Impact of emulsifier on separation of oil-in-water emulsion by dynamic membrane

doi:10.16085/j.issn.1000-6613.2018-0766

Abstract

Abstract:

Ceramic tube supported zirconium dioxide dynamic membrane was applied to the separation of oil-in-water emulsion by crossflow microfiltration. Effects of four industrial emulsifiers, i.e., span 80 (SP-80), sodium dodecyl sulfate (SDS), sodium dodecyl sulfate (SLS) and sodium dodecyl benzene sulfonate (SDBS) were investigated. The influence of emulsifier type and concentration, emulsion temperature and flow rate and operating pressure on the process were investigated by orthogonal experiment. The results show that the maximum steady permeate flux exists under operating conditions of SDS, 1.0g/L, 50?C, 120L/h and 0.14MPa. Single factor experimental results show that the steady permeation flux decreases with the increase of emulsifier concentration, and increases first and then decreases with the increase of emulsion temperature. Inorganic salt ions, Na⁺, Ca²⁺ and Al³⁺ can cause a stability loss of emulsion. As the Al³⁺ is more than 0.75g/L, the stability of the emulsion is completely destroyed, which was more beneficial to improving the permeability flux. Based on the experimental results, molecular simulation method was adopted to study the emulsification under experimental operating conditions. Relationship between oil-water interface formation energy (E) of SDS and water interface diffusion coefficient (D) with emulsifier concentration and emulsion temperature was analyzed. Simulation results show that the absolute values of the E and D gradually increase with the increase of concentration and temperature. The experimental and numerical results show that the emulsifying effect of the emulsifier determines the average oil drop size within an emulsion and affects the stable permeation flux according to the plugging mechanism in the separation of oil-in-water emulsion. The simulation results have successfully explained the experimental permeation phenomena from a microscopic perspective. This fundamental research can provide a basis for industrial application of dynamic membrane treatment of oil-water.

Key words: membrane, separation, emulsifier, molecular simulation, permeation flux

摘要：

利用管状陶瓷膜基氧化锆动态膜分离油水乳化液，研究了4种工业常见乳化剂[斯盘80（SP-80）、十二烷基磺酸钠（SDS）、十二烷基硫酸钠（SLS）和十二烷基苯磺酸钠（SDBS）]对分离过程的影响。利用正交实验方法考察了乳化剂种类和浓度、乳化液温度和流量以及操作压力对过程的影响。正交实验结果表明，在SDS、1.0 g/L、50℃、120L/h和0.14MPa操作条件下，油水混合物稳定渗透通量最大。单因素实验结果表明，当乳化剂浓度增大时，稳定渗透通量减小；当乳化液温度升高时，稳定渗透通量先增加后降低。无机盐离子Na⁺、Ca²⁺和Al³⁺的存在均可使稳定渗透通量增加。当Al³⁺大于0.75g/L时，乳化液的稳定性被完全破坏，更有利于提高渗透通量。基于实验结果，采用分子模拟方法研究了不同实验条件下乳化剂的乳化效果，分析了SDS的油水界面形成能（E）和水的界面扩散系数（D）与乳化剂浓度和乳化液温度的关系。模拟结果表明，E和D绝对值均随着乳化剂浓度和乳化液温度增加而增大。实验和模拟结果均表明，乳化剂的乳化效果决定了油滴的平均粒径，基于油水分离的堵塞机理，也由此影响了稳定渗透通量。模拟结果从微观角度解释了实验现象，研究结果可为动态膜处理油水乳化液的工业应用提供依据。

关键词: 膜, 分离, 乳化剂, 分子模拟, 渗透通量

CLC Number:

TQ09

Xuefang ZHANG, Yanqiu PAN, Pengpeng CHEN, Lu YU. Impact of emulsifier on separation of oil-in-water emulsion by dynamic membrane[J]. Chemical Industry and Engineering Progress, 2019, 38(02): 790-797.

张雪芳, 潘艳秋, 陈鹏鹏, 俞路. 乳化剂对动态膜分离油水乳化液过程的影响[J]. 化工进展, 2019, 38(02): 790-797.

Figures/Tables 13

References 18

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元素分析		核磁基础数据		平均结构单元参数
元素	分率	类型	分率	类型	分率
碳元素	0.839	芳环氢	0.040	芳香碳率	0.168
氢元素	0.124	α位取代氢	0.082	环烷碳率	0.200
氮元素	0.023	β位取代氢	0.602	烷基碳率	0.632
杂元素	0.014	γ位取代氢	0.276	烷链支化度	0.322
				芳香环系缩合度参数	0.440
氢碳元素比（H/C）	1.770	平均相对分子质量	537	芳香环系周边氢取代率	0.603

元素分析		核磁基础数据		平均结构单元参数
元素	分率	类型	分率	类型	分率
碳元素	0.839	芳环氢	0.040	芳香碳率	0.168
氢元素	0.124	α位取代氢	0.082	环烷碳率	0.200
氮元素	0.023	β位取代氢	0.602	烷基碳率	0.632
杂元素	0.014	γ位取代氢	0.276	烷链支化度	0.322
				芳香环系缩合度参数	0.440
氢碳元素比（H/C）	1.770	平均相对分子质量	537	芳香环系周边氢取代率	0.603

实验号	因素					评价指标
实验号	乳化剂种类	浓度 /g?L^-1	操作压力/MPa	流量 / L?h^-1	温度 /℃	稳定渗透通量 / L?m^-2 ?h^-1	油截留率 /%
1	SDS	0.25	0.08	60	20	42.25	98.35
2	SDS	0.5	0.10	80	30	68.29	98.02
3	SDS	0.75	0.12	100	40	156.47	97.88
4	SDS	1.00	0.14	120	50	480.97	97.12
5	SDBS	0.25	0.14	80	40	341.56	97.75
6	SDBS	0.50	0.12	60	50	305.24	97.34
7	SDBS	0.75	0.10	120	20	203.59	98.56
8	SDBS	1.00	0.08	100	30	151.86	98.25
9	SLS	0.25	0.10	100	50	273.65	97.25
10	SLS	0.50	0.08	60	40	92.18	98.11
11	SLS	0.75	0.14	120	30	352.14	97.55
12	SLS	1.00	0.12	80	20	125.36	96.05
13	SP-80	0.25	0.12	120	30	240.32	99.01
14	SP-80	0.50	0.14	100	20	201.36	99.25
15	SP-80	0.75	0.08	80	50	112.96	98.76
16	SP-80	1.00	0.10	60	40	79.88	98.56

实验号	因素					评价指标
实验号	乳化剂种类	浓度 /g?L^-1	操作压力/MPa	流量 / L?h^-1	温度 /℃	稳定渗透通量 / L?m^-2 ?h^-1	油截留率 /%
1	SDS	0.25	0.08	60	20	42.25	98.35
2	SDS	0.5	0.10	80	30	68.29	98.02
3	SDS	0.75	0.12	100	40	156.47	97.88
4	SDS	1.00	0.14	120	50	480.97	97.12
5	SDBS	0.25	0.14	80	40	341.56	97.75
6	SDBS	0.50	0.12	60	50	305.24	97.34
7	SDBS	0.75	0.10	120	20	203.59	98.56
8	SDBS	1.00	0.08	100	30	151.86	98.25
9	SLS	0.25	0.10	100	50	273.65	97.25
10	SLS	0.50	0.08	60	40	92.18	98.11
11	SLS	0.75	0.14	120	30	352.14	97.55
12	SLS	1.00	0.12	80	20	125.36	96.05
13	SP-80	0.25	0.12	120	30	240.32	99.01
14	SP-80	0.50	0.14	100	20	201.36	99.25
15	SP-80	0.75	0.08	80	50	112.96	98.76
16	SP-80	1.00	0.10	60	40	79.88	98.56

A	——	膜表面积，m²
c _f	——	进料液中油浓度， mg/L
c _p	——	渗透液中油浓度， mg/L
D _m	——	膜管内径， m
E _t ，E _s ，E _ow	——	分别为油水乳化剂体系的总能量、乳化剂单分子能量、单独油水体系的能量， kJ/mol
J	——	渗透通量， L/(m²?h)
L	——	膜管有效长度， m
m	——	渗透液质量， g
n	——	乳化剂分子个数
R	——	油截留率， %
t	——	取渗透液的操作时间， h
V	——	渗透液体积， L
ρ	——	混合液密度（近似取水的密度）， g/L