In this paper, a novel microalgal attached membrane photobioreactor based on the modified polyvinylidene difluoride (PVDF) / polyvinyl pyrrolidone (PVP) composite membrane for microalgae direct air carbon capture is developed and optimized. The Computational Fluid Dynamics (CFD) simulation, molecular dynamic study (MDS) and experimental study are adopted to investigate the synergy between light transmission and fluid flow, CO 2 transmission mechanism inside the membrane and microalgae cells. The modified composite membrane is proposed and processed to improve the carbon sequestration rate of the microalgal attached membrane photobioreactor (AM-PBR). First, the synergy angle between the light transmission direction and fluid flow direction of the flat-plate photobioreactor (FP-PBR) is analyzed. To improve the synergy of light and fluid flow, the AM-PBR is proposed. Secondly, for the MDS part, the models of PVDF membrane and polytetrafluoroethylene (PTFE) membrane are developed. A three-layer simulation model is proposed to reveal the transmission mechanism of CO 2 from the gas-liquid layer to the microalgae cell membrane layer. Several parameters including CO 2 diffusion coefficient, CO 2 concentration profile and velocity profile of CO 2 are analyzed to compare the performance of different membranes and working conditions. Then, for verification of the simulation work, AM-PBR experiments are designed. To further enhance the CO 2 transmission and microalgae attached performance, different PVDF/PVP composite membranes are assessed. The carbon sequestration rate of the modified membrane is improved according to the experiments. Finally, the novel microalgae membrane photobioreactor with the modified PVDF/PVP membrane is developed and the carbon sequestration rate of the PBR system is improved. The results showed that the best ratio for PVDF and PVP is 2:1 with 20 wt% solution, and with this modified membrane the carbon sequestration rate of the PVDF/PVP-based AM-PBR is 18.61% higher than the original PVDF-based AM-PBRs. The proposed novel AM-PBR is especially useful for low-concentration CO 2 direct air carbon capture.
In recent years, the demand for wearable devices has promoted the research of flexible thermoelectric generators. Herein, this work reports a facile method to prepare the flexible Ag 2 Se/polyvinyl pyrrolidone (PVP) composite films. The Ag 2 Se nanorods are synthesized by the template method and then mixed with PVP solution to form the composite film optimized by the content of Ag 2 Se. The maximum power factor of the film is 16.18 µW m −1 K −2 at 320 K, and the thermoelectric generator (TEG) has an output voltage and power of 5.49 mV and 55.57 nW at a temperature difference of 40 K, respectively. Moreover, the Ag 2 Se/PVP film has good flexibility and can withstand multiple bending, the electrical conductivity reaching 89.8% and 76 % at 500 and 1000, respectively. PVP has an excellent protective capabilities effect so that the TE performance can remain stable in 40 days, and then the electrical conductivity only drops to 89 % of the initial value at 50 days. This work provides an effective method for preparing wearable thermoelectric devices, which can be extended to other composite materials.
A m-Cresol Purple-polyvinylpyrrolidone (m-CP-PVP) composite-film was immobilized on the surface of a potassium ion-exchanged glass optical waveguide using the spin-coating method. The optical properties of the film were probed by UV-visible Spectroscopy and Fourier Transform Infrared Spectroscopy. The transmittance variation and the structural properties of the m-CP-PVP composite film/K+-exchanged glass optical waveguide sensor were studied before and after reaction with an amine and volatile organic gases. When the sensing film was exposed to an amine gas, the color changed from yellow to purple/blue. This simply designed sensor was able to measure trimethylamine (TMA) gas down to a concentration of 0.1 ppb at room temperature, and its response and recovery times were 1.4 s and 5.6 s, respectively.
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