Table 2. Proposed band assignments of the FTIR spectra of biochar.

Wavenumbers (cm -1)	Characteristic vibrations	Reference
3670 - 3650	ν(OH) from non-hydrogen bonded O-H groups	( Sharma et al., 2004)
3600 - 3200	ν(OH) from sorbed water and hydrogen-bonded biochar O-H groups	( Keiluweit et al., 2010)
~2980	2990-2950 cm -1 asymmetric aliphatic v(CH) from terminal –CH 3 groups	( Socrates, 2001)
~2890	2870-2890 cm -1 symmetric aliphatic v(CH) from terminal –CH 3 groups	( Socrates, 2001)
2700-2100	P-OH groups produce one or two broad bands in the 2700 -2100 region 2100 - 2250cm -1 C≡C bonds 2100 - 2360cm 1 Silane Si-H 2100 - 2270cm -1 Dimides, Azides and Ketenes	( Stuart, 2004)
1700	v(C=O) from carboxylic acids amides, esters and ketones 1740- 1650	( Socrates, 2001)
1540 - 1650	C==O stretching vibrations for amides, aromatic C=C stretching and carboxylate anion vibrations.	( Calderón et al., 2006)
1580 - 1600	vibration of C=C bonds	( Davis et al., 1999)
1424	Carbonate (ν 3; asymmetric stretch)	( Socrates, 2001)
1200- 950	P–O (asymmetric and symmetric stretching of PO 2 and P(OH) 2 in phosphate)	( Jiang et al., 2004)
1100-1000	Si-O-Si asymmetric stretching	( Falaras, 1999)
1020 - 1030	C–O stretching of ethers and primary amine C–N stretches	( Keiluweit et al., 2010) ( Claoston et al., 2014)
~875	Out-of-plane bending for CO 3 2− and – v(M-O-H) O-H bending bands from clay minerals associated with biochar	( Zhao et al., 2013) ( Farmer, 1974)
796 and 780	quartz doublet	( Farmer, 1974)
462-464	Si-O-Si	( Qian & Chen, 2013)
452	Si-O rocking	Shahrokh Abadi et al., 2015