Flower-like and nanorods ZnO deposited on rGO as efficient photocatalysts for removal of polychlorinated biphenyls (PCBs)

Figures & data

Figure 1. Several published articles regarding PCBs removal. Keywords: "PCBs or polychlorinated biphenyls" AND "removal or elimination or degradation." Inset: Main PCBs removal techniques. Source: ScienceDirect.

Figure 2. A schematic mechanism for obtaining GO and rGO-ZnO nanocomposites.

Figure 3. XRD patterns of ZnO nanoparticles and ZnO-rGO nanocomposites.

Table 1. Average crystalline sizes of the ZnO and ZnO-rGO materials.

Sample	Scherrer’s equation (nm)	W-H method (UDSM) (nm)
ZnO	80.90	76.17
ZnO-rGO-Rods	28.90	27.05
ZnO-rGO-Flowers	28.40	28.28

Figure 4. SEM micrographs of (a) ZnO nanoparticles (b) ZnO-rGO-Rods and (c) ZnO-rGO-Flowers (d-f) TEM micrographs of ZnO-rGO-Rods.

Table 2. Chemical composition of ZnO and ZnO-rGO materials.

	Elemental composition (atomic %)
Material	Zn	O	C
GO	0	43.29	56.71
ZnO	60.33	39.67	0
ZnO-rGO-Flowers	14.1	22.43	63.47
ZnO-rGO-Rods	33.6	21.75	44.65

Figure 5. UV-DRS spectra. Inset: ${(F(R)\mathit{\text{* hν}})}^2$ vs. $h\nu$ plots for ZnO-rGO nanocomposites.

Figure 6. Photoluminescence spectra of ZnO nanopowder and ZnO-rGO nanocomposites.

Figure 7. Scheme of molecular structures of PCBs mixtures with different degrees of chlorination.

Figure 8. TOC profiles for PCBs degradation using (a) ZnO nanoparticles and (b) ZnO-rGO-Flowers and ZnO-rGO-Rods nanocomposites.

Table 3. Overview of photocatalysis investigations for degradation of PCBs.

Matrix	Catalyst	Mass of catalyst	PCB congeners	[PCB]0	Light source	Reaction time	% Removal	Refs.
Aqueous solution	TiO2	62.5 mg	PCB 28, 52, 101, 138, 153 and 180	0.35	UV lamp, 365 nm	180 min	63	[38]
Acetone	TiO2	20 mg	PCB 28	1 mg/L	Mercury lamp, 300 W	30 min	∼87	[39]
Acetone	TiO2	1 ug/mL	Aroclor® 1254	1 ug/mL	Xenon lamp, 250-800 nm	32 h	∼90	[40]
Methanol–water soil solution	TiO2	200 mg	PCB 8, 28, 30, 31, 33, 74	10 mg/L	UV lamp, 254 nm, 100 W	120 min	34-77	[41]
Aqueous solution	e-beam irradiated TiO2	100 mg/L	Aroclor® 1254	110,8 mg/L	UV lamp T8, 15 W	4 h	89,5/98,4	[42]
Aqueous solution	TiO2 NPs	250 mg	Aroclor® 1254 and 1260	1 ppm	UV fluorescent lamp, 365 nm, 15 W	15 min	42/51	[16]
Aqueous After Removal from Mussels	TiO2@WO3 @SnO2/PEG	250 mg	PCB 15, 28, 52, 153 and 138	–	Fluorescent light, 400 nm, 36 W	6 h	83,7	[43]
Methanol–water soil solution	TiO2-Graphene	200 mg	PCB 8, 28, 30, 31, 33, 74	10 mg/L	UV lamp, 254 nm, 100 W	120 min	58-100	[41]
Soil -Aqueous system	TiO2/FC-143	50 mg	PCB 1, 4, 18, 52, 101, 138, 180, 194,207, 209	0,0009 mg	UV lamp, 285-300 nm, 21 W (16)	4 h	59/94	[44]
Acetonitrile/Water	TiO2/H2O2	1 mg/mL	PCB 2, 10, 47, 77, 78*	100 uM	Xenon lamp, 300-800 nm, 1000 W	210 min	76-100	[45]
Aqueous solution	CM-n-TiO2 NPs	250 mg	Aroclor® 1254 and 1260**	1 ppm	UV lamp, 365 nm, 15 W	15 min	100	[16]
Aqueous-Methanol solution	rGO/ZnO	15 mg	PCB 28, 52, 101, 138, 153, 180	0,06 ppm	UV lamp, 365 nm, 100 W	8 h	95.6**	This work

*The congeners were evaluated individually in different experiments.

**Mineralization degree.

Figure 9. Proposed photocatalytic mechanism of the ZnO-rGO nanocomposites for PCBs degradation.

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