Introducing a back filter: the impact of metal type on reducing particulate matter and sulfide emissions from diesel...

This study introduces a back filter installed at the end of the exhaust pipe of city buses. The impact of the metal type used in its construction on the absorption of suspended particles and the reduction of sulfides in diesel engine exhaust gases is investigated. The back filter is constructed from three metals: copper, zinc, and nickel. The nickel sample was prepared by electroplating nickel onto 316 steel surfaces (316SNi), while hot-dip galvanized steel was used as a substitute for zinc. Poly tetrafluoroethylene (PTFE) powder was utilized to enhance soot adsorption, sandwiched between two metal plates in each back filter. When in contact with metal, PTFE produces a positive charge on the Surface. As a result, the neutralization of the soot charge upon contact with the positively charged metal leads to an increase in soot deposition on the back filter. The results indicated that the amount of soot deposited and Sulfide absorption on the 316SNi filter was greater than on the other two types in the absence and presence of PTFE powder. To interpret these findings, impedance spectroscopy was employed to assess the electrical resistance of the absorbed soot, and X-ray diffraction was used to identify the mineral compounds formed on the filter Surface. The significant differences observed can be attributed to the lower thermal conductivity of 316SNi compared to the other metals, the reduced electrical resistance of soot adsorbed on 316SNi, and the formation of nickel sulfide as a kinetic product on its surface.