污泥基生物炭负载纳米零价铁去除Cr(VI)的性能与机制

曾涛涛; 农海杜; 沙海超; 陈胜兵; 张晓玲; 刘金香

doi:10.13801/j.cnki.fhclxb.20220324.001

污泥基生物炭负载纳米零价铁去除Cr(VI)的性能与机制

doi: 10.13801/j.cnki.fhclxb.20220324.001

南华大学　污染控制与资源化技术湖南省高校重点实验室，衡阳 421001

基金项目: 国家自然科学基金(52170164)；湖南省教育厅创新平台开放基金项目(19K081)

详细信息

通讯作者:
刘金香，博士，教授，硕士生导师，研究方向为水处理理论与技术及污染控制　 E-mail：cafardworm@163.com

中图分类号: X703
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出版历程
- 收稿日期: 2022-01-10
- 修回日期: 2022-03-08
- 录用日期: 2022-03-13
- 网络出版日期: 2022-03-25
- 刊出日期: 2023-02-15

Performance and mechanism of Cr(VI) removal by sludge-derived biochar loaded with nanoscale zero-valent iron

Hunan Province Key Laboratory of Pollution Control and Resource Reuse Technology, University of South China, Hengyang 421001, China

Funds: National Natural Science Foundation of China (52170164); Opening Funding for Innovation Platform of Education Department in Hunan Province (19K081)

摘要

摘要: 针对电镀、冶金、印染等行业产生的含铬废水所导致的环境污染难题，以城市污泥热解获得的污泥基生物炭(SB)为载体，制备了污泥基生物炭负载纳米零价铁(nZVI-SB)材料用于去除水中的Cr(VI)，探究了铁炭质量比、初始pH值、投加量、温度等因素对去除Cr(VI)的影响。通过SEM-EDS、XRD和XPS等手段对nZVI-SB去除Cr(VI)的机制进行分析。结果表明：nZVI-SB对Cr(VI)废水具有较好的去除能力。在投加量0.5 g/L、初始pH=2、温度40℃条件下， Fe与SB质量比为1∶1的nZVI-SB(1∶1)对Cr(VI)吸附量最大为150.60 mg/g。Cr(VI)去除过程可通过Langmuir吸附等温式与准二级动力学方程进行拟合。nZVI-SB对Cr(VI)去除机制主要包括吸附、还原和共沉淀。本文表明污泥基生物炭与纳米零价铁可以协同发挥除Cr(VI)作用。
- 污泥基生物炭 /
- 纳米零价铁 /
- Cr(VI) /
- 吸附量 /
- 机制 /
- 还原
Abstract: Chromium-containing wastewater was generated in electroplating, metallurgy, printing and dyeing industries, which caused environmental pollution. The sludge-derived biochar (SB) was obtained from the pyrolysis of municipal sludge, and then loaded with nanoscale zero-valent iron (nZVI) to prepare sludge-derived biochar loaded with nanoscale zero-valent iron (nZVI-SB) for the removal of Cr(VI) from water. The effect of the iron to carbon mass ratio, initial pH value, dosage and temperature on the removal of Cr(VI) were explored. SEM-EDS, XRD and XPS were used to characterize the mechanisms of Cr(VI) removal. The results show that nZVI-SB has a desirable removal capacity for Cr(VI). Under the conditions of dosage 0.5 g/L, pH=2 and 40℃, the maximum adsorption capacity of Cr(VI) is 150.60 mg/g by nZVI-SB(1∶1) with a mass ratio of 1∶1 between Fe and SB. The Cr(VI) removal process can be fitted by Langmuir adsorption isotherm and pseudo-second-order kinetic equations. The removal mechanisms of Cr(VI) mainly include adsorption, reduction and co-precipitation. The present study confirms SB and nZVI can synergically remove Cr(VI).
- sludge-derived biochar /
- nanoscale zero-valent iron /
- Cr(VI) /
- adsorption capacity /
- mechanism /
- reduction

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图 1 SB (a)和污泥基生物炭负载纳米零价铁(nZVI-SB)(1∶1)处理Cr(VI)前(b)、处理Cr(VI)后(c)的SEM-EDS图像

Figure 1. SEM-EDS images of SB (a) and sludge-derived biochar loaded with nanoscale zero-valent iron (nZVI-SB)(1∶1) before (b) and after (c) treatment of Cr(VI)

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图 3 SB和nZVI-SB(1∶1)的N₂吸附-脱附等温线(a)和孔径分布(b)

dV/dW—Pore volume

Figure 3. N₂ adsorption-desorption isotherms (a) and pore size distributions (b) of SB and nZVI-SB(1∶1)

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图 2 nZVI-SB(1∶1)处理Cr(VI)前(a)、处理Cr(VI)后(b)的TEM图像

Figure 2. TEM images of nZVI-SB(1∶1) before (a) and after (b) treatment of Cr(VI)

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图 4 SB和nZVI-SB(1∶1)去除Cr(VI)前、去除Cr(VI)后的XRD图谱(a)及nZVI-SB(1∶1)的XPS全谱图(b)

Figure 4. XRD patterns of SB and nZVI-SB(1∶1) before and after adsorption of Cr(VI) (a) and XPS full spectrum of nZVI-SB(1∶1) (b)

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图 5 不同Fe∶C质量比对Cr(VI)去除的影响

Figure 5. Effect of different Fe∶C mass ratio on Cr(VI) removal

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图 6 初始pH对nZVI-SB(1∶1)去除Cr(VI)的影响

Figure 6. Effect of initial pH on the removal of Cr(VI) by nZVI-SB(1∶1)

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图 7 不同pH值下Cr(VI)形态分布曲线图

C₀—Initial mass concentration of Cr(VI) in solution

Figure 7. Cr(VI) form distribution curves under different pH values

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图 8 nZVI-SB(1∶1)投加量对nZVI-SB(1∶1)去除Cr(VI)的影响

Figure 8. Influence of nZVI-SB(1∶1) dosage on the removal of Cr(VI) by nZVI-SB(1∶1)

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图 9 (a)吸附时间对nZVI-SB(1∶1)去除Cr(VI)的影响；准一级(b)、准二级(c)动力学拟合曲线和颗粒内扩散拟合曲线(d)

Figure 9. (a) Effect of adsorption time on the removal of Cr(VI) by nZVI-SB(1∶1); Quasi-first (b), quasi-second (c) kinetic fitting curves and intra-particle diffusion fitting curve (d)

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图 10 (a)温度对nZVI-SB(1∶1)去除Cr(VI)的影响；(b) Langmuir吸附等温线；(c) Freundlich吸附等温线

Figure 10. (a) Influence of temperature on the removal of Cr(VI) by nZVI-SB(1∶1); (b) Langmuir adsorption isotherm; (c) Freundlich adsorption isotherm

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图 11 nZVI-SB(1∶1)的XPS图谱：(a) C1s；(b) O1s；(c) Fe2p；(d) Cr2p

Figure 11. XPS spectra of nZVI-SB(1∶1): (a) C1s; (b) O1s; (c) Fe2p; (d) Cr2p

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图 12 nZVI-SB(1∶1)对Cr(VI)去除机制^[15]

Figure 12. Schematic of Cr(VI) removal mechanisms by nZVI-SB(1∶1)^[15]

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图 13 nZVI-SB(1∶1)洗脱再生试验

Figure 13. nZVI-SB(1∶1) regeneration test

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表 1 样品名称缩写

Table 1. Abbreviation name of samples

Sample	Fe/wt%	SB/wt%
nZVI-SB(1∶4)	20.0	80.0
nZVI-SB(1∶2)	33.3	66.7
nZVI-SB(1∶1)	50.0	50.0
nZVI-SB(2∶1)	66.7	33.3
Notes: nZVI—Nanoscale zero-valent iron; SB—Sludge-based biochar.

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表 2 污泥及污泥基生物炭(SB)消解液中重金属浓度

Table 2. Heavy metal concentrations in digestion solution of sludge and sludge-based biochar (SB) (mg·L⁻¹)

Sample	Zn	Pb	Cu	Ba	Cd	Cr
Sludge	5.28	0.34	2.37	7.32	0.06	0.14
SB	7.81	0.51	3.01	8.67	0.09	0.13
Specified value in GB/T 5085.3—2007^[18]	100.00	5.00	100.00	100.00	1.00	15.00

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表 3 SB和nZVI-SB的元素组成

Table 3. Elemental composition of SB and nZVI-SB wt%

Sample	C	N	O	Na	Mg	Al	Si	K	Ca	Cr	Fe
SB	40.48	8.46	34.94	0.19	0.39	3.26	6.43	0.88	3.05	0.33	1.59
nZVI-SB(1∶4)	36.63	7.56	33.05	0.22	0.48	0.63	0.76	0.28	0.30	0.22	19.87
nZVI-SB(1∶2)	30.41	6.41	27.55	0.18	0.36	0.51	0.62	0.23	0.24	0.18	33.31
nZVI-SB(1∶1)	23.92	3.11	21.45	0.14	0.27	0.28	0.35	0.19	0.21	0.16	49.92
nZVI-SB(2∶1)	16.48	1.76	14.45	0.06	0.13	0.11	0.16	0.08	0.08	0.06	66.63

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表 4 nZVI-SB(1∶1)对Cr(VI)的吸附动力学参数

Table 4. Adsorption kinetic parameters of Cr(VI) adsorption by nZVI-SB(1∶1)

				Intraparticle diffusion model
	q_e/(mg·g⁻¹)	K/(min⁻¹)	R²	K_d/(mg·(m·min^0.5)⁻¹)	C	R²
Quasi-first order dynamics model	38.57	0.0113	0.855	5.858	22.731	0.971
Quasi-second-stage dynamics model	103.07	0.0005	0.999	0.038	98.551	0.946
Notes: q_e—Equilibrium adsorption capacity; K—Adsorption rate constant; R²—Linear correlation coefficient; K_d—Particle diffusion constants; C—Constant.

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表 5 nZVI-SB(1∶1)对Cr(VI)的吸附等温线拟合参数

Table 5. Adsorption isotherm fitting parameters of Cr(VI) by nZVI-SB(1∶1)

Temperature/℃	Langmuir			Freundlich
Temperature/℃	q_m/(mg·g⁻¹)	K_L	R²	K_F	n	R²
20	141.55	0.457	0.999	98.48	8.93	0.821
30	143.84	0.338	0.999	104.73	9.99	0.744
40	151.23	0.433	0.999	106.38	9.07	0.766
Notes: q_m—Maximum adsorption capacity; K_L—Adsorption equilibrium constant of the Langmuir model; K_F—Adsorption equilibrium constant of Freundlich model; n—Constants related to the adsorption intensity.

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表 6 nZVI-SB(1∶1)和其他吸附剂对Cr(VI)的吸附能力比较

Table 6. Comparison of the adsorption capacity of Cr(VI) by nZVI-SB(1∶1) and other adsorbents

Adsorbent	pH	Temperature/℃	Adsorption capacity/(mg·g⁻¹)	Ref.
Sludge biochar (500℃)	7	25	7.93	[13]
Bentonite-supported nanoscale zero-valent iron (B-nZVI)	5	25	39.48	[23]
Ficus carica biosorbent	3	30	19.68	[36]
Magnetic nanoparticle-Phosphorene-Titanium nano tubes (MNP-PN-TNT)	9	25	35.00	[2]
Nanoscale zero-valent iron grafted on acid-activated attapulgite (A-nZVI)	7	27	4.94	[31]
HNO₃ modified quinoa biochar	4	—	55.85	[37]
ZnO modified hyacinth biochar	—	25	43.48	[38]
Halloysite nanotubes/ploy composites	2	25	855.66	[39]
nZVI-SB(1∶1)	2	40	150.60	This study

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表 7 nZVI-SB(1∶1)去除Cr(VI)前、去除Cr(VI)后的C1s、O1s、Fe2p和Cr2p XPS光谱的成分和相应的相对百分比

Table 7. Composition and relative percents of C1s, O1s, Fe2p and Cr2p XPS spectra before and after Cr(VI) removal by nZVI-SB(1∶1)

	Components	Relative percentage/%		Binding energy/eV
	Components	Before	After	Before	After
C1s	C—C	58.99	59.78	284.64	284.69
	C—O	26.24	24.00	286.06	286.27
	C=O	14.77	16.22	288.54	288.72
O1s	Fe—O	32.07	30.05	529.95	529.99
	C—O	29.94	57.76	531.17	531.40
	C=O	37.99	12.19	532.04	532.58
Fe2p	Fe⁰	0.36	0.00	706.70	—
	Fe(II)	70.31	67.96	711.10/724.39	711.11/724.45
	Fe(III)	29.33	32.04	714.41/728.15	714.44/728.55
Cr2p	Cr(III)	—	84.39	—	577.01/586.85
Cr2p	Cr(VI)	—	15.61	—	580.40/590.28

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