Because the content of other elements were negligible,
and hence the O content (fO) was calculated by equation of
fO = 100−fC −fH −fN. The H/C and (O + N)/C atomic ratios of five
biosorbent were calculated to evaluate their aromaticity and polarity,
respectively. FTIR spectra were recorded in the 4000–400cm−1
region by a Nicolet FTIR spectrophotometer (model 560) with a
resolution of 4.0cm−1.