Electrochemical Conversion of Dichloroacetic Acid to Chloroacetic Acid in Conventional Cell and in Two Microfluidic Reactors

Oxidation of organics in water by active chlorine performed in microfluidic electrochemical reactors: a new way to improve the performances of the process

Wastewater polluted by organics can be treated by using electro-generated active chlorine, even if this promising route presents some important drawbacks such as the production of chlorinated by-products. Here, for the first time, this process was studied in a microfluidic electrochemical reactor with a very small inter-electrode distance (145 μm) using a water solution of NaCl and phenol and a BDD anode. The potential production of chloroacetic acids, chlorophenols, carboxylic acids, chlorate and perchlorate was carefully evaluated. It was shown, for the first time, up to our knowledge, that the use of the microfluidic device allows to perform the treatment under a continuous mode and to achieve higher current efficiencies and a lower generation of some important by-products such as chlorate and perchlorate. As an example, the use of the microfluidic apparatus equipped with an Ag cathode allowed to achieve a high removal of total organic carbon (about 76%) coupled with a current efficiency of 17% and the production of a small amount of chlorate (about 30 ppm) and no perchlorate. The effect of many parameters (namely, flow rate, current density and nature of cathode) was also investigated.

Self-Organized Implanting of Micro/Nanofiltration Membranes in Advanced Flow μ-Reactors

A low-cost, simple, and one-step synthesis of cellulose acetate nanoparticles (CANPs) has been invented using a continuous-flow advanced microfluidic reactor. For this purpose, the CANPs are self-organized inside a cross-junction microchannel by flowing cellulose acetate (CA) dissolved in N,N-dimethylformamide (DMF) through the axial inlet and the antisolvent water through the pair of side inlets. The preferential solubility (insolubility) of DMF (CA) to antisolvent water stimulates the in situ synthesis of CANPs at the DMF/water miscible interface following a phase-inversion process. Subsequently, nanofiltration, ultrafiltration, and microfiltration membranes of different porosities and permeabilities have been prepared from freshly synthesized CANPs. The porosity, thickness, transparency, and wettability of the membranes are tuned by varying the thickness of the membranes, size of the nanoparticles, and the porosity of the membranes. The as-synthesized CANPs show enhanced bactericidal properties with and without loading an external drug, curcumin, which has been validated against the Gram-negative Pseudomonas aeruginosa species. Importantly, enabling a pulsatile flow during the synthesis, the CANPs are embedded as nanofiltration membranes inside the microfluidic channel. Such microfluidic devices have been used to separate a corrosive dye from water. Concisely, the proposed in situ synthesis of CANPs in the continuous-flow microfluidic reactors, their usage for fabricating membranes with tunable wettability and transparency, and their subsequent integration into the microfluidic channel show the potential of the invention for a host of applications related to health care and environmental remediation.

Advances in electro- and sono-microreactors for chemical synthesis

The anatomy of electrochemical flow microreactors is important to safely perform chemical reactions in order to obtain pure and high yielding substances in a controlled and precise way that excludes the use of supporting electrolytes. Flow microreactors are advantageous in handling unstable intermediates compared to batch techniques and have efficient heat/mass transfer. Electrode nature (cathode and anode) and their available exposed surface area to the reaction mixture, parameters of the spacer, flow rate and direction greatly affects the efficiency of the electrochemical reactor. Solid formation during reactions may result in a blockage and consequently decrease the overall yield, thus limiting the use of microreactors in the field of electrosynthesis. This problem could certainly be overcome by application of ultrasound to break the solids for consistent flow. In this review, we discuss in detail the aforementioned issues, the advances in microreactor technology for chemical synthesis, with possible application of sonochemistry to deal with solid formations. Various examples of flow methods for electrosynthesis through microreactors have been explained in this review, which would definitely help to meet future demands for efficient synthesis and production of various pharmaceuticals and fine chemicals.