This study aims to demonstrate the efficiency of dichloromethane (DCM) regeneration from a methanolic effluent by a combination of distillation and membrane pervaporation process. The presence of an azeotrope (MeOH/DCM/water) makes the regeneration of DCM via distillation alone impossible. A process simulation using ProSim software was carried out in order to evaluate the behavior of the azeotropic mixture. Two secondary treatments aiming to purify the DCM contained in the azeotrope were investigated. The first is the washing of the azeotrope with water. ProSim software was used to target the optimal conditions for washing before the experimental test. Residual water was recovered in the organic phase, meaning that the quality specifications for DCM were not reached. The second process studied for DCM purification was a pervaporation step. The feasibility of this had been proven at laboratory scale. The recovered DCM had the quality of a new solvent, and the whole process (distillation + pervaporation) reached a global DCM regeneration yield of 71.8% before optimization. This yield was limited by the distillation of methylal (also called dimethoxymethane) present in the methanolic effluent at the end of the distillation of the azeotrope, a compound retained by the pervaporation membrane. The pervaporation was performed on a hydrophilic Hybsi membrane letting methanol and water pass through and retaining the DCM (membrane surface = 0.15 m 2 ). Optimization and scaling up were then carried out with a semi-industrial pervaporation pilot (membrane surface = 1.05 m 2 ) which enabled the industrial scale-up. In order to facilitate the steering of the process and to ensure continuous and efficient monitoring of the regeneration operation, online monitoring by near-infrared probe (NIR) had been implemented allowing the composition of the mixture to be determined with an accuracy of ±0.05% on each compound. Finally, an assessment had been conducted of the regeneration pathways for methanol recovery at the bottom of the distillation column, for maximizing the regeneration of methanolic effluents by separating heavy compounds and methylal from methanol.

In this study, the retention potential and the fouling of ultrafiltration (UF) multichannel hollow fiber membrane regarding nanoparticles (NPs) have been assessed. Filtration experiments of fluorescent 10 nm and 1.5 nm NPs (respectively NP-10 and NP-1.5) suspensions filtered individually were carried out under different transmembrane pressures. A complexification of the feed suspension through the mix of NPs sizes and/or the salinity adding have been investigated. The retention rate (RR), the fouling location and the membrane productivity have been analyzed and compared in each case to determine the influence of salinity and polydispersity of the feed suspensions on NP retention. Results show that RR of NP-10 stays constant when NPs are filtered in ideal suspension (NP-10 / ultrapure water), or when they are filtered with NP-1.5 and/or with 50 mmol L −1 of NaCl and reaches at least 99%. However, RR of NP-1.5 is modified by the presence of NP-10 and/or 50 mmol L −1 of NaCl. This retention rate is considerably decreased by the complexification of suspensions tested. Estimation of NPs quantity blocked at the membrane at the end of the filtration by mass balance showed no significative variation for NP-1.5 (relative to the RR obtained) while a larger quantity of NP-10 remained blocked at the membrane with the adding of NP-1.5 and/or salts in feed suspension. Location of NPs by Confocal Laser Scanning Microscopy (CLSM) at the end of the filtration showed that filtered individually, NP-10 are blocked in membrane skin and on membrane surface while NP-1.5 are blocked in the entire membrane material. Filtered simultaneously, the location of these two sizes of NPs is not modified but NP-1.5 seems to form clusters in the membrane material and the participation of NP-10 and NP-1.5 to the deposit formed on the membrane surface is increased. The adding of salinity leads to the same observations than the filtration of both sizes mixed.

The prehydrolysate stream from a Kraft dissolving pulp mill can be valorized by fermentation of the hemicellulosic sugars into biofuels or bioproducts, such as ethanol or butanol, instead of the typical practice of combustion to produce energy. An obstacle facing the use of Kraft hemicelluloses prehydrolysate for biofuels production is the low sugar concentration and the presence of fermentation inhibitors that include organic acids, furans and phenolic compounds. A precondition to ensure the survival of the fermentation microorganisms and to have high fermentation yields is to remove the inhibitors. Concentration of the prehydrolysate is also necessary to reduce the size of the processing equipment and decrease the energy cost. The purpose of this study was to develop a strategy for the concentration and detoxification of hemicelluloses prehydrolysate prior to its conversion into biofuels. Experiments were conducted to screen and select suitable organic membranes among 7 samples of reverse osmosis, nanofiltration, and ultrafiltration membranes. Three membranes (Dow NF270, Trisep TS40, and Trisep XN45) showed the highest sugar retentions relative to inhibitors removal. They were however not efficient for the removal of the phenolic compounds. It was also found that flocculation with ferric sulfate as coagulant could be utilized as a secondary detoxification step that can be combined with nanofiltration. The optimization of the flocculation step with a jar test showed that the highest phenolics removal (∼80%) can be obtained when the ratio of ferric ions to phenols is 1 g/g, and the pH is between 6.5 and 7.5. A new process concept for the detoxification and concentration has been developed based on these experimental results.

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