聚乙二醇对羟基磷灰石除氟性能的影响

马明明; 崔淑慧; 杨家琴

聚乙二醇对羟基磷灰石除氟性能的影响

西安工程大学　环境与化工学院, 陕西西安710048

基金项目: 西安市科技计划项目(22NYYF051)

详细信息

通讯作者:
马明明，博士，教授，研究方向：功能材料绿色制备，　E-mail；18220593193@163.com

中图分类号: O69;TB332
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- 被引次数: 0
出版历程
- 收稿日期: 2023-08-30
- 修回日期: 2023-12-07
- 录用日期: 2023-12-09
- 网络出版日期: 2024-01-02
- 刊出日期: 2024-07-15

Effect of polyethylene glycol on fluoride removal performance of hydroxyapatite

College of Environmental and Chemical Engineering, Xi'an Polytechnic University, Xi'an 710048, China

Funds: Scientific Research Project supported by Xi’an City (22NYYF051)

摘要

摘要: 为改善羟基磷灰石(HAP)合成过程易团聚导致其除氟效率不高的不足，本文应用清洁简便、绿色环保的电化学合成法，将亲水性强、分散性优异的非离子型表面活性剂聚乙二醇(PEG)加入到制备HAP的混合支持电解液中，在铜片作工作电极的表面制备出新型HAP复合材料(PEG/(HAP)，并与纯HAP的晶体结构、孔径、比表面积、表面形貌、元素占比和官能团对比，以揭示PEG/HAP 除氟效率高于HAP的内在机制。结果发现，PEG/HAP与HAP有相同的晶面结构特征蜂、元素和化学键，但PEG/HAP的各元素含量占比、羟基和磷酸根离子官能团的吸收峰位和吸收强度与HAP 有一定差异；PEG使HAP从短棒状的表面形貌变成有利于交换和吸附氟离子的多孔和孔隙结构，其平均孔径由16.58 nm 减小到 11.93 nm，比表面积从24.29 m²/g 增加到29.83 m²/g；虽然PEG/ HAP与HAP的吸附类型均为IV型的H3滞后环，二者介孔分布范围一致，但PEG/ HAP的微孔和介孔数量明显高于HAP。尽管两种材料对氟离子的吸附反应均显示熵增、吸热和自发过程特征，吸附等温模型均符合Langmuir-Freundlich，但PEG/HAP的颗粒内扩散速率常数略大于HAP，PEG/HAP的吸附氟离子容量(9.56 mg/g)高于HAP( 8.36 mg/g)；且去除氟离子的循环再生次数从HAP的4次增加到PEG/HAP的6次。此外，PEG的存在并没有影响制备条件参数如支持电解液pH值对HAP吸附氟离子容量的影响趋势，但却使HAP吸附氟离子容量增加。共存阴离子如Cl⁻、NO₃ ⁻、SO₄ ²⁻、CO₃ ²⁻均不干扰PEG/HAP和HAP对氟离子的吸附。
- 聚乙二醇 /
- 羟基磷灰石 /
- 电化学合成 /
- 除氟性 /
- 吸附性
Abstract: The removal efficiency of hydroxyapatite (HAP ) to fluoride was low due to its easy agglomeration during the synthesis process. Based on this, a clean,simple, green and environmentally fiendly electrochemcial synthesis method was applied to improve the fluoride removal efficiency. Polyethylene glycol (PEG), a non ionic surfactant with strong hydrophilicity and excellent dispersion,was added to the mixed support electrolyte for preparing HAP. A new type of HAP composite (PEG/(HAP) was prepared on the surface of copper sheet as the working electrode. By contrast to HAP, the crystal structure, pore size, specific surface area, surface morphology, elemental proportion, and functional groups of PEG/HAP were analyzed to reveal the instrinsic mechnism of the higher fluoride removal efficiency of PEG/HAP than HAP. The results showed that PEG/HAP and HAP had the same crystal plane structure characteristics, elements and chemical bonds, while the proportion of various elements as well as the absorption peaks and instensity of hydroxyl and phosphate ion functional groups in PEG/HAP had certain differences compared to HAP. PEG transformed HAP from a short rod-shaped surface morphology to a porous and porous structure that facilitated the exchange and adsorption of fluoride ions. Average pore size of PEG/HAP decreased from 16.58 nm of HAP to 11.93 nm, and its specific surface area increased from 24.29 m²/g OF HAP to 29.83 m²/g. Although the adsorption types of PEG/HAP and HAP were both IV type H3 hysteresis loop, and their mesoporous distribution ranges were consistent, the number of micropores and mesopores in PEG/HAP were significantly higher than those in HAP. Although the adsorption reactions of both materials for fluoride ions exhibited entropy increase, endothermic, and spontaneous process characteristics with the adsorption isotherm model conforming to Langmuir-Freundlich, the intra particle diffusion rate constant of PEG/HAP was slightly higher than HAP. Therefore, the maximum adsorption capacity of PEG/HAP for fluoride ions can reach 9.56 mg/g, which was higher than that of HAP of 8.36 mg/g. Compared with 4 times of recycle regeneration for removing fluoride ions of HAP, PEG/HAP can arrived at 6. In addition, the presence of PEG did not affect the change trend of preparation parameters such as electrolyte pH on the adsorption capacity of HAP for fluoride ions. However, PEG increased the adsorption capacity of HAP for fluoride ions. All coexisiting ions such as Cl⁻, NO³⁻, SO₄ ²⁻, and CO₃ ²⁻ did not interfere with the adsorption of fluoride ions for PEG/HAP and HAP.
- Polyethylene glycol /
- Hydroxyapatite /
- Electrochemical synthesis /
- Defluoridation /
- adsorptivity

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图 1 PEG/二水磷酸二氢钙(DCPD) (a), 聚乙二醇/羟基磷灰石(PEG/HAP) (b)和标准HAP (c)的XRD

Figure 1. XRD images of PEG/Calcium phosphate dihydrate (DCPD) (a), Polyethylene glycol / hydroxyapatite (PEG/HAP) (b) and Standard HAP(c)

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图 2 HAP (a) 和PEG/HAP的SEM

Figure 2. SEM images of HAP(a) and PEG/HAP(b)

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图 3 HAP 和PEG/ HAP的氮气吸附/脱附曲线

Figure 3. Nitrogen adsorption/desorption curves of HAP and PEG/HAP

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图 4 HAP和PEG/HAP的孔径分布曲线

Figure 4. Curves of the pore size distribution of HAPand PEG/HAP

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图 5 HAP 和PEG/HAP的XPS 曲线

Figure 5. XPS curves of HAP and PEG/HAP

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图 6 HAP 和PEG/HAP的红外光谱曲线

Figure 6. FTIR spectrum curves of HAP and PEG/HAP

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图 7 pH对PEG/HAP和HAP 吸附容量影响

Figure 7. Effect of pH on PEG/HAP and HAP for adsorption capacity

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图 8 温度对PEG/HAP吸附容量的影响

Figure 8. Effect of temperature on adsorption capacity of PEG/HAP

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图 9 PEG/HAP和HAP吸附F⁻的lnK_d与1/T 线性曲线

Figure 9. Linear curves of lnK_d vs. 1/T of PEG/HAP and HAP adsorption F⁻

(F⁻concentration ×mg/L: a. 1.5; b. 2.0; c. 4.0; d. 6.0;e. 8.0; f. 10.0 )

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图 10 共存阴离子对PEG/HAP(a)和HAP(b)吸附容量影响

Figure 10. Effects of coexisting ions on PEG/HAP(a) and HAP adsorption capacity

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图 11 吸附时间对PEG/HAP (a)和HAP( b)除氟效率的影响

Figure 11. Effect of adsorption time on defluoridationl efficient of PEG/HAP (a) and HAP( b)

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表 1 HAP和PEG/HAP的孔结构参数

Table 1. Pore structure parameters of HAPand PEG/HAP

Material	Parameters
Material	BET Surface Area/(m²·g⁻¹)	Average pore diameter/nm
HAP	24.29	16.58
PEG/HAP	29.83	11.93

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表 2 2种材料元素占比

Table 2. The atomic ratio of the two materials

Atomic/% Material	C	O	P	Ca
HAP	14.18	59.29	12.47	14.06
PEG/HAP	17.43	56.22	11.23	15.12

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表 3 PEG/HAP和HAP吸附F⁻的热力学参数

Table 3. Thermodynamic parameters of PEG/HAP and HAP adsorption F⁻

F⁻initial concention mg/L	T/K	$\Delta {G}^{\ominus } $/(kJ·mol⁻¹)		$\Delta {S}^{\ominus } $/(J·K⁻¹·mol⁻¹)		$\Delta {H}^{\ominus } $/(kJ·mol⁻¹)
F⁻initial concention mg/L	T/K	PEG/HAP	HAP	PEG/HAP	HAP	PEG/HAP	HAP
1.5	288.15	−20.6064	−20.8255	183.9473	108.6640	32.3980	10.4860
	298.15	−22.4459	−21.9122
	308.15	−24.2854	−22.9988
	318.15	−26.1248	−24.0855
	328.15	−27.9643	−25.1721
2	288.15	−20.6560	−20.8680	164.4675	112.0162	26.7353	11.4095
	298.15	−22.3007	−21.9881
	308.15	−23.9454	−23.1083
	318.15	−25.5900	−24.2285
	328.15	−27.2347	−25.3486
4	288.15	−18.1882	−17.3630	164.1350	169.6522	29.1073	31.5223
	298.15	−19.8296	−19.0595
	308.15	−21.4709	−20.7560
	318.15	−23.1123	−22.4525
	328.15	−24.7536	−24.1491
6	288.15	−16.6281	−15.7314	174.6855	167.8098	33.7075	32.6230
	298.15	−18.3750	−17.4095
	308.15	−20.1218	−19.0876
	318.15	−21.8687	−20.7657
	328.15	−23.6155	−22.4438
8	288.15	−15.8648	−14.9546	135.6928	151.0870	23.2351	28.5811
	298.15	−17.2217	−16.4655
	308.15	−18.5786	−17.9764
	318.15	−19.9356	−19.4872
	328.15	−21.2925	−20.9981
10	288.15	−15.2550	−14.6329	128.7755	129.4490	21.8517	22.6678
	298.15	−16.5427	−15.9274
	308.15	−17.8305	−17.2219
	318.15	−19.1182	−18.5164
	328.15	−20.4060	−19.8109
Notes：$\Delta {G}^{\ominus } $，$\Delta {S}^{\ominus } $ and $\Delta {H}^{\ominus } $ are standard Gibbs function change value, entropy change, and enthalpy change, respectively.

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表 4 PEG/HAP与HAP的 Langmuir-Freundlich模型拟合参数

Table 4. Fitting parameters of Langmuir-Freundlich of PEG/HAP and HAP

Model	T/K	q_m / (mg·g⁻¹)		b		n		R²
Model	T/K	PEG/HAP	HAP	PEG/HAP	HAP	PEG/HAP	HAP	PEG/HAP	HAP
Langmuir-Freundlich	288.15	4.6058	3.4550	3.0896	3.0662	1.2522	3.8708	0.9701	0.9615
	298.15	5.8948	4.3757	3.2896	27.3055	1.2079	2.8634	0.9858	0.9694
	308.15	6.8707	5.6192	2.8382	4.3399	0.8620	1.3814	0.9914	0.9818
	318.15	8.7941	7.2896	2.7633	3.3643	0.9144	1.4300	0.9757	0.9960
	328.15	10.2706	8.9194	2.9674	2.7605	0.9658	1.3416	0.9822	0.9941
Notes: b in table 4 is the adsorption constant; n is the non-uniformity coefficient and R² is the correlation coefficient

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表 5 PEG/HAP动力学方程拟合参数

Table 5. Fitting parameters of kinetics equation for PEG/HAP

Equation	Parameters		R²
Pseudo first-order model	k₁/min⁻¹	Q_e/(mg·g⁻¹)	0.8953
Pseudo first-order model	0.0171	3.4672	0.8953
Pseudo econd-order model	k₂ /(g·mg⁻¹·min⁻¹	Q_e/(mg·g⁻¹)	0.9854
Pseudo econd-order model	0.0050	4.1203	0.9854
Elovich	A/(mg·g⁻¹·min⁻¹)	B/(g·mg⁻¹)	0.9663
Elovich	0.2526	1.2902	0.9663
Morrist intraparticle diffusion model	k₃/(g·g⁻¹·min^−0.5)	C	0.9876
Morrist intraparticle diffusion model	0.1774	0.6684	0.9876
Notes:k₁ is the adsorption rate constant of the quasi first order kinetic model; k₂ is the adsorption rate constant of the quasi second order kinetic model; B is the desorption coefficient; A is the constant adsorption rate; k₃ is the internal diffusion rate constant; C is for Boundary-layer thickness;Q_e is the equilibrium adsorption capacity

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表 6 HAP不同动力学模型的拟合参数

Table 6. Fitting parameters of kinetics equation for HAP

Equation	Parameters		R²
Pseudo first-order model	k₁/min⁻¹	Q_e/(mg·g⁻¹)	0.9186
Pseudo first-order model	0.0136	3.1689	0.9186
Pseudo econd-order model	k₂/(g·mg⁻¹·min⁻¹)	Q_e/(mg·g⁻¹)	0.9770
Pseudo econd-order model	0.0043	3.8226	0.9770
Elovich	A/(mg·g⁻¹·min⁻¹)	B/(g·mg⁻¹)	0.9595
Elovich	0.1740	1.3443	0.9595
Morrist intraparticle diffusion model	k₃/ (g·g⁻¹·min^−0.5)	C	0.9915
Morrist intraparticle diffusion model	0.1712	0.3834	0.9915
Notes: k₁ is the adsorption rate constant of the quasi first order kinetic model; k₂ is the adsorption rate constant of the quasi second order kinetic model; B is the desorption coefficient; A is the constant adsorption rate; k₃ is the internal diffusion rate constant; C is for Boundary-layer thickness;Q_e is the equilibrium adsorption capacity

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表 7 HAP和PEG/HAP吸附容量

Table 7. Adsorption capacity of HAP and PEG/HAP

q/(mg·g⁻¹) Materials	1 st	2 nd	3 rd	4 th	5 th
HAP	2.36	2.38	2.32	2.34	2.36
PEG/HAP	2.68	2.70	2.70	2.66	2.64
Notes: q is HAP or PEG/HAP adsorption capacity to F⁻ in model waste water

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表 8 两种材料氟离子去除率

Table 8. Defluoridation efficient of two materials

Defluoridationl efficient/% Materials	1 st	2 nd	3 rd	4 th	5 th
HAP	59.0	59.5	58.0	58.5	59.0
PEG/HAP	67.0	67.5	67.5	66.5	66.0

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表 9 HAP和PEG/HAP循环再生次数

Table 9. Recycling regeneration times of HAP and PEG/HAP

C_F⁻/(mg·L⁻¹) Materials	First time	Second time	Third time	Fourth time	Fifth time	Sixth time
HAP	0.65	0.75	0.86	0.94	1.12	-
PEG/HAP	0.42	0.51	0.64	0.73	0.86	0.94
Notes: C_F⁻ is the remain concentration of F⁻ in model waste water

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表 10 PEG/HAP与同类氟离子吸附剂吸附参数

Table 10. Adsorption parameters of PEG/HAP and similar fluoride ion adsorbents

Absorbents	Solution pH	Adsorption capacity / (mg·g⁻¹)	References
PEG/HAP	6.0	9.56	This work
Citric acid/HAP	8.31	2.678	[40]
Road tea-leaves	3	0.126	[41]
Polylactic acid/HAP	-	6.06	[42]

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