TY - JOUR
T1 - Mobility and bioaccessibility of arsenic (As) bound to titanium dioxide (TiO2) water treatment residuals (WTRs)
AU - Zimmerman, Amanda Jo
AU - Garcia Gutierrez, Danira
AU - Shaghaghi, Negar
AU - Sharma, Aakriti
AU - Deonarine, Amrika
AU - Landrot, Gautier
AU - Weindorf, David C.
AU - Siebecker, Matthew G.
N1 - Publisher Copyright:
© 2023 Elsevier Ltd
PY - 2023/6/1
Y1 - 2023/6/1
N2 - This work systematically describes arsenic mobility and potential bioaccessibility of arsenic-enriched titanium dioxide water treatment residuals (TiO2 WTRs) by employing a suite of wet chemical experiments and spectroscopic measurements. Specifically, Environmental Protection Agency (EPA) digestion method 3051a indicated <3% of total arsenic in the solid phase was released, and arsenic assessed by EPA method 1340 for bioaccessibility was below detection limits. A novel finding is while the arsenic appeared to be stable under highly acidic digestion conditions, it is in fact highly mobile when exposed to simple phosphate solutions. On average, 55% of arsenic was extracted from all samples during a 50-day replenishment study. This was equivalent to 169 mg kg−1 arsenic released from the solid phase. Macroscopic desorption experiments indicated arsenic likely formed inner-sphere bonds with the TiO2 particles present in the samples. This was confirmed with X-ray absorption spectroscopy (XAS), where an interatomic distance of 3.32 Å and a coordination number (CN) of 1.79 titanium atoms were determined. This translates to a configuration of arsenic on TiO2 surfaces as a bidentate binuclear inner-sphere complex. Thus, both macroscopic and spectroscopic data are in agreement. During incubation experiments, arsenic(V) was actively reduced to arsenic(III); the amount of arsenic(III) in solution varied from 8 to 38% of total dissolved arsenic. Lastly, elevated concentrations and mobility of vanadium in these systems merit further investigation. The high mobility of arsenic and its potential for reduction when reintroduced into the environment, particularly in agriculturally important areas, presents an important risk when waste products are not properly managed.
AB - This work systematically describes arsenic mobility and potential bioaccessibility of arsenic-enriched titanium dioxide water treatment residuals (TiO2 WTRs) by employing a suite of wet chemical experiments and spectroscopic measurements. Specifically, Environmental Protection Agency (EPA) digestion method 3051a indicated <3% of total arsenic in the solid phase was released, and arsenic assessed by EPA method 1340 for bioaccessibility was below detection limits. A novel finding is while the arsenic appeared to be stable under highly acidic digestion conditions, it is in fact highly mobile when exposed to simple phosphate solutions. On average, 55% of arsenic was extracted from all samples during a 50-day replenishment study. This was equivalent to 169 mg kg−1 arsenic released from the solid phase. Macroscopic desorption experiments indicated arsenic likely formed inner-sphere bonds with the TiO2 particles present in the samples. This was confirmed with X-ray absorption spectroscopy (XAS), where an interatomic distance of 3.32 Å and a coordination number (CN) of 1.79 titanium atoms were determined. This translates to a configuration of arsenic on TiO2 surfaces as a bidentate binuclear inner-sphere complex. Thus, both macroscopic and spectroscopic data are in agreement. During incubation experiments, arsenic(V) was actively reduced to arsenic(III); the amount of arsenic(III) in solution varied from 8 to 38% of total dissolved arsenic. Lastly, elevated concentrations and mobility of vanadium in these systems merit further investigation. The high mobility of arsenic and its potential for reduction when reintroduced into the environment, particularly in agriculturally important areas, presents an important risk when waste products are not properly managed.
KW - Arsenic
KW - Drinking water
KW - Mobility
KW - Speciation
KW - Titanium
UR - http://www.scopus.com/inward/record.url?scp=85151036324&partnerID=8YFLogxK
U2 - 10.1016/j.envpol.2023.121468
DO - 10.1016/j.envpol.2023.121468
M3 - Article
C2 - 36958654
AN - SCOPUS:85151036324
SN - 0269-7491
VL - 326
JO - Environmental Pollution
JF - Environmental Pollution
M1 - 121468
ER -