BACKGROUND:

1. Determination of the Composition of Chrome Plating BathsK. Andrzejewski1,2*, Y.E. Oh1,2*, J. Podell1,2*, M. Lieberman1; 1University of Notre Dame, Notre Dame, Indiana 46556; 2Marian High School, Mishawaka, Indiana 46544 Figure 6 represents the concentration of chromium in a 1:100,000 dilution at the wavelength 267.716 nm for the different Plating Tanks. The 10.0805ppm standard was left off to show the sample data points more clearly. WASH TANK The wash tank is used to rinse, soak, clean and prepare rolls for plating, as well as a catch bin for grinding the rolls in some plants. Samples from four plants were tested for hexavalent chromium using an iodine/starch indicator test, with color changes determined by UV-Vis. Cr Standard Figure 13. Plant 1 A wash tank BACKGROUND: An American Chrome Plating Company (name withheld by request) performs chrome plating on work rolls which are used in the steel and aluminum industries to flatten metal sheeting. The work puts great wear and tear on the rolls, so replating must be performed frequently (every 2-4 days). With a focus on making the company’s practices more ‘green’, it is important to maintain optimal concentrations of chemicals (in particular, chromium) in the plating baths. It is also important to minimize hazardous waste products for both ecological and economic reasons. There are several American locations for the company, labeled as Plants 1 through 5. (No samples were available from Plant 5; Plant 1 has two separate plating tanks –A and B; Plant 4 has two plating tank cells – A and B.) Each plant has a wash or soak tank where the rolls are processed before and/or after plating. Potentially hazardous materials collect in these tanks. Figure 1. Newly plated work roll. Figure 3. Plating Bath Samples taken from the tanks 1A and 1B. GOALS: 1) Analyze and determine the major elements composing the 6 different plating baths. 2) Determine density of plating baths to devise a possible method for detecting composition changes. 3) Analyze and determine composition of wash tanks to determine hazardous components. 4) Determine possible methods to reduce the amounts of hazardous materials, or to reduce the level of hazard. Figure 12 demonstrates the concentrations of chromium in the wash tank samples as determined through a starch indicator/iodine test measured by UV-Vis. Figure 7 illustrates the concentration of chromium in the Plant 1 A Tank at the wavelength 267.716 nm during the progression of one week. After the sample was taken on Wednesday, 300 lbs. of chromic acid flake was added to the tank. Figure 14. Wash tank waste sample from Plant 1 A The water in the Plant 1 A tank is continuously collected and periodically siphoned off at great expense due to hazardous waste content. The walls of the tank are coated with an accumulation of solid material that remains behind. X-Ray Fluorimetry (XRF) was used to determine the makeup of the metallic solid, as well as the tank wall itself. Figure 2. Work roll about to be inserted in Plant 1A plating bath Figures 15 and 16 show the x-ray fluorimeter (XRF) data for percentage of metal ions from wash tank materials. Figures 8 and 9 represent the change in percentages of the sample content before and after the addition of chromic acid. CHROMIUM CONTENT • CONCLUSIONS AND FUTURE PLANS • All studies thus far have been preliminary investigations and further experimentation and repetition is necessary. Throughout the following year, plans hope to address the following: • Further examination of non-chromium content of plating baths via ICP-OES. • Repetition of chromium studies via ICP-OES. • Repetition of daily sample procedures. • Separation and dilution of the four wash tank samples and ICP-OES determination of the composition. • Examination of possible methods to reduce wash tank hazards. • Exploration of methods to monitor chrome plating bath contents via density. Chromium content of the samples was determined by ICP-OES (Inductively Coupled Plasma - Optical Emission Spectrometry). In this process, a sample is nebulized to micro-droplet particles which are passed through an extremely hot plasma stream. Particles are excited, releasing electrons, which return and emit light. Emission spectra are determined to identify specified elements. Figures 4 and 5 show chromium concentrations in ppm from ICP-OES examination. Figure 4. ICP Concentration Results for the Plating Tanks DENSITY Density of each sample was determined with the intention of developing an efficient chromium concentration indicator. This investigation is yet to be pursued. Figure 10. Initial Average Densities of the Plant Plating Baths (from 10 mL aliquots) l Figure 11 shows the density of the daily samples from the Plant 1 A tank. They were calculated to determine the effect of adding the chromic acid flake to the bath. REFERENCES Norseth, T. “The Carcinogenicity of Chromium and Its Salts.” Editorial. British Journal of IndustrialMedicine. 9 October 1986: 649-651. Zaki, Nabil. “Chromium Plating.” Product Finishing Magazine. 6 January 2000: 1-10. ACKNOWLEDGEMENTS: Dr. Doug Miller, Jordan Hall of Science, Notre Dame, IN Kaneb Center RET Program, Notre Dame, IN Center for Environmental Science and Technology (CEST), Notre Dame, IN Jon Loftus, Research Technician, CEST, Notre Dame, IN