Method 1313 – pH-dependence
Method 1313: Liquid-Solid Partitioning (LSP) as a Function of Eluate pH for Constituents in Solid Materials Using a Parallel Batch Extraction Procedure
Summary:
Method 1313 test is designed to provide the liquid-solid partitioning curve of constituents as a function of eluate pH. The method consists of parallel batch extractions of solid material, each with an aliquot of either dilute acid or base. The acid or base added to each extract is determined from a prior knowledge of the neutralization capacity of the material or from a pre-test titration step. Parallel extractions provide aqueous extracts at nine target pH value from pH 2 through 13 plus the natural pH of the material (i.e., when no acid or base is added). In order to facilitate the approach to equilibrium, paricle size reduction of material samples may be required. Eluate concentrations for constituents of potential concern (COPCs) are plotted as a function of eluate pH and may be compared to quality control and assessment limits for interpretation of method results.
Detailed Description:
Method 1313 is used to determine the liquid-solid partitioning (LSP) between water and a solid material at equilibrium over a broad range of pH. The procedure is comprised of nine parallel batch extractions of particle-size reduced material over a pH range between 2 and 13 by the addition of pre-determined amounts of acid or base to achieve specified final pH values.
A known mass of solid material is placed in each of nine extraction vessels and contacted with water at a liquid-solid ratio (L/S) of 10 mL/g-dry. Nitric acid or sodium hydroxide is added to each vessel to obtain a specified final pH value based on a pre-test titration curve. The nine vessels are tumbled in an end-over-end fashion for a time comensurate with the maximum particle-size. Eluate pH and conductivity are recorded. Analytical samples are filtered and preserved for chemical analysis.
Constituent concentrations [mg/L] or mass release [mg/kg] are plotted as a function of eluate pH. Constituent concentrations over the pH range typically show characterisitic LSP behavior for cationic, amphoteric, oxyanionic and high soluble species. The results of this test are used to (i) obtain maximum (available) release values, (ii) show equilibrium concentrations when the environment dominates pH. Results form the basis for geochemical speciation modeling of release-controlling phases.
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Overview Presentation of Method 1313