Bioremediation of arsenic-contaminated groundwater by sequestration of arsenic in biogenic pyrite. (September 2018)

• Record Type: Journal Article
• Authors: Saunders, James A.; Lee, Ming-Kuo; Dhakal, Prakash; Ghandehari, Shahrzad Saffari; Wilson, Ted; Billor, M. Zeki; Uddin, Ashraf
• Is Part Of: Applied geochemistry. Volume 96(2018)
• Page Start: 233
• Page End: 243
• Publication Date: 2018-09
• Subjects: Arsenic -- Sulfate reducing bacteria -- Bioremediation -- Arsenian pyrite; Environmental geochemistry -- Periodicals; Water chemistry -- Periodicals; Geochemistry -- Social aspects -- Periodicals; Geochemistry -- Periodicals; 551.9
• DOI: 10.1016/j.apgeochem.2018.07.007
• Languages: English
• ISSNs: 0883-2927

Abstract

Abstract: Pyrite (FeS2 ) is the most common sulfide mineral in the Earth's crust, and it commonly contains minor amounts of arsenic. Here we show that authigenic pyrite can remove arsenic from contaminated groundwater and this can be used as a new and relatively inexpensive remediation process. Laboratory batch experiments presented show that fine-grain natural pyrite is an effective sorber of dissolved arsenic. Arsenic sorption onto pyrite is shown to increase with increasing pH, particularly at pH > 5 and at elevated dissolved arsenic concentration. We also present results from a field experiment at an arsenic-contaminated industrial site, which demonstrates the results of stimulation of natural sulfate-reducing bacteria in groundwater by injection of a labile organic carbon source, iron, and sulfate. Within a week, bacterial sulfate reduction triggered the formation of biogenic pyrite nanoparticles, which sequestered arsenic by adsorption and co-precipitation. Microscopic and X-ray diffraction analyses confirmed that pyrite was the only iron-sulfide formed, and that no arsenic-only sulfide phase precipitated (e.g. orpiment or realgar). Pyrite occurs as either 1–10 μm euhedral crystals or similar-sized framboids both of which contain 500–4000 mg/kg arsenic. As a result, dissolved arsenic decreased from its initial concentration of 0.3–0.5 mg/L to below the regulatory clean-up standard for the site of 0.05 mg/L in a matter of weeks. In addition to the potential of this technique to remediate anthropogenic arsenic contamination, it is possible that it can be modified to inexpensively treat individual small drinking-water wells contaminated by natural sources of arsenic in many developing nations. Highlights: By injecting ferrous sulfate and molasses, SRB were stimulated to form biogenic arsenian pyrite that removed the bulk of dissolved arsenic.. Arsenic sequestration results from initial sorption and then later incorporation into the growing pyrite crystal lattice. Arsenian pyrite is the most insoluble and stable sulfide phases with greater capability of removing dissolved arsenic than other arsenic-bearing solids. Optimization of this process could lead to an effective remediation of groundwater contaminated by anthropogenic or natural arsenic sources.