Dead end and Cross flow microfiltration (MF) of oil-in-water emulsions using inexpensive ceramic membranes. During dead-end MF of oil-in-water emulsions (50-250 mg/L feed concn.), the titania-clay membrane provided optimal flux and rejection of. Among all membranes, titanium-fly ash composite membranes gave the best performance for oil-in-water emulsion treatment.
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CHAPTER-1
Introduction and Literature Review
Introduction and Literature Review
- Fly ash material
- History
- Physical Properties
- Chemical Properties
Essentially, the classification of fly ash is based on the type of coal (anthracite, bituminous, subbituminous and lignite) used during combustion (Ahmaruzzaman, 2010; Iyer and Scott, 2011; Blissett and Rowson, 2012). This is based on the composition of aluminum oxide, silica, iron oxide and lime in fly ash. The general classification of coal fly ash generally ignores the mineralogical aspects of the coal.
- Applications
- Overview of Membrane Processes
- Separation process based classification
- Industrial applications of membrane technology
- Polymeric membranes
- Ceramic membrane fabrication methods
- State-of-the-art
- Preparation of ceramic membrane supports
- Literature review for titania coating on ceramic membrane support
- Ceramic membrane based microfiltration of oil-in-water emulsions
- Possible scope for further research
- Preparation, characterization and application of ceramic membranes from mixed clays
- Preparation, characterization, optimization and application of low cost fly ash based ceramic membranes
- Preparation, characterization and application of TiO 2 –Fly ash composite membrane
- Response Surface Methodology for the MF performance of membranes
- Preparation, characterization and application of TiO 2 –clay, γ-Al 2 O 3 – clay and clay membranes
- Cross flow microfiltration studies for TiO 2 –clay and clay membranes
- Objective of the Thesis
- Organization of the Thesis
Using Moroccan clay, Saffaj et al. 2006) prepared ceramic membrane support by extrusion method and sintered at different temperatures. Using refined fly ash as raw material and adopting the slip casting method, Fang et al. 2013) prepared asymmetric MF ceramic membranes. Using coal-based fly ash, Jedidi et al. 2011) reported the preparation of extrusion-based ceramic membrane support fabrication at a sintering temperature of 1125 °C.
Using a commercial ceramic membrane, Lobo et al. 2006) studied the effect of pH and cross-flow velocity on the ultrafiltration of oil-in-water emulsion. Abadi et al (2011) used a tubular commercial ceramic α-alumina membrane for the microfiltration of oil-in-water emulsions in cross-flow operation.
RSM-based optimization of process parameters of dead-end and cross-flow MF of oil-in-water emulsions using fly ash and titanium fly ash membranes.
Chapter 2 addresses the experimental and modeling methodology adopted in the Ph.D
These include results obtained from characterization and cross-flow studies for flux and repulsion characteristics. In addition, RSM-based optimization was performed on the cross-flow MF data to evaluate the optimality of process parameters such as feed concentration, cross-flow rate and operating pressure. These include characterization results and the dead-end MF performance of the membranes for oil-in-water emulsions.
For the best membrane identified in Chapter 6, Chapter 7 presents the cross-flow MF-based comparative assessment of clay composite and clay membranes.
Chapter 8 summarizes the conclusions obtained from the research output in this work
CHAPTER-2
Materials and Methods
Materials and Methods
- Preparation, characterization and application of ceramic membranes from mixed clays
- Starting materials
- Dead end Microfiltration .1 Experimental set up
- Preparation, characterization, optimization and application of low cost fly ash based ceramic membranes
- Membrane fabrication
- Dead end flow microfiltration experiment
- RSM based simulation studies
- Preparation, characterization and application of TiO 2 -Fly ash composite membranes
- Synthesis of TiO 2 -Fly ash composite membrane
- Characterization
- Cross flow microfiltration .1 Experimental set up
- RSM modeling studies
- Preparation, characterization and application of TiO 2 -clay, γ-Al 2 O 3 - clay composite and clay membranes
- Materials
- Preparation of membranes
- Characterization
- Dead end Microfiltration of oil-in-water emulsions
- Cross Flow MF studies for TiO 2 –clay and clay membranes
- Membrane fouling analysis
Then the membrane was removed and water on the outer surface was removed with tissue paper and the wet weight (WW) of the membrane was measured. Then the membrane was immersed in water to measure the weight of the membrane when it was saturated with water (WA). The chemical stability of the membrane was determined by exposing the membrane individually to acid (pH 1) and alkali solution (pH 14).
The water flux and hydraulic permeability of the membrane were determined using a home-made dead-end filtration setup consisting of stainless steel. The average pore size of the membrane in terms of radius is estimated by assuming the presence of cylindrical pores using the following equation derived from Hagen-Poiseuille equation. The droplet size of the emulsion (200 mg/L) was determined using a particle size analyzer (Malvern Mastersizer 2000, Model APA 5005).
Furthermore, the average pore size of the membrane was also evaluated with N2 gas permeation tests performed on an indigenous permeation structure. For each membrane, the average value of CA was measured by performing experiments at five distinct locations on the membrane surfaces. Equations 2.6 and 2.7 were used to estimate the permeate flux and membrane oil rejection values.
As a result, pore blocking occurs on the surface of the membrane and not within the membrane pores.
CHAPTER-3
Preparation, Characterization and Application of Ceramic Membranes from Mixed Clays
Preparation, characterization and application of ceramic membranes from mixed clays
- Overview
- Results and Discussion
- Particle size distribution (PSD)
- XRD analysis
Section 3.2.9 then summarizes the retail cost analysis, followed by a summary of the research findings in Section 3.3. The particle size distribution (PSD) of the raw materials was made to give an idea of the particle size and their particle uniformity. The size of the raw materials determines the porosity and pore size of the sintered membrane.
Pore growth depends mainly on the initial particle size of the raw materials and the compaction pressure (Tsuru, 2001). On the other hand, coarser particles need higher sintering temperature, resulting in macroporous membranes with reduced mechanical strength (Wang et al., 2007). The particle size distribution of the individual raw materials and powder mixture used to manufacture four fly ash-based membranes (SP1–SP4) is shown in Fig.
This specifies that the width of the particle size distribution provides good mixing and uniform distribution between the particles. According to the literature (Monash and Pugazhenthi 2011b; Vasanth et al., 2011a), no phase change is observed in the quartz during sintering. In light of the above, it can be concluded that quartz is thermally stable at the sintering temperature examined.
The XRD reflections of the membranes (SP1-SP4) before and after sintering are shown in Figure 3.3.
2θ (degree)
FESEM analysis
The superficial observation of the FESEM images indicates that the membranes have no pinholes and cracks. It is observed that the pore diameter of the membrane decreases with an increase in the TiO2 content, which is due to binding ability of TiO2 during sintering. It is well documented in the literature that the membrane pore size is significantly affected by TiO2.
Pore Size (µm)
Porosity
Consequently, the porosity of the membranes increases with an increase in TiO2 content and a maximum porosity of 48. It is noticed that the surface porosity of the membranes, determined by FESEM analysis, is higher due to the difficulty in determining the threshold of the pores of the membranes. . The chemical stability of the membranes was evaluated in terms of mass loss after the membrane was kept in contact with acidic and alkaline solutions separately.
As the TiO2 content increases, the weight loss of the membranes due to acid corrosion decreases from 6 to 2%. Membrane weight loss due to alkali is found to be approximately 1% for all membranes. The results show that the membranes have better corrosion resistance in acidic and basic media.
Mechanical strength
Hydraulic permeability and average pore size of membranes
Water flux J×105 (m3/m2s)
Applied Pressure (kPa)
Among the prepared membranes, the membrane with the lowest pore size (SP4) was tested for oil-in-water emulsion separation.
Applied Pressure (kPa)Permeate Flux 107 (m3/m2s)
Cost estimation
Based on the retail cost of raw materials, the average price of ceramic membranes is estimated at Rs. Cost is always seen as a major fear in the membrane process, mainly due to energy consumption and membrane replacement. The use of classical membranes in wastewater treatment requires a high energy input to maintain constant efficiency due to the lower permeability of the membranes.
In general, membranes made from clay-based raw materials have higher permeability than conventional membranes; as a result, lower energy costs. Currently, natural clay and fly ash are the most preferred membrane materials compared to other materials due to their low cost. Typically, the membrane separation process using aluminum and zirconium based membranes is more expensive than those.
In addition, the improved antifouling ability of the clay-based membranes extends the backwash interval and membrane life which also increases the price gap between the clay membranes and commercial membranes.
Summary
CHAPTER-4
Preparation, Characterization, Optimization and Application of Low Cost Fly ash Based Ceramic
Membranes
Preparation, characterization, optimization and application of low cost fly ash based ceramic membranes
- Overview
- Results and Discussion
- Particle size distribution
- Porosity
- Chemical stability
- SEM analysis
- Water flux and Hydraulic permeability
- Dead end MF of oil-in-water emulsions
- Summary
For the fly ash, it has been reported that quartz (SiO2) and corundum (Al2O3) crystalline phases exist (Suresh and Pugazhenthi, 2016). Compared to water flux, the membrane flux is significantly low for the MF of emulsion. From Table 4.3, it can be understood that the membranes prepared from low-cost materials performed well in treating the oil-in-water emulsions.
The cost estimate presented in Table 4.4 indicated significant variation due to variations in equipment costs and flux production (or feed treated). After insignificant interaction, terms in Eq. 4.3), the identification of any other insignificant model terms requires a further model reduction strategy to achieve model improvement. Obtained results from successive model fit studies are shown in Table 4.8 and confirm that quadratic model is suitable to represent permeate flux.
The parameters of the second-order response model for ANOVA of membrane flux M1 and M3 are presented in Tables 4.9 and 4.10, respectively. The sequential model fitting results are shown in Table 4.11 and confirm that the quadratic model is the most appropriate model to represent rejection. The results obtained for the analysis performed are presented in Table 4.8 and 4.11 for the effect of pressure and feed concentration, respectively.
The results obtained for the second-order response model using ANOVA analysis for rejection data for membranes M1 and M3 are shown in Table 4.12 and Table 4.13, respectively. For validation of the ANOVA results, it must be such that the plot between the residuals. Dead-end flow microfiltration is an efficient and prominent process for the separation of oil-in-water emulsions.
CHAPTER-5
Preparation, characterization and application of TiO 2 -Fly ash composite membranes
- Overview
- Results and discussion
- Contact angle and FESEM micrographs
- Droplet size distributions
- Cross-flow MF of oil-in-water emulsions .1 Effect of applied pressure
Further, compared to the M2 membrane, the TiO2-Fly ash composite membrane is very hydrophilic and this is due to the TiO2 layer. For the M2 membrane, the rate of flux decline is higher than that existing for the TiO2-Fly ash membrane. The fluxes of the TiO2-Fly ash composite membrane were higher than those of the M2 membrane for all MF directions.
However, for the TiO2-Fly ash composite membrane, the flux decline was slower than that observed for the M2 membrane (only 1% flux decline for the TiO2-Fly ash composite membrane). After modification, the pores of the TiO2-Fly ash composite membrane became smaller and increased the hydrophilic nature of the M2 membrane. Compared to the M2 membrane, higher flux restoration efficiency was observed for the TiO2-Fly ash composite membrane in every direction.
This confirms that the TiO2 fly ash membrane has a greater hydrophilic nature than the M2 membrane. The highest performance indices were observed for TiO2 fly ash membrane in all cross-flow MF runs. The variation of membrane performance indices with cross-flow velocity for fly ash membrane (M2) and TiO2 fly ash membrane is shown in Fig.
However, the increase in efficiency index is significant for the TiO2 fly ash membrane casing.
