Migration and Transformation of Heavy Metals During the CO<sub>2</sub>-Assistant Thermal Treatment of Oily Sludge

Thermal treatment has significant advantages in resource recovery for oily sludge (OS). However, the instability of heavy metals (HMs) within the residue poses a considerable risk of secondary pollution. This study explored the migration and transformation of HMs from OS under varying conditions (i....

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Main Authors: Jiantao Li, Fawei Lin, Xuan Guo, Chujun Luan, Hongdi Yu, Rundong Li, Beibei Yan, Guanyi Chen
Format: Article
Language:English
Published: MDPI AG 2024-11-01
Series:Energies
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Online Access:https://www.mdpi.com/1996-1073/17/22/5545
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author Jiantao Li
Fawei Lin
Xuan Guo
Chujun Luan
Hongdi Yu
Rundong Li
Beibei Yan
Guanyi Chen
author_facet Jiantao Li
Fawei Lin
Xuan Guo
Chujun Luan
Hongdi Yu
Rundong Li
Beibei Yan
Guanyi Chen
author_sort Jiantao Li
collection DOAJ
description Thermal treatment has significant advantages in resource recovery for oily sludge (OS). However, the instability of heavy metals (HMs) within the residue poses a considerable risk of secondary pollution. This study explored the migration and transformation of HMs from OS under varying conditions (i.e., temperature, constant-temperature duration time, and different ratios of O<sub>2</sub> and CO<sub>2</sub>). The elevation of the pyrolysis temperature augmented the decomposition of organic matter and total petroleum hydrocarbons (TPHs). However, the increased temperature also diminished the stabilization of HMs, and facilitating the HM’s transfer to oil and gas, particularly for HMs (i.e., As and Pb) with low boiling points. The constant-temperature duration time exhibited a weak impact on HM transformation, but the internal heating mechanism of microwave pyrolysis promoted the stabilization of HMs through vitrification. The existing O<sub>2</sub> with oxidizing properties facilitated the oxidation of organic matter and TPHs to CO<sub>2</sub> and H<sub>2</sub>O, which also promoted the transformation of HMs into oxidized states for stabilization. Comparatively, CO<sub>2</sub> promoted the thermal cracking and disrupted the stability of HMs to a certain extent. Above all, this work revealed the migration and transformation of HMs in OS varied with the thermochemical methods and possessed an important significance for the immobilization and stabilization of HMs.
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spelling doaj-art-15143e9a88b847d1872e4f60d205c6fd2024-11-26T18:01:46ZengMDPI AGEnergies1996-10732024-11-011722554510.3390/en17225545Migration and Transformation of Heavy Metals During the CO<sub>2</sub>-Assistant Thermal Treatment of Oily SludgeJiantao Li0Fawei Lin1Xuan Guo2Chujun Luan3Hongdi Yu4Rundong Li5Beibei Yan6Guanyi Chen7School of Environmental and Municipal Engineering, Tianjin Chengjian University, Tianjin 300384, ChinaSchool of Environmental Science and Engineering, Tianjin University/Tianjin Key Lab of Biomass/Wastes Utilization, Tianjin 300072, ChinaSchool of Environmental Science and Engineering, Tianjin University/Tianjin Key Lab of Biomass/Wastes Utilization, Tianjin 300072, ChinaSchool of Environmental Science and Engineering, Tianjin University/Tianjin Key Lab of Biomass/Wastes Utilization, Tianjin 300072, ChinaSchool of Environmental Science and Engineering, Tianjin University/Tianjin Key Lab of Biomass/Wastes Utilization, Tianjin 300072, ChinaSchool of Energy and Environment, Shenyang Aeronautical University, Shenyang 110136, ChinaSchool of Environmental Science and Engineering, Tianjin University/Tianjin Key Lab of Biomass/Wastes Utilization, Tianjin 300072, ChinaSchool of Mechanical Engineering, Tianjin University of Commerce, Tianjin 300134, ChinaThermal treatment has significant advantages in resource recovery for oily sludge (OS). However, the instability of heavy metals (HMs) within the residue poses a considerable risk of secondary pollution. This study explored the migration and transformation of HMs from OS under varying conditions (i.e., temperature, constant-temperature duration time, and different ratios of O<sub>2</sub> and CO<sub>2</sub>). The elevation of the pyrolysis temperature augmented the decomposition of organic matter and total petroleum hydrocarbons (TPHs). However, the increased temperature also diminished the stabilization of HMs, and facilitating the HM’s transfer to oil and gas, particularly for HMs (i.e., As and Pb) with low boiling points. The constant-temperature duration time exhibited a weak impact on HM transformation, but the internal heating mechanism of microwave pyrolysis promoted the stabilization of HMs through vitrification. The existing O<sub>2</sub> with oxidizing properties facilitated the oxidation of organic matter and TPHs to CO<sub>2</sub> and H<sub>2</sub>O, which also promoted the transformation of HMs into oxidized states for stabilization. Comparatively, CO<sub>2</sub> promoted the thermal cracking and disrupted the stability of HMs to a certain extent. Above all, this work revealed the migration and transformation of HMs in OS varied with the thermochemical methods and possessed an important significance for the immobilization and stabilization of HMs.https://www.mdpi.com/1996-1073/17/22/5545oily sludgepyrolysisheavy metalsCO<sub>2</sub>
spellingShingle Jiantao Li
Fawei Lin
Xuan Guo
Chujun Luan
Hongdi Yu
Rundong Li
Beibei Yan
Guanyi Chen
Migration and Transformation of Heavy Metals During the CO<sub>2</sub>-Assistant Thermal Treatment of Oily Sludge
Energies
oily sludge
pyrolysis
heavy metals
CO<sub>2</sub>
title Migration and Transformation of Heavy Metals During the CO<sub>2</sub>-Assistant Thermal Treatment of Oily Sludge
title_full Migration and Transformation of Heavy Metals During the CO<sub>2</sub>-Assistant Thermal Treatment of Oily Sludge
title_fullStr Migration and Transformation of Heavy Metals During the CO<sub>2</sub>-Assistant Thermal Treatment of Oily Sludge
title_full_unstemmed Migration and Transformation of Heavy Metals During the CO<sub>2</sub>-Assistant Thermal Treatment of Oily Sludge
title_short Migration and Transformation of Heavy Metals During the CO<sub>2</sub>-Assistant Thermal Treatment of Oily Sludge
title_sort migration and transformation of heavy metals during the co sub 2 sub assistant thermal treatment of oily sludge
topic oily sludge
pyrolysis
heavy metals
CO<sub>2</sub>
url https://www.mdpi.com/1996-1073/17/22/5545
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