Interlaboratory study of the reproducibility of the single-pass flow-through test method : measuring the dissolution rate of LRM glass at 70 {sup {degree}}C and pH 10.

Abstract

An international interlaboratory study (ILS) was conducted to evaluate the precision with which single-pass flow-through (SPFT) tests can be conducted by following a method to be standardized by the American Society for Testing and Materials - International. Tests for the ILS were conducted with the low-activity reference material (LRM) glass developed previously for use as a glass test standard. Tests were conducted at 70 {+-} 2 C using a LiCl/LiOH solution as the leachant to impose an initial pH of about 10 (at 70 C). Participants were provided with LRM glass that had been crushed and sieved to isolate the -100 +200 mesh size fraction, and then washed to remove fines. Participants were asked to conduct a series of tests using different solution flow rate-to-sample mass ratios to generate a range of steady-state Si concentrations. The glass dissolution rate under each test condition was calculated using the steady-state Si concentration and solution flow rate that were measured in the test. The glass surface area was estimated from the mass of glass used in the test and the Si content of LRM glass was known. A linear relationship between the rate and the steady-state Si concentration (at Si concentrations less than 10 mg/L) was used to estimate the forward dissolution rate, which is the rate in the absence of dissolved Si. Participants were asked to sample the effluent solution at least five times after reaction times of between 3 and 14 days to measure the Si concentration and flow rate, and to verify that steady-state was achieved. Results were provided by seven participants and the data sets provided by five participants were sufficient to determine the forward rates independently.