Preparation and applications of microfiltration carbon membranes for the purification of oily wastewater

Highly efficient removal of emulsified oil from oily wastewater by microfiltration carbon membranes made from phenolic resin/coal

Oily wastewater treatment is a major problem for a large variety of industrial sectors. Membrane filtration is quite promising for oil-in-water emulsion treatment by virtue of numerous eminent advantages. Here, microfiltration carbon membranes (MCMs) were prepared by the blends of phenolic resin (PR)/coal as precursor materials for efficient removal of emulsified oil from oily wastewater. The functional groups, porous structure, microstructure, morphology and hydrophilicity of the MCMs were analysed by Fourier transform infrared spectroscopy, bubble-pressure method, X-ray diffraction, scanning electron microscope and water contact angle, respectively. The effect of coal amount in precursor materials on the structure and properties of MCMs was mainly investigated. Under operation at 0.02 MPa for trans-membrane pressure and 6 mL min-1 for feed flowrate, the optimal oil rejection and water permeation flux are correspondingly attained to 99.1% and 21,388.5 kg m-2 h-1 MPa-1 for MCMs made by the precursor containing 25% coal. Besides, the anti-fouling ability of the as-prepared MCMs is greatly improved in comparison with the one merely made by PR. In summary, the result indicates that the as-prepared MCMs are very promising for oily wastewater treatment.

Separation of oil-water emulsion by cellulose acetate ultrafiltration membranes

This study reports the separation of oil from water using cellulose acetate (CA) ultrafiltration (UF) membranes. The CA membranes were fabricated by varying bath temperatures such as 5 ± 2°C, 25 ± 2°C and 45 ± 2°C using the phase inversion technique and assess their performance based on the oil removal efficiency. Changing the coagulation bath temperature (CBT) at that stage of membrane formations affects the porosity, pore size, hydraulic resistance, morphological structure and performance of membranes. The obtained results revealed increased porosity and pore size and also decreased hydraulic resistance of the membranes as the CBT increases. Field Emission Scanning Electron Microscopy (FESEM) images indicate that a large number of surface pores are visibly found at the higher bath temperature. Atomic force Microscopy (AFM) images show increased average roughness (Ra) of the membrane as the CBT of the membrane increases. The water flux and permeate flux of all the membranes tend to increase with an increase in CBT. From Chemical Oxygen Demand (COD) studies, the oil removal efficiency was maximum for the lower bath temperature membrane. The results indicate that conditions of the coagulation bath significantly affect the porous structure, morphology and performance of the membrane.

Constructing a composite microfiltration carbon membrane by TiO2 and Fe2O3 for efficient separation of oil-water emulsions

Membrane-based separation technology has attracted enormous attention for oil/water emulsion treatment. Here, composite microfiltration carbon membranes (MCMs) were prepared from the precursor of phenolic resin doping with TiO2 and Fe2O3 via the processes of stereotype and pyrolysis. The functional groups, thermal stability, porous structure, microstructure, morphology, and hydrophilicity of the membrane samples were analyzed by Fourier-transform infrared spectroscopy, thermogravimetric analysis, bubble pressure method, X-ray diffraction, scanning electron microscope, and water contact angle, respectively. The effect of dopant amount on the separation performance of MCMs was investigated. The results show that a mixed matrix system is constructed by TiO2 and Fe2O3 in MCMs, which is beneficial for further optimizing the pore size, porosity, and hydrophilicity of MCMs for oily wastewater treatment by varying the dopant amount. The maximum oil rejections are achieved at 98.9% and 99.6% for MCMs with a dopant content of TiO2 and Fe2O3 at 25%, respectively. In brief, this study offers an attractive strategy for improving the separation performance of MCMs for oily wastewater.

Fouling of the Nanofiltration Membrane NF270 Used for Separation of Fermentation Broths: Impact of Feed Pretreatment Process

Recent findings regarding nanofiltration (NF) have led to indications that it can be successfully used for separation of various biological solutions. As a novelty, this paper is the first to investigate the impact of the feed pretreatment process on the NF membrane performance used for separation of 1,3-propanediol (1,3-PD) fermentation broths. For this purpose, prior to the NF process, the feed was purified by microfiltration (MF) and ultrafiltration (UF) processes. Subsequently, the long-term NF process was carried out with the use of a commercial, flat-sheet, thin-film, polyamide NF270 nanofiltration membrane. Thereinto, to determine the dominant fouling mechanism, Hermia’s model was used. With regards to the pretreatment processes performed, it has been determined that the MF membrane (0.14 µm) provided the reduction in the number of bacteria cells present in the permeate, while the UF membrane (450 Da) allowed obtaining the sterile permeate. Consequently, the NF permeate flux for the UF permeate was significantly higher. Analysis of the fouling mechanisms showed that during the separation of the MF permeate, formation of a cake layer on the NF membrane surface was dominant. In turn, with regards to the UF permeate, membrane blocking occurred in two separate phases involving standard blocking and then cake layer formation. Finally, a strategy of NF membrane cleaning with the use of sodium hydroxide (NaOH) solution has been proposed.

Critical review on microfibrous composites for applications in chemical engineering

Microfibrous composites (MCs) are novel materials with unique structures and excellent functional properties, showing great potential in industrial applications. The investigation of the physicochemical properties of MCs is significant for accommodating the rapid development of high-efficiency chemical engineering industries. In this review, the characteristics, synthesis and applications of different types of previously reported MCs are discussed according to the constituent fibres, including polymers, metals and nonmetals. Among the different types of MCs, polymer MCs have a facile synthesis process and adjustable fibre composition, making them suitable for many complex situations. The high thermal and electrical conductivity of metal MCs enables their application in strong exothermic, endothermic and electrochemical reactions. Nonmetallic MCs are usually stable and corrosion resistant when reducing and oxidizing environments. The disadvantages of MCs, such as complicated synthesis processes compared to those of particles or powders, high cost, insufficient thorough study, and unsatisfactory regeneration effects, are also summarized. As a result, a more systematic investigation of MCs remains necessary. Despite the advantages and great application potential of microfibrous composites, much effort remains necessary to advance them to the industrial level in the chemical engineering industry.

Synthesis, characterization of cellulose acetate membrane and application for the treatment of oily wastewater

This study reports the synthesis of cellulose acetate (CA) membranes of different weight percentages of the polymer ranging from 5 to 17.5 wt% with 2.5% increment and their behaviour towards oil removal from water. The membrane showed decreased water content and porosity and also increased hydraulic resistance upto 3.38 kPa/(l m^-2 h^-1) as the concentration of polymer increases. The Atomic Force Microscopic studies reveal that the membrane shows decreased arithmetic mean roughness from 36.291 to 5.935 nm as the concentration of the polymer increases from 5% to 17.5%. Field Emission Scanning Electron Microscopy shows the surface morphology of the CA membrane. X-ray diffraction studies indicate that in the membrane having above 15% polymer concentration, the polymer chains orient to regularity showing higher crystallinity. The thermal studies indicate their stability upto 280°C, and exothermic decompositions from 338°C to 380°C implying the compactness of chains as polymer concentration increases. From Total Organic Carbon studies, the oil rejection was found to be maximum (96.4%) for the highest concentration of polymer in the membrane.

A brief review on carbon selective membranes from polymer blends for gas separation performance

The development of carbon membranes for the separation of various gases has gained interest among researchers due to their superior performance in gas separation. The preparation of carbon membranes by blending materials has many advantages including time and cost effectiveness for tuning the properties of the membranes. Here we review the recent research progress that has been made in the context of breakthroughs and challenges in the development of carbon membrane materials. In addition, we provide information regarding carbon membrane fabrication in terms of the selection of precursors and additives, carbon membrane process conditions, and coating conditions that influence the performance of gas separation of the resulting carbon membranes. The perspectives and future research directions for carbon membranes are also presented.

Treatment and reclamation of hydrocarbon-bearing oily wastewater as a hazardous pollutant by different processes and technologies: a state-of-the-art review

Hydrocarbon-containing oily wastewater generated by various industries creates a major environmental problem all over the world since petroleum products are commonly used as energy sources and raw materials in various industries. In case of offshore/coastal oil recovery operations, produced water is discharged through either shore side outfalls or coastal rim releases. In many cases, current disposal practices leads to severe environmental pollution by contamination of petroleum hydrocarbon to the surface, ground, and coastal waterways. Therefore, it is necessary to evaluate the performance of various processes for the recovery of petroleum hydrocarbons from wastewater. In this paper, a detailed review on the different separation/treatment processes of oily wastewater is presented. Previous and recent research works are reviewed in the area of oil-water separation from wastewater and also highlight the new developments in these areas. Various separation processes and technologies such as gravity separation, flotation process, membrane process, adsorption process, biological treatment, freeze/thaw process, and photocatalytic oxidation process (PoPs)/advanced oxidation processes (AoPs) are discussed and reviewed. The adsorption properties of a wide variety of porous sorbent materials in oily wastewater treatment, particularly in the area of oil spill cleanup, are also reviewed. The advantages and disadvantages of each process are critically discussed and compared.

Recent developments of carbon based nanomaterials and membranes for oily wastewater treatment

Carbon-based nanocomposite membranes have recently drawn tremendous attentions among membrane scientists due to their excellent chemical, mechanical stability and antifouling properties against oil deposition/adsorption.

Fabrication and gas permeation of CMS/C composite membranes based on polyimide and phenolic resin

Supported carbon molecular sieving membranes were prepared by a novel precursor 6FAPB-CBDA type polyimide on the surface of carbon sheets, which have a most promising potential for gas separation applications.