Fabrication and optimization of a clay-bonded SiC flat tubular membrane support for microfiltration applications

SiC has excellent structural and mechanical properties and also has excellent properties related to membrane performance. High processing temperature increases the costs of SiC products and thus limits their use. In this study, we fabricated SiC-based ceramic support layers using a clay-bonding technique. Kaolin, a well-known clay, was used as a binder for silicon-carbide particles. Three different SiC powders were used on the basis of particle size for fabrication by the extrusion method, which converts powders into flat tubular form. The resultant supports are sintered at 1300–1500 °C in air and evaluated for their structural properties, pore characteristics and permeability. It is evident from the study that we can produce a support layer with small-sized SiC powder that has a high open porosity and high strength with a smaller pore size and lower permeability in comparison with layers produced with a large-sized starting SiC powder. Additionally, the produced support layer could be used as a stand-alone membrane for 1 µm particles.     

Refining of biodiesel by ceramic membrane separation

A ceramic membrane separation process for biodiesel refining was developed to reduce the considerable usage of water needed in the conventional water washing process. Crude biodiesel produced by refined palm oil was micro-filtered by ceramic membranes of the pore size of 0.6, 0.2 and 0.1 μm to remove the residual soap and free glycerol, at the transmembrane pressure of 0.15 MPa and temperature of 60 °C. The flux through membrane maintained at 300 L m^− 2 h^− 1 when the volumetric concentrated ratio reached 4. The content of potassium, sodium, calcium and magnesium in the whole permeate was 1.40, 1.78, 0.81 and 0.20 mg/kg respectively, as determined by inductively coupled plasma-atomic emission spectroscopy. These values are lower than the EN 14538 specifications. The residual free glycerol in the permeate was estimated by water extraction, its value was 0.0108 wt.%. This ceramic membrane technology was a potential environmental process for the refining of biodiesel.     

Hybrid ceramic membrane microfiltration and electrolysis process for Cu-removal from aqueous solutions

This study aims to fabricate a low-cost ceramic microfiltration membrane by mixing kaolin 4.2 wt%, silica 5.8 wt%, starch 20 wt%, graphite 30 wt%, and sodium silicate 40 wt%. The produced paste was molded into a cylinder (1.0 cm high, 5 cm diameter) and dried in an oven at 90°C for 1 h, and then sintered in a furnace at 650 °C for 2 h. The characterization of the produced ceramic membrane was performed by X-ray diffraction analysis, Fourier transformed infra-red spectroscopy, and scanning electron microscopy. Furthermore, the contact angle of the membrane surface was measured, thus demonstrating that the surface is hydrophilic. The fabricated ceramic membrane was investigated for its chemical resistance in strongly acidic and alkaline media. The mass loss of membrane in HCl solution at pH = 2 for 200 h was not more than 0.18%, while it was 2% in alkaline NaOH solution (pH = 12). The fabricated ceramic membrane was combined with an electrolysis process for applying as a new hybrid process for copper ions removal from an aqueous solution. The effects of three operating parameters of electric voltage, initial pH, and initial copper concentration on the performance of copper removal percentage were investigated. To investigate the independent effect of the hybrid electrolysis process versus microfiltration, two experiments with and without an electric field were conducted in 100 min. The copper concentration was decreased from 350 to 160 ppm only by applying the microfiltration method, whereas hybrid electrolysis and microfiltration decreased the copper concentration from 350 to 10 ppm. The regeneration of the composite membrane was evaluated in four consecutive cycles. The percentage of copper ions removal after 4 cycles without washing is about 97%. The proposed process is effective and fast for copper ions removal from the solution, with an excellent yield of 97.4%.     

Treatment of oily wastewater using low cost ceramic membrane: Comparative assessment of pore blocking and artificial neural network models

This work addresses the performance and modeling of the separation of oil-in-water (o/w) emulsions using low cost ceramic membrane that was prepared from inorganic precursors such as kaolin, quartz, feldspar, sodium carbonate, boric acid and sodium metasilicate. Synthetic o/w emulsions constituting 125 and 250 mg/L oil concentrations were subjected to microfiltration (MF) using this membrane in batch mode of operation with varying trans-membrane pressure differentials (ΔP) ranging from 68.95 to 275.8 kPa. The membrane exhibited 98.8% oil rejection efficiency and 5.36 × 10⁻⁶ m³/m² s permeate flux after 60 min of experimental run at 68.95 kPa trans-membrane pressure and 250 mg/L initial oil concentration. These experimental investigations confirmed the applicability of the prepared membrane in the treatment of o/w emulsions to yield permeate streams that can meet stricter environmental legislations (<10 mg/L). Subsequently, the experimental flux data has been subjected to modeling study using both conventional pore blocking models as well as back propagation-based multi-layer feed forward artificial neural network (ANN) model. Amongst several pore blocking models, the cake filtration model has been evaluated to be the best to represent the fouling phenomena. ANN has been found to perform better than the cake filtration model for the permeate flux prediction with marginally lower error values.     

Performance of a new ceramic microfiltration membrane based on kaolin in textile industry wastewater treatment

A ceramic microfiltration membrane with a porosity of 40.2%, mean pore diameter of 0.27?μm, and a flexural strength of 55?MPa was prepared and applied for treatment of two types of textile dye-bath effluents. The ceramic membrane had a water permeability of 1376?L/m².h.bar and showed excellent corrosion resistance against basic medium. Considerable removal of COD (25%), TDS (31%), BOD (39%), turbidity (21%), sulphates (34%), chlorides (33%), and color (26%) from textile effluents was achieved in the microfiltration treatment along with complete (100%) removal of TSS. This study revealed that filtration of textile effluents using a sub-micron range ceramic membrane (0.27?μm) is more effective than traditional microfiltration membranes (2–10?μm). The flux data fitted well with the standard pore blocking model indicating that the removal of various contaminants is due to adsorption of solutes on the interior surfaces of membrane pores.     

Effect of elaboration parameters of a membrane ceramic on the filtration process efficacy

The formation of the flat membrane from kaolin and potassium phosphate was investigated with a particular focus on the appropriate elaboration parameters and the effect of their separation performance. The first step consisted in the fabrication of flat ceramic membrane supports from mechanochemicaly-treated kaolin (K) and starch (S). The mechanical properties, permeability and porosity of these supports were studied as a function of the milling time of kaolin, the starch content, the sintering temperature and time. The optimization of the elaboration parameters led to the fabrication of supports from kaolin milled for 30 min and 5% starch at sintering temperature of 1100 °C and sintering time of 1 h. In the second step, the potassium phosphate was added as a binder in the kaolin- 5% starch mixture. In this case, we noted the improvement of the permeability without reduction of the mechanical strength and porosity. Also, the separation performances and the fouling of membranes elaborated with different potassium phosphates were evaluated using Bovine Serum Albumin (BSA) solution.     

One-step dip-coating method for preparation of ceramic nanofiber membrane with high permeability and low cost

Ceramic nanofiber membrane (CNM) based on attapulgite (APT) without any intermediate layer neither any cracks was fabricated by a one-step dip-coating method. The effects of sintering temperature and dip-coating time on the physicochemical properties and performances of prepared CNMs were investigated. The increase of the sintering temperature up to 700 °C reduced the bending strength, porosity and chemical stability of APT-based CNMs. Meanwhile, with the dip-coating time increased, the membrane thickness increased thereafter reduced. The APT-based CNM fabricated at a sintering temperature of 600 °C and with a dip-coating time of 15 s had an average pore size of 20.4 nm, high porosity (above 60 %), good permeability of 118 L/m² h bar and a rejection of 96.6 % polymers with a molecule weight of 600 kDa. All these properties clearly suggest the practicability of the one-step dip-coating method to prepare ceramic nanofiber membranes.     

Integrated preparation of alumina microfiltration membrane with super permeability and high selectivity

A dual-layer alumina microfiltration membrane with super permeability and high selectivity was prepared by co-sintering the membrane and the support. Silica sol as sintering aid for the supports can also promote adhesion between supports and membranes. Tape-casting technique was introduced here to form the pre-membranes which were directly transfer-coated on the green support bodies. The optimum co-sintering conditions and the effects of organic agent content and membrane thickness on the membrane performance were comprehensively investigated. The optimized ceramic membrane had an average pore size of 249 nm and a water permeance of 5040 Lm⁻² h^-1 bar^-1 after co-sintering at 1300 °C for 2 h, which also exhibited a rejection rate of 96.2% for the carbon ink with an average particle size of 237 nm. This work provides a new method for efficient and low-cost preparation of high-performance ceramic membranes.     

Design and preparation of high permeability porous mullite support for membranes by in-situ reaction

The natural mineral kaolin combined with alumina additives Al(OH)₃,α-Al₂O₃ and AlF₃ was used to prepare porous mullite ceramic membrane supports using an in-situ reaction. The effects of composition and sintering temperature on the sintering behavior, pore structure, permeability and microstructure of the resulting porous mullite supports were extensively investigated. The experimental results showed that excess SiO₂ in kaolin can be consumed by adding alumina precursors, which resulted in a stiff skeleton of interlinked needle-like mullite crystals in-situ during the sintering. The needle-like mullite crystals touched each other and formed a short network, which acted as a porous skeletal network structure. This network resulted in a highly permeable porous structure. The resulting support is suitable for the preparation of asymmetric ceramic membranes. The densification and pore structure of the support can be effectively adjusted by control of the quantity of alumina precursors in the composition and the sintering temperature. Sintering the subject mullite compositions at 1500 °C for two hours resulted in support structures with an average porosity of 45.9%, an average pore size of 1.3 µm and a penetrating porosity of 35.9%.     

The effects of performance and cleaning cycles of new tubular ceramic microfiltration membrane fouled with a model yeast suspension

The efficiency of crossflow microfiltration processes is limited by membrane fouling and concentration polarization leading to permeate flux decline during operation. The experiments that were carried out in the laboratory were conducted to determine and investigate the performance, behaviour and the fouling susceptibility of new ceramic tubular microfiltration membranes during the crossflow filtration of yeast suspensions. The tubular membranes of nominal pore size 0.5 microns were fouled over a varied range of concentration, temperatures, pH, crossflow velocities and system pressures. The typical filtration conditions were at a temperature of 25°C, a system pressure of 1.5 bar and a concentration of 0.03 g/L yeast suspension. These parameters varied during subsequent investigations. After each experiment, the membrane and the rig were cleaned using a three stage cleaning process and was reused in order to replicate industrial filtration conditions. The effects of repeated fouling and cleaning cycles upon membrane flux over time and cleaning efficiency are investigated and their influence over time is also documented. For every experiment, the flux data was recorded over a 50 min period and the membrane was changed after the PWF declined considerably due to excessive fouling over time. Chemical cleaning consisted of a sequential application of a 1% caustic solution through the rig followed by a 2% hypochlorite solution and a 2% nitric solution, all at 50°C. The permeate flux was shown to decrease with filtration time during the development of the fouling layer. Once the fouling layer was developed and established, there appeared to be a leveling of permeate flux. The experimental results are presented in the report and the flux values at different conditions are presented.     

Effect of phase composition of natural quartz raw material on characterization of microfiltration ceramic membranes

The results of development of multi-layer ceramic membranes on the basis of natural quartz raw material from Mongolia are presented. The influence of the phase composition and temperature of calcination on the porosity, morphology and mechanical strength of large-porous ceramic support obtained by the method of isostatic pressing was studied. It was established that multi-layer ceramic membranes obtained by the application of water suspension of high-disperse quartz sand of Mongolia and alumosilicate binder with the addition of 15–35 wt% of quartz are characterized by optimal properties. The developed tubular ceramic membranes with the average pore size 5.3 µm, coefficient of air permeability (4.17–4.41)×10⁻¹³ m², productivity by water 46.3–48.0 m³/(h×m²×bar) and mechanical strength 2.27–2.53 MPa are perspective for wide use in microfiltration processes.     

附加湍流器强化陶瓷膜微滤过程的研究

通过在管式陶瓷膜内设置不同结构形式的湍流器，试验和比较了不同主体流速和膜滤压差等工艺条件下的膜滤速率及能耗，分析了湍流器所产生的强化膜滤过程的效果以及试验条件下的一般规律。     

陶瓷膜通道相互作用的实验分析及CFD优化

提出陶瓷膜过滤时,通道之间存在3种效应关系（壁厚效应、干扰效应、遮挡效应）,并用实验进行了验证。对于多通道陶瓷膜构型的设计,要考虑3种效应。膜孔径小于200 nm的陶瓷膜,可以增大其通道的排布密度,通过提高装填密度可以提高单位体积的处理量;膜孔径大于500 nm的陶瓷膜,中间的通道对通量几乎没有贡献,提高装填密度意义不大。固定膜元件的外径,选取通道直径a_c和壁厚a_w,并设定两参数的比值为α,采用计算流体力学（CFD）软件进行模拟计算,获得了通量与处理量随孔径与α值的变化关系。     

Asymmetric TiO2 hybrid photocatalytic ceramic membrane with porosity gradient: Effect of structure directing agent on the resulting membranes architecture and performances

Asymmetric TiO₂ hybrid photocatalytic ceramic membranes with porosity gradient have been fabricated via acid-catalyzed sol–gel method. Different structure directing agents (SDAs) i.e. Pluronic P-123, Triton X-100, Tween 20 and Tween 80 were incorporated in the preparation of TiO₂ sol to obtain a porous multilayered TiO₂ coated on the alumina ceramic support. Six different SDA-modified membrane specimens were fabricated. Four of which were coated with the TiO₂ sols prepared using only one type of SDA. The remaining two specimens were fabricated via multilayer coating of different TiO₂ sols prepared using different types of SDAs. Physico-chemical and morphological properties of different TiO₂ layers were thoroughly investigated. The membrane M1 which had the most porous TiO₂ sub-layers showed a high pure water permeability of 155 L m⁻² h⁻¹ bar⁻¹. The membrane showed a relatively high Rhodamine B (RhB) removal of 2997 mg m⁻² over 8 h treatment duration in the batch photoreactor, second only to the Pluronic-based TiO₂ membrane (specific RhB removal of 3050 mg m⁻²). All membrane specimens exhibited good performances while operated in the flow-through photocatalytic membrane reactor. Over 91% of RhB removal capability was retained after 4 treatment cycles. All membranes also showed self-cleaning property by retaining >90% of initial flux after 4 treatment cycles. The flexibility of optimizing membrane performances by fine-tuning the porosity gradient configuration of the photocatalytic layer has also been demonstrated.     

Preparation of microfiltration membrane supports using coarse alumina grains coated by nano TiO2 as raw materials

To increase the mixing uniformity of coarse alumina grains with a small amount of nano TiO₂ particles, TiO₂ particles were prepared on the surface of coarse Al₂O₃ grains by in-situ hydrolysis of TiCl₄. The coated coarse Al₂O₃ powder was used to prepare microfiltration membranes supports. The effects of TiO₂ content and sintering temperatures on the bending strength, porosity and pore size distribution of the obtained supports were studied. The results show that the melted nano TiO₂ grains locate mainly at the neck of Al₂O₃ grains, which increases the bending strength of the support by increases the neck area. However, the bending strength is weakened if the TiO₂ content is excessive. No aggregated nano TiO₂ grainsare found. The resulting supports sintered at 1650 °C for 2 h yields a bending strength of 55.4 MPa, a porosity of 38% with a mean pore size of 8.0 μm.     

Manufacture and optimization of tubular ceramic membrane supports

The manufacturing and optimization of centrifugally casted ceramic membrane supports is presented. For the optimization, the effect of three different powder sizes (0.25, 0.31 and 0.61 μm) and a sintering temperature range between 1050 and 1400 °C was investigated. The ceramic tubes were characterized according to tube dimensions, mercury porosimetry, water permeability, SEM and mechanical strength. It was shown that the centrifugal casting technique delivers highly reproducible support properties. A novel strength testing apparatus was developed to determine the mechanical strength of the ceramic tubes. It was found that the strength varied between 3300 MPa and 300 MPa, depending on the porosity of the supports. With increased sintering temperature, water permeability and porosity decreased, while strength and linear shrinkage increased. The pore diameter of the supports produced by the 0.31 and 0.61 μm powders decreased, while that of the 0.25 μm powders remained constant (72 nm) with increasing sintering temperature. The 0.61 μm powder sintered at the lowest sintering temperature resulted in the support with the highest porosity, pore diameter and porosity, but the lowest mechanical strength and linear shrinkage. An overall improvement concerning pure water permeability was seen when the support in this study was compared to our own previous studies and similar studies in literature.     

Study of ceramic ultrafiltration membrane support based on phosphate industry subproduct: Application for the cuttlefish conditioning effluents treatment

The development and the characterisation of a new support for ultrafiltration membranes prepared from the mud of the hydro cyclone laundries of phosphate are presented. The choice of this material is based mostly on its low cost (considering its abundance in the Tunisian ores). Indeed, the use of this material for membrane preparation allows a good management of this subproduct which represents a major problem in phosphate transformation industry due to the resulting environmental pollution.Paste from the mud of the hydro cyclone laundries of phosphate was extruded and heated at 900 °C to produce a porous tubular support having an average pore diameter and a porosity of about 1.05 μm and 39%, respectively. The properties regarding to mechanical and chemical resistances are very interesting. The deposition of the ultrafiltration layer from zirconium material was performed by slip-casting method. The heating treatment at 700 °C leads to an average pore size of 5 nm. The determination of the water permeability shows a value of 86 l/h m² bar. This membrane can be used for crossflow ultrafiltration. The application of the cuttlefish effluent treatment shows an important decrease of turbidity, inferior to 1.5 NTU and chemical organic demand (COD), retention rate of about 60%. So, it seems that this membrane is suitable to use for wastewater treatment.     

Elaboration and characterisation of low cost ceramic support membrane

Abstract

A porous tubular ceramic membrane was prepared from low cost Tunisian clay. The characterisation of the raw material and the effect of the sintering temperature on the morphology, pores size distribution and the mechanical properties of the ceramic membrane were studied. A ceramic membrane fired at 1000°C for 1?h presented a mean pore diameter of ～1·04?μm. The porosity was equal to 38?vol.-%. The filtration of a 0·5?g?L^?1 bovine serum albumin solution indicated that the limiting flux of permeate was 245?L?h^?1?m^?2?bar^?1, which corresponded to a retention rate of about 13%.     

无机陶瓷微滤膜处理含油乳化液废水的污染机理探讨

讨论了用陶瓷微滤膜处理含油乳化废水过程的膜污染情况,初步探讨了此分离过程的污染机理;给出了阻力的大致分布,为采用有效方法控制污染提供了依据。     

陶瓷雕刻肌理与当代陶瓷装饰的关系

随着国家经济的高速腾飞,民众的生活水平也日益提高,简单程式化的装饰已经满足不了我们普罗大众的审美情趣。随着陶瓷装饰的设计思维越发的现代化,当代多元化的装饰元素不停的更新。其中陶瓷雕刻这一装饰题材,则富有无与伦比的亲和力以及强烈的装饰感。本文将陶瓷雕刻作为主要的研究对象,着力探讨陶瓷雕刻的造型语言、肌理技法等的审美表达。通过对比陶瓷雕刻语言运用到当代陶瓷装饰中的可行性,也为当代陶瓷装饰的发展带来新的推动力。