The photothermal properties of hydrogel nanocomposite embedded with ZnO/CuO based on PVA/GA/activated carbon for solar-driven interfacial evaporation

Using the renewable energy, especially solar energy, is an environmental-friendly approach for seawater desalination. Solar evaporation is a promising freshwater harvesting strategy rich in energy, including solar and water energy. Herein, we propose a solar evaporation hybrid hydrogel including polyvinyl alcohol (PVA) and glutaraldehyde (GA) as a polymer network, semiconductor oxide nanoparticles (ZnO, CuO) and activated carbon as a photothermal material. Structural properties of hybrid hydrogel were characterized by X-ray diffraction (XRD) analysis, surface morphology by field emission scanning electron microscope (FE-SEM), chemical bonding by Fourier transform infrared spectroscopy (FTIR) and optical absorption and absorption coefficient (α) of components by UV–Vis spectroscopy. The result showed in visible region, PVA:ZnO:AC hydrogel nanocomposite has a strong absorption (55%) compare of the PVA:CuO:AC hydrogel nanocomposite (35%). In addition, by distillation measurements, the evaporator system demonstrated for PVA:CuO:AC and PVA:ZnO:AC Hydrogel an evaporation rate of 2.29 kg m⁻² h⁻¹ and 5.19 kg m⁻² h⁻¹ with the evaporation efficiency of 30.66% and 70.80%, respectively, under 0.1 sun irradiation. For PVA:CuO:AC hydrogel, the hardness of Caspian seawater decreased from 6648 to 115 ppm and ion conductance from 8641 (μS) to 244 (μS) and for the PVA:ZnO:AC Hydrogel decreased to 97 ppm and ion conductance to 206 (μS). Experiments showed that with changing type of the ZnO or CuO semiconductor oxide nanoparticles can effectively on regulate the optical properties of the evaporator. Eventually, this work begins a new point of synthesizing cost-effective photothermal absorbers based on metal oxides material and activated carbon nanocomposite.