Rejection and Recovery of Heavy Metals from MSW Melting Fly Ash by Carrier-in-Pulp Method
Melting has become a popular pre-treatment method for municipal solid waste (MSW) incineration residues in Japan.Although the method is effective in stabilizing the hazardous organic substances such as dioxin,it concentrates the heavy metals such as Zn,Pb,Cu,and Cd in a newly formed fly ash (melting fly ash).Melting fly ash is classified as a hazardous waste because of the leaching potential of these heavy metals in landfill environment.Extraction and recovery of these metals seem to be more environmentally and economically attractive than disposing the material to landfill after immobilization process.This study proposes a Carrier-in-Pulp (CIP) method as a new hydrometallurgical route to reject and recover heavy metals from fly ash.In this method,a carrier material which recovers the extracted metals is added simultaneously with fly ash to leaching solutions and is harvested from the pulp by physical separation method like magnetic separation or sieving.To demonstrate the effect of CIP method,shaking flask experiments were conducted under various conditions using NaCl solution as lixiviant and iron powder or granular activated carbon as carrier materials.In the CIP method using iron powder,more than 97 wt% of Pb and Zn were extracted from the ash to the solution phase.However,the iron powder which was harvested from the pulp by magnetic separation,recovered only Pb (more than 94%) through cementation,leaving behind Zn ions in the solution phase.Due to this problem,granular activated carbon (GAC) was considered as an alternative carder material.Single- and multi-metal adsorption experiments using granular activated carbon were conducted as a preliminary study.Around 85% Pb and 88% Zn were recovered by GAC in the single-metal adsorption experiment,while 60% Pb and 70% Zn in the multi-metal experiment.These results showed that activated carbon was superior to the iron powder since it was able to recover both Pb and Zn through adsorption.The leaching test conducted on the residue after the CIP-Fe treatment revealed that the solubilisation of Pb was successfully suppressed to meet landfilling guidelines.
Leaching Heavy metals Fly ash Cementation Adsorption
R.D.Alorro N.Hiroyoshi S.Mitani M.Ito M.Tsunekawa
Laboratory of Mineral Processing and Resources Recycling,Division of Solid Waste,Resources and Geo-environmental Engineering,Graduate School of Engineering,Hokkaido University,Japan
国际会议
XXIV International Mineral Processing Congress(第24届国际矿物加工大会)
北京
英文
3610-3617
2008-09-24（万方平台首次上网日期，不代表论文的发表时间）