EVALUATING PAINT-SLUDGE CHARS FOR ADSORPTION OF SELECTED PAINT SOLVENTS

At Ford, a study had been carried out to investigate the technical fea sibility of converting paint sludge to activated char and reusing the char in paint spray-booth water to capture paint solvents from spray-b ooth air. As part of the study several chars were made from a paint sl udge and six dried paints to evaluate their effectiveness as adsorbent s by conducting a series of liquid-phase adsorption experiments. Three commonly-used paint solvents and p-nitrophenol were selected as adsor bates. The three paint solvents were toluene, 2-methyl-1-propanol (iso -butanol), and 2-butoxyethanol (butylcellosolve). In this paper, the r esults of the pyrolysis and adsorption experiments are presented along with practical implications. The primary findings include the followi ng: (1) Black-paint chars showed substantially larger surface area and higher adsorption capacity (based on total weight) than white-paint c hars which had high ash contents due tb the white pigment, titanium di oxide; (2) the adsorption capacity of the paint-sludge char was betwee n those of black-paint and white-paint chars, and was 5-20% that of a commercial activated carbon; (3) titanium dioxide in white-paint chars did not improve the chars' affinity for hydrophilic compounds such as 2-methyl-1-propanol and 2-butoxyethanol; (4) coal could be added to p aint sludge to improve the quality of the resulting char and to reduce ash content; and (5) the pyrolysis of paint sludge could present an a ttractive opportunity for reusing and recycling a waste product for po llution abatement and as a vehicle component.