改性凹凸棒土吸附剂去除水中的Cr(VI)

王家宏; 孙彤彤; 陈瑶

doi:10.13801/j.cnki.fhclxb.20200103.001

改性凹凸棒土吸附剂去除水中的Cr(VI)

doi: 10.13801/j.cnki.fhclxb.20200103.001

陕西科技大学　环境科学与工程学院，西安 710021

基金项目: 陕西省教育厅专项科研计划(15JK1095)

详细信息

通讯作者:
王家宏，博士，教授，博士生导师，研究方向为环境功能材料、工业水处理　E-mail：wangjiahong@sust.edu.cn

中图分类号: X523；TB332
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出版历程
- 收稿日期: 2019-09-25
- 录用日期: 2019-12-13
- 网络出版日期: 2020-01-03
- 刊出日期: 2020-08-15

Removal of Cr(VI) from water by modified attapulgite adsorbent

School of Environmental Science and Engineering, Shaanxi University of Science & Technology, Xi’an 710021, China

摘要

摘要: 以凹凸棒土为载体，合成了乙二胺(EDA)改性凹凸棒土(ATP)吸附剂EDA/ATP复合材料。采用FTIR、TGA对吸附剂进行表征，同时将其应用于对水中Cr(VI)的吸附，研究了溶液初始浓度、吸附时间、溶液pH、Cl⁻与PO₄³⁻阴离子浓度对吸附的影响。FTIR和TGA结果表明乙二胺已成功接枝到凹凸棒土表面。吸附实验表明，25℃时EDA/ATP复合材料对Cr(VI)的最大吸附容量为153.78 mg·g⁻¹，吸附在800~900 min内达到平衡，吸附符合Freundlich吸附等温模型和拟二级动力学模型；在初始溶液pH为2~10条件下，随着pH的增加，吸附量先增加再降低，pH为3时，吸附量最大；Cl⁻对吸附影响较小，PO₄³⁻对吸附的影响较大，当PO₄³⁻浓度达到20 mmol·L⁻¹时，Cr(VI)最大吸附量下降了83 mg·g⁻¹；实验表明EDA/ATP可作为一种潜在处理水中Cr(VI)的吸附剂。
- 凹凸棒土 /
- 乙二胺 /
- 改性 /
- 吸附 /
- Cr(VI) /
- 水处理
Abstract: Ethylenediamine modified attapulgite(EDA/ATP) adsorbent was synthesized by using clay-based adsorbent ATP as carrier. The EDA/ATP composite adsorbent was characterized by FTIR and TGA. The adsorbent was applied to the adsorption of Cr(VI) in aqueous. The effects of initial concentration of Cr(VI) solution, adsorption time, solution pH and the anion concentration Cl⁻ and PO₄³⁻ on the adsorption of Cr(VI) were studied. The FTIR and TGA results show that EDA has been successfully grafted onto the surface of ATP. The adsorption experimental results show that at 25℃ the maximum adsorption capacity of EDA/ATP composite for Cr(VI) is 153.78 mg·g⁻¹, and the adsorption reaches equilibrium within 800~900 min. The adsorption experimental data conform to Freundlich adsorption isotherm model and the pseudo-second-order kinetics. The initial pH of solution is ranging from 2 to 10. With the increase of pH, the adsorption capacity first increases and then decreases. When the pH is 3, the adsorption capacity reaches the maximum adsorption amount. PO₄³⁻ has greater effect on the adsorption than Cl⁻, and the maximum adsorption capacity decreases by 83 mg·g⁻¹ when the concentration of PO₄³⁻ is 20 mmol·L⁻¹. The experimental results show that EDA/ATP composite can be used as a potential adsorbent for Cr(VI) in water treatment.
- attapulgite /
- ethylenediamine /
- modification /
- adsorption /
- Cr(VI) /
- water treatment

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图 1 凹凸棒土(ATP)和乙二胺改性凹凸棒土(EDA/ATP)复合材料的红外光图谱

Figure 1. FTIR spectra of attapulgite (ATP) and ethylenediamine modified attapulgite (EDA/ATP) composite

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图 2 ATP和EDA/ATP复合材料的TGA曲线

Figure 2. TGA curves of ATP and EDA/ATP composite

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图 3 pH=3条件下EDA/ATP复合材料吸附剂在不同温度下对Cr(VI)的吸附等温线

Figure 3. Adsorption isotherm of Cr(VI) adsorption by EDA/ATP composite at different temperatures under pH=3 condition

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图 4 25℃时吸附时间对EDA/ATP复合材料吸附剂去除Cr(VI)的影响

Figure 4. Effect of time on Cr(VI) adsorption by EDA/ATP composite at 25℃

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图 5 25℃时pH对EDA/ATP复合材料吸附剂去除Cr(VI)的影响

Figure 5. Effect of solution pH on Cr(VI) adsorption by EDA/ATP composite at 25℃

Inset: Zeta potentials of EDA/ATP composite at different solution pH values

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图 6 EDA/ATP复合材料吸附Cr(VI)前后的XPS全谱(a)、吸附后的Cr 2p(b)及吸附前后N 1s(c)的XPS图谱

Figure 6. XPS full scan of EDA/ATP composite before and after Cr(VI) adsorption(a), the XPS spectra of Cr 2p after adsorption(b) and N 1s before and after adsorption(c)

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图 7 25℃时Cl⁻和PO₄³⁻离子浓度对 EDA/ATP复合材料吸附剂去除Cr(VI)的影响

Figure 7. Effect of Cl⁻ and PO₄³⁻ ionic concentrations on Cr(VI) adsorption by EDA/ATP composite at 25℃

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表 1 EDA/ATP复合材料吸附剂对Cr(VI)的吸附等温线拟合参数

Table 1. Adsorption isotherm fitting parameters of Cr(VI) by EDA/ATP composite adsorbent

Temperature/℃	Equation parameters of Langmuir			Equation parameters of Freundlich
Temperature/℃	q_m/(mg·L⁻¹)	b/(L·mg⁻¹)	R²	n	K_f	R²
15	130.55	0.87	0.866	17.17	100.27	0.990
25	149.25	0.76	0.818	14.81	111.84	0.989
35	136.05	1.06	0.825	30.21	104.40	0.993
Notes：q_m—Theoretical maximum adsorption capacity；b—Affinity coefficient；R²—Determination coefficient；n—Adsorption intensity；K_f—Freundlich constants related to adsorption capacity.

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表 2 EDA/ATP复合材料吸附剂对Cr(VI)的拟一级、拟二级动力学参数

Table 2. Simulated parameters of Cr(VI) adsorption by EDA/ATP composite using pseudo-first-order and pseudo-second-order kinetics

Adsorbent	q_e/(mg·g⁻¹)	Pseudo-first-order kinetics equation			Pseudo-second-order kinetics equation
Adsorbent	q_e/(mg·g⁻¹)	k₁/ [g· (mg·min)⁻¹]	q_cal/ (mg·g⁻¹)	R²	k₂/[g· (mg·min)⁻¹]	q_cal/ (mg·g⁻¹)	R²
EDA/ATP	127.85	1.38×10⁻³	105.12	0.837	2.26×10⁻⁴	147.06	0.998
Notes: q_e—Equilibrium adsorption capacity；q_cal—Maximum theoretical adsorption capacity calculated by the corresponding kinetic equation；k₁, k₂—Pseudo-first-order kinetic and pseudo-second-order kinetic equation constants, respectively.

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