Hexavalent chromium in drinking water: Chemistry, challenges and future outlook on Sn(II)- and photocatalyst-based treatment

Abstract

• Wide occurrence of Cr(VI) in US source drinking water.

• A strong dependence of occurrence on groundwater sources.

• Elucidate Redox and equilibrium chemistry of Cr(VI).

• Sn(II)-based and TiO₂-based reductive treatments hold extreme promise.

• Key challenges include residual waste, Cr(VI) re-generation and socioeconomic drivers.

Chromium (Cr) typically exists in either trivalent and hexavalent oxidation states in drinking water, i.e., Cr(III) and Cr(VI), with Cr(VI) of particular concern in recent years due to its high toxicity and new regulatory standards. This Account presented a critical analysis of the sources and occurrence of Cr(VI) in drinking water in the United States, analyzed the equilibrium chemistry of Cr(VI) species, summarized important redox reaction relevant to the fate of Cr(VI) in drinking water, and critically reviewed emerging Cr(VI) treatment technologies. There is a wide occurrence of Cr(VI) in US source drinking water, with a strong dependence on groundwater sources, mainly due to naturally weathering of chromium-containing aquifers. Challenges regarding traditional Cr(VI) treatment include chemical cost, generation of secondary waste and inadvertent re-generation of Cr(VI) after treatment. To overcome these challenges, reductive Cr(VI) treatment technologies based on the application of stannous tin or electron-releasing titanium dioxide photocatalyst hold extreme promise in the future. To moving forward in the right direction, three key questions need further exploration for the technology implementation, including effective management of residual waste, minimizing the risks of Cr(VI) re-occurrence downstream of drinking water treatment plant, and promote the socioeconomic drivers for Cr(VI) control in the future.

Graphical abstract

Keywords

Chromium / Chemistry / Treatment / Future outlook

References

[1] Benjamin M M (2004). Water Chemistry. Chapter 12: Redox Chemistry. Long Grove: Waveland Press, Inc.

[2] Blute N, Wu X Y, Cron C, Abueg R, Froelich D, Fong L (2014). Hexavalent chromium treatment implementation in Glendale, Calif. Journal- American Water Works Association, 106(3): E160–E175

[3] Chebeir M, Chen G, Liu H (2016). Frontier review: Occurrence and speciation of chromium in drinking water distribution systems. Environmental Science. Water Research & Technology, 2(6): 906–914

[4] Chebeir M, Liu H (2016). Kinetics and mechanisms of Cr(VI) formation via the oxidation of Cr(III) solid phases by chlorine in drinking water. Environmental Science & Technology, 50(2): 701–710

[5] Chebeir M, Liu H (2018). Oxidation of Cr(III)–Fe(III) mixed-phase hydroxides by chlorine: Implications on the control of hexavalent chromium in drinking water. Environmental Science & Technology, 52(14): 7663–7670

[6] Chen G, Feng J, Wang W, Yin Y, Liu H (2017). Photocatalytic removal of hexavalent chromium by newly designed and highly reductive TiO₂ nanocrystals. Water Research, 108: 383–390

[7] Chen G, Liu H (2020). Photochemical removal of hexavalent chromium and nitrate from ion-exchange brine waste using carbon-centered radicals. Chemical Engineering Journal, 396: 125236

[8] Choi Y S, Shim J J, Kim J G (2004). Corrosion behavior of low alloy steels containing Cr, Co and W in synthetic potable water. Materials Science and Engineering, 385(1-2): 148–156

[9] Coyte R, McKinley K L, Jiang S, Karr J, Dryer G S, Keyworth A J, Davis C C, Kondash A J, Vengosh A (2020). Occurrence and distribution of hexavalent chromium in groundwater from North Carolina, USA. Science of the Total Environment, 711: 135135

[10] Eary E L, Rai D (1987). Kinetics of chromium(III) oxidation to chromium(VI) by reaction with manganese dioxide. Environmental Science & Technology, 21(12): 1187–1193

[11] Eary L E, Rai D (1988). Chromate removal from aqueous wastes by reduction with ferrous iron. Environmental Science & Technology, 22(8): 972–977

[12] Gonzalez S, Lopez-Roldan R, Cortina J L (2013). Presence of metals in drinking water distribution networks due to pipe material leaching: A review. Toxicological and Environmental Chemistry, 95(6): 870–889

[13] Henrie T, Plummer S, Orta J, Bigley S, Gorman C, Seidel C, Shimabuku K, Liu H (2019). Full-scale demonstration testing of hexavalent chromium reduction via stannous chloride application. AWWA Water Science, 1(2): e1136

[14] Hering J G, Harmon T C (2004). Geochemical controls on chromium occurrence, speciation, and treatability. Water Research Foundation Report. Denver, USA

[15] Izbicki J A, Groover K (2018). Natural and man-made hexavalent chromium, Cr(VI), in groundwater near a mapped plume, Hinkley, California—study progress as of May 2017, and a summative-scale approach to estimate background Cr(VI) concentrations. U.S. Department of the Interior – U.S. Geological Survey. Reston, Virginia

[16] Jacobs J, Testa S M (2005). Cr(VI) Handbook. Boca Raton: CRC Press

[17] Kennedy A, Croft R, Flint L, Arias‐Paić M (2020). Stannous chloride reduction–filtration for hexavalent and total chromium removal from groundwater. AWWA Water Science, 2(2): e1174

[18] Loeb S K, Alvarez P J, Brame J A, Cates E L, Choi W, Crittenden J, Dionysiou D D, Li Q, Li-Puma G, Quan X, Sedlak D L, Waite T D, Westerhoff P, Kim J H (2019). The technology horizon for photocatalytic water treatment: sunrise or sunset? Environmental Science & Technology, 53(6): 2937–2947

[19] Oze C, Bird D K, Fendorf S (2007). Genesis of hexavalent chromium from natural sources in soil and groundwater. Proceedings of the National Academy of Sciences of the United States of America, 104(16): 6544–6549

[20] Oze C, Fendorf S, Bird D K, Coleman R G (2004). Chromium geochemistry in serpentinized ultramafic rocks and serpentine soils from the Franciscan complex of California. American Journal of Science, 304(1): 67–101

[21] Pan C, Liu H, Catalano J G, Qian A, Wang Z M, Giammar D E (2017). Rates of Cr(VI) generation from Cr_xFe_1–x(OH)₃ solids upon reaction with manganese oxide. Environmental Science & Technology, 51(21): 12416–12423

[22] Pan C, Troyer L D, Catalano J G, Giammar D E (2016). Dynamics of chromium (VI) removal from drinking water by iron electrocoagulation. Environmental Science & Technology, 50(24): 13502–13510

[23] Pan Z, Zhu X, Satpathy A, Li W, Fortner J D, Giammar D E (2019). Cr(VI) adsorption on engineered iron oxide nanoparticles: Exploring complexation processes and water chemistry. Environmental Science & Technology, 53(20): 11913–11921

[24] Peng C Y, Hill A S, Friedman M J, Valentine R L, Larson G S, Romero A M Y, Reiber S H, Korshin G V (2012). Occurrence of trace inorganic contaminants in drinking water distribution systems. Journal- American Water Works Association, 104(3): E181–E193

[25] Percival S L, Knapp J S, Edyvean R G J, Wales D S (1998). Biofilms, mains water and stainless steel. Water Research, 32(7): 2187–2201

[26] Plummer S, Gorman C, Henrie T, Shimabuku K, Thompson R, Seidel C (2018). Optimization of strong-base anion exchange O&M costs for hexavalent chromium treatment. Water Research, 139: 420–433

[27] Seidel C J, Najm I N, Blute N K, Corwin C J, Wu X Y (2013). National and California treatment costs to comply with potential hexavalent chromium MCLs. Journal- American Water Works Association, 105(6): E320–E336.

[28] United States Environmental Protection Agency (2015). Unregulated Contaminant Monitoring Rule 3 (UCMR3). Access at the website of

[29] Vengosh A, Coyte R, Karr J, Harkness J S, Kondash A J, Ruhl L S, Merola R B, Dywer G S (2016). Origin of hexavalent chromium in drinking water wells from the piedmont aquifers of North Carolina. Environmental Science & Technology Letters, 3 (12): 409–414

RIGHTS & PERMISSIONS

Higher Education Press