Janus Polypyrrole Nanobelt@Polyvinyl Alcohol Hydrogel Evaporator for Robust Solar-Thermal Seawater Desalination and Sewage Purification

Abstract

The state-of-the-art solar-thermal evaporators demonstrating high energy utilization efficiency, a high evaporation rate, and salt rejection are highly desirable in solar-driven low-energy water purification/harvesting. Herein, a novel Janus solar evaporator is constructed by loading polypyrrole (PPy) nanobelts on the polyvinyl alcohol (PVA) hydrogel. The PPy nanobelts present a high solar absorption of 98.3%, leading to a localized solar-thermal efficiency of 82.5% when insulated from bulk water by the PVA hydrogel. The porous PVA hydrogel and the hydrophilic PPy nanobelts enable the efficient three-dimensional water transport. Taking advantages of the synergistic effect in the water-energy nexus, the Janus PPy nanobelt@PVA hydrogel evaporator evaporates water with a high rate of 2.26 kg m −2 h −1 via 80.1% solar energy from 1 sun irradiance with a low PPy loading of ∼3 mg cm −2 even at a rate of 2.64 kg m −2 h −1 via 96.3% solar energy for a biomimetic conical evaporator. The Janus evaporator presents superior salt-resistant desalination and contaminant purification performance in seawater and sewage. Furthermore, a portable solar-thermal purifier equipped with the Janus evaporator desalts real seawater far above the drinking water standard with over a 99.9% salt rejection rate and eliminates 95.8% of chemical oxygen demand in real sewage, highlighting its potential for advanced clean water harvesting.

Stable and Salt-Resistant Janus Evaporator Based on Cellulose Composite Aerogels from Waste Cotton Fabric

“…(e) Evaporation rate of JCA-2 evaporator under 0.5 to 3 sun. (f) Comparison of the evaporation rate and light-to-vapor efficiency of this work with other currently researched Janus solar steam generators. ,,− (g) Mass change of the JCA-2 evaporator tested in pure water for 10 h. (h) Water evaporation rate of the JCA-2 evaporator in 10 test cycles. The inset picture shows the mass changes of the JCA-2 evaporator after the 1 and 10 repeat cycle test.…”

Membrane-free osmotic desalination at near-room temperatures enabled by thermally responsive polyionic liquid hydrogels

“…We have classified the water harvesting through photothermal conversion into two categories, (1) seawater evaporation and (2) LCST phase transformation. 15,23,35–55 By comparing different types of hydrogels, the rate of fresh water collection through an LCST phase transition is faster, and our work reached a collection rate of 6.5 kg m −2 h −1 . The polyionic hydrogel relies on solar power to trigger a hydrophilic/hydrophobic phase transformation at the LCST.…”

Self-Assembly of a Graphene Oxide Liquid Crystal for Water Treatment

“…Very recently, solar-driven interfacial evaporation has aroused great interest. − An indispensable component in such a system is solar absorber materials, and GMs are competitive candidates on account of their broadband absorption and excellent photothermal properties. , Thanks to their light weight, our LCI-GMs float directly at the air–water interface, thus spontaneously setting up two-dimensional water pathways that help suppress heat loss and boost photothermal conversion efficiency by the establishment of a local heating zone close to the gas–liquid interface . As shown in Figure S15a–d, the temperature at the air–water interface in the system with LCI-GM or H-GM (approximately 68 °C) is higher than the temperature of the bulk water (approximately 50 °C), whereas the system without a solar absorber has nearly the same temperature at both locations (approximately 38.5 °C).…”