Scavenging Rhodamine B dye using moringa oleifera seed pod

Figures & data

Figure 1. Structure of Rhodamine-B dye.

Figure 2. SEM micrograph of (a) MOSPR and (b) MOSPAC (magnification = 500×).

Figure 3. FTIR spectrum of (a) MOSPR and (b) MOSPAC.

Table 1. FTIR spectra characteristics of raw and acid activated moringa olifera seed pod (MOSP).

Wave numbers (cm^−1)				Band assignments
I.R peaks	MOSPR	MOSPAC	Differences
1	3447	3412	−35	O–H stretching, H-bonding of alcoholic phenols
2	2926	2930	4	C–H stretching of alkanes
3	1649	1612	−12	N–H bend of alkenes
4	1423	1462	39	C–C (in ring) stretching of aromatics
5	1254	1254	0	C–N stretching of aromatic amines
6	1115	1094	−21	C–N stretching of aliphatic amines
7	910	920	10	O–H bending of carboxylic acids
8	635	773	38	C–Cl stretch of alkyl halides

Figure 4. EDX spectra of (a) MOSPR (b) MOSPAC.

Table 2a. Energy dispersive X-ray (EDAX ZAF) quantification of MOSPR.

Element	Wt. %	At %	K-ratio	Z	A	F
C	61.69	81.18	0.2522	1.0356	0.3947	1.0001
O	6.28	6.20	0.0083	1.0183	0.1304	1.0001
Me	2.13	1.38	0.0115	0.9772	0.5531	1.0017
Al	1.97	1.15	0.0125	0.9485	0.6686	1.0024
Cl	2.15	0.96	0.0195	0.9181	0.9636	1.0235
K	13.92	5.63	0.1299	0.9251	0.9952	1.0140
Ca	6.08	2.40	0.0542	0.9470	0.9388	1.0030
Ce	2.55	0.29	0.0199	0.7319	1.0616	1.0027
Cu	3.24	0.80	0.0269	0.8307	1.0016	1.0000
Total	100.00	100.00

Table 2b. Energy dispersive X-ray (EDAX ZAF) quantification of MOSPAC.

Element	Wt. %	At %	K-ratio	Z	A	F
C	78.44	88.80	0.2367	1.0156	0.2971	1.0001
O	5.23	4.44	0.0076	0.9987	0.1451	1.0002
Si	1.32	0.64	0.0117	0.9579	0.9124	1.0028
P	12.20	5.36	0.1074	0.9193	0.9573	1.0004
Ca	0.74	0.25	0.0069	0.9273	1.0014	1.0020
Fe	2.07	0.50	0.0177	0.8410	1.0180	1.0000
Total	100.00	100.00

Table 3. Different functional groups on MOSPAC.

Adsorbent	Different functional groups on MOSPAC
	Carboxylic (mmolg^−1)	Phenolic (mmolg^−1)	Lactonic (mmolg^−1)	Basic (mmolg^−1)	Acidic (mmolg^−1)
MOSPAC	0.696	–	0.341	0.054	1.037

Figure 5. Plot of pH_pzc of acid activated moringa oleifera seed pod (MOSPAC).

Figure 6. Plot of adsorption of Rh-B dye onto MOSPAC against adsorption time at various initial dye concentrations at 30 °C.

Figure 7. Plot of percentage Rh-B dye removal at different pH.

Figure 8. Plot of percentage Rh-B dye removal at different temperatures.

Table 4a. Isotherm parameters for Rh-B dye adsorption onto MOSPAC at 30 °C.

Langmuir		Freundlich		Temkin		DBR
qm (mg/g)	1250	Kf	139.4	KT (mol/g)	8.592	Xm (mg/g)	934.4
KL (l/mg)	0.1096	n	1.817	bT (mol/kJ)	0.0142	β (10^−6)	1.00
RL	0.0086	1/n	0.5504	R^2	0.9940	Εa (kJ/mol)	0.707
R^2	0.9979	R^2	0.9920			R^2	0.9968

Table 4b. Isotherm parameter for Rh-B dye adsorption onto MOSPAC at 40 °C.

Langmuir		Freundlich		Temkin		DBR
qm (mg/g)	175.4	Kf	629.7	KT (mol/g)	15.61	Xm (mg/g)	181.6
KL (l/mg)	2.5915	n	1.542	bT (mol/kJ)	0.0120	β (10^−6)	1.00
RL	0.0004	1/n	0.6486	R^2	0.9080	Εa (kJ/mol)	2.236
R^2	1.0000	R^2	0.9893			R^2	0.9989

Table 4c. Isotherm parameters for Rh-B dye adsorption onto MOSPAC at 50 °C.

Langmuir		Freundlich		Temkin		DBR
qm (mg/g)	125	Kf	81.4	KT (mol/g)	3.626	Xm (mg/g)	944.0
KL (l/mg)	0.1538	n	1.304	bT (mol/kJ)	0.0054	β (10^−6)	−9
RL	0.0060	1/n	0.767	R^2	0.9974	Εa (kJ/mol)	0.2357
R^2	0.9981	R^2	0.9224			R^2	0.9976

Table 5. Comparison of maximum monolayer adsorption capacities of Rh-B dye on various adsorbents.

Adsorbents	qm (mg/g)	References
Modified Coir pith	14.90	[64]
Baker’s yeast	25.00	[65]
Cedar cone	4.55	[66]
Sugarcane baggase	51.50	[67]
Acid treated Kaolinite	23.70	[68]
Acid treated montmorillonite	188.67	[68]
Raw dika nut waste	212.77	[69]
Acid treated dika nut waste	232.00	[69]
Raphia hookerie fruit epicarp	666.67	[56]
Jute stick powder	87.70	[70]
Microwave treated nilotica leaf	24.39	[71]
Fly ash	10.00	[72]
Artocarpus odoratissimus	131.00	[46]
Casuarina equisetifolia cone powder	49.50	[47]
Peat from Brunei Darussalam	162.90	[73]
Moringa olifera seed pod	1250.00	This work

Table 6. Parameters of the pseudo-first order, pseudo-second order and Elovich kinetic models together with their regression coefficient for MOSPAC at 30 °C.

	200 mg/l	400 mg/l	600 mg/l	800 mg/l	1000 mg/l
Pseudo-first order kinetic model
k1 (min^−1)	0.0550	0.0528	0.0385	0.0325	0.0443
qe calc (mg/g)	62.565	108.245	144.301	284.975	370.591
qe exp (mg/g)	188.933	406.089	605.522	834.444	1014.989
SSE (%)	24.320	56.287	87.163	103.840	121.780
R^2	0.8937	0.8746	0.7885	0.8395	0.9318
Pseudo-second order kinetic model
k2 (min^−1)	0.0023	0.0013	0.0009	0.0004	0.0004
qe calc (mg/g)	192.308	416.667	625.000	833.333	1000.000
qe exp (mg/g)	188.933	406.089	605.522	834.444	1014.989
SSE (%)	0.650	1.999	3.681	0.210	2.833
h	85.059	225.695	351.563	277.778	400.000
R^2	0.9998	0.9998	0.9999	0.9995	0.9998
Elovich model
Β	0.0374	0.0194	0.0134	0.0090	0.0080
α	627.831	2652.872	4644.563	2865.565	6148.686
R^2	0.8495	0.7902	0.7800	0.8762	0.9019

Figure 9. Plot of intraparticle diffusion model for Rh-B dye adsorption onto MOSPAC.

Table 7. Parameters of the intra-particle kinetic model together with their regression coefficients for MOSPAC at 30 °C.

	200 mg/l	400 mg/l	600 mg/l	800 mg/l	1000 mg/l
kdiff1	38.960	84.367	128.020	164.700	177.470
C1	31.970	79.362	114.760	136.940	253.780
R^21	0.9181	0.8833	0.9190	0.9486	0.9763
kdiff2	1.6707	2.8442	4.6599	12.8430	16.3400
C2	172.800	377.850	554.810	691.100	841.920
R^22	0.8062	0.8422	0.9590	0.9839	0.9629

Table 8. Thermodynamic parameters for adsorption of Rh-B dye onto MOSPAC.

Temp (K)	ΔG^o (kJ mol^−1)	ΔH^o (kJ mol^−1)	ΔS^o (Jk^−1 mol^−1)	Ea (kJ mol^−1)	A (10^11)
303	−27.381	127.562	507.894	33.780	2.023
313	−36.515
323	−30.096

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