Date kernel biochar: A green approach to methylene blue removal from polluted water in Iraq

Figures & data

Table 1. Operating conditions employed in the full factorial design methodology.

	HR (^oC/min)	Temp (^oC)	Time (min)
+	30	550	90
0	20	450	60
−	10	350	30

Table 2. Experimental matrix based on full factorial design for three process variables: pyrolysis temperature, holding time, and heating rate.

	Operating conditions
Run	HR (^oC/min)	Temp (^oC)	Time (min)
1	30	550	90
2	10	550	90
3	30	350	90
4	10	350	90
5	30	550	30
6	10	550	30
7	30	350	30
8	10	350	30
9	20	450	60
10	20	450	60
11	20	450	60

Table 3. Proximate and ultimate analyses of Khestawi date kernels.

Proximate analysis (wt%, dry basis)
MC	VM	FC	AC
7.85	79.51	19.46	1.02
Ultimate analysis (wt%, dry basis)
C	H	N	O
24.34	8.66	0.78	51.75

Table 4. Percentage of MB removal from polluted water using biochar.

Run	Biochar production conditions			% R (%)
	HR (^oC/min)	Temp (^oC)	Time (min)
1	30	550	90	23.0
2	10	550	90	23.9
3	30	350	90	38.1
4	10	350	90	36.4
5	30	550	30	35.4
6	10	550	30	41.5
7	30	350	30	55.9
8	10	350	30	57.0
9	20	450	60	26.9
10	20	450	60	29.1
11	20	450	60	28.0

Figure 1. Interaction effects plot showing the influence of pyrolysis temperature, holding time, and heating rate on date kernel-based biochar adsorption capacity for methylene blue (MB) removal.

Figure 2. Main effect plots illustrating the influence of pyrolysis temperature, holding time, and heating rate on date kernel-based biochar adsorption capacity for methylene blue (MB) removal.

Table 5. Results of the ANOVA (analysis of variance) for process variables.

Term	Effect	Coef	SE Coef	T-value	P-value	VIF
Constant	*	38.9081	0.396	98.35	0.000	1.00
HR	−1.6048	−0.8024	0.396	−2.03	0.180	1.00
Temp	−15.9534	−7.9767	0.396	−20.16	0.002	1.00
Time	−17.1177	−8.5588	0.396	−21.63	0.002	1.00
HR*Temp	−1.9194	−0.9597	0.396	−2.43	0.136	1.00
HR*Time	2.0138	1.0069	0.396	2.55	0.126	1.00
Temp*Time	2.0768	1.0384	0.396	2.62	0.120	1.00
HR*Temp*Time	0.6293	0.3147	0.396	0.80	0.510	1.00
Ct Pt	*	−10.8955	0.758	−14.38	0.005	1.00

Figure 3. Adsorption isotherms of methylene blue (MB) on Biochar Obtained at pyrolysis conditions: heating rate of 20°C/min, pyrolysis temperature of 450°C, and holding time of 60 min.

Table 6. Model parameters of the adsorption isotherms for methylene blue (MB) adsorption on biochar.

Adsorbent	Freundlich model		Langmuir model
	KF	n	b	Qm
Biochar obtained at pyrolysis conditions of (20 °C/min, 450 °C, 60 min)	1.64	1.48	0.022	46.5
Activated biochar (ABC-1)	7.12	1.97	–	–
Activated biochar (ABC-2)	0.34	2.38	–	–

Figure 4. Adsorption isotherms of methylene blue (MB) on Activated Biochar Samples: ABC-1 (Biochar Activated with organic 1) and ABC-2 (Biochar Activated with organic 2).

Table 7. Performance of different adsorbents in the removal of MB from polluted water.

Adsorbent	Adsorption capacity (KF)	Reference
Coconut shell carbon	0.149	(Okeola & Odebunmi, 2010)
Calcined raw kaolin	6.57	(Ghosh & Bhattacharyya, 2002)
Calcined pure kaolin	9.01	(Ghosh & Bhattacharyya, 2002)
Spent coffee grounds	5.19	(Franca et al., 2009)
Wheat shells	1.46	(Bulut & Aydın, 2006)
Waste sludge	1.21	(Sarioglu & Atay, 2006)
Activated carbon (C28)	52	(Belhachemi & Addoun, 2011)
Waste potato peels	9.61	(Öktem et al., 2012)
Neem leaf powder	4.95	(Bhattacharyya & Sharma, 2005)
Date kernel-derived biochar	1.64	This study
Activated biochar (ABC-1)	7.12	This study
Activated biochar (ABC-2)	0.34	This study

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