Removal of Hexavalent Chromium by Using Sustainable Green Materials as Low-Cost Adsorbents

Table 5

The surface functional group shift in peaks.

	Wave number range (cm^-1) before treatment	Wave number range (cm^-1) after treatment	Assignment
Green tea residue	3444	3416	-OH or N-H
	3130	3128	-OH or N-H
	2923	2923	Aliphatic C-H
	2852	—	Aliphatic C-H
	1736	—	C=O
	1653	1637	C=O
	1400	1401	Phenyl groups
	1386	—	Aliphatic C-H group
	1235	—	–SO3 stretching/P=O, C-O
	1150	—	C-O-C
	1064	1071	C-O
Pu-erh residue	3441	3441	-OH or N-H
	3312	3328	-OH or N-H
	3063	—	-OH or N-H
	2923	2923	Aliphatic C-H
	2854	—	Aliphatic C-H
	1655	1678	C=O
	1517	—	Amide II of proteins, N-H, C-N
	1456	1456	N-H bending, C-H
	1367	—	Aliphatic C-H group
	1106	—	C-O-C
	1028	1025	C-O
Tieguanyin residue	3443	—	-OH or N-H
	3335	3330	-OH or N-H
	2922	2922	Aliphatic C-H
	2853	2853	Aliphatic C-H
	1736	—	C=O
	1656	1655	C=O
	1537	—	Amide II of proteins, N-H, C-N
	1456	1459	N-H bending或C-H
	1380	—	Aliphatic C-H group
	1240	—	–SO3 stretching/P=O, C-O
	1160	—	C-O-C
	1067	1022	C-O