Thermodynamic studies indicate that the adsorption of ions by UVS-NZVI is more in line with the Langmuir model when Pb²⁺ or Cd²⁺ existed alone. For the mixed solution of Pb²⁺ and Cd²⁺, only the adsorption of Pb²⁺ by UVS-NZVI conforms to the Langmuir model. In addition, the maximum adsorption capacities of UVS-NZVI for Pb²⁺ and Cd²⁺ are 93.01 and 46.07 mg g^-1, respectively. Kinetic studies demonstrate that the determination coefficients (R ²) of the pseudo first-order kinetic model for UVS-NZVI adsorption of Cd²⁺ and Pb²⁺ are higher than those of the pseudo second-order kinetic model and Elovich kinetic model. Highly efficient performance for metal removal makes UVS-NZVI show potential application to heavy metal ion adsorption.