Ni(II) removal using date seed powder biosorbent: Process parameters classification and RSM modeling

Figures & data

Figure 1. SEM images of the DSP surface (a) before and (b) after adsorption

Table 1. Process variables and their coded levels for the RSM design

Independent variables Xn	Symbol	Coded levels
		−1	0	1
X1: Mass (g)	A	0.05	0.294231	0.6
X2: Stirring time (min)	B	5	30.1923	60
X3: Particle size (μm)	C	100	200	700
X4: pH	D	1	7	13

Table 2. ANOVA for response surface reduced quadratic model analysis of variance table

Source	Sum of Squares	Mean Square	F Value	p-value	Comment
				Prob > F
Model	2750.50	458.42	50.10	< 0.0001	Significant
A-Mass	99.69	99.69	10.89	0.0038	Significant
B-Stirring time	185.37	185.37	20.26	0.0002	Significant
C-Particle size	173.65	173.65	18.98	0.0003	Significant
D-pH	1620.32	1620.32	177.09	< 0.0001	Significant
B^2	59.59	59.59	6.51	0.0195	Significant
D^2	831.88	831.88	90.92	< 0.0001	Significant
Residual	173.84	9.15

Table 3. Statistical indices for the development model of Ni(II) removal

Std Dev.	3.02	R-squared	0.9406
Mean	84.58	Adj R-squared	0.9218
C.V. %	3.58	Pred R-squared	0.8893
PRESS	323.66	Adeq precision	32.013
BIC	145.99	AICc	143.41

Figure 2. 2D and 3D models for different parameters of the Ni(II) removal

Figure 3. Optimization of absorbent mass, pH, particle size and stirring time parameter on Ni(II) removal efficiency