Turning Corn Stalk Trashes into a Photothermal Agent for Interfacial Solar Water Evaporation for Sustainable Water Purification

Abstract

Biomass-based photothermal materials have a higher photothermal conversion efficiency and contribute significantly to improved solar water evaporation systems. This work aims to transform corn stalk (CS) trash into efficient photothermal materials with centralized and less-contact area water supply systems to achieve enhanced interfacial heat accumulation. We successfully synthesized cornstalk biochar synthesized via pyrolysis to maintain the environmental concern and is deposited onto a scalable, and cost-effective (<1$) polyurethane foam (triangle shape, where the tip plays the wick and centralized water supply). The detailed characterizations validate the porous structure of CS biochar-coated PU foam (CSB@PU), and enhance interfacial heat accumulation up to 47.8 °C under 1 kW m⁻² solar irradiation which is endowed via thermal management of polystyrene foam (PS). This reproducible interfacial heat accumulation and sustainable evaporator bestow a water evaporation rate of up to 1.38 kg m⁻² h⁻¹, and solar-to-vapor conversion efficiency (84%) under one sun which is more efficient than other biomass-derived evaporators. Inductively coupled plasma-optical emission spectroscopy analysis validates the reductions of primary (Na⁺, K⁺, Mg²⁺, and Ca²⁺) and heavy metal ion (Fe³⁺, Hg²⁺, Cd²⁺, and Pb²⁺) concentrations in condensate, insights the potential of CSB@PU to advance the water treatment technologies.