Actual NO_X and SO_X removal rates in the atmospheric environment of concrete permeable blocks containing TiO₂ powders, coconut shell powders, and zeolite beads

This study examined actual nitrogen oxide (NO_X) and sulfur oxide (SO_X) removal rates of concrete permeable blocks in the atmospheric environment. To give the concrete permeable block a NO_X and SO_X removal function, TiO₂ submicron particle or coconut shell powder was embedded in the surface layer, and zeolite bead was embedded in the base layer. Using an actual factory production line, concrete permeable block specimens were prepared by adding TiO₂ submicron particles and coconut shell powder to the surface layer of the concrete permeable block. The prepared concrete permeable block specimens were placed in a parking lot, and then NO_X and SO_X removal rates were directly measured for 6 months on the concrete permeable block specimens placed in the parking lot. Test results showed that the clear day removal rates of NO_X and SO_X for the concrete permeable block specimens embedded with TiO₂ submicron particles during the day was 84% and 70%, respectively. Compared to the concrete permeable blocks embedded with coconut shell powder, the NOx removal rate of the specimens embedded with TiO₂ submicron particles was 1.45 times higher, while the SO_x removal rate was similar. However, during cloudy days and nights, the NO_X removal rate of the concrete permeable block specimens embedded with TiO₂ submicron particles was zero. On the other hand, NO_X and SO_X removal rates of the concrete permeable block specimens embedded with coconut shell powder and zeolite bead were maintained at approximately 51% and 77% for 6 months, respectively, in the atmospheric environment regardless of weather and day light conditions. Consequently, the coconut shell powder added to the surface layer of the concrete permeable block is a practically promising material in reducing the NO_X in the atmospheric environment regardless of weather and day light conditions.