Table 2.

The major peaks and assignment in FTIR spectra of NT-1 before and after Cu(II) adsorption

Position of absorption peak (cm−1)	Peak assignment	Type of group
3600−3200	O−H vibration	OH forming hydrogen bonds
2927, 2958	Asymmetric and symmetric stretching vibrations of C−H	Aliphatic CH, CH2, and CH3
1743	C=O vibration	COOH
1650 ± 10	C=O vibration; Asymmetric stretching vibration of COO−	Protein amide I Carboxylate ion
1550 ± 10	CON−H deformation	Protein amide II; aromatic heterocyclic compounds
1458	C=C vibration; C−H2, C−H3 bending deformation	Aromatic carbon Aliphatic CH2 and CH3
1400	COO− symmetric stretching vibration	Carboxylate ion
1319	O−H in-plane bending deformation	Phenolic hydroxyl group
1242	C−N vibration; −P, −S	Protein amide III; phosphates and sulfates on the biofilm surface
1150 ± 10	C−O vibration	C-O in esters; aliphatic OH
1072 ± 10	C−O−C vibration	Polysaccharide ring
1030 ± 20	P−OCH3 vibration	Phosphate esters
930 ± 10	P−O−P vibration	Polyphosphate esters
860−750	C−H out-of-plate bending deformation	CH of aromatic heterocyclic compounds
615 ± 10	O−H out-of-plate bending deformation	OH of polysaccharide ring