Kaolinite loaded amorphous zero-valent iron enhanced removal of cadmium (II) from aqueous solution

Amorphous materials tend to have excellent chemical reactivity, which provides us with a new idea to amorphize zero-valent iron (ZVI) to enhance its activity. Therefore, in this study, amorphous zero-valent iron (AZVI) was synthesized by introducing ethylenediamine (EDA) and loaded on kaolinite to prepare a composite material (K-AZVI) for enhancing the removal of cadmium (II) (Cd(II)) in water. SEM and XRD were used to characterize the structure and morphology of the samples, and the microstructure of the composites was studied by TEM, FTIR, and XPS. The results showed that the spherical AZVI particles were dispersed and loaded on kaolinite in a “core-shell” structure. Compared with the crystalline composite (K-ZVI), K-AZVI had a larger particle size and better electron transfer ability. The adsorption process of K-AZVI for Cd(II) conformed to the pseudo-second-order kinetic model. When K-AZVI (dosage = 1.00 g/L, EDA/Fe(II) = 2, pH = 5.0, and T = 298 K) was mixed with Cd(II) (50 mg/L), the removal rate could reach more than 90% within 20 min. The mechanism of removing Cd(II) was mainly the synergistic effect of the corrosion products of K-AZVI and Cd(II) adsorption and co-precipitation. During the reaction, more γ-FeOOH was generated on the surface of K-AZVI, which had a high affinity for Cd(II). Therefore, K-AZVI has great potential for the remediation of Cd(II) in water.