Generation of ZnO/GO Nanocomposite from Waste Polyethylene terephthalate Botles and Zn Dusts: Photoremoval of Benzo[b]fluoranthene, Benzo[a]pyrene, Benzo[k]fluoranthene and Indeno[1,2,3-cd]pyrene

Currently, there is a great environmental and economic need to convert polyethylene terephthalate (PET) bottles into high-value metal materials. Metal frameworks demonstrate great dominance over other materials owing to high surface area and exceptional porosities. Herein, a simple chemical approach was employed to produce metal-oxide nanoparticles (ZnO) embedded on mesoporous carbon (GO) via carbonization of waste PET bottles and metal (Zn) dust application. The XRD pattern of the raw PET bottle showed a maximal peak of PET at 25.4° while Zn dust containing ZnO/GO nanocomposites (NCs) exhibited an intense peak at 23.56° which can be indexed to the {002} peak of the graphitic structure of carbon and broad peak at between 31.8°, 34.43°, 6.3°, 47.5°, 56.6°, 62.9°, 66.6°, 68.1°, and 69.2°, respectively, exhibiting ZnO wurtzite structure. XPS results exhibited high-resolution spectra of C 1s, and O 1s states for GO and C 1s, O 1s and Zn 2p states for Zn. The significant peak around 296 eV in both samples originated from the aromaticity of GO, indicated by the pi-pi* shake-up satellite peak. Raman spectra showed that Zn peaks at 319 cm−1, 428 cm−1, 569 cm−1, and 1119 cm−1 can be attributed to the E2, E2High, E1(LO), and A1(LO)-E1(LO) vibration modes of ZnO while the bands at 1340 cm−1 and 1588 cm−1 correspond to the D and G bands of GO. The FESEM image of the ZnO/GO NCs showed the uniform distribution of ZnO nanoparticles (NPs) on the surface of GO sheets. The effect of increasing photoremoval times (5, 10, 15, 20 and 30 min), increasing pH values (3.0, 5.0, 7.0, 9.0 and 11.0), PET concentrations (0.1, 0.5, 0.75 and 1.0 g/l), Zn concentrations (0.1, 0.5, 0.75 and 1.0 mg/l) and ZnO/GO nanocomposite concentrations ( 1, 2, 3 4 and 5 mg/l) on the photoremoval of Benzo[b]fluoranthene (BbF), Benzo[a]pyrene (BaP), Benzo[k]fluoranthene (BkF) and Indeno[1,2,3-cd]pyrene (I[1,2,3-cd]P) PAHs were investigated. Maximum 99.86% BbF, 99.01% BaP, 98.06% BkF and 97.45% I[1,2,3-cd]P PAH removal efficiencies was observed at pH=7.0, with 1.9 mg/l ZnO/GO NC concentration , after 20 min photoremoval time and at 25oC with 1.0 g/l PET concentration with 2.0 mg/l ZnO/GO NCs, after 20 min photoremoval time, at pH=7.0 and at 25oC at a UV power of 10 Wm2 and at a Zn concentration of 0.5 mg/l. The reusability studies showed that no significant changes in the photocatalytic efficiency of the nanocomposite after the 50-recycle use. The excellent stability of the nanocomposite demonstrate that 1.9 mg/l ZnO/GO NC with a Zn concentration of 0,2 mg/l exhibited perfect photoremoval yields for pollutants like PAHs namely BbF, BaP, BkF and I[1,2,3-cd]P). After 20 min irradiation a variation in transmittance up to 9% and no significant surface changes and RMS fluctuations were recorded for all ZnO/GO nanocomposites. ANN architectures robustly predicted the photocatalytic degradation of four PAHs as influenced by the individual process parameters. In all processes, the observed PAH photoegradation was in close agreement with the ANN predicted values. The R2 values of 1.00 imply that ANN predicted PAH photodegradation was in close agreement with the observed values, an indication that the optimized ANN configurations efficiently.