Abstract:

Objective The interface solar steam generator (ISSG) has received widespread attention as a novel, sustainable water resource acquisition method with low energy consumption, low cost, and environmental friendliness. Among them, the ISSG based on textile production technologies such as weaving, knitting, and non-woven offers advantages of low cost and industrialization readiness. By designing a special knitted spacer structure to integrate the photothermal evaporation layer, water supply structure, and floating layer through weaving in 2-D or 3-D forms, it is expected to achieve a good combination of high-efficiency light absorption and conversion, rapid and stable water supply, and excellent thermal management, thereby effectively enhancing the evaporation performance of the ISSG.

Method Based on the designability of knitted spacer fabrics, the photothermal evaporation layer was knitted with polyester composite fibers covered by graphene/carbon nanotubes, and the floating layer was woven with polyester filament. The spacer yarn prepared by two-dimensional knitting technology on KBL-24-2-90 high-speed knitting machine was used to connect the photothermal evaporation layer and the floating layer. A self-floating weft knitted profiled spacer fabric interface solar steam generator (SWF) was prepared on MN-TYPE knitting machine generator. The water transfer performance, light absorption performance, evaporation performance and wastewater treatment performance were studied and analyzed.

Results Through the water transfer experiment of the spacer yarn prepared by two-dimensional knitting technology, it was found that the liquid transmission speed of the spacer yarn was 1 cm/min, and the results showed that the spacer yarn could achieve rapid moisture transfer. The SWF evaporator was able to run without light for 900 seconds, and the light absorption rate in the UV-visible to near-infrared light region was as high as 96%. The SWF evaporation performance was tested using a simulated light source consisting of an AM 1.5 filter and an xenon lamp, with an evaporation rate of 1.80 kg/(m²·h) at a light intensity of 1 kW/m², and an evaporation efficiency of 95.73%. The SWF was tested for cyclic stability in a 3.5% sodium chloride solution, and the test results showed that SWF has good cyclic stability, with no significant difference in evaporation rate after 10 uses, and an evaporation efficiency was 1.51 kg/(m²·h) even in a 15% sodium chloride solution. The evaporation performance of dye solutions containing methylene blue solution and methyl orange solution was tested, and there was a clear color change in the methylene blue solution, methyl orange solution, and the steam water collected during evaporation. The color of the steam water collected was almost transparent.

Conclusion Using the 3-D knitting technology, a solar steam generator SWF made from self-floating weft knitted special-shaped spacer fabric interface was prepared. The test results show that the special-shaped solar evaporator has highly efficient light absorption performance, self-floating performance, high efficiency water supply performance, and can achieve highly efficient solar photothermal conversion, which is applicable to seawater desalination, wastewater treatment and other areas. The novelty of this study lies in the new preparation idea and development of fabric-based solar evaporators.

Key words: spacer fabric, light and heat conversion, solar evaporation, seawater desalination, wastewater purification