花生壳生物炭-黏土吸附水中的Cr(VI)

doi:10.15541/jim20190350

摘要/Abstract

摘要：

重金属铬的污染会严重威胁到土壤和水体的环境安全, 而水中的六价铬化合物则具有很强的迁移性、富集性和氧化性等特性, 更具有危害性且难以处理。吸附法是一种能简单、高效地处理含重金属污水的处理技术。在磁力搅拌条件下采用花生壳生物炭分别与高岭土和膨润土混合制备而成两种生物炭-黏土材料, 并分别对这两种生物炭-黏土的表面特性进行表征。结果发现所选用的两种黏土均能不规则地负载在生物炭的表面。吸附实验结果显示, 生物炭-高岭土(Biochar@Kaolin)吸附铬(VI)的能力显著高于生物炭-膨润土(Biochar@Bentonite)。从吸附动力学方程的分析可以看出, 合成的两种生物炭负载黏土吸附水中的铬(VI)均符合伪二级动力学方程。从吸附等温线分析中可以得到, Biochar@Bentonite吸附铬(VI)的过程符合Langmuir模型, 而Biochar@Kaolin吸附铬(VI)的过程符合Freundlich模型。研究结果显示, 采用生物炭-黏土的复合材料修复环境中的重金属污染具有广阔的应用前景。

关键词: 吸附, 花生壳, 黏土-生物炭, 铬(VI)

Abstract:

Heavy metal chromium pollution seriously threatens the environmental safety of soil and water body. The Cr(VI) compound has strong migration ability, enrichment and strong oxidizing ability. These properties make Cr(VI) ions more dangerous and difficult to handle. Adsorption technology is a simple and effective method for treatment of heavy metal pollution. The two clay-biochars are made by mixing biochar derived from peanut shell and two kinds of clays (Kaolin and bentonite) under magnetic stirring conditions. A variety of characterizations suggest that clays uniformly deposit on the surface of biochar. Adsorption experiments indicate that the sorption of Cr(VI) ions from wastewater on Kaolin-biochar is significantly higher than that of bentonite-biochar. Adsorption kinetic of Cr (VI) on two clay-biochars follows satisfactorily the pseudo-second order model due to high correlation coefficient (R²>0.999). Adsorption isotherms of Cr(VI) on Biochar@Bentonite are fitted by Langmuir model, whereas the Freundlich model fits better the Cr(VI) sorption on Biochar@Kaolin. These findings are crucial for the potential application of clay-biochar composites for the treatment of the immobilization of heavy metals in environmental remediation.

Key words: adsorption, peanut shell, clay-biochar, Cr(VI)

中图分类号:

TQ174

王海, 阳柠灿, 邱木清. 花生壳生物炭-黏土吸附水中的Cr(VI)[J]. 无机材料学报, 2020, 35(3): 301-308.

WANG Hai, YANG Ningcan, QIU Muqing. Adsorption of Cr(VI) from Aqueous Solution by Biochar-clay Derived from Clay and Peanut Shell[J]. Journal of Inorganic Materials, 2020, 35(3): 301-308.

图/表 12

Table 1 Characterizations of Biochar, Biochar@Kaolin and Biochar@Bentonite

Sample	BET specific surface area/(m²·g^-1)	Average pore width/nm
Biochar	2.79	39.37
Biochar@Kaolin	6.15	83.41
Biochar@Bentonite	3.08	56.18

Fig. 1 SEM images of the Biochar@Kaolin and Biochar@Bentonite before and after the reaction with Cr(VI)

Fig. 2 TEM images of the Biochar@Kaolin and Biochar@Bentonite before and after the reaction with Cr(VI)

Fig. 3 EDS spectra of the Biochar@Kaolin and Biochar@Bentonite before and after the reaction with Cr(VI)

Fig. 4 XRD patterns of Biochar, Biochar@Kaolin and Biochar@Bentonite

Fig. 5 FT-IR spectra of Biochar, Kaolin, Bentonite, Biochar@Kaolin and Biochar@Bentonite

Fig. 6 XPS spectra of Biochar@Kaolin (a) and Biochar@Bentonite (b)

Fig. 7 Effect of pH on the removal of Cr (VI) by the Biochar@Kaolin (a) and Biochar@Bentonite (b)

Fig. 8 Effect of SO42- on the removal of Cr (VI) by the Biochar@Kaolin (a) and Biochar@Bentonite (b)

Fig. 9 Adsorption data and modeling for Cr(VI) ions removal by Biochar, Biochar@Kaolin and Biochar@Bentonite, respectively

Table 2 Pseudo-first order kinetic and pseudo-second order kinetic parameters of Cr(VI) ions removal by Biochar, Biochar@Kaolin and Biochar@Bentonite

Sample	Pseudo-first-order			Pseudo-second-order
Sample	q_e/(mg·g^-1)	k₁/min^-1	R²	q_e/(mg·g^-1)	K₂/(g·mg^-1·min^-1)	R²
Biochar	6.54	0.056	0.967	7.80	0.063	0.990
Biochar@Kaolin	7.07	0.092	0.947	8.91	0.122	0.986
Biochar@Bentonite	7.70	0.048	0.971	9.41	0.052	0.991

Table 3 Parameters of adsorption isotherms for Cr(VI) ions removal by Biochar, Biochar@Kaolin and Biochar@Bentonite at 20, 30 and 40 ℃, respectively

T/℃	Sample	Langmuir adsorption model			Freundlich adsorption model
T/℃	Sample	Q_max/(mg·g^-1)	K_L/(L·mg^-1)	R²	K_F/((mg·g)^-1/ⁿ)	1/n	R²
20	Biochar@Kaolin	15.58	0.0029	0.978	3.57	0.0064	0.995
20	Biochar@Bentonite	20.54	0.035	0.980	6.75	0.0042	0.903
30	Biochar@Kaolin	68.98	0.0063	0.940	4.55	0.0083	0.992
30	Biochar@Bentonite	23.64	0.058	0.967	10.53	0.0033	0.942
40	Biochar@Kaolin	76.62	0.13	0.795	9.61	0.0028	0.996
40	Biochar@Bentonite	27.23	0.28	0.956	14.82	0.0016	0.852

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