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Colloid particle size plays an important role in contaminant adsorption and clogging in the hyporheic zone, but it remains unclear how the particle size changes during the transport of colloids. This study investigated the variation of the particle size of colloids in the overlying water and the effects of settlement and hyporheic exchange via laboratory experiments and numerical simulations with two main factors settlement and hyporheic exchange being considered. The results show that the particle size distribution varies when colloids transport in hyporheic zone, and both settlement and hyporheic exchange are involved in the exchange of colloids between stream and streambed. Large-sized particles are mainly controlled by settlement and advection and thus their concentration in the overlying water decreases more quickly; but small-sized particles are mainly controlled by hyporheic exchange and thus their concentration decreases more slowly, and some particles can be resuspended. The increase of retention coefficient and settling velocity will accelerate the transfer of colloids into the streambed. This study may provide important insights into the variation of the particle size of colloids in the overlying water and the effects of settlement and hyporheic exchange. Highlights: The distribution of colloidal particle size varies during the transport process in hyporheic zone. Larger sized colloidal particles are affected by settlement more when transport in hyporheic zone, while smaller sized are affected by both hyporheic exchange and settlement. The increase of retention coefficient and settling velocity will accelerate the transfer of colloids into the streambed, and the effect of settling velocity is more sensitive than that of retention coefficient. [ABSTRACT FROM AUTHOR]

With characteristics of high resources, complex composition, and high toxicity, the treatment and disposal of waste printed circuit boards (WPCBs) have attracted widespread attention, and pyrolysis is regarded as a potential recovery method. In this study, the behaviors, kinetics, and mechanisms of WPCBs pyrolysis were systematically investigated. The pyrolysis process could be divided into three stages: evaporation stage, reaction stage, and stabilization stage. The mass losses of these stages at different heating rates were determined to be < 1%, 10.84–14.11%, and 6.37–8.82%, respectively. Four model-free methods (Friedman, Tang, Starink, and Bosewell) and the distributed activation energy method (DAEM) were used to reveal the pyrolysis kinetics of WPCBs. According to the model-free methods, the apparent activation energy (Eα) decreased with increasing conversion (α) in the range of 0.05–0.25, then increased in the α range of 0.30–0.75, and finally decreased. The Bosewell method possessed the highest fitting degree, and the Eα was calculated as 133.94–204.01 kJ/mol. The components in volatile products were detected using thermogravimetry–mass spectrometry (TG–MS), and the main components were identified as CO2, CH4, H2O, phenol, etc. Based on characteristics of these products, the pyrolysis mechanisms of brominated and non-brominated structures in brominated epoxy resins were expounded. [ABSTRACT FROM AUTHOR]

Background: 3D printing is revolutioning many industrial sectors and has the potential to enhance also the biotechnology and bioprocessing fields. Here, we propose a new flexible material formulation to 3D print support matrices with complex, perfectly ordered morphology and with tuneable properties to suit a range of applications in bioprocess engineering. Findings: Supports were fabricated using functional monomers as the key ingredients, enabling matrices with bespoke chemistry, such as charged groups, chemical moieties for further functionalization, and hydrophobic/hydrophilic groups. Other ingredients, e.g. crosslinkers and porogens, can be employed to fabricate supports with diverse characteristics of their porous network, providing an opportunity to further regulate the mechanical and mass transfer properties of the supports. Through this approach, we fabricated and demonstrated the operation of Schoen gyroid columns with (I) positive and negative charges for ion exchange chromatography, (II) enzyme bioreactors with immobilized trypsin to catalyse hydrolysis, and (III) bacterial biofilm bioreactors for fuel desulphurization. Conclusions: This study demonstrates a simple, cost-effective, and flexible fabrication of customized 3D printed supports for different biotechnology and bioengineering applications. [ABSTRACT FROM AUTHOR]