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Improving the evaporation rate of solar steam generation (SSG) has always been a research hotspot to solve the shortage of water resources. Using cotton, Fe3O4, polyvinyl alcohol (PVA) and diatomite (DM) as raw materials, DM/PVA/Fe3O4@cotton composites with both firmness and hydrophilicity were prepared. Fe3O4 has a wide range of light absorption characteristics and good photothermal conversion performance, and is an ideal photothermal conversion material. PVA enhances the adhesion between Fe3O4, cotton and DM and enhances the hardness of the sample and the internal porous structure. The existence of DM greatly improves the hydrophilicity of the sample, ensuring that the water in the lower layer can be continuously transported to the surface of the sample, and DM makes the surface of the sample rough, which reduces the reflection of sunlight and improves the efficiency of light heat conversion. Under one-sun irradiation, the temperature of the sample surface increases by 52.6 °C, the evaporation rate can reach 1.32 kg m−2 h−1 and the evaporation efficiency is 82.9%. Using this sample as the photothermal conversion layer of the SSG device, the removal rate of salt ions in seawater is more than 98% and the removal rate of heavy metal ions in sewage is close to 100%. This work provides a new idea and design method for SSG in the field of seawater desalination and sewage treatment. [ABSTRACT FROM AUTHOR]

• The sample produced in this work has a large specific surface area and absorbance. • The evaporation device has the advantages of low cost, high water delivery efficiency, and simple production. • The samples produced in this work have high photothermal conversion efficiency. Solar-driven interfacial water evaporation is an emerging water purification technology. However, the high cost and low evaporation efficiency limit the wide application of solar-driven interfacial water evaporation technology. In this work, we use the dough fermented flour and yeast powder production, and then after fermentation of dough to produce high temperature carbonization of carbon materials, the preparation of the sample surface formed a large number of pits, increased specific surface area and the absorbance of the sample, and increased the solar-thermal conversion efficiency of the sample. It is found that the evaporation rate and evaporation efficiency of the sample made in this work is 1.5 kg m−2h−1 and 94.2 % respectively under one solar irradiation intensity. The maximum surface temperature of the sample can reach 43.3℃ during the experimental test, which has good evaporation performance. It provides a new idea for making economical and environmentally friendly materials in the field of solar-driven water evaporation. [ABSTRACT FROM AUTHOR]