Low Cost Modified Biochars from Peanut Shells for the Removal of Textile Dyes

Nunes, Nelson; Santos, Maria Teresa; Martins, Angela

doi:10.21577/0103-5053.20220156

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Article • J. Braz. Chem. Soc. 34 (6) • 2023 • https://doi.org/10.21577/0103-5053.20220156 copy

Low Cost Modified Biochars from Peanut Shells for the Removal of Textile Dyes

Authorship SCIMAGO INSTITUTIONS RANKINGS

Biochars from peanut shell wastes were produced and further modified with KOH and HNO₃ to efficiently remove two industrial dyes, Mordant Orange 1 and Green Malachite oxalate, in aqueous systems. The materials were characterized through elemental analysis, N₂ adsorption isotherms, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and the determination of the point of zero charge, pH_PZC. The basic and, particularly, the acid treatments increased the specific surface area by 15 and 43%, respectively, and the pH_PZC shifted from 6.2 to 9.1 or 3.3 upon treatments with KOH or HNO₃. These modifications impacted the adsorption behavior of the dyes; in the case of Mordant Orange 1, the adsorption capacity increased 2 and 4 times, respectively, when compared with the parent biochar. These results show that the performance of biochars can improve substantially through simple modifications using acid or basic treatments that not only increase the specific surface area but also modify adsorbent/adsorbate interactions.

Keywords:
alkali or acid treatment; biochars; peanut shells; pyrolysis; dye adsorption

Sample	Yield^a / %	Elemental analysis / wt.%				Atomic ratio O/C	Ash / %	pH_PZC	S_BET / (m² g^-1)
Sample	Yield^a / %	C	H	N	O^b	Atomic ratio O/C	Ash / %	pH_PZC	S_BET / (m² g^-1)
PSB	78	61.4	2.0	1.7	29.6	0.48	5.3	6.2	18.1
PSB-KOH	73 (94)	50.0	2.5	1.2	31.5	0.63	14.8	9.1	20.9
PSB-HNO3	48 (62)	54.4	2.0	3.2	40.3	0.74	0.1	3.3	25.9

Dye	Parameter	Adsorbent
Dye	Parameter	AC-P	PSB	PSB-KOH	PSB-HNO3
Mordant Orange 1 (MO‑1)	q_m / (mg g^-1)	299.2 ± 6.8	4.7 ± 0.2	9.7 ± 0.6	20.8 ± 3.4
	K_L / (L mg^-1)	2.5 ± 0.6	0.26 ± 0.03	0.051 ± 0.007	0.16 ± 0.05
	R²	0.988	0.994	0.994	0.961
	R²_adj	0.983	0.992	0.993	0.947
	FSE	11.927	0.104	0.169	0.922
Langmuir isotherm
Green Malachite oxalate (MG)	q_m / (mg g^-1)	321.0 ± 5.1	14.7 ± 0.5	37.9 ± 1.6	49.1 ± 2.6
	K_L / (L mg^-1)	4.2 ± 0.5	0.9 ± 0.2	3.5 ± 0.5	2.7 ± 0.4
	R²	0.995	0.980	0.996	0.993
	R²_adj	0.992	0.973	0.993	0.991
	FSE	9.757	0.826	0.783	1.109
Mordant Orange 1 (MO‑1)	K_F / (mg g^-1)	231.7 ± 9.1	1.2 ± 0.1	0.8 ± 0.1	3.7 ± 0.5
	n	11.4 ± 2.2	2.3 ± 0.2	1.7 ± 0.1	1.8 ± 0.2
	R²	0.989	0.983	0.984	0.970
	R²_adj	0.985	0.978	0.979	0.959
	FSE	11.359	0.173	0.283	0.811
Freundlich isotherm
Green Malachite oxalate (MG)	K_F / (mg g^-1)	218.2 ± 21.7	7.1 ± 0.9	29.9 ± 1.1	36.4 ± 0.7
	n	8.3 ± 2.3	4.4 ± 0.8	2.7 ± 0.4	2.5 ± 0.2
	R²	0.960	0.942	0.983	0.992
	R²_adj	0.934	0.919	0.972	0.989
	FSE	29.503	1.421	1.637	1.179

Treatment		Dye	q_m / (mg g^-1)
Washed, dried, powdered, sieved and activated with NaOH at 145 °C for 8 h³³33 Acemioğlu, B.; Int. J. Coal Prep. Util. 2022, 42, 671. [Crossref] Crossref...		Remazol Orange RGB	15.43
Washed, dried at 110 °C, grinded and sieved (2 mm), activation with H₃PO₄ (1:1.5) at 650 °C for 2 h under N₂, soaked in 1% of NaHCO₃ and washed, dried and sieved < 0.5 mm³⁴34 Garg, D.; Majumder, C. B.; Kumar, S.; Sarkar, B.; J. Environ. Chem. Eng. 2019, 7, 103365. [Crossref] Crossref...		Direct Blue-86	21.60
Washed, dried at 100 °C for 12 h, crushed and sieved, pyrolyzed at 800 °C for 5 h¹²12 Georgin, J.; Dotto, G. L.; Mazutti, M. A.; Foletto, E. L.; J. Environ. Chem. Eng. 2016, 4, 266. [Crossref] Crossref...		Direct Black 38 Reactive Red 141	141.3 307.5
Washed, sieved (0.75 mm), impregnation with KOH for 24 h, heating at 800 °C for 2 h under N₂, washing with HCl until pH neutral¹⁹19 Han, X.; Chu, L.; Liu, S.; Chen, T.; Ding, C.; Yan, J.; Cui, L.; Quan, G.; BioResources 2015, 10, 2836. [Crossref] Crossref...		Methylene Blue	204.08
Dried, sieved (0.8-1.6 mm), mixed with H₃PO₄ (88%) using a ratio peanut-shell:acid = 1:1.5), heating at 650 °C under N₂ for 2 h, soaked with NaHCO₃ to neutralize excess acid³⁵35 Garg, D.; Kumar, S.; Sharma, K.; Majumder, C. B.; Groundwater Sustainable Dev. 2019, 8, 512. [Crossref] Crossref...		Acid Yellow 36	66.7
Impregnation with H₃PO₄ (10%) during 24 h, followed by drying at 75 °C for 72 h, pyrolysis at 450 °C for 1.5 h²⁴24 Kouadio, D. L.; Diarra, M.; Tra, B. T. D.; Akesse, D. P. V.; Soro, B. D.; Aboua, K. N.; Meite, L.; Kone, M.; Dembele, A.; Traore, K. S.; Int. J. Innov. Appl. Stud. 2019, 26, 1280. [Crossref] Crossref...		Yellow 11	5.59
This study	PSB-KOH	Mordant Orange 1	9.7
This study	PSB-HNO3	Mordant Orange 1	20.8
This study	PSB-KOH	Green Malachite oxalate	37.9
This study	PSB-HNO3	Green Malachite oxalate	49.1

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