Dual Cross-Linking Coal Tar-Derived Phenolic Resin Porous Carbon-Based Hydrogel Solar Evaporators for Efficient Wastewater Purification

Abstract

Porous carbon-based hydrogel evaporators show extensive application potential in the field of solar-driven water evaporation due to their wide availability, excellent hydrophilicity, and abundant porous structure. However, the closed pore structure of the single-molecule cross-linked hydrogel and the high production cost of the nanoporous carbon materials not only affect the salt resistance of the carbon-based hydrogel but also restrict its large-scale application. Herein, we developed a uniform porous APRC-PVA/PEG hydrogel evaporator by integrating poly(vinyl alcohol) (PVA)/polyethylene glycol (PEG) dual-network hydrogels with broadband solar-absorbing, cost-effective porous carbon nanosheets (APRC) derived from coal tar-based phenolic resin. The rich pores and three-dimensional double-network structure of the evaporator ensured excellent water transport performance and a high light absorption rate (≈98%). Meanwhile, the low thermal conductivity of the evaporator (dry: 0.09 W m^–1 K^–1; wet: 0.29 W m^–1 K^–1) reduces thermal loss to the bulk water, enabling a water evaporation rate of 1.45 kg m^–2 h^–1 under 1 sun irradiation and a low enthalpy of evaporation of 1614.605 J g^–1. The evaporator also shows good potential in the field of brine, industrial wastewater, and organic dye wastewater.