Remediation of arsenic–cationic metals from smelter contaminated soil by washings of Na₂EDTA and phosphoric acid: removal efficiencies and mineral transformation

ABSTRACT

Sequential and combined soil washing tests of Na₂EDTA and phosphoric acids were conducted to remediation soil contaminated with arsenic and cationic metals (cadmium, copper, and lead) at a former metal smelter. The aim of the testing was to improve the heavy metals removal efficiency and investigate the mechanism of the influence of soil minerals on washing efficiency, including the influence on soil mineral, metal oxides, and functional groups of soil surface. The results indicated that the combined washing of Na₂EDTA and phosphoric acid was effective in removing both arsenic and cationic metals from contaminated soil and had synergy effect for most target metals. The results of metal removal efficiency indicated that the washing agent, washing mode, and washing times influenced the removal efficiencies of arsenic and cationic metals. The spectroscopic analysis demonstrated that sequential and combined washings were effective in dissolving and reforming soil minerals compared with single washing. The promoted complexation, ligand exchange, desorption, and inhibition of adsorption resulted in the synergistic effect for most target metals under combined washing.

GRAPHICAL ABSTRACT

KEYWORDS:

• Combined washing
• contaminated soil
• minerals transformation
• oxide species
• spectroscopic analysis

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Chuan-Hai Xia http://orcid.org/0000-0001-8005-0136

Additional information

Funding

This research was supported by the Research Fund for the Doctoral Program of Higher Education [20120003110033]; Yantai Key Research and Development Plan [2019XDHZ103].