Search

Polymeric membranes have not been widely used to treat oily wastewater due to their susceptibility to fouling. The aim of the present work is to develop a low-cost, facile modification technique to achieve superhydrophilicity and fouling resistance of hydrophobic PVDF membranes in oil-water separation applications. PVDF microfiltration membranes with 0.1, 0.2 and 0.45 µm pore size were modified with mixtures of different concentrations of dopamine (DA) and polyethyleneimine (PEI) using different deposition times (6, 12 and 24 h). The modified membranes were characterized for their surface physicochemical properties, pH tolerance, and performance in filtration of a model oil emulsion. The PDA/PEI coating was shown to produce superhydrophilic membrane surfaces with very high oil rejection (>98% with 1 µm nominal pore size), and greatly reduced irreversible fouling by oily wastewater. The excellent oil rejection and fouling resistance is attributed to the hydration water layer formed by the PDA/PEI coating both on the membrane surface and inside membrane pores.

Oily wastewater is generated in large amounts by different industry segments, such as food and beverage, oil and gas, cosmetics, and metal processing. Its incorrect disposal causes soil and water contamination, generating environmental and public health problems. In this sense, the use of membranes able to remove the oil present in the wastewater has shown to be a promising technology that can treat a larger range of oily wastewaters than conventional systems without losing the high oil removals. Catalytic membrane processes can combine the separation and catalyzed degradation of the oil, minimizing fouling and increasing the membrane lifespan. Thus, this chapter aims to approach the main aspects of oily wastewater treatment by catalytic membranes, including enzymatic and advanced oxidation processes, as photocatalysis, electrocatalysis, and Fenton-like processes. The chapter is organized in six sections: introduction, oily wastewater, membranes for oily wastewater treatment, catalytic membranes, conclusions, and future trends.

Membrane technology is an interesting alternative to conventional gelatin clarification methods, resulting in the elimination of refining chemical agents. In this work, the application of a permanent magnetic field as a pre-treatment of the gelatin solutions was proposed as a strategy to improve the microfiltration (MF) performance. Filtration tests were performed using a 1.5% swine gelatin solution at 40 °C through cellulose acetate membranes in a tangential flow module. Prior to the filtrations, the feed solutions were pretreated by the circulation of the solution through magnetic fields with different flux densities, 0.7 T and 1.34 T, for 2 h. The magnetic induction of the solution significantly increased the permeate flux and the recovery of hydraulic permeance by 63% and 122%, respectively, showing the application of the magnetic field in the solution of gelatin is an attractive alternative to improve the performance of the process.

The use of magnetic field in protein solution (bovine serum albumin/BSA) was proposed as a strategy to improve the ultrafiltration (UF) performance. Permeation tests of BSA (2.5 g L−1 and pH 6.5) through a 50 kDa hydrophilic polyethersulfone (PES) membrane were carried out in a tangential flow module. The magnetic induction effect (MI) on the feed solutions was studied by submitting the feed to the magnetic field (magnetic flux density 0.7 T and 1.4 T) for 0.5 h, 2 h and 12 h before permeation runs. Positive effects were observed in the permeate flux with flux increase up to 195% compared to control. Also, a reduction in the fouling resistance from 59% (control) to 18% and 16% using 2 h of magnetic induction under 0.7 and 1.4 T, respectively, was noted. This behavior can be attributed to changes in structure and zeta potential of the BSA solution after magnetic field exposition, then increasing the repulsion between the membrane surface and the protein molecules.

Behavior of nanofiltration (NF270 and NP030) and reverse osmosis (BW30 and ORAK) polymeric membranes in systems with dense CO 2 was evaluated. The influence of transmembrane pressure on the CO 2 permeate flux at subcritical and supercritical conditions was assessed and membrane characterization (FTIR-ATR, zeta potential, Hansen’s solubility parameters) was performed. The results of CO 2 permeation suggest that selectivity of polymeric matrix depends, in great extent, on the interaction between solvent and polymer. This behavior corroborates with the presence of hysteresis phenomenon in permeability curves and solubility results. Also, zeta potential showed a decrease in the membrane point of zero charge (PZC) after pressurization/depressurization cycle, suggesting possible CO 2 sorption in the membrane polymer. Nevertheless, the oil retention for NP030 and ORAK membranes was up to 85% and no damage to the membrane structure was found. Both membranes presented potential for concentration of fatty acids under dense phase CO 2 .

Poultry processing plants generate large amounts of wastewater in the many steps necessary to provide high quality and safe products. Carcass chilling is one of these steps, where the temperature of the carcass is reduced from 40°C to 4°C, for reducing the growth rate of microorganisms and affecting flavour, texture and appearance. In this operation, carcasses are continually displaced through a series of two tanks (called pre-chiller and chiller) filled with cold water, thus being responsible for a considerable amount of wastewater generation. This work aimed to regenerate the wastewater of the pre-chiller tank employing microfiltration (pore size 0.10 and 0.20 µm) and ultrafiltration (UF; MWCO 10 and 50 kDa) polymeric membranes in bench and pilot scales, with the final purpose of reuse. Membrane performance was evaluated in terms of the capacity of removing the contaminants and producing sufficient permeate flux in different working pressures. Bench-scale UF membrane presented the highest initial permeate flux of 112.1 L/m2h at 200 kPa. The four membranes tested presented good retention of microorganisms, with apparent rejection of up to 100%. Pilot-scale membranes presented better apparent rejection, with retentions above 99% for turbidity, apparent colour and fat content. Moreover, organic matter retention was also very high, up to 94% for chemical oxygen demand and 92% for total organic carbon. The use of membranes seems to be a promising approach for recycling and reuse of poultry pre-chiller wastewater.

Membrane emulsification has been drawing attention due to its many application possibilities. This study aimed to assess the preparation and stability of oil in water (O/W) emulsions by membrane emulsification technique. Microporous ceramic membranes with mean pore size 0.2 μm and 0.8 μm were used for producing sunflower oil in water emulsions, displaying mean droplet size ranging from 2.9 to 11.6 μm and from 4.8 to 16.2 μm, respectively. The effect of the oil concentration (10%–20%), surfactant concentration (1%–4%), tangential velocity (0.12 m s−1 to 0.24 m s−1), and feed pressure (100 kPa–300 kPa) on the process performance was investigated using an experimental design. All the parameters significantly influenced the mean droplet size, the droplet size distribution, and the emulsion stability. Depending on the emulsification conditions, monodisperse and polydisperse emulsions were obtained. The use of a membrane with 0.2 μm mean pore size led to better results than those obtained with a 0.8 μm membrane, since they yielded emulsions displaying smaller droplet size and narrower size distribution. The emulsions prepared using this membrane were stable up to 100 days.

In this work, andiroba oil extraction ( Carapa guianensis ) was investigated using pressurized n -butane as solvent at 25, 35 and 45 °C and pressures of 7, 10 and 13 bar. Andiroba oil yield as high as 18 wt% was obtained at the lowest temperature and pressure (25 °C and 7 bar) for an extraction period of 45 min. Regarding chemical composition, the major components observed in the extracts were palmitic and oleic acids, while for the phenolic compounds values between 11.2 and 35.7 (mg EAG/100 g) were experimentally observed. For the antioxidant activity, DPPH radical scavenging method employed for the extraction conditions of 25 °C and 13 bar and 45 °C/7 bar provided inhibition percentages of 22.2% and 17.4%, respectively. Extraction with n -butane thus showed to be a promising alternative technique to conventional extraction methods, as very mild operating conditions and eco-friendly solvent can be used to provide good results without any residues in the final product.

Membrane performance is decreased by fouling, reducing permeate flux and membrane lifespan. This paper assesses ultrafiltration of a model textile effluent assisted by permanent magnetic field as an alternative to improve the water permeability recovery. Ultrafiltration was performed in a tangential module and model solutions, composed of carboxymethylcellulose (CMC) and sodium sulphate (Na2SO4). The feed was permeated through 30 kDa polysulphone membrane with and without the presence of a permanent magnetic field of 0.41 T, perpendicular to the membrane surface. Magnetic induction (MI) of feed solution was also investigated by recirculation of the feed stream through the magnetic field for 3 h. The increase in feed concentration did not affect permeate flux, while the presence of salt resulted in a severe flux decline. Effective water permeability recovery was obtained when the magnetic field was applied in the ultrafiltration process, although the MI of the CMC and Na2SO4 solutions also caused some enhancement in permeability recovery. Scanning electron microscopy images showed differences between the assays done with and without the presence of magnetic field. The magnetic field application in ultrafiltration of CMC and Na2SO4 solutions has proved to be an attractive alternative for improving the permeability recovery.

Macauba is a Brazilian palm tree with high edible oil productivity and of great interest to many applications. In the oil extraction process, solvent recovery is one point of major concern, due to its high energy consumption and oil quality losses. Those drawbacks can be partially overcome by integration of membrane technology to the usual solvent distillation step. The present work tested four ultrafiltration (UF) and one nanofiltration (NF) membrane (Microdyn-Nadir) on the solvent recovery of synthetic mixtures of macauba oil and n-hexane. Membranes were pre-treated before use with different solvents in specific time lengths, according to preliminary studies. The membrane performance was evaluated by permeate flux and oil retention. Macauba (pulp and kernel) oil was evaluated by determinations of acidity, peroxide value and fatty acid profile. Membranes showed usual flux behaviour, compatible with other studies concerning oil/solvent mixtures permeation, although its values were quite above the expected. Best results for retention (>30%) are related to the membranes with lower molar mass cut-off (MMCO), and the best balance between permeate flux and oil retention was found for the NF membrane (12.4 g m−2 h−1, 34.7%).

Several pre-treatments and solvents were tested through permeation in commercial polymeric membranes (UH004, UP005, UP010 and UH050 – Microdyn-Nadir) with different molar mass cut-offs (4 kDa, 5 kDa, 10 kDa and 50 kDa, respectively), in order to evaluate their efficiency and stability through non-aqueous solvent permeation. After pre-treatments and permeations, membranes were characterised with contact angle, Fourier Transform Infrared Spectroscopy (FTIR), and Field Emission Scanning Electronic Microscopy (FESEM) to evaluate structural integrity. The results of solvent permeation suggest that selectivity of the polymeric matrix depends not only on pore size, but also, in great extent, on the interaction between solvent and polymer. A strong relation can be noted between the conditioning length and permeability for ethanol pre-treatments. Permeability to n -hexane increased from 4 to 18 times after pre-treatment, depending on the time of exposure to ethanol and n -hexane. Characterisation analyses show no significant changes on the membranes surface. In some cases, discrepancies observed among permeate fluxes and contact angles might be an indicative of the occurrence of swelling and plasticisation. However, results suggest the feasibility in the use of these membranes for the recovery of solvents in the oil industry, if suitable process parameters are chosen.

Strategies to control biofouling without using antimicrobial chemicals are needed to prevent the spread of antibiotic resistance genes and disruption of microbial activities in biological treatment. This study developed an environmentally friendly biofouling resistant membrane by incorporating d -tyrosine onto a commercial nanofiltration membrane using FAU type zeolite nanoparticles that covalently bound to the membrane surface as carriers for slow release. The d -tyrosine loaded membrane had similar water permeability as the unmodified membrane, but greatly reduced initial cell attachment and strongly inhibited subsequent biofilm formation without inactivating the bacteria. The membrane slowly released d -tyrosine in the time course of over 5 days, and retained its anti-biofouling capability in repeated 24 h efficacy tests for as long as 6 days. In nanofiltration operation, the d -tyrosine incorporated zeolite coating completely inhibited cell adhesion on the membrane surface and significantly alleviated membrane flux decline.

Membrane separation processes are widely employed for protein concentration in the food industry. The major drawback is permeability reduction caused by concentration polarization and fouling. The present work evaluated the influence of a permanent magnetic field applied to the ultrafiltration process (UF) of protein solutions, as an alternative to improve the permeation performance and the permeability recovery. Permeation tests of bovine serum albumin (BSA) and milk as the feed protein solutions through a 50 kDa hydrophilic polyethersulfone (PES) membrane were carried out in a tangential flow module. The feed pH was varied (4.0, 6.5 and 8.0) and ionic strength was modified by sodium chloride (NaCl). Permanent magnets were placed so as to obtain a maximum 0.7 T magnetic field perpendicular to the membrane surface. The magnetic induction effect (MI) on the feed solutions was also studied by submitting the feed to the magnetic field for 2 h before permeation run. The presence of magnetic field and the MI effect of the solution were effective in increasing both the permeate flux and the recovery of hydraulic permeability. The magnetic field application in the UF of protein solutions has proven to be an attractive alternative for improving process performance.

The aim of this study was to evaluate the influence of different solvents and time conditionings in the permeation of n-hexane and oil/n-hexane solutions through several reverse osmosis (ORAK – Osmonics, BW30 – Dow Filmtec) and nanofiltration (NF270 – Dow Filmtec, NP030 – Microdyn Nadir) polymeric membranes. The study of the influence of membrane conditioning on the n-hexane flux was carried out using different solvents (n-hexane, ethanol, n-propanol, iso-propanol and butanol) as pretreating agents in different time intervals. Membrane performance was tested by measuring n-hexane fluxes and rejections of dissolved castor oil. The conditioning with ethanol increased n-hexane fluxes in the polyamide membranes ORAK, NF270 and BW30, while the polyethersulfone membrane NP030 did not present any increase in permeability. An increase in contact angle after membrane conditioning was detected, as well as a reduction in free surface energy. This suggests that pretreatment steps alter the surface hydrophilic character. Salt rejections for all the membranes decreased after the pretreatments and permeation with n-hexane for 8 h. These rejections dropped from 87–99% to 72–77% for membranes NF270, NP030 and BW30; and from 99% to 88% for ORAK, which showed better stability to solvent exposure. For castor oil, the highest retention was 60% for reverse osmosis membrane ORAK. The results obtained in this work with commercial RO and NF membranes, normally used in aqueous solutions operations, indicate that most of these membranes do not present adequate stability towards non-aqueous solvents.