Kinetic, isotherm and thermodynamic aspects of Cu2+ biosorption onto Rosa damascena leaf as a low-cost biosorbent: Optimization of process variables by Response Surface Methodology

doi:10.21203/rs.3.rs-1120602/v1

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Kinetic, isotherm and thermodynamic aspects of Cu2+ biosorption onto Rosa damascena leaf as a low-cost biosorbent: Optimization of process variables by Response Surface Methodology

https://doi.org/10.21203/rs.3.rs-1120602/v1

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In this study, the Rosa damascena leaf powder was evaluated as a biosorbent for copper removal from aqueous solutions. Optimized conditions of 4.0 g/L biosorbent dosage, pH of 5.5 and initial copper concentration of 55 mg/L obtained by Response Surface Methodology were employed for Cu2+ biosorption by R. damascena leaves and up to 88.7 % Cu2+ was removed. The biosorption data were well ﬁtted to the pseudo-second order and Elovich kinetic models. The Langmuir and Dubinin-Radushkevich isotherm models were also best fit the experimental data showing monolayer isotherm with qmax value of 25.13 mg/g obtained at optimum conditions. Thermodynamic parameters showed the spontaneity, feasibility and exothermic nature of adsorption. Scanning electron microscopy, Energy-Dispersive X-Ray, and Fourier transform infrared spectroscopy were used to characterize the biosorbent before and after Cu2+ biosorption, revealing outstanding structural characteristics and high surface functional groups availability. In addition, immobilized R. damascena leaves adsorbed 90.7 % of copper from aqueous solution, which is greater than free biosorbent (85.3 %). It can be concluded that R. damascena might be employed as a low-cost biosorbent for removing heavy metals from aqueous solutions.

Biological sciences/Biotechnology

Biological sciences/Plant sciences

Earth and environmental sciences/Environmental sciences

Table 1. Box-Behnken design factors with coded and un-coded factors, and data of the experimental response

Run	Factor 1 A: Biosorbent dosage (g/L)	Factor 2 B: pH	Factor 3 C: initial Cu²⁺ conc. (mg/L)	Response: Cu²⁺ removal percentage	Predicted values
1	1(-1)	2(-1)	60(0)	44.25	47.28
2	5(+1)	2(-1)	60(0)	64.03	68.36
3	1(-1)	6(+1)	60(0)	51.67	57.53
4	5(+1)	6(+1)	60(0)	87.68	78.62
5	1(-1)	4(0)	30(-1)	56.80	57.22
6	5(+1)	4(0)	30(-1)	77.90	78.31
7	1(-1)	4(0)	90(+1)	56.90	47.58
8	5(+1)	4(0)	90(+1)	64.34	68.67
9	3(0)	2(-1)	30(-1)	62.97	56.93
10	3(0)	6(+1)	30(-1)	68.43	67.18
11	3(0)	2(-1)	90(+1)	50.91	47.29
12	3(0)	6(+1)	90(+1)	55.39	57.54
13-17^*	3(0)	4(0)	60(0)	60.20	57.24

^*mean value of five center point assays

Table 2. Analysis of variance (ANOVA) data of the response surface quadratic model for the biosorption of Cu²⁺ ions onto R. damascena

Source	SS	df	MS	F-value	p-value Prob > F
Model	1423.4	4	355.8	10.26	0.0008*
Residual	416.4	12	34.70	-	-
Lack of Fit	321.4	8	40.18	1.69	0.321**
Pure Error	95.0	4	23.74	-	-
Correlation Total	1839.8	16	-	-	-
R²= 0.87	Adj. R²= 0.80	Pred. R²= 0.70	Adeq. precision = 9.8	CV%= 8.83	Mean= 59.92

Df: Degree of freedom, SS: Squares sum, MS: Mean sum of squares, CV: Coefﬁcient of variation, *Significant at p ˂ 0.05, **Not significant at p > 0.05.

Table 3. Analysis of variance (ANOVA) for the coefﬁcients of quadratic model for the biosorption of Cu²⁺ ions onto R. damascena

Model term	CE	df	SE	F-value	p-value Prob > F
Intercept	57.24	1	1.96	-	-
A-Biosorbent dosage	10.54	1	2.08	25.63	0.0003
B-pH	5.13	1	2.08	6.06	0.03
C-initial Cu²⁺ conc.	-4.82	1	2.08	5.36	0.039
A²	5.71	1	2.86	3.98	0.069

CE: Coefficient Estimate, df: Degree of freedom, SE: Standard error.

Table 4. Kinetic model parameters for the biosorption of Cu²⁺ ions onto R. damascena

Parameters		Values
Experimental data	**q_e(exp.) (mg/g)**	17.1
Pseudo-first order	**q_e(cal.) (mg/g)**	13.4
	k₁ (min^-1)	0.029
	R²	0.980
Pseudo-second order	**q_e(cal.) (mg/g)**	18.6
	k₂(g/mgmin)	0.005
	h(g/mgmin)	1.55
	R²	0.983
Elovich	α (g/mg min)	1.30
	β (g/mg)	0.303
	R²	0.971
Intra-particle diffusion	**K_i(mg/g min^0.5)**	0.22
	*C_i* (mg/g)	6.25
	R²	0.801

Table 5. Isotherm model parameters for the biosorption of Cu²⁺ions onto R. damascena

Isotherms	Parameters	Values
Langmuir	**q_max(mg/g)**	25.13
	b ( L/mg)	0.095
	*R_L*	0.062-0.201
	R²	0.979
Freundlich	*1/n*	0.313
	**K_f(L/mg)**	5.98
	R²	0.735
Temkin	A (L/mg)	1.9
	b(J/mol)	551.4
	R²	0.807
Dubinin–Radushkevich	*q_o* (mg/g)	21.1
	β×10^-6(mol²/J²)	6.0
	E (K/J mol)	9.13
	R²	0.926

Table 6. Thermodynamic values for the Cu²⁺ ions biosorption onto R. damascena

Temperature (K)	ΔG (K/Jmol)	ΔH (K/Jmol)	ΔS (K/Jmol)	R²
298	-1.39	-21.7	0.077	0.982
308	-2.00
318	-2.94

No competing interests reported.

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Editorial decision: Major revision
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Kinetic, isotherm and thermodynamic aspects of Cu2+ biosorption onto Rosa damascena leaf as a low-cost biosorbent: Optimization of process variables by Response Surface Methodology

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