Ca(OH)2-modified Camellia oleifera shell biochar: preparation, characterization, and adsorption of NH4+ and PO43−

Min Chen; Xichang Wu; Yu Wang; Jie Wang; Chaochan Li; Tianhua Yu; Anping Wang; Min Chen; Xichang Wu; Yu Wang; Jie Wang; Chaochan Li; Tianhua Yu; Anping Wang

doi:10.48130/bchax-0026-0002

Figures (13) Tables (5)

Figure 1.
Biochar screened for adsorption of NH₄⁺ and PO₄³⁻.
Figure 2.
SEM images of (a), (b) the biochar (BC-500), and (c), (d) the Ca(OH)₂-modified biochar (BC5-500).
Figure 3.
Adsorption-desorption isotherms and pore size distribution of (a) BC-500, and (b) C5-500.
Figure 4.
FT-IR spectra of BC-500, BC5-500, and their derivatives after adsorption of NH₄⁺ (BC5-500-N) and PO₄³⁻ (BC5-500-P).
Figure 5.
XRD patterns of (a) BC-500, and (b) BC5-500 before and after adsorption (BC5-500, BC5-500-N, and BC5-500-P).
Figure 6.
XPS analysis of BC-500 and BC5-500 before and after adsorption: (a) survey spectra, (b)–(e) high-resolution C 1s, O 1s, Ca 2p, and N 1s spectra of BC5-500 and BC5-500-N, (f)–(h) high-resolution C 1s, O 1s, and Ca 2p spectra of BC5-500 and BC5-500-P, and (i) high-resolution P 2p spectrum of BC5-500-P.
Figure 7.
Adsorption of NH₄⁺ and PO₄^3– on BC5-500 as a function of solution pH.
Figure 8.
(a) Adsorption kinetics of NH₄⁺ on BC5-500. (b) Adsorption kinetics of PO₄³⁻ on BC5-500.
Figure 9.
Adsorption isotherms of (a) NH₄⁺, and (b) PO₄³⁻ on BC5-500.
Figure 10.
Influence of reaction temperature on the adsorption capacity of BC5-500 for NH₄⁺ and PO₄^3–.
Figure 11.
Reusability of BC5-500 for the adsorption of NH₄⁺ and PO₄^3– over five consecutive cycles.
Figure 12.
Removal of NH₄⁺ and PO₄^3– from actual swine wastewater by BC5-500.
Figure 13.
Schematic diagram of the adsorption mechanism of NH₄⁺ and PO₄^3– on BC5-500.

Biochar name	Adsorbate (mg·g⁻¹)		Reaction kinetics	pH range	Ref.
Biochar name	NH₄⁺	PO₄³⁻	Reaction kinetics	pH range	Ref.
BS600	114.64	31.05	Pseudo-second-order kinetics	8.5–9.7	[22]
MgB	15.22	−	Pseudo-first-order kinetics	6.0–8.0	[23]
SB	> 28.2	> 120	Pseudo-second-order kinetics	Unadjusted pH	[24]
MgB-A	37.72	73.29	Pseudo-second-order kinetic	4.0–8.0	[25]

Table 1.

Comparison among modified biochars for NH₄⁺ and PO₄³⁻ adsorption

Biochar name S_BET (m²·g⁻¹) Total pore volume (cm³·g⁻¹) Average pore size (nm)

BC-500 3.71 0.0048 5.24

BC5-500 4.29 0.0079 20.01

Table 2.
Physical properties of BC-500 and BC5-500
Biochar name Adsorbate Pseudo-first-order kinetic model Pseudo-second-order kinetic model
Q_e K₁ R² Q_e K₂ R²

BC5-500 NH₄⁺ 15.33 0.04148 0.9371 16.27 0.00012 0.9863
PO₄^3– 194.94 0.06142 0.7500 209.65 0.00047 0.9962

Table 3.
Kinetic parameters for NH₄⁺ and PO₄³⁻ adsorption onto BC5-500
Biochar name Adsorbate Langmuir Freundlich

Q_m K_L R² n K_F R² 1/n

BC5-500 NH₄⁺ 41.87 0.00574 0.967 1.145 0.632 0.962 0.873

PO₄^3– 243.33 0.0380 0.868 3.335 43.077 0.990 0.300

Table 4.
Parameters of the adsorption isotherms for NH₄⁺ and PO₄^3– onto BC5-500

Biochar name	Adsorbate	Temperature (°C)	K₀	ΔG⁰	ΔH⁰	ΔS⁰
BC5-500	NH₄⁺	293	0.219	3.700	45.645	167.890
		298	0.195	4.067
		303	0.118	5.390
		308	0.121	5.417
		313	0.144	5.036
		318	0.180	4.535
	PO₄³⁻	293	0.945	0.1367	–20.896	–71.714
		298	0.912	0.228
		303	0.675	0.99
		308	0.575	1.416
		313	0.551	1.551
		318	0.517	1.751

Table 5.

Thermodynamic parameters for the adsorption of NH₄⁺ and PO₄^3– onto BC5-500

Biochar name	S_BET (m²·g⁻¹)	Total pore volume (cm³·g⁻¹)	Average pore size (nm)
BC-500	3.71	0.0048	5.24
BC5-500	4.29	0.0079	20.01

Biochar name	Adsorbate	Pseudo-first-order kinetic model			Pseudo-second-order kinetic model
Biochar name	Adsorbate	Q_e	K₁	R²	Q_e	K₂	R²
BC5-500	NH₄⁺	15.33	0.04148	0.9371	16.27	0.00012	0.9863
BC5-500	PO₄^3–	194.94	0.06142	0.7500	209.65	0.00047	0.9962

Biochar name	Adsorbate	Langmuir			Freundlich
Biochar name	Adsorbate	Q_m	K_L	R²	n	K_F	R²	1/n
BC5-500	NH₄⁺	41.87	0.00574	0.967	1.145	0.632	0.962	0.873
BC5-500	PO₄^3–	243.33	0.0380	0.868	3.335	43.077	0.990	0.300