“…Results showed that in pH above 10, the PDE was pH-dependent and did not depend on the base type. To produce protons and anionic radicals in nucleophilic reactions, strong bases are needed, and the higher the pH, the greater is the ability to remove protons from the environment [ 10 , 13 ]. Therefore, at high pH, the proton is easily removed from glycerol and, given the uniformity of the cation in the structure of sodium hydroxide and sodium carbonate, if the temperature is sufficient, the reaction is carried out with high efficiency.…”
Section: Resultsmentioning
confidence: 99%
“…[ 20 ] proposed a combined mechanism in their research while Kamarehie et al . [ 10 ] only considered nucleophilic substitution. Figure 9.…”
Section: Resultsmentioning
confidence: 99%
“…In the BCD method in which glycerine without iron powder is used, the main reaction takes place through nucleophilic substitution. Hai et al [17] and Xiao et al [20] proposed a combined mechanism in their research while Kamarehie et al [10] only considered nucleophilic substitution.…”
Section: Resultsmentioning
confidence: 99%
“…Incineration is the oldest and most reliable method for PCB disposal [ 5 ]. For destruction of PCBs, although in recent years new methods have been developed, such as using an electron beam accelerator [ 6 ], plasma [ 7 ], lasers [ 8 ], microwaves [ 9 , 10 ], adsorption [ 11 ] and absorption [ 12 ], yet most studies have focused on chemical methods [ 13 ]. One of the practical and relatively inexpensive methods of purifying transformer oils and treating soil polluted with PCBs that is mostly used in developed countries is base-catalysed decomposition (BCD) [ 14 , 15 ].…”
In this research, a method based on base-catalysed decomposition (BCD) was developed using sodium hydroxide and glycerol for dechlorination of transformer oils with low levels of polychlorinated biphenyls (PCBs). PCB removal and dechlorination efficiencies were measured by gas chromatography and the silver nitrate titration method, respectively. PCB dechlorination and removal efficiencies after 4 h at 250°C and in the presence of iron were 97.4% and 99.8%, respectively. However, in the absence of iron the same efficiencies were calculated to be 79.4 and 99.7%, respectively. The dielectric loss factor of oil refined at 250°C was 0.0064 and did not meet the required standards to be reused in the transformers. However, that refined at 200°C satisfied the standards with acceptable conversion rates. Use of iron, besides increasing conversion rates, changed the mechanism of the reaction from nucleophilic substitution to a combination of hydrodechlorination and nucleophilic substitution. In the presence of iron, highly chlorinated PCBs were converted to less chlorinated PCBs, and this caused the concentration of less chlorinated PCBs to reach a peak and then decline thereafter. The production of PCB 36 confirmed this. However, in the absence of iron particles, all changes in the PCB concentration curves were downward.
“…Results showed that in pH above 10, the PDE was pH-dependent and did not depend on the base type. To produce protons and anionic radicals in nucleophilic reactions, strong bases are needed, and the higher the pH, the greater is the ability to remove protons from the environment [ 10 , 13 ]. Therefore, at high pH, the proton is easily removed from glycerol and, given the uniformity of the cation in the structure of sodium hydroxide and sodium carbonate, if the temperature is sufficient, the reaction is carried out with high efficiency.…”
Section: Resultsmentioning
confidence: 99%
“…[ 20 ] proposed a combined mechanism in their research while Kamarehie et al . [ 10 ] only considered nucleophilic substitution. Figure 9.…”
Section: Resultsmentioning
confidence: 99%
“…In the BCD method in which glycerine without iron powder is used, the main reaction takes place through nucleophilic substitution. Hai et al [17] and Xiao et al [20] proposed a combined mechanism in their research while Kamarehie et al [10] only considered nucleophilic substitution.…”
Section: Resultsmentioning
confidence: 99%
“…Incineration is the oldest and most reliable method for PCB disposal [ 5 ]. For destruction of PCBs, although in recent years new methods have been developed, such as using an electron beam accelerator [ 6 ], plasma [ 7 ], lasers [ 8 ], microwaves [ 9 , 10 ], adsorption [ 11 ] and absorption [ 12 ], yet most studies have focused on chemical methods [ 13 ]. One of the practical and relatively inexpensive methods of purifying transformer oils and treating soil polluted with PCBs that is mostly used in developed countries is base-catalysed decomposition (BCD) [ 14 , 15 ].…”
In this research, a method based on base-catalysed decomposition (BCD) was developed using sodium hydroxide and glycerol for dechlorination of transformer oils with low levels of polychlorinated biphenyls (PCBs). PCB removal and dechlorination efficiencies were measured by gas chromatography and the silver nitrate titration method, respectively. PCB dechlorination and removal efficiencies after 4 h at 250°C and in the presence of iron were 97.4% and 99.8%, respectively. However, in the absence of iron the same efficiencies were calculated to be 79.4 and 99.7%, respectively. The dielectric loss factor of oil refined at 250°C was 0.0064 and did not meet the required standards to be reused in the transformers. However, that refined at 200°C satisfied the standards with acceptable conversion rates. Use of iron, besides increasing conversion rates, changed the mechanism of the reaction from nucleophilic substitution to a combination of hydrodechlorination and nucleophilic substitution. In the presence of iron, highly chlorinated PCBs were converted to less chlorinated PCBs, and this caused the concentration of less chlorinated PCBs to reach a peak and then decline thereafter. The production of PCB 36 confirmed this. However, in the absence of iron particles, all changes in the PCB concentration curves were downward.
“…After separation, the dark-brown precipitate was washed several times with methanol to remove the residuals. After washing, the final product was dried at 70 °C for 24 h. After preparation of treated PAC and PAC/γ ≈ Fe 2 O 3 nanocomposite, their characterizations were determined using SEM, XRD, and BET techniques [1] , [2] , [3] , [4] , [5] , [6] , [7] , [8] , [9] , [10] , [11] , [12] , [13] , [14] , [15] , [16] .…”
Section: Experimental Design Materials and Methodsmentioning
Three types of adsorbents of powdered activated carbon (PAC), treated PAC, and PAC/γ ≈ Fe2O3 nanocomposite were used. The adsorption experiments were performed in batch conditions. pHZPC of PAC/γ ≈ Fe2O3 was 6.7. As a result, at lower than pHZPC, acidic pH, the adsorption of alizarin red S on PAC/γ ≈ Fe2O3 was favourable. The maximum of alizarin red S adsorption of PAC, treated PAC, and PAC/γ ≈ Fe2O3 was 24.5 mg/g, 57.8 mg/g, and 112.56 mg/g, respectively. The models of Langmuir and pseudo-first-order were a fit model to describe the adsorption isotherm and the Kinetic, respectively. The PAC/γ ≈ Fe2O3 is a promising class of the adsorbents in the adsorption of various dyes from textile effluents.
Per‐ and polyfluoroalkyl substances (PFAS) are a recalcitrant group of chemicals and can be found throughout the environment. They often collect in wastewater systems with virtually no degradation prior to environmental discharge. Some PFAS partitions to solids captured in wastewater treatment which require further processing. Of all the commonly applied solids treatment technologies, incineration offers the only possibility to completely destroy PFAS. Little is known about the fate of PFAS through incineration, in particular, for the systems employed in water resource recovery facilities (WRRF). This review covers available research on the fate of PFAS through incineration systems with a focus on sewage sludge incinerators. This research indicates that at least some PFAS destruction will occur with incineration approaches used at WRRFs. Furthermore, PFAS in flue gas, ash, or water streams used for incinerator pollution control may be undetectable. Future research involving full‐scale fate studies will provide insight on the efficacy of PFAS destruction through incineration and whether other compounds of concern are generated.
Practitioner points
Thermal processing is the only commercial approach available to destroy PFAS.
Thermal degradation conditions required for destruction of PFAS during incineration processes are discussed.
Fate of PFAS through water resource recovery facility incineration technologies remains unclear.
Other thermal technologies such as smoldering combustion, pyrolysis, gasification, and hydrothermal liquefaction provide promise but are in developmental phases.
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