Microwave-assisted magnetic biochar for removal of hexavalent chromium from aqueous solution

Figures & data

Figure 1. Effect of (a) pH, (b) contact time (c) sorbent dose (d) competing ions on Cr(VI) removal by MTWB and MRHB.

Table 1. Isotherm modeling parameters for MTWB and MRHB.

Isotherm models	Parameters	MTWB	MRHB
Langmuir	QL (mg g^-1)	38.16	17.60
	KL (L g^-1)	0.24	0.12
	R^2	0.96	0.97
Freundlich	QF (mg^1-n g^-1 L^n)	59.15	42.56
	n	0.21	0.26
	R^2	0.86	0.89

Table 2. Kinetic modeling parameters for MTWB and MRHB.

Pseudo-first-order model			Pseudo-second-order model
qe (mg g^−1)	k1 (min^−1)	R^2	qe (mg g^−1)	k2 (g mg^−1 min^−1)	R^2
MTWB
24.54	0.08	0.94	196	0.001	0.99
MRHB
20.41	0.075	0.83	192.30	0.0052	0.99

Figure 2. The FTIR (transmittance spectra) of (a, c) unloaded and (b, d) Cr(VI) loaded biochars.

Figure 3. SEM micrographs of (a) MTWB and (b) MRHB.

Figure 4. EDS analyses of unloaded (a) MTWB (c) MRHB and Cr(VI) loaded (b) MTWB (d) MRHB (e) Photoluminescence (PL) measurements of MTWB and MRHB.

Figure 5. The C1s, O1s and Cr2p spectra of biochars.

Figure 6. The Fe2p3 spectra of biochars.