Facile fabrication of low-cost starch-based biohydrogel evaporator for efficient solar steam generation

Abstract

Solar evaporation is an emerging technology in the field of seawater desalination and wastewater purification to address global water shortage, while the unsatisfactory evaporation rate and high raw material cost seriously restrict its practical application. In this work, a biohydrogel-based evaporator was developed by using low-cost starch as biohydrogel substrate and carbon nanotubes (CNTs) as light absorber for high-efficient solar stream generation. Due to the lower vaporization enthalpy in the CNTs/starch hybrid biohydrogel, the composite evaporator presented an evaporation rate as high as 2.77 kg m−2 h−1 with an evaporation efficiency of ~88% under 1.0 sun, both of which were 2.89 and 4.95 times higher than those of the starch hybrid biohydrogel and pure water, respectively. Meanwhile, the prepared biohydrogel-based evaporator exhibited fascinating salt fouling resistance, remarkable stability and outstanding solar evaporation performance during treating real seawater and multiple types of wastewaters (with the broad pH range of acid and alkali wastewater (0–14), dye wastewater, heavy metal wastewater, and practical reverse osmosis wastewater). These results suggested that the starch-based biohydrogel evaporator would provide a possibility of practical large-scale application for efficient desalination and wastewater purification.