Exploring the Sorption Mechanism of Ni(II) on Illite: Batch Sorption, Modelling, EXAFS and Extraction Investigations.

ABSTRACT: The sorption mechanism of nickel (Ni) at the illite/water interface was investigated using batch, sorption modelling, extended X-ray absorption fine structure (EXAFS), and extraction approaches. The results showed that Ni(II) sorption on illite was strongly dependent on pH, contact time, temperature, and initial Ni(II) concentration. At a low initial Ni(II) concentration, the ion exchange species of ?X₂Ni° and the inner-sphere complexes including ?S^sONi⁺, ?S^wONi⁺ and ?S^wONiOH° species are observed on the sorption edges of Ni(II) on illite. As the initial Ni(II) concentration increased to 1.7?×?10^-3?mol/L, precipitates including surface-induced precipitation of s-Ni(OH)₂ and amorphous Ni(OH)₂ became more significant, especially under neutral to alkaline conditions. EXAFS analysis confirmed that Ni-Al layered double hydroxide (LDH) can gradually form with an increase in the contact time. At pH 7.0, ?-Ni(OH)₂ was produced in the initial stage and then transformed to the more stable form of Ni-Al LDH with increasing contact time because of the increased Al³⁺ dissolution. With an increase in temperatures, ?-Ni(OH)₂ phase on illite transformed to Ni-Al LDH phase, indicating a lower thermodynamic stability compared to Ni-Al LDH phase. These results are important to understand the geochemical behaviors to effectively remediate soil contaminated with Ni(II).

SUBMITTER: Zhao X 

PROVIDER: S-EPMC5561197 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature