Figure shows the adsorption and desorption curves of the samples. At first glance, the SPC/NaOH lignin sample (black) and SPC sample (blue) adsorb significantly more water than the untreated sample (red), for the same P/P0 value. On average, the SPC/NaOH and SPC samples adsorb 2.8 and 1.5 times more water, respectively. However, no significant change in water adsorption could be detected for the ML and NaOH samples compared to the original lignin. This is clear evidence that the additional carbonyl functions have a strong influence on water adsorption.