Spent coffee ground-based cellulose nanofiber/ reduced graphene oxide aerogel for efficient solar-driven interfacial evaporation via directional freezing technology

With the development of coffee industry, it's a big problem to dispose the growth of spent coffee ground. Landfill and incineration of it could lead to environmental pollution and waste of resources. It contains 8.6–24.3 % cellulose and it could be considered as a green and cheap source of cellulose nanofiber aerogel. In this work, Aerogels for solar-driven interfacial evaporation were successfully fabricated through directional freezing technology and spent coffee ground. The water evaporation rate of aerogel could reach to 1.651 kg·m⁻²·h⁻¹. It also exhibited wonderful long-term performance of solar desalination, and its daily average water production was 14.38 kg·m⁻², which was sufficient to support the drinking water need of four adults.