Recovery of Palladium from Strong Acidic Solution Using Sulfur-Impregnated Carbonaceous Bamboo

Abstract

Palladium (Pd) is used in various fields and is a highly rare resource in nature. Recovery of Pd from domestic wastes called “urban mines” is desired in Japan. Bamboo is an abundant biomass resource in Japan, and the promotion of its utilization is desired. In our previous studies, sulfur-impregnated carbonaceous adsorbent with high heavy metal removal has been prepared from biomass resources using sulfur with a high affinity for heavy metals. In this study, sulfur-impregnated carbonaceous bamboo was prepared from bamboo powder by pyrolyzing at 800 °C with sulfur under nitrogen atmosphere for recovering Pd from strong acidic solution. Sulfur-impregnated carbonaceous bamboo had porous structure, high specific surface areas and sulfur content. Palladium could be recovered from strong acidic solution by precipitation of Pd metals on the surface of sulfur-impregnated carbonaceous bamboo, while little amount of Pd was recovered using raw bamboo powder and non-sulfur-impregnated carbonaceous bamboo. The Pd adsorption capacity of sulfur-impregnated carbonaceous bamboo was about 120 mg-Pd/g-carbon, which was about twice as that of a commercially available activated carbon. The adsorption and reduction reaction of Pd on the surface of sulfur-impregnated carbonaceous bamboo occurred rapidly, and it was observed that Pd particles were larger as the reaction time increased. Palladium was precipitated as smaller particles on the surface of sulfur-impregnated carbonaceous bamboo than those on the surface of commercially activated carbon.