Photocatalytic H2 Production from Microplastics Containing Shower Gels and Personal Care Products with Cobalt Oxide Nanocomposite

Abstract: Microplastics (MPs) pose a significant threat to human health, primarily through their entry into the food chain through the consumption of contaminated fish. Additionally certain personal care products including shower gels, face cleansers, hand gels, detergents, tootphasete and creams are recognized as potential sources of microplastic pollution due to presence of polymers like polyethylene and polystyrene. In the present study, cobalt oxide (Co 3 O 4 ) nanocomposites (NCs) were synthesized and employed as photocatalysts for hydrogen production under solar simulated conditions from microplastics namely Polyamide (PA, Nylon), Polyacrylate (PAR), Polyethylene (PE), Polymethyl methacrylate (PMMA) and Acrylates Copolymer (AC). The aforementioned nanocomposite was utilized to degrade some microplastics extracted from shower gels and facial creams for hydrogen (gas) generation. The Co 3 O 4 nanocomposites were generated in controlled laboratory conditions. The structural, morphologic and, surface characteristics of the nanocomposite were characterized using XRD, SEM, FTIR, HRTEM, EDX and UV-vis absorption spectrum analysis. The influence of some operational parameters including photodegradation time, and Co 3 O 4 nanocomposite concentrations on H 2 efficiency from PA, PAR, PE, PMMA and AC microplastics were investigated. The maximal H 2 productions were detected as 180 mmol/g Co 3 O 4 NP.h, for PE; 108 mmol/g Co 3 O 4 NP.h for PAK and 105 mmol/g Co 3 O 4 NP.h, for PA at 100 mg/l PE, PAK and PA microplastic concentrations, respectively, after 0.40 h retention time at 2 mg/l Co 3 O 4 NPs concentrations. The maximal H 2 productions were found to be slightly low in PMMA (82 mmol/g Co 3 O 4 NP.h and AC (87 mmol/g Co 3 O 4 NP.h) after 0.4 h at 2 mg/l Co 3 O 4 NPs at initial 100 mg/l PMMA and AC microplastic concentrations. XRD analysis confirms whether the Co 3 O 4 catalyst is in the spinel phase with crystallite size. The SEM investigation revealed that Co 3 O 4 NPs has small particles shaped distribution and with interconnected agglomerated particles. The average particle size of Co 3 O 4 NPs was less than 15 nm. In our study, the surface area of Co 3 O 4 NPs were measured as 82 m 2 /g, indicating more contact points in large surface resulting in more H 2 production with Brunauer–Emmett–Teller (BET) analysis. Peaks are typically around 0.7 keV ( L α ) and 6.9 keV ( K α )- for Co, and around 0.5 keV for O 2 . The band gap energy around 2.35 eV provides sufficient force for the decomposition of the microplastics mentioned above. The main FTIR spectrum values are 1145 cm -1 , 1397 cm -1 , 1645 cm -1 and 3500 cm -1 for C=O, O-H, C=O and O-H bonds, respectively. The specific geometric forms of Co 3 O 4 NPs, such as cubes, rods, or plates, were in the range of 10 and 50 nm and are visualized in HRTEM graphs. The maximal H 2 productions were detected as 180 mmol/g Co 3 O 4 NP.h, for PE; 108 mmol/g Co 3 O 4 NP.h for PAK and 105 mmol/g Co 3 O 4 NP.h, for PA at 100 mg/l PE, PAK and PA microplastic concentrations, respectively, after 0.40 h retention time at 2 mg/l Co 3 O 4 NPs concentrations. The maximal H 2 productions were found to be slightly low in PMMA (82 mmol/g Co 3 O 4 NP.h and AC (87 mmol/g Co 3 O 4 NP.h) after 0.4 h at 2 mg/l Co 3 O 4 NPs at initial 100 mg/l PMMA and AC microplastic concentrations. The reusability studies showed that the Co 3 O 4 NPs nanocomposites exhibited the same H 2 productions for 64 cycle and these nanoparticles possessed slightly improved photocatalytic degradation of microplastics.