Effects of Selected Good’s pH Buffers on Nitrate Reduction by Iron Powder

Abstract

The effects of three selected Good’s pH buffers on the performance of an Fe0 ∕nitrate∕ H2 O system were evaluated. The Good’s pH buffer itself did not reduce nitrate directly. Nitrate reduction by iron powder at near-neutral pH was negligible in an unbuffered system, but it was greatly enhanced with the presence of the buffer. A significant amount of aqueous Fe2+ (or Fe3+ ) was released after adding the Good’s pH buffer into the Fe0 ∕ H2 O system with or without nitrate. In general, the pH of the buffered solution increased from the initial pH ( =∼4.6–5.3 , depending on buffer’s pKa ) to near-neutral pH. After the initial pH hiking, the pH in the system was more or less stable for a period of time ( ∼5–10 h , usually concurrent with a fairly stable aqueous Fe2+ ). The pH then drifted to ∼7.1 to 8.6, depending on the buffer’s initial concentration, the buffer’s pKa , and the consumption of Fe2+ concurrent with nitrate reduction. While a common assumption made by researchers is that Good’s pH buffers do not...