Utilization of hydroxyapatite in waste fishbone for stabilization of lead in fly ash

Abstract

In 2016, approximately 32.9 million tons of municipal solid waste were incinerated that led to the generation of about 3.5 million tons of solid residues. The majority of the incineration residues including fly ash were then landfilled. Fly ash contains heavy metals including lead (Pb). Currently, there are different methods for stabilizing the heavy metals, which might be costly and not eco-friendly or might cause an increase in the volume of residues to be landfilled. In the present research, an effort was made to use waste fishbone material as an environment-friendly substance for heavy metal stabilization in fly ash with emphasis on Pb. Hydroxyapatite is the main component of fishbone that can react with divalent heavy metals including Pb to form a highly insoluble phases such as lead-apatite product. The experiments indicated that HAP in fishbone is a promising material for stabilizing Pb in fly ash; however, it has not yet been possible to achieve the levels below the standard landfill criterion. Therefore, additional techniques were employed to enhance the effectivity of Pb stabilization in fly ash by using HAP of waste fishbone. We examined the influence of various settling times, liquid/solid (L/S) ratios