SWBC was then analyzed using FT-IR. As presented in Fig. 2b, the FT-IR spectrum of SWBC is very similar to that of hollocellulose. The bands relating the cellulose characteristics are identified at peaks 3348, 2925 and 1048 and indicate O–H, C–H and C–O–C stretching, respectively. A small peak is observed around 1736 cm−1, which indicates a compound of the hemicellulose band, whereas a constituent of the lignin bands around 1500 and 1600 cm−1[21] cannot be observed clearly, which indicates a low lignin content. These results agree with the chemical characterization as discussed previously. It appears that part of the carrageenan polymer was involved in the SWBC. This is indicated by the appearance of peaks at 932 and 850 cm−1, which show the link of the 3,6-anhydro-d-galactose and d-galactose-4-sulfate, respectively [8] and [22].