The positions of these peaks do not change very much, while their profiles vary greatly.
This is mainly because of the variation of the chemical states of these functional groups in OTAB and CMTAB. The peaks of CMTAB at 2665, 1575 and 1185 cm−1, which are not observed in the spectrum of OTAB, are probably due to new bond formation between EDTA and the biomass in the chemical modification process