Performances of nanofiltration on industrial phosphoric acid purification

Phosphoric acid production is of major importance to the Tunisian economy. However, the quality produced is not suitable for other than agricultural use due to mineral and organic impurities. In this study, the purification of industrial phosphoric acid with a maximum P2O5 concentration of 25% was achieved by nanofiltration.  Six solutions of different P2O5 concentration were used. The removal of organic (total carbon) and inorganic impurities such as magnesium, iron, chrome, zinc, cadmium and vanadium, were studied.The performances of nanofiltration (NF) Nadir NP 30 membrane were determined in terms of permeate flux and P2O5 and impurities retention taking into account the effect of transmembrane pressure, P2O5 concentration and membrane prea-treatment by purified phosphoric acid solution.Results showed that for the industrial 25% P2O5 acid solution, the use of NF membrane achieved a retention of 87.35%, 86.73%, 87.57%, 78.41% and 73.17%, respectively, for iron, aluminum, chrome, magnesium, vanadium and organic matter (kerogen and humic acids) under a pressure of 20 bar. P2O5 permeation increased with the increase of its concentration in the acidic feed solution. The best permeation is provided by 25% P2O5 feeding acid solution which is of almost 98%

New Ceramic Microfiltration Membranes from Tunisian Natural Materials: Application for the Cuttlefish Effluents Treatment

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Optimization of peptide production by enzymatic hydrolysis of tuna dark muscle by-product using commercial proteases

A protein hydrolysate was prepared from proteins of tuna dark muscle by-product. The hydrolysis conditions (time, temperature, pH and enzyme concentration) using Alcalase and Neutrase were optimized by response surface methodology (RSM). The regression coefficient close to 1.0, observed during experimental and validation runs, indicated the validity of the model. The hydrolysate produced under the optimum conditions determined by RSM using Alcalase, had a low rate of peptide fraction of molecular weight of 1-4 kDa. Meanwhile, the results obtained by hydrolysis under optimal conditions determined by a complementary study (temperature 55°C, time 60 min, 1% enzyme concentration and pH 8.5) show that the hydrolysate produced had a high rate of the peptide fraction of molecular weight of 1-4 kDa. The amino acid composition of the protein hydrolysate prepared proved to have the potential for application as an ingredient in balanced fish diets and as a source of nitrogen in microbial growth media.Keywords: Alcalase, neutrase, tuna dark muscle, RSM, optimization, protein hydrolysate, peptides, degree of hydrolysisAfrican Journal of Biotechnology Vol. 12(13), pp. 1533-154

Étude préliminaire du traitement d’effluents contenant de l’encre de seiche par centrifugation et procédés à membranes

Il s’agit d’une étude préliminaire sur le traitement d’effluents de conditionnement de la seiche avant congélation en vue de réduire la charge polluante des rejets et de valoriser l’encre qu’ils contiennent. Deux types de procédés ont été mis en oeuvre : d’une part, la centrifugation, qui permet de fractionner la suspension d’encre de seiche entre un culot noir à DCO (Demande Chimique en Oxygène) élevée et un surnageant limpide et, d’autre part, l’ultrafiltration (UF) et la microfiltration (MF). Les flux de perméat obtenus par les deux procédés à membranes sont du même ordre de grandeur (25 à 30 L·h‑1·m‑2 sous 1,5 bar). La rétention moyenne en DCO est de 65 % et la rétention en COT (Carbone Organique Total) et azote protéique (NTK) de plus de 95 %. Cependant le colmatage irréversible de la membrane de MF conduit à préférer l’UF, plus facilement régénérable.Industries that condition fish products have to cope with the problem of processing their usually protein-rich wastewaters. An example of such an industry that discards a large amount of wastewater is the CALEMBO Company (Sfax-Tunisia), which uses 50 m3 per metric ton a day to condition cuttlefish for freezing. In order to conserve water, high-salinity bore water is sometimes used. This high salinity water is responsible for the difficulties encountered during the biological treatment of wastewaters and the recovery of valuable by-products. In this respect, membrane processes, used in the treatment and exploitation of effluents from industries that process sea products, are very attractive. The first membrane filtration trials on sea-product effluents date back to the 1980’s, but they did not result in major developments. Legislative pressures and the increasing costs of water and effluent-processing, as well as the improvement of membrane efficiencies, have made membrane treatment processes much more interesting for wastewater treatment processes. The GEPEA Laboratory at Nantes University has carried out research on membrane technologies to clean up polluted process waters, enhance substances such as soluble fish proteins, and to recover substances responsible for the flavour of bivalves and shellfish.This paper presents preliminary research on the treatment and exploitation of water used in cuttlefish conditioning. Treatment processes used include centrifugation, microfiltration and ultrafiltration. Centrifugation is used to determine the distribution of the effluent between the black residue and the clear supernatant, whereas membrane processing is used to reduce wastewater pollution and concentrate pigments.The effluent studied was reconstituted from pure cuttlefish-ink samples taken directly from the animal and salt waters of the same salinity as the bore water used by the CALEMBO Company (Table 1). The samples were reconstituted in ratios of 1 to 50 for centrifugation and 1 to 100 for membrane filtration. Centrifugation trials were carried out using a KR 22i type JOUAN centrifuge, whereas ultrafiltration and microfiltration trials were carried out using the laboratory apparatus represented in figure 1. The main characteristics of membranes used are indicated in table 2. Operating conditions were determined according to the capacities of the feed pump: transmembrane pressure Ptm = 1.5 bar, circulation velocity U = 1.5 m·s‑1 and temperature T = 25°C. The parameters measured on initial feed solutions and the fractions obtained were COD (Chemical Oxygen Demand), TOC (Total Organic Carbon) and nitrogen content (NTK). Filtration trials were carried out according to two different procedures, either with constant feed composition to determine the best operating conditions, or with increasing effluent concentration together with monitoring of the Volumetric Reduction Factor (VRF).Centrifugation of the cuttlefish-ink suspension produced two phases: a very dense black residue and relatively clear supernatant. The volumetric distribution and the COD and TOC contents of the different fractions are presented in table 3. The supernatant represented about 75% of crude effluent volume. Organic matter was concentrated in the residue and consisted primarily of suspended particles.At a constant concentration, the ultrafiltration (UF) and microfiltration (MF) processes behaved differently. A rapid drop in flux in the first minutes followed by stabilization at 30 L·h‑1·m‑2 after 30 min was observed for the MF process, whereas a rapid stabilization at approximately 25 L·h‑1·m‑2 was observed for the UF process. The drop in flux at the beginning of MF process may be due to the partial fouling of the membrane pores by melanin particles ranging in sizes from 55 to 160 nm, which are of the same order of magnitude as the membrane pores of 100 nm. On the other hand, the small decrease in flux in the case of ultrafiltration resulted essentially from the formation of a polarization layer and possible interactions between the membrane material and the solution.Batch-concentration trials were carried out for 5 and 4 h using UF and MF respectively, the operating time being dictated by the dead volume of the equipment (0.75 L). The permeate flux variation as a function of the volumetric reduction factor (VRF) is illustrated in figure 3. The MF flux was slightly higher despite the higher initial concentration of organic substances. For a VRF of 2.64 (final concentration), J = 2.8 L·h‑1·m‑2 for MF and 15.2 L·h‑1·m‑2 for UF. Despite the significantly different permeabilities of the MR and UF membranes to pure water (2690 against 34 L·h‑1·m‑2·bar‑1), their very similar J values are a consequence of the internal pore fouling of the MF membranes.Analyses performed on the initial feed samples, and on the different fractions of ink suspensions obtained by MF and UF following concentration, are presented in table 5. Retention ratios for UF were very slightly higher than those found for MF, about 65% for COD, 98% for TOC and 95% for NTK. From the point of view of pollution remediation, and considering permeate COD values, the efficiency of the membrane technique does not seem sufficient.Following ultrafiltration, membrane regeneration was possible by simply rinsing the membrane with water. On the other hand, the same procedure proved inefficient for the microfiltration (PVDF) membrane. The black pigment remained stuck to the membrane surface and most likely inside the pores as well. Furthermore, chemical regeneration (NaOH 0.1 M, 20 min, 25°C) was not enough to recover the membrane’s initial permeability.To conclude, the ultrafiltration process is better adapted to the treatment of cuttlefish washing wastewater. However, considering the level of residual COD in the ultrafiltration permeate, more efficient post-treatment techniques must be developed

Effectiveness of carbon polymeric nanofiltration composite membrane in treating industrial textile wastewater

Today, the trend is towards the use of low-cost materials to develop green processes in the aim to reduce cost and impact on environment. The use of low-cost materials of natural origin has been proven to be very promising for the fabrication of ceramic membranes for wastewater treatment. In this article, fabrication and testing of high performance microporous carbon membrane for nanofiltration (NF) separation based on mineral coal and phenolic resin are reported. The preparation of the NF composite membrane involved carbonizing a polymeric precursor deposited on a porous supported membrane, using the vacuum slip-casting process to obtain a homogeneous NF top layer almost without defects by one-step coating-carbonization cycle. To ensure a better final membrane texture, several parameters including the viscosity of the casting suspension, the casting time and the carbonization temperature were considered. A crack-free NF membrane with a thickness layer of 1.36 μm, a mean pore size of 1.1 nm, and a molecular weight cut-off of 400 Da was obtained using 1 min casting time and 45% of phenolic resin. These membranes were tested in the treatment of textile wastewater. Promising results in terms of permeate flux and pollutant retention (COD (72%), salinity (45%)) were obtained. The results further showed that the treated wastewater could be recycled into the textile industry or can be discharged into the municipal sewerage in compliance with legislations. In addition, a carbonization temperature of 650°C yielded best membranes in terms of average pores size and membrane permeability with minimum energy consumption.www.deswater.comam2023Chemical Engineerin

Bi-objective optimization of tuna protein hydrolysis to produce aquaculture feed ingredients

Fish meal is commonly employed as protein source in aquaculture diets. The enrichment of this ingredient with fish protein hydrolysates (FPH) and free amino acids has proved to improve larval development and feed assimilation. In this work, we produced tuna head hydrolysates using a sequential enzymatic treatment employing Alcalase and Flavourzyme. Statistical modelization coupled with bi-objective optimization were employed to optimize the operating parameters (i.e. pH, temperature and duration of the Flavourzyme treatment) for producing a FPH with a desired molecular weight profile. More specifically, this work focused on the content of small peptides between 700–2500 Da (F 2500 ) and that of free amino acids (F 250 ), supported by their benefits as aquaculture feed ingredients. The optimal reaction conditions for maximimizing the release of free amino acids F 250 (i.e, pH 7.2, 43–49 °C, Flavourzyme treatment above 160 min) were detrimental for the content of F 2500 . A bi-objective optimization approach was then proposed, able to find a set of intermediary solutions (Pareto Front) presenting maximal F 2500 for a range of free amino acids level between 2–30%. This allows the selection of the operating parameters for producing a FPH with a desired weight profile, based on the specific needs of the farmed species

Tubular ultrafiltration ceramic membrane based on titania nanoparticles immobilized on macroporous clay-alumina support: Elaboration, characterization and application to dye removal

The development of new membranes with improved separation properties, high mechanical and thermal stability using inexpensive and naturally abundant materials is of utmost importance for sustainable development and environmental applications. Ceramic materials due to their high chemical, mechanical and thermal stability in combination to their facile surface functionalization have inspired material scientists to design innovative low-cost ceramic-based membrane supports. This study focuses on the preparation and characterization of novel asymmetric ultrafiltration ceramic membrane coated with single separation layer made of TiO2 nanoparticles, and its application to removal of alizarin dye from aqueous solutions. The membrane was prepared by a simple and one-step deposition of micrometer-thick titania layer on the internal surface of the tubular-shape porous clay-alumina membrane support from an aqueous colloidal suspension of titanium oxide (TiO2) nanoparticles with size of 10 nm. The colloidal suspension was prepared in the presence of 0.2 wt.% of Dolapix, and 30 g of an aqueous solution of polyvinyl alcohol at 12 wt.% and 66 mL of H2O. Microfiltration tubular supports of 10 mm/7 mm (outer/inner diameter) were prepared through an extrusion method followed by a sintering process using China Clay Rajmahal grade and alumina, as mineral precursors. The composition of 25% of clay and 75% of alumina was selected in this work as it showed a lower sintering temperature (T-f = 1350 degrees C) which could ensure low cost elaboration process, an average water flux of 850 L h(-1) m(-2) bar(-1) as well as enhanced mechanical performance (approximate to 37 MPa) and large porosity (48%) with an average pore diameter of 0.75 mu m. SEM characterization showed that at the sintering temperature of 800 degrees C, the TiO2 nanoparticles coated densely and homogeneously the ceramic support forming a thin layer of about 4.2 mu m in thickness and leading to a clear reduction of the mean pore size (50 nm approximatively) while providing a water permeability of 117 L h(-1) m(-2) bar(-1). The so-designed ultrafiltration (UF) tubular ceramic membrane has proved efficient for alizarin red dye removal with a retention rate of 99% and a permeate flux of 70 L h(-1) m(-2) at pH 9 and a transmembrane pressure of 5 bar. (C) 2017 Elsevier B.V. All rights reserved

Physico-Chemical Study of Coating Formulation Based on Natural Apatite for the Elaboration of Microfiltration Membrane

This work deals with the experimental characterization of the rheological properties of a dip solution which will be used to elaborate a new apatite/clay microfiltration membrane by deposition using slip casting process of the active layer on a tubular support based on natural clay previously prepared. So, the rheological study of various coatings with different concentration of apatite powder, polyvinyl alcohol (PVA) and water under different conditions regarding temperature and stirring time was done. It was found that the suitable suspension should follow a rheo- thickner behavior having a viscosity in the range of 30-35 mPa s at room temperature of 25 to 30°C. The optimum conditions then found to achieve these properties were: a suspension of 4% of apatite, 40% of PVA stirred for 180minutes. The study reveals also that the thickness of the active membrane layer depends on the coating time