The Proof-of-Concept: The Transformation of Naphthalene and Its Derivatives into Decalin and Its Derivatives during Thermochemical Processing of Sewage Sludge

Jacek Łyczko,Jacek A Koziel,Chumki Banik,Andrzej Białowiec

doi:10.3390/en14206479

Jacek Łyczko, Jacek A Koziel + Show 2 more

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https://doi.org/10.3390/en14206479

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Abstract

One solution for sewage sludge (SS) management is thermochemical treatment due to torrefaction and pyrolysis with biochar production. SS biochar may contain toxic volatile organic compounds (VOCs) and polyaromatic hydrocarbons (PAHs). This study aimed to determine the process temperature’s influence on the qualitative PAHs emission from SS-biochar and the transformation of PAHs contained in SS. SS was torrefied/pyrolyzed under temperatures 200–600 °C with 1 h residence time. The headspace solid-phase microextraction (SPME) combined with gas chromatography and mass spectrometry (HS-SPME-GC-MS) analytical procedure of VOCs and PAHs emission was applied. The highest abundance of numerous VOCs was found for torrefaction ranges of temperature. The increase of temperatures to the pyrolytic range decreased the presence of VOCs and PAHs in biochar. The most common VOCs emitted from thermally processed SS were acetone, 2-methylfuran, 2-butanone, 3-metylbutanal, benzene, decalin, and acetic acid. The naphthalene present in SS converted to decalin (and other decalin derivatives), which may lead to SS biochar being considered hazardous material.

Highlights

Sewage sludge (SS), being the main solid waste of the wastewater treatment process (Dai et al, 2014), is produced in large quantities on a global scale
The increase of temperature to the typical pyrolytic range caused the mass yield of biochar to be only ~36% of the initial mass of SS (Figure 2)
The experiment revealed for the first time that pyrolysis might be used for the mitigation of volatile organic compounds and polyaromatic hydrocarbons emission from biochars produced from sewage sludge

Summary

Introduction

Sewage sludge (SS), being the main solid waste of the wastewater treatment process (Dai et al, 2014), is produced in large quantities on a global scale. There are three main categories of methods of SS disposal: agricultural use, landfilling, and incineration [4]. New approaches, technologies, and techniques are under investigation and development, such as SS gasification, pyrolysis, torrefaction, hydrothermal carbonization, and hydrothermal liquefaction [5]. One promising option is the waste-to-carbon concept [6,7], where organic waste is converted to carbon materials: carbonized solid fuels [8], different types of biochar [9], and hydrochar [10]. The main goals of using thermochemical methods are the generation of carbonized solid fuels, the mitigation of contaminants in the environment, and the increase of nutrient content in biochar. Torrefaction [6] and pyrolysis [11] are the most used for biochar production from SS [12]

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