Characterization and application of magnetic biochar for the removal of phosphorus from water

SILVA, TERESA CRISTINA F.; VERGÜTZ, LEONARDUS; PACHECO, ANDERSON A.; MELO, LARISSA F.; RENATO, NATALIA S.; MELO, LEÔNIDAS C.A.

doi:10.1590/0001-3765202020190440

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ENGINEERING SCIENCES • An. Acad. Bras. Ciênc. 92 (3) • 2020 • https://doi.org/10.1590/0001-3765202020190440 copy

Characterization and application of magnetic biochar for the removal of phosphorus from water

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Activated biochars were prepared from residues of medium density fiberboard (MDF) produced by the furniture industry. Biomass residue was pre-treated with FeCl₃ in two different FeCl₃:biomass ratios (0.5:1 and 1:1, w/w) aiming to produce a matrix embedded with iron oxide. The pyrolysis process produced maghemite on the biochar surface and its magnetic properties were confirmed by its attraction to a hand magnet and its magnetic susceptibility. Samples were also characterized using scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), surface area by BET-N₂, Fourier transform infrared (FTIR), X-ray diffraction, magnetic susceptibility, and cation exchange capacity (CEC). Magnetic biochar exhibited up to twelve-fold higher surface area than the non-magnetic biochar, which varies according the maghemite particles content. Iron oxide on biochar surface also contributed for increasing CEC around ten-fold compared to non-magnetic biochars. Phosphorus adsorption isotherms showed that these magnetic biochars have high capacity to sorb oxyanions like phosphate, especially at lower pH. Thus, these magnetic biochars could be used to clean water bodies contaminated with oxyanions in acidic conditions.

Key words
adsorption; biochar; eutrophication; isotherms; phosphorus; water treatment

Sample	κ_lf	κ_hf	χ_lf	χ_fd
	10^-8 m³ kg^-1			%
CBC	0.00	0.00	0.00	0.00
0.5FeBC	3372	3164	12701.04	6.17
1.0FeBC	7137	6716	19557.18	5.90

Element	Line	Concentration
Element	Line	Wt. %
		CBC	0.5FeBC	1.0FeBC
C	Kα	-	41.884	33.912
O	Kα	81.742	23.949	21.792
Na	Kα	11.485	4.811	4.817
P	Kα	4.599	0.107	0.175
Fe	Kα	2.173	29.25	39.303

CBC			0.5FeBC			1.0FeBC
Surface area (m² g^-1)	pH	CEC cmol_c kg^-1	Surface area (m² g^-1)	pH	CEC cmol_c kg^-1	Surface area (m² g^-1)	pH	CEC cmol_c kg^-1
2.309	1.0	37.4	9.338	1.0	382.6	28.758	1.0	347.8
	2.0	34.8		2.0	373.9		2.0	278.3
	3.0	36.0		3.0	374.2		3.0	295.6
	4.0	34.6		4.0	417.4		4.0	339.1

	pH	Linear		Freundlich		Langmuir		Langmuir-Freundlich
		SE	R² _Adj	SE	R² _Adj	SE	R² _Adj	SE	R² _Adj
CBC	1	0.010	0.973	0.016	0.923	0.042	0.500	0.006	0.991
CBC	2	0.017	0.985	0.017	0.985	0.028	0.959	0.019	0.983
CBC	3	0.024	0.976	0.297	-2.598	0.028	0.967	0.027	0.970
CBC	4	0.030	0.953	0.029	0.958	0.033	0.946	0.031	0.950
0.5FeBC	1	0.282	0.883	0.185	0.950	0.125	0.977	0.127	0.976
0.5FeBC	2	0.152	0.952	0.100	0.979	0.264	0.856	0.110	0.975
0.5FeBC	3	0.265	0.871	0.054	0.995	0.131	0.968	0.029	0.998
0.5FeBC	4	0.101	0.928	0.046	0.985	0.136	0.868	0.050	0.983
1.0FeBC	1	0.154	0.931	0.035	0.996	0.124	0.955	0.038	0.996
1.0FeBC	2	0.178	0.932	0.070	0.989	0.194	0.919	0.076	0.988
1.0FeBC	3	0.234	0.894	0.083	0.987	0.123	0.971	0.073	0.990
1.0FeBC	4	0.092	0.918	0.047	0.979	0.106	0.891	0.051	0.975

	CBC pH 1	CBC pH 2	CBC pH 3	CBC pH 4	0.5FeBC pH 1	0.5FeBC pH 2	0.5FeBC pH 3	0.5FeBC pH 4	1.0FeBC pH 1	1.0FeBC pH 2	1.0FeBC pH 3	1.0FeBC pH 4
Kf	0.00017	0.64198	0.70371	0.00995	1.01493	0.03508	3.4E-16	0.89565	0.73767	0.01311	0.51763	0.52438
n	0.42881	1.73612	2.35539	0.79003	2.90061	0.14043	0.82117	2.55736	2.18957	0.84572	2.98759	3.06315

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[1] Correspondence to: Natalia dos Santos Renato E-mail: natalia.renato@ufv.br