Fabrication of stable MWCNT bucky paper for solar-driven interfacial evaporation by coupling γ-ray irradiation with borate crosslinking

Herein, we report a facile solution process for preparing multi-walled carbon nanotube (MWCNT) bucky paper for solar-driven interfacial water evaporation. This process involves vacuum filtrating a dispersion of MWCNTs that was modified by polyvinyl alcohol (PVA) under γ-ray irradiation on a cellulose acetate microporous membrane, followed by borate crosslinking. Fourier transform infrared spectroscopy, Raman spectroscopy, and thermogravimetry confirmed the success of PVA grafting onto MWCNTs and borate crosslinking between modified MWCNT nanoyarns. The as-prepared crosslinked MWCNT bucky papers (BBP membranes) were used as a solar absorber, by placing them on a paper-wrapped floating platform, for interfacial water evaporation under simulated solar irradiation. The BBP membranes showed good water tolerance and mechanical stability, with an evaporation rate of 0.79 kg m−2 h−1 and an evaporation efficiency of 56% under 1 sun illumination in deionized water. Additionally, the BBP membranes achieved an evaporation rate of 0.76 kg m−2 h−1 in both NaCl solution (3.5 wt%) and sulfuric acid solution (1 mol L−1), demonstrating their impressive applicability for water reclamation from brine and acidic conditions. An evaporation rate of 0.70 kg m−2 h−1 (very close to that from deionized water) was obtained from the solar evaporation of saturated NaCl solution, and the BBP membrane exhibited unexpected stability without the inference of salt accumulation on the membrane surface during long-term continuous solar evaporation.