Mechanical Treatment of MSWI Fly Ash: A Way Forward to Inhibit PCB Reformation

Ishrat Mubeen,Xiaoqing Lin,Xiaodong Li,Mi Yan,Shengyong Lu,Alfons Buekens,Dwi Hantoko,Zhiliang Chen,Jianhua Yan

doi:10.4209/aaqr.2019.04.0213

Abstract

ABSTRACT Fly ash from municipal solid waste incinerators has been classified as hazardous waste due to the presence of unintentionally-produced Persistent Organic Pollutants (POPs), with Polychlorinated biphenyls (PCB) being a major group among such POPs. Fly ash can be mechanically (MC) treated to destroy organic pollutants before final disposal or reuse. In this study, model fly ash (MFA) doped with 0.2% CuCl2 was artificially prepared and subjected to high intensity ball milling for 0 (original sample), 1, 2, 4, and 8 h of treatment. Furthermore, to explore PCB reformation in the MC treated fly ash, de novo tests were conducted at single reaction time, temperature, and air flow rate. It was found that the sum of PCB, dioxin like PCB, and corresponding International Toxic Equivalent concentrations (∑PCB, ∑dl-PCB and ∑I-TEQ, respectively) were greatly reduced both in gas and in solid phase of MFA after 8 h of treatment. Though chlorination degree successively decreased with prolonged milling, the homologue and isomer signatures of PCB were varied in concentration. Reformation of few isomers was also observed. Results from present study suggest that MC treatment is an effective method to control reformation of pollutants in the long term. However, few suggestions are made for further ongoing research work on MC treatment of fly ash, which are based on surprising results and experimental limitations obtained in this study.

Highlights

Polychlorinated biphenyls (PCB) are semi volatile, toxic, stable and persistent chlorinated aromatic compounds, and are classified as Persistent Organic Pollutants (POPs)
Particle surface observed by Scanning Electron Microscopy (SEM) indicated that model fly ash (MFA) consists of many large size particles before MC treatment (Fig. S2(a)) and after 1 h treatment particles reduced in size (Fig. S2(b))
Similar trend was observed for ∑I-toxic equivalence quantity (TEQ) concentrations in gas and solid phase at 0, 1, 2, 4, and 8 milling hours and 99% reduction of ∑I-TEQ of MFA in both phases was achieved after 8 h

Summary

Introduction

Polychlorinated biphenyls (PCB) are semi volatile, toxic, stable and persistent chlorinated aromatic compounds, and are classified as Persistent Organic Pollutants (POPs). In our previous work on MFA milling, reformation in terms of total output of PCDD/F and dl-PCB, as well as erratic reformation of certain isomers (e.g., penta-CB #123) after 8 h milling without any additive have been observed in gas phase (Mubeen et al, 2017).

Results

Conclusion