Table 4.

Assignment of the principal IR absorption bands in the spectra of unprocessed SS and its chars

Location of wave numbers (cm-1)			Band assignment of functional group/component
Unprocessed SS	SS chars	Vibrations
			3335	N-H stretch & O-H stretch	Aliphatic secondary amines stretch and hydroxy group
3275	3273	O-H stretch	Hydroxy group
2955		C-H stretch	Aliphatic methylene group
2920	2920
2850	2850
	1649	C=O	Primary amide, carboxylates (H-bonded C=O carbonyl stretch)
1626	1629	C=O stretch C=C stretch	Carboxylate and conjugated aromatic ring mode
1620
1535	D	N-H in plane	Secondary amides
	1452	C-O stretch	Carbonate ion
1408	D	N-O stretch	A source of nitrate in unprocessed biowaste
1381	1377	Methyl C-H bend N-O stretch	Provides indication of long-chain aliphatic compounds Nitrate in solid wastes
1232	1259	C-O stretch C-N stretch	Carboxylic acids or Tertiary amide
	1024	C-O stretch	Characteristic polysaccharide bands for C-O stretching of polysaccharides or polysaccharide-like
1010	1006
796	798	NH2 out of plane	Primary amine groups
	719	Methylene C-H rocking	Provides indication of long-chain aliphatic compounds
	657-692	O-H or C-H out of plane bend S-O bend	Skeletal vibrations of hydroxy out of plane bend or C-H bending vibration, as corroborated with bands at 1200-1000, 1600-1300 Inorganic sulphates