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A new and low-cost surface-functionalized corn straw adsorbent for adsorptive removal of sodium dodecylbenzene sulfonate: Adsorbent preparation and adsorption performance
No full textUtilization of greywater can relieve the pressure of water scarcity. However, the widespread presence of anionic surfactants in greywater poses threats to the environment and the health of the human and ecosystem. In this study, bioinspired polyethyleneimine-tannic acid (PEI-TA) complexes were innovatively used for coating of corn straw (CS) and the as-prepared PEI-TA modified CS (PEI-TA@CS) was applied for adsorptive removal of the commonly found sodium dodecylbenzene sulfonate (SDBS) in greywater. The adsorption performance of the modified CS was maximized under the following optimized preparation conditions: 5 g/L of PEI concentration with molecular weight of 3000 Da, 0.5 g/L of TA concentration and 3 h of modification time. Investigation of the adsorption conditions showed that adsorption of SDBS on the adsorbent were pH-independent at pH <= 7 and the adsorption process reached equilibrium in about 3 h. The pseudo-second-order model and Freundlich model fit well the kinetic and isotherms data, respectively, and the nature of the adsorption was exothermic and spon-taneous. Mechanism analysis showed that the adsorption of SDBS was dominated by hydrophobic interactions. With a dosage of 100 mg, PEI-TA@CS could satisfactorily remove 94.95 % of SDBS from its aqueous solution (50 mg/L). Even in the complex synthetic greywater, the removal of SDBS still reached as high as 81.99 %. The overall results indicated that PEI-TA@CS has promising applications in the removal of anionic surfactants from greywater
Role of mesoscale structure in gas-solid fluidization: Comparison between continuum and discrete approaches
No full textThe coarse-grained discrete particle model (DPM) is fast growing into a powerful tool and a useful counterpart of the widely used two-fluid model (TFM) in simulation of large-scale reactors. This work aims to study the role of mesoscale modeling in both TFM and DPM approaches to understand the advantage and disadvantage of each approach for further development. Both simulation approaches with and without considering mesoscale structures in drag modeling are systematically investigated through simulations of an industrial diameter-transformed fluidized bed reactor with complex reactions. It is found that considering mesoscale drag can obviously improve the prediction in solid concentration for both approaches, and the effect of mesoscale drag for TFM modeling is more significant than for DPM approach. Besides, the DPM approach can reveal local heterogeneous structures without using mesoscale drag because it can distinguish different parcels in each fluid cell, but it overestimates the accumulation of solid particles below the distributor, as the large coarse-grain ratio may over-enhance the particle collision. For reaction, the coke content can be better predicted by both approaches with mesoscale drag, and the DPM simulation can capture more heterogeneous distribution of coke content than TFM modeling. The predicted temperature and product distribution still have obvious deviation from industrial data, suggesting a need of mesoscale heat and mass transfer modeling. The underlying mechanisms are further analyzed together with proposing future work
Bioelectrocatalysis for CO2 reduction: recent advances and challenges to develop a sustainable system for CO2 utilization
No full textActivation and turning CO2 into value added products is a promising orientation to address environmental issues caused by CO2 emission. Currently, electrocatalysis has a potent well-established role for CO2 reduction with fast electron transfer rate; but it is challenged by the poor selectivity and low faradic efficiency. On the other side, biocatalysis, including enzymes and microbes, has been also employed for CO2 conversion to target Cn products with remarkably high selectivity; however, low solubility of CO2 in the liquid reaction phase seriously affects the catalytic efficiency. Therefore, a new synergistic role in bioelectrocatalysis for CO2 reduction is emerging thanks to its outstanding selectivity, high faradic efficiency, and desirable valuable Cn products under mild condition that are surveyed in this review. Herein, we comprehensively discuss the results already obtained for the inte-gration craft of enzymatic-electrocatalysis and microbial-electrocatalysis technologies. In addition, the intrinsic nature of the combination is highly dependent on the electron transfer. Thus, both direct electron transfer and mediated electron transfer routes are modeled and concluded. We also explore the biocompatibility and syn-ergistic effects of electrode materials, which emerge in combination with tuned enzymes and microbes to improve catalytic performance. The system by integrating solar energy driven photo-electrochemical technics with bio-catalysis is further discussed. We finally highlight the significant findings and perspectives that have provided strong foundations for the remarkable development of green and sustainable bioelectrocatalysis for CO2 reduction, and that offer a blueprint for Cn valuable products originate from CO2 under efficient and mild conditions
