Construction of a low-latent heat solar evaporator with agricultural waste

Solar-powered interfacial evaporation, a zero-energy technology, holds potential for implementation in seawater desalination. However, the limited evaporation rate poses a significant obstacle to the widespread adoption of this technology. Consequently, the development of low-latent heat solar evaporators emerges as a crucial solution to address this bottleneck issue. In this study, a low-latent heat solar evaporator was constructed using cotton stalk through a straightforward process. The cotton stalk underwent a mild delignification process to enhance cellulose exposure, followed by immersion of polyvinyl alcohol (PVA) precursor solution into the treated cotton stalk. Through the synergistic effects of delignification and PVA, the resultant PVA-Cotton stalk evaporator exhibits a remarkably low latent heat, measuring 1120 kJ kg−1. Thus, the rate of evaporation achieves a significant value of 2.95 kg m−2 h−1 when exposed to 1 sun irradiation. Furthermore, the water collection rate of the PVA-Cotton stalk evaporator under 1 sun irradiation demonstrates a notable achievement of 2.0 kg m−2 h−1, surpassing the rates observed in most currently reported solar evaporators. The evaporation rate exhibits a linear growth with increasing light intensity. Remarkably, the PVA-Cotton stalk evaporator attains an unmatched rate of evaporation at 8.95 kg m−2 h−1 when exposed to 3 sun irradiation, representing the highest reported value at this level of irradiation.