Abstract
Novel and environmentally benign adsorbents were prepared via a simple sulfuric acid treatment process using the wastes of astringent persimmon, a type of biomass waste, along with persimmon tannin extract which is currently employed for the tanning of leather and as natural dyes and paints. The effectiveness of these new biosorbents was exemplified with regards to hydrometallurgical and environmental engineering applications for the adsorptive removal of uranium and thorium from rare earths, cesium from other alkaline metals such as sodium, hexa-valent chromium from zinc as well as adsorptive recovery of gold from chloride media. Furthermore, reductive coagulation of gold from chloride media for the direct recovery of metallic gold and adsorptive recovery of palladium and platinum using chemically modified persimmon tannin extract were studied. OPEN
Highlights
Within the last decades, increasing attention has been paid towards energy saving hydrometallurgical processes for the recovery of valuable metals and the removal of hazardous materials
By effectively using special characteristics of persimmon tannin extract and persimmon wastes which have not been utilized to date, new separation technologies were developed using adsorption gel prepared from these feed materials by a simple treatment in boiling sulfuric acid in the authors’ previous research works
(2) Adsorptive removal of cesium(I) from other alkaline metals such as sodium, which can be expected to be useful for the remediation of water resources or wetlands that have been polluted by the accidents of atomic energy facilities or atomic energy wastes
Summary
Within the last decades, increasing attention has been paid towards energy saving hydrometallurgical processes for the recovery of valuable metals and the removal of hazardous materials. From the technical and economical points of view, in recent years, much attention has been focused on low cost adsorbents prepared from various biomass wastes as they are relatively inexpensive, environmentally benign, biodegradable and renewable In such biomass wastes, the chemical components which exhibit effective adsorption behaviors include several polysaccharides such as pectic acid, alginic acid, chitin and cellulose, polyphenol compounds such as lignin and tannin, and proteins. During the preparation of dried persimmon fruits and astringent persimmon extract, large quantities of peels and juice residue, or biomass wastes, are generated. These wastes still contain large amounts of persimmon tannin. Schematic structure of persimmon tannin where m stands for the number of the unit
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