Abstract
Freshwater scarcity is a global threat to modern era of human society. Sorption-based atmospheric water harvesting (AWH) is prospective to provide fresh water for remote water-stressed areas lacking in water and electricity. Adsorbent material plays a vital role in such AWH systems. Here, we report a solid adsorbent synthesized by impregnating hygroscopic salt lithium chloride (LiCl) into solidified activated carbon fiber felt (ACFF modified by silica sol). Composite samples immersed with different mass concentrations of silica sol are prepared and characterized for dynamic water uptake, equilibrium water uptake, textural and thermal properties. AS5Li30 (ACFF + 5 wt% silica gel + 30 wt% LiCl) exhibits an efficient water uptake of 2.1 g/g at 25 °C and 70% relative humidity (RH). The material further demonstrates a heat storage capacity of 5456 kJ/kg. Its low regeneration temperature (< 80 °C) and good cycle stability make it feasible to be used in practical water production applications, driven by solar energy and other low-grade energy. Estimation results show that water harvesting unit can produce 1.41 gH2O/gAS5Li30 under 25 °C and 75% RH.
Highlights
Freshwater scarcity is a global threat to modern era of human society
After cooling down to room temperature, the ACFF was immersed into the silica sol with varied mass concentrations at an ambient temperature for 1 h, sufficient for the silica sol to well distribute inside the gaps and pores of the ACFF
Composite adsorbents lithium chloride (LiCl)@ACFF were synthesized for atmospheric water harvesting
Summary
Freshwater scarcity is a global threat to modern era of human society. Sorption-based atmospheric water harvesting (AWH) is prospective to provide fresh water for remote water-stressed areas lacking in water and electricity. List symbols A/ACFF Activated carbon fiber felt AWH Atmospheric water harvesting c Fitting parameter of Eq (3) d Fitting parameter of Eq (3) k Fitting parameter of Eq (2) n Fitting parameter of Eq (2) P Pressure, Pa R Gas universal constant, J/(mol /K) S Silica sol T Temperature, K W Water uptake, g/g x0 Fitting parameter of Eq (2). Traditional solid physical porous adsorbents, like silica gels, zeolites, are usually limited by poor water uptake or high regeneration temperature. Like hygroscopic salts, have higher water harvesting performance and reasonable regeneration temperature, but they usually suffer from the difficulty in desorption process caused by deliquescence and disadvantages of agglomeration, corrosion and decreasing cycling stability[9,10,11,12]
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