Jean-Christophe Remigy

TREATMENT OF TEXTILE DYE EFFLUENT USING A POLYAMIDE-BASED NANOFILTRATION MEMBRANE

Abstract Experiments were run with seven dyes and a Desal 5DK membrane (cut-off, 150–300 g/mole). The effects of concentration, pH and salt on flux and retention were studied. The cut-off of the membrane explains that the retention of the relative high molecular weight dyes (as direct red 80 or direct yellow 8) is always almost 100%. For anionic dyes as acid orange 10 or acid red 4, the amphoteric nature of polyamide explains the lower retention at pH 3 than 6. This effect is more pronounced and reversed for basic blue 3, a cationic dye. The membrane is sensitive to fouling since most of the dyes are used for polyamide textile dying. Moreover, the presence of salt leads to a further decrease in flux.

Treatment of textile dye effluents using a new photografted nanofiltration membrane

A nanofiltration membrane has been developed by UV-photografting. Sodium p-styrene sulfonate was used for the modification of a polysulfone ultrafiltration membrane. The membrane cut-off was estimated. The grafted membranes have been evaluated for the removal of five different dyes with an aim to reuse water in the process house. The effect of different parameters such as dye class, pH and the presence of salt was evaluated. It is observed that the newly developed membranes show acceptable performance both in terms of flux and rejection. Dye retention was higher than 97% and hydraulic permeability 0.23–0.28 m3.m−2.d−1 at 0.4 MPa. The influence of pH on the performance of membranes in terms of fouling and retention was established and compared to a commercial membrane (Desal 5DK).

From ultrafiltration to nanofiltration hollow fiber membranes: a continuous UV-photografting process☆

A new way to prepare nanofiltration membranes, consisting of in-line external modification of the skin of a polysulfone ultrafiltration hollow fibre skin, is described. The paper presents a continuous process (dip-coating followed by photografting) and the influence of the operating conditions on the membrane characteristics. This study is focused on a simplified model based on the evaluation of the two sources of monomer available for grafting: one is monomer contained in the thin film drawn from the dip bath, second is contained in the pores of the membrane. The results show that two extreme types of modification can be produced, depending on the experimental conditions: a high rate coupled with a short dip contact time leads essentially to an external grafting whereas a low rate coupled with a long dip residence time leads essentially to an “in pore” grafting.

New composite membrane for water softening

Abstract A novel route to the preparation of nanofiltration membranes has been proposed. The method consists of the photografting of polymer on to the surface of porous membranes. The method was tested with polysulfone ultrafiltration membranes and poly(acrylic acid) in water solution. It has been shown that the surface modification is stabilised by crosslinking with N, N′-methylene bis acrylamide and that the grafting does not require any photoinitiator and any purification of the reactants. Moreover, by the proper choice of the wavelengths, the UV irradiation does not induce any significant copolymerisation of the reactants inside the aqueous solution. The irradiation conditions, the monomer concentration and the permeability of the support membrane were examined. The water softening properties of the novel membranes were measured in dead-end mode and at a 95% recovery. A large range of performances has been obtained which demonstrates the feasibility of the UV irradiation as an environmentally friendly and versatile (flexible) technology to prepare nanofiltration membranes.

Filtration of biological sludge by immersed hollow-fiber membranes: influence of initial permeability choice of operating conditions

Recent progress in membrane technology, combined with increasing concern about environment protection, led industrialists and researchers to the development of advanced treatments for domestic wastewater. Membrane bioreactor technology seems to be promising. This study is performed in the context of a regional program for design and optimization of membrane bioreactors for domestic water reuse. We focused on the management of membrane fouling by alternative period of filtration, backflushing, or static state. Moreover, we show how the membrane initial permeability is important in such systems. The experiments were performed on sludge.

Towards green membranes: preparation of cellulose acetate ultrafiltration membranes using methyl lactate as a biosolvent

Ultrafiltration membranes were prepared using cellulose acetate (CA) as a polymer, LiCl and CaCl2 as porogens and methyl-(S)-lactate as a solvent. CA, methyl lactate and the porogens used in this work are obtained from renewable resources; they are biodegradable, non-toxic and non-volatile organic compounds. Flat sheet ultrafiltration membranes were prepared by the phase inversion technique. A molecular weight cut-off between 15 and 35 kDa (polyethylene glycol) and pure water permeability between 13 and 177 litres h− 1m− 2 bar− 1 were obtained. These parameters are in the ideal range for water treatment industry. Improvement of pollutant degree and ecotoxicity of the process was evaluated by ‘green’ metrics by the P (pollutants, persistent and bioaccumulative) and E (ecotoxicity) parameters. Both of these variables were recorded as zero using our method. This study represents a step ahead towards the production of ultrafiltration polymeric membranes by a ‘greener’ process than current methods.

Improving PVDF Hollow Fiber Membranes for CO2 Gas Capture

Poly(vinylidene fluoride) (PVDF) hollow fiber membranes were obtained by the phase inversion technique. The influence of internal coagulant viscosity (0.001 to 3 Pa s) and air gap (0.6 to 86.4 cm) on the structure and mechanical resistance of the fibers was studied. A “sponge-like” structure free of macrovoids was obtained by using polyvinyl alcohol (PVA) with N-methyl pyrrolidinone and water as internal coagulant (viscosity 3 Pa s). The effect of the air-gap was studied in order to control the structure and obtain mechanically resistant membranes with tensile strength at break between 2.2 and 54.3 N/mm2 and pure water permeability ranging from 4 to 199 Lh−1m−2bar−1. CO2 permeability of these membranes was measured and found to be in the range of 365 to 53200 NLh−1m−2bar−1. The “Dusty Gas” model (DGM) was used to calculate the pore size of the membranes from CO2 permeability experiments, obtaining pore radius values going from 0.6 to 10.8 µm. Results from modeling were compared with pore sizes observed in SEM images showing that this model can accurately predict pore radius of sponge-like structures; however, pore sizes of membranes presenting sponge-like structures together with finger-like pores were inaccurately predicted by the DGM.

Membrane Reactor Based on Hybrid Nanomaterials for Process Intensification of Catalytic Hydrogenation Reaction: an Example of Reduction of the Environmental Footprint of Chemical Synthesis from a Batch to a Continuous Flow Chemistry Process

Membrane processes represent a well matured technology for water treatment with low environmental footprints compared to other type of processes. We have now combined this technology with nanomaterials, ionic liquids (negligible vapor pressure), and poly(ionic liquids) in order to enlarge the field of applications while benefiting from the advantages of membranes. We have modified flat sheet water filtration membrane and used it as both catalytic support and reactor with the advantages to make the reaction and the separation of products in only one step. For this purpose, catalytic metallic nanoparticles of palladium (diameter of ca. 2 nm) were synthesized in a gel-poly(ionic liquid) layer grafted at the surface of polymeric filtration membranes by UV-photografting method. The so obtained catalytic membrane was successfully applied in the hydrogenation of trans-4-phenyl-3-buten-2-one in forced flow-through configuration, which gave full conversion in a few seconds (2.6 s) showing advantages over the batch reactor process (in that case, palladium nanoparticles were synthesized in the ionic liquid [MMPIM][NTf2] (1,2-dimethyl-3-propylimidazolium bis-(trifluoromethylsulfonyl)imide)). Nevertheless, the catalytic membrane used in submerged mode no more prevailed over the batch reactor. Catalytic nanoparticles remain highly active in the membrane after 12 cycles of reaction without need of recuperation. Results were compared to one obtains with a similar system in batch reactor conditions, showing high efficiency of our process in term of selectivity and reactivity, combined to an important compactness, the productivity of the catalytic hollow fiber membrane reactor and permitting to operate at larger scale with promising results in an environmental friendly way in term of energy and product (metal, solvent) consuming.