Powdered activated carbon prepared from Leucaena leucocephala biomass for cadmium removal in water purification process

Figures & data

Table 1. Some adsorbents used for removal of cadmium ion from water.

Adsorbent	Reference
Cucumber peel activated carbon	(Basu, Guha, & Ray, 2018)
Humic acid-based carbon materials	(Jin et al., 2018)
nano-montmorillonite	(Liu et al., 2018)
Punica granatum (pomegranate) carpellary membrane	(Saini, Kumar, Chawla, & Kaur, 2017)
Rice husk	(Khan, Khan, Ding, Khan, & Alam, 2018)
Lotus seedpod-derived biochar	(Chen et al., 2018)
Magnetite/carbon nanocomposites	(Andelescu, Nistor, Muntean, & Rădulescu-Grad, 2018)
Aguaje (Mauritia flexuosa) based activated carbon.	(Obregón-Valencia & Sun-Kou, 2014)

Figure 1. SEM images of (a) the raw material of Leucaena leucocephala at magnification 150x, (b) the raw material of Leucaena leucocephala at magnification 550x, (c) activated carbon at magnification 150x and (d) activated carbon at magnification 550x.

Figure 2. Removal of cadmium at a different contact time.

Figure 3. Initial concentration versus removal of cadmium.

Figure 4. Solution pH versus removal of cadmium.

Figure 5. Effect of temperature on removal of cadmium.

Figure 6. 1/q_e vs 1/C_e plot of Langmuir isotherm of Cd(II) ion adsorption for NaOH:carbonized sample ratios of 3:1 (a), 2:1 (b) and 1:1 (c).

Table 2. Isothermic and kinetics models for the adsorption of Cd²⁺ by Leucaena leucocephala based activated carbon.

Sample	Temperature, °C	Langmuir Isotherm			Freundlich Isotherm
		qm (mg/g)	KL (l/mg)	R^2	KF	l/n	R^2
1:1	30	31.153	8.231	0.9671	3.8763	0.9878	0.8265
	40	31.447	5.483	0.9655	3.8045	1.0455	0.7990
	50	31.67	0.589	0.9542	5.1123	2.3296	0.9003
2:1	30	40.984	8.133	0.9855	5.6249	2.1227	0.9703
	40	50.505	4.500	0.9783	4.7040	1.5924	0.9000
	50	53.191	5.371	0.9707	4.8970	1.6174	0.8874
3:1	30	54.054	3.627	0.9627	4.8448	1.7987	0.9401
	40	64.013	2.600	0.9609	4.2177	1.2863	0.7513
	50	70.423	3.302	0.9873	5.7397	2.3551	0.9701

Table 3. Comparison of different adsorption capacity for different cadmium adsorbent.

Adsorbent	Maximum adsorption (mg/g)	Reference
Leucaena leucocephala activated carbon	70.42	This work
Humic acid-based carbon materials	26.3	(Jin et al., 2018)
Nano-montmorillonite	17.61	(Liu et al., 2018)
Punica granatum (pomegranate) carpellary membrane	111.11	(Saini et al., 2017)
Lotus seedpod-derived biochar	51.18	(Chen et al., 2018)
Magnetite/carbon nanocomposites	76.67	(Andelescu et al., 2018)
Aguaje (Mauritia flexuosa) based activated carbon.	26.33	(Obregón-Valencia & Sun-Kou, 2014)

Figure 7. ln qe vs ln Ce linear plot of Freundlich isotherm of Cd(II) ion adsorption for NaOH:carbonized sample ratios of 3:1 (a), 2:1 (b) and 1:1 (c).

Figure 8. log (qe-qt) vs t linear plot of pseudo first order (a) and t/qt vs t linear plot of pseudo second order (b) kinetic model of Cd(II) ion adsorption using Leucaena leucephala activated carbon.

Table 4. Kinetic models for Cd(II) ion adsorption using Leucaena leucephala activated carbon.

	Pseudo first order			Pseudo second order
Sample	qe (mg/g)	K1	R^2	qe (mg/g)	K2	R^2
1:1	33.58	0.0438	0.9650	2.0 x 10^-8	1.24 x 10^15	0.3376
2:1	33.6	0.0433	0.4851	2.0 x 10^-4	12.42 x 10^-6	0.1391
3:1	33.4	0.0451	0.8521	1111.1	4.06 x 10^-7	0.1092

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