CHARACTERISTICS AND ADSORPTION PROPERTIES OF IRON-COATED SAND

This study was conducted to develop a process for coating hydrated iro n oxide on the surface of quartz sand to utilize the adsorbent propert ies of the coating and the filtration properties of the sand, Three co ating parameters were investigated: pH, Fe concentration at which iron oxide was prepared, and the coating temperature. A Scanning Electron Microscope (SEM) and X-Ray Diffractometer (XRD) were used to observe t he surface properties of the coated layer. Acid resistance was used to evaluate the attachment strength of the coated layer. Batch adsorptio n tests were performed to compare the effects of each coating paramete r on the adsorption of heavy metals on the coated layer. Energy Disper sive Analysis of X-ray (EDAX) was used for characterizing metal adsorp tion sites on the iron-coated sand. The results indicated that the coa ted sand had more pores and higher specific surface area because of th e attachment of iron oxide. The coated sand produced at higher pH((coa ting)) had better adsorption efficiencies of metals but had worse acid resistance. A high-temperature coating process enhanced the stability of the oxide coatings. Comparing heavy metal removal by adsorption on iron-coated sand and chemical precipitation, adsorption was shown to be capable of removing heavy metals over a wider pH range and to much lower levels than precipitation. The results from EDAX analysis showed that copper ions were chemisorbed on the surface of iron-coated sand. (C) 1997 IAWQ. Published by Elsevier Science Ltd.