Chemistry Research

The objective this semester was to become familiar with the microwave equipment and determine a standard procedure for all oil digestions, and to complete the analysis of experiments conducted last semester. Each experiment is summarized below.

Experiment 1

Objective: To determine the best pressure to ensure a complete digestion of the sample and obtain the highest metal count.

Procedure: 0.25 g of use motor oil from Dr. Esterline's car was digested using 10 mL of nitric acid. The only difference between the digestions was the pressure at which it was held. The microwave was programmed to ramp to the desired pressure in 4.5 minutes and then held it there for 5 minutes.

Results:

Pressure (psi)	Results (total ppm)	Results (w/o Fe)	Appearance
550	4768	1201	clear/colorless/no oil
500	2195	1101	clear/colorless/no oil
450	2241	1032	clear/colorless/no oil
400	10730	1370	crystal clear/colorless/no oil residue
350	2535	1211	cloudy/slightly yellow/trace oil droplets
200	11137	1045	cloudy/yellow/oil droplets

Conclusions: 400 psi is the best pressure to digest the samples at and is now going to be used as a standard for all digestions. Digestion at higher pressures resulted in much longer cooling times needed after digestion. Also at these higher pressures, problems with sample loss when venting the digestion bomb was very difficult to avoid which probably accounts for the lower metal counts.

Problem: In all the samples the iron count fluctuates tremendously, thus if the iron is ignored the values are more consistent. What is the fluctuations in iron count caused by?

Experiment 2

Once the procedure for the digestion of samples was standardized (minus the temperature probe because it was not working), the microwave was used to digest samples of the different used motor oil sources being studied.

Objective: The objective is to determine an average metal count of the oils being studied to have data for comparisons after Dowex or Duolite treatments. A more specific goal was to prepare different used motor oil samples, each containing roughly the same amount of a particular metal. After doing so, each sample would be treated with the same ion-exchange resin (e.g. Duolite, Dowex, etc...) followed by microwave digestion and metal analysis (by ICP emission spectrometry in our own Water Quality Laboratory) to discover the metal preference for each ion-exchange polymer.

Procedure: Three samples of each oil were digested using 10 mL of nitric acid and microwaved at the 400 psi setting. A particular metal sulfate was added to one liter of used motor oil in an attempt to bring the metal level up to 1 Molar.

Results:

Oil	Purpose	Total metal count (ppm)
Nickel added	Metal preference studies	1275
Copper added	Metal preference studies	1155
Lead added	Metal preference studies	1478
All 3 metals added	Metal preference studies	1644
Dr. Esterline's car	Used for most experiments	928

Conclusions: Adding metal salts to the used motor oil in an attempt to bring metal levels up did not increase the metals levels substantially, but did succeed in increasing their levels to a point where they are close to the same concentration. Further analysis of these oil samples by treatment with ion-exchange resins will proceed.

Experiment 3

Objective: To determine the cause of the iron count fluctuations. Samples sent to be analyzed as being possible sources of iron contamination:

• Nitric acid diluted to 100 ml as done after digesting each oil sample
• Distilled water used for the dilutions
• Samples of nitric acid digested in the bombs without oil and then diluted with distilled water

Results: The results are not back from being analyzed but it is hypothesized that the extra Fe is coming from the rusty ceiling and hoods in our chemistry labs. Therefore precautions are being taken to avoid these sources of rust. Another possibility is that the fluctuation in metal count is being caused by (1) the 0.250 gram oil sample size not being large enough to give consistency or (2) the metal contaminants in the used motor oil are in particulates (small chunks suspended in the used motor oil) which would cause inconsistency from one oil sample to the next.

Experiment 4

Objective: To digest a 0.5 g and 1.0 g sample to see if it is possible to use a larger sample and get more consistent results.

Results: On all trials the microwave aborted the run due to a sample venting part way through the heating program. The larger sample size was producing too much of the gaseous digestion products, causing the pressure to climb beyond the safety limits of the high-pressure digestion bombs. Our research then turned to organic reactions using the microwave, specifically esterifications.

Summary of Research for Spring Semester 1997

Work Completed by: Lisa Schlater & David Ziemnik

Under the Supervision of: Dr. Daniel T. Esterline

The second focus of research this semester was with the oil project. Untreated Permafix oil was treated using a procedure provided by Permafix (an oil recycling company in Dayton, Ohio). The oil was treated with 6M sulfuric acid, mixed and then left to separate. The water layer was removed and the sample was centrifuged to remove the remaining water. Samples of the non-treated oil, the treated oil, and the sludge that was removed from the oil were digested by using the standard procedure. Batch systems were also conducted to test the metal removal ability of Dowex and Doulite. One gram of resin was added to 20 mL of treated Permafix oil. The system was left for one week and a sample was digested. Resins were also added to samples of oil with either nickel, copper, lead, or eleven metals added to it. This test was to determine of the resins had a preference between metals. Dowex MR-3 and Doulite C-280 were also tested to determine if they performed better than the Dowex and Doulite already being used. A batch system with consecutive treatments of samples was also conducted to determine a break through volume and to see how much of the metals can be removed.

Results:

1. The total metal content of the Permafix before the acid/centrifugation procedure was 12,000 ppm. After the treatment the metal count was down to 3,400 ppm.
   • How much metal would 3M or 12M acid remove?
   • Is it the acid removing the metals or is it the centrifugation process?
   • How much metal would be removed if the procedure was repeated: twice, three times?
2. In a comparison of the total metal count remaining after being treated with Dowex and Dowex-MR-3, and Doulite and Doulite-C-280, the numbers show that the Dowex already being used for most of the studies is better (plain Dowex), but Doulite-C-280 appears to be slightly better than the plain Doulite.
3. In looking at the data involving the oil with metal nitrates added, it appears that Dowex does a better job of removing the metals.

1. The results of the batch system are inconclusive for two reasons: The first is that not all of the series are completed and samples are still being analyzed in the water quality laboratory and secondly the number that have been obtained fluctuate between treatments. Instead of steadily decreasing the samples will be low and then the next week will be high. More analysis of how to eliminate the error in the data and to determine the problem with the procedure is needed.

Chemistry Home Page

Last modified: July 19, 1999. JG.