Removal of radium from groundwater using a modified bauxite refinery residue

Removal of radium from groundwater using a modified bauxite refinery residue

Radium (Ra) removal by an unconventional sorbent, a
modified bauxite refinery residue (MBRR), is investigated
for a groundwater extracted in Missouri, USA. Th e MBRR
treatment causes substantial reductions of both gross α and
combined 226/228Ra activities from 0.955 ± 0.005 and 0.66
± 0.005 Bq L−1 to below detection limits (0.037 Bq L−1 or
1 pCi L−1). Column breakthrough occurs at 0.555 Bq L−1
for gross α and 0.185 Bq L−1 for combined 226/228Ra (15 and
5 pCi L−1; USEPA’s maximum contaminant levels) after 54
and 40 d run time, respectively. At 84 d the MBRR media
continues to remove 24.3% of raw water gross α and 39.7%
of the combined 226/228Ra. The treatment effluent has an
initial pH of 10.9, outside the USEPA guides (6.5–8.5); this
may be readily mitigated by posttreatment acid injection, or
by raw water blending. The MBRR simultaneously removes
other potentially hazardous trace elements (e.g., Cu, Zn,
and Fe) to extremely low concentrations. In addition,
toxicity characteristic leaching procedure testing of spent
MBRR suggests that metals are bound tightly, such that it is
nonhazardous, permitting cost-effective disposal to landfill without special confinement or storage. Consequently,
MBRR may be utilized as an alternative adsorbent for
treating Ra-contaminated groundwater.

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