RESUMEN
A low-energy emulsification process is hollow-fiber emulsification. In this process, the lumen diameter of the membrane mostly determines the droplet size. To gain smaller droplets, approaches for downsizing the inner diameter of membranes have to be carried out. In this work, we describe a new method for the fabrication of parallel microfluidic porous-wall channels of a homogeneous cylindrical shape with lumen diameters down to 7 µm. Parallel and symmetric porous-wall channels are induced into polyvinylidene fluoride membranes during the casting process. The technique comprises liquid-induced phase separation and phase-separation micromolding using thin glass and carbon fibers as molds and an in-house designed tool to position the fibers. The channel positioning and alignment are verified within this work. We show and investigate the droplet formation in these porous-wall channels via hollow-fiber emulsification. The formed droplets are very small in diameter and size distribution. The droplet formation at varying flow rates and channel diameters is examined in detail. Moreover, an area of sufficient operating conditions is given using Weber and capillary numbers. As a numbering-up approach, we show the simultaneous formation of spherical droplets in two parallel channels. With the proposed membrane fabrication using micromolding, we push the downscaling approach of hollow-fiber emulsification to lower micron ranges of the channel diameter. With these small channels, droplets with a diameter down to 25 µm were produced, which are more attractive for most applications.
RESUMEN
Textile production is one of the main sources of freshwater consumption by industries worldwide. In addition, according to the world bank, 20 % of the wastewater generated globally is caused by textile wet-processing. Textile wet-processing includes the processes in textile production where garments are dyed or given the final functions like water-repellency. Several thousand chemicals were used in this process, some of which are highly toxic. Discharging untreated or insufficiently treated wastewater in water bodies results in high pollution levels, severely impacting the environment and human health. Especially in textile-producing countries like India, environmental pollution and water consumption from textile wet-processing have severe impacts. Next to the high volume of chemicals used in textile production, the high salt concentration in textile wastewater also poses a challenge and is critical for freshwater systems. Moreover, textile wastewater is one of the most difficult to treat wastewater. Currently, used treatment technologies do not meet the requirements to treat textile wastewater. Therefore, the further development of efficient treatment technologies for textile wastewater is critically important. Hence, in the interdisciplinary project, effect-based monitoring demonstrates the efficiency of electrically-driven water treatment processes to remove salts and micropollutants from process water (EfectroH2O), a low-energy Zero Liquid Discharge (ZLD) textile wastewater treatment technology is being developed consisting of a combination of capacitive deionization (CDI) and advanced oxidation processes (AOP). In addition to treatment technology development, methods for evaluating the efficiency of treatment technologies also need to be improved. Currently, mainly physicochemical parameters such as pH, biochemical oxygen demand (BOD) and chemical oxygen demand (COD) are tested worldwide to check water quality. However, these methods are insufficient to make a statement about the toxic potential of such complex mixtures as textile wastewater. Therefore, also next to chemical analyses, effect-based methods (EBM) are used to verify the treated wastewater.