Performance and mechanisms of immobilization remediation for Cd contaminated water and soil by hydroxy ferric combined acid-base modified sepiolite (HyFe/ABsep)

In order to simultaneously improve the remediation capability of Cd contaminated water and soil, hydroxy iron-ABsep (HyFe/ABsep) was synthesized by a two-step modified (acid-base composite treatment, and hydroxy group was by using NaOH and Fe (NO3)3·9H2O). Results showed that HyFe/ABsep had developed pores and a rougher surface morphology, and the salt-soluble ion content was increased, surface-loaded iron species was mainly composed of FeOOH. Adsorption process of Cd2+ by HyFe/ABsep conformed best to the preudo-second-order model and Redlich-Paterson models, respectively. The behavior over a whole range of adsorption was consistent with chemical adsorption being the rate-controlling step and the theoretical maximum adsorption capacity obtained for the HyFe/ABsep was 220.9 mg·g−1 at 298 K, which was 4.87 times than Sep. HyFe/ABsep also had a more excellent passivation effect on available Cd in soil, being 36.83%–48.46% under the treatments of 0.5%–4% HyFe/ABsep, The structure and morphology of HyFe/ABsep were characterized through SEM-EDS, TEM, FTIR, XRD and XPS indicated that the mainly mechanisms of Cd sorption may include precipitates, ion exchange and complexation of active silanol groups. Therefore, HyFe/ABsep can employ as an effective agent for immobilization remediation of Cd contaminated water and soil. [Display omitted] •An eminent cadmium adsorption material was synthesized by a two-step modified sepiolite.•HyFe/ABsep possesses an excellent adsorption capacity for Cd2+ in solution.•HyFe/ABsep were further used to immobilize Cd in soils.•Effects and mechanisms involved in Cd immobilization was proposed.