Summary
Steward has been routinely sending samples to an EPA certified lab to conduct TCLP tests. Steward stopped performing in-house TCLP tests per EPA method and Battelle’s protocol. This report provides the information on TCLP testing results by an EPA certified lab, as well as how Steward and Battelle conducted TCLP tests and the testing results. Thiol-SAMMS was tested against TCLP requirements in at least three instances. The first two, conducted by Battelle and Steward, had slight deviations from strict EPA 1311 protocol. Battelle reported the results of a modified TCLP test in the report “Self-Assembled Mercaptan on Mesoporous Supports (SAMMS) Technology for Mercury Removal and Stabilization,” PNNL-11691 UC-2030, Sept. 1997. The Battelle evaluation also reported results of separate evaluation of RCRA metals. In that test resultant concentrations of mercury, silver and lead were reduced below TCLP standards. Steward also has conducted TCLP tests. An outside EPA certified lab conducted TCLP tests following strict EPA protocol. Thiol-SAMMS passed all of these evaluations.
Procedure & Results - Battelle
Battelle used a modified method. They began with a sample mass of ~1 g (dry basis) rather than the required 100g due to limited amounts available in 1997. The SAMMS had ~ 80% surface functionalization of the theoretically available sites to tether the silane. (Deviation from 1131) The contacting solution was a spiked 0.1M NaNO3 aqueous solution of 200 ppmw mercury concentration. The solution to solids (adsorbent) ratio was 2000 cc/gram. The sample was stirred in contact solution.
After contacting for sufficient time to saturate the thiol-SAMMS, the loaded SAMMS was filtered and rinsed with aliquots of DI water until the pH of rinsate was the same as the fresh DI water. The SAMMS thus obtained was added to sodium acetate, pH=4.7 per method 1311using a solid to solution ratio of 20 cc/g and held 24 hours. The sample was extracted over 8 hours +/- 2 hours. The analysis is in Table 1.
An additional assessment was performed on a waste water sample containing RCRA metals. The analysis is in Table 2. This SAMMS sample was one made with only ~25% surface functionalization of the theoretically available surface sites.
Table 1 TCLP Leachate Concentration, ppm
| Sample pH | Hg | Ag | Cr | Pb | Ba | Ni | Zn |
|---|---|---|---|---|---|---|---|
| 3 | 0.0006 | 0 | 0.07 | 0 | 0.58 | 0.06 | 0.33 |
| 7 | 0.0006 | 0 | 0 | 0 | 0.55 | 0 | 0.31 |
| 9 | 0.0002 | 0 | 0 | 0 | 0.44 | 0 | 0.3 |
| EPA TCLP | 0.2 | 5.0 | 5.0 | 5.0 | 100 | - | - |
| Land disposal. limit | - | 0.072 | 5.2 | 0.51 | - | - | 0.32 |
| Drinking water limit | 0.002 | - | - | - | - | - | - |
Table 2. RCRA Metals in Waste Water Sample before and after Treatment with SAMMS, ppmw
| Sample pH | Hg | Ag | Cr | Pb | Ba | Ni | Zn |
|---|---|---|---|---|---|---|---|
| Before | |||||||
| 3 | 6.20 | 1.80 | 1.79 | 7.22 | 7.18 | 3.96 | 2220 |
| 7 | 6.00 | 0.45 | 1.13 | 5.25 | 7.12 | 2.75 | 2212 |
| 9 | 6.35 | 1.04 | 0.58 | 2.90 | 7.15 | 1.32 | 2222 |
| After | |||||||
| 3 | 0.0008 | <0.005 | 1.67 | 2.26 | 8.64 | 5.06 | 2185 |
| 7 | 0.0008 | <0.05 | 0.07 | 0 | 8.21 | 1.54 | 2114 |
| 9 | 0.0007 | <0.005 | 0 | 0 | 8.82 | 1.19 | 2201 |
| EPA TCLP | 0.2 | 5.0 | 5.0 | 5.0 | 100 | - | - |
| Land disposal. limit | - | 0.072 | 5.2 | 0.51 | - | - | 0.32 |
| Drinking water limit | 0.002 | - | - | - | - | - | - |
Procedure & Results - Steward
Steward conducted TCLP tests prior to receiving details of the Battelle method. A weight of SAMMS of 2 g was used. After contacting, the sample was collected and washed in ~1 liter/g excess water. Steward used the same contacting solution, spiked 0.1M NaNO3 aqueous solution of 200 ppmw mercury concentration. The solution to solids (adsorbent) ratio was 2000 cc/gram. Sample was stirred in contact solution. Please note the different rinsing condition compared to the Battelle procedure.
The rinsed and dried sample was submitted to Applied Technical Services, Chattanooga, TN for TCLP measurement. Mercury was measured using EPA method 245.1. The reported mercury concentration was 0.1 ppm. That surpasses the TCLP limit. The higher number compared to Battelle probably reflects the different rinsing practice.
Steward points out the mercury capacity in contact with a solution containing 20 ppm mercury is significantly higher than one in contact with a solution of 30 ppb. It is possible SAMMS exposed to 30ppb would pass TCLP with no rinsing.
Procedure & Results – an EPA certified lab
An outside lab certified by EPA has been used to conducted TCLP tests for mercury laden SAMMS after two field trial tests on customer sites. Please note that the mercury laden SAMMS passes TCLP without any rinsing. This enabled the used adsorbents to be disposed of in a non-hazardous landfill without generating secondary waste.