Bentonite-assisted construction of magnesium-silicate-based composite as efficient adsorbent for organic dye removal

Figures & data

Figure 1. (a) Schematic diagram of the synthetic pathway of MS-Bt. The SEM images of (b) Bt, (c) intermediate and (d) MS-Bt. (e) STEM image and corresponding element mapping for MS-Bt.

Figure 2. (a) XRD patterns and (b) FT-IR spectra of samples.

Figure 3. N₂ adsorption-desorption isotherms and the size of the corresponding pore size contribution pore capacity of (a,b) MS, (c,d) MS-Bt and (e,f) Bt.

Figure 4. Adsorption properties and XRD patterns of the products prepared by (a,b) different addition ratios of Bt, (c,d) different hydrothermal time and (e,f) different hydrothermal temperature.

Figure 5. Plot of adsorption amount with (a) adsorption time, (b) solution concentration, (c) solution pH and (d) reaction temperature.

Figure 6. (a) Isotherm model and (b) kinetic model of MS-Bt.

Table 1. Corresponding fitting parameters for the adsorption of MB on the MS-Bt by using Langmuir and Freundlich isotherm models.

Samples	Langmuir			Freundlich
	qm (mg g^−1)	kL (L mg^−1)	R^2	kF	1/n	R^2
MS-Bt	241.29	6.87	0.9107	167.90	15.69	0.9098

Table 2. Kinetic fitting parameters for the adsorption of MB on the MS-Bt by using PFO and PSO models.

Model	qep (mg g^−1)	k1 (min^−1)	k2 (g mg^−1 min^−1)	R^2	Eq.
PFO	202.63	0.037		0.9638	(6)
PSO	234.52		2.0*10^−4	0.9884	(7)

Table 3. Adsorption of MB onto sodium Bt: thermodynamic parameters.

Samples	T	ΔG (kJ mol^−1)	ΔH (kJ mol^−1)	ΔS (kJ mol^−1 K^−1)	R^2
MS-Bt	298.15	−4.27	25.20	98.82	0.9623
	308.15	−5.26
	318.15	−6.24
	328.15	−7.23

Figure 7. (a) XRD patterns and (b) FT-IR spectra of MS-Bt before and after adsorption of MB.

Table 4. Comparison of the removal rates and maximum adsorption for MB on different adsorbents.

Adsorbents	c (mg L^−1)	qm (mg g^−1)	Removal rates (%)	Ref
MS-Bt	200	199.91	99.95	This work
Sep-AAM	20	99.92	99.92	[46]
meso-MgSi	80	203	95	[47]
MSH-1.75	200	307	99.5	[48]
HG@MS	50	243.48	97.39	[49]
MgSiFM	20	147.70	94.82	[50]
MgSi/RGO	100	433	–	[51]
MS	800	526.32	65.79	[52]
PFB-mZVI	800	42.8	5.35	[53]
Philippines Bt	100	160	–	[54]

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Data availability statement

The data that support the findings of this study are available from the corresponding author.