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•Fe0 activated peroxymonosulfate (PMS) was used to improve sludge dewatering.•Sludge dewatering was elevated synergistically by Fe0 activated PMS at 50 °C.•Hydroxyl radical was ...predominant radicals in Fe0 activated PMS conditioning.•Fe0 recovery rate of 98.6% and high sludge dewatering efficiency in circle tests.•ZVI-PMS was feasible in technique, economics and applicability.
In this study, zero valent iron (ZVI) activated peroxymonosulfate (PMS) as novel technique (i.e. ZVI-PMS technology) was employed to enhance sludge dewatering. In optimal sludge dewatering conditions of ZVI and KHSO5 dosages, the specific resistance to filtration (SRF) was reduced by 83.6%, which was further decreased to 90.6% after combination of ZVI-PMS with thermal treatment at 50 °C (i.e. ZVI-PMS-T technology). Subsequently, the ESR spectrum and quenching tests demonstrated that OH, rather than SO4−, was predominant radicals in ZVI-PMS conditioning. Thereafter, the variation of physicochemical properties and the distributions and compositions of extracellular polymeric substances (EPS) were further investigated to uncover the influence of these techniques on sludge bulk properties. The results indicated that sludge particles were disintegrated into smaller particles and surface charges were neutralized, sludge flowability were elevated obviously after treatments. In ZVI cycle experiment, the high dewatering efficiency was maintained by ZVI-PMS and ZVI-PMS-T pretreatment.
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•SO42−, Na+ and NH4+ in liquid had insignificant impact on sludge dewatering.•The presence of PO43− in liquid had adverse effects on dewaterability.•The accumulation of VFAs in liquid ...was beneficial to improve dewatering.•Humic acids had higher influence on dewaterability than other substances.•Microbial succession during fermentation improved resistance to sludge dewatering.
Anaerobic fermentation is a promising process to recover volatile fatty acids from waste activated sludge, but this process seriously deteriorates sludge dewaterability. Although several efforts were made in the past, the mechanism of how anaerobic fermentation deteriorates the dewatering performance remains largely unknown. This work therefore aims to fill the gap by exploring the variations in both liquid and solid phases before and after alkaline anaerobic fermentation and identifying their impacts on dewatering. Experimental results showed that 1418.6 ± 15.4 s of capillary suction time and (50.08 ± 1.37) × 1012 m/kg of specific resistance to filtration were determined in fermented sludge, which were 20.3- and 5.1-fold of those measured in raw sludge. The mechanism explorations revealed that anaerobic fermentation increased proteins, polysaccharides, humic acids and PO43− concentrations but decreased Ca2+ amount in liquid phase. The increases of proteins and humic acids increased the viscosity but decreased the zeta potential of liquid. The decline of Ca2+ not only decreased the zeta potential but also deteriorated the flocculability. The increase of PO43− decreased the zeta potential while the increase of polysaccharides increased the viscosity. Among these components, the release of humic acids was identified to the major contributor to the deterioration of sludge dewatering. Besides, anaerobic fermentation increased loosely bound extracellular polymeric substances, which benefited fermented sludge to wrap water especially bound water and enhanced sludge viscosity. It was also found that anaerobic fermentation caused transformation of microbes from Gram-negative to Gram-positive, which increased the resistance of mechanical forces and negative charges on sludge flocs.
Abstract
This paper studies the effects of five parameters, including fiber diameter, crystallinity, thickness, packing density, and surface roughness, on the transparency of electrospun polymethyl ...methacrylate/polydimethylsiloxane (PMMA/PDMS) nanofibrous membranes after heat treatment. The PMMA/PDMS membranes produced at an electrospinning voltage of 20 kV reaches 54.85% transparency with the diameter 0.759 μm, crystallinity 14.81%, thickness 9.2 μm, roughness 0.659 μm, and packing density
α
0.0081% after the heat treatment from 80 to 200°C. In general, the PMMA/PDMS membranes present higher transparency with the decrease of diameter, crystallinity, thickness, roughness, and packing density. The influencing parameters on transparency are first quantified by multiple nonlinear regressions with a
R
2
of the model equals 0.869. A composite scaled sensitivity (CSS
j
) analysis shows that the most influential factor is the nanofibrous membrane thickness with a CSS
j
value of 1, followed by fiber diameter with a CSS
j
value of 0.515. The CSS
j
values for packing density, membrane roughness and crystallinity are 0.385, 0.361, and 0.173, respectively. Finally, the nanofibrous membrane transparency is a function of nanofiber material density, fiber diameter, and nanofibrous membrane thickness based on the Chandrasekhar radiative transfer equation and the Rayleigh's Scattering Theory.
The escalating CO2 emissions in recent years underlined the need for advanced Carbon Capture and Utilization (CCU) technologies. This context has spurred the exploration of novel materials for ...promoting CCU efficiency, among which electrospun nanofibers have emerged as a promising candidate. Electrospinning coupled with various post-treatment (such as heat-treating, in-situ growth, selective removal, etc.) offers a versatile approach to fabricate diverse nanofibers, including polymeric, carbonaceous, metallic, and composite fibers, with tunable surface morphologies and chemical properties. This paper provides a comprehensive review of electrospun nanofibers in CCU processes, including adsorption, membrane separation and absorption, electrochemical and photo-electrochemical reduction, thermal catalytic hydrogenation, and more. Each CCU technology is examined in depth to cover the recent research achievements with a specific focus on the contributions of electrospun nanofibers. Lastly, a critical discussion and a list of potential future research directions for this evolving field are provided.
•Latest electrospun nanofiber-based CCU technologies are thoroughly reviewed.•Electrospinning enables creating various nanofibers, aiding multiple CCU technologies.•Provide critical discussion and future directions for this evolving research field.
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•Ni0.6Fe2.4O4 was prepared successfully to achieve greater catalytic performance than typical Ni1.0Fe2.0O4.•The dominant radicals (SO4− and HO) generated in Ni0.6Fe2.4O4/PS system ...were verified.•The high Ni/Fe interactions and Ni dispersion may attribute to the superior catalytic performance of Ni0.6Fe2.4O4.
The catalytic performances of magnetic NixFe3−xO4 catalysts in persulfate (PS) activation for tetracycline (TC) degradation are first investigated. In this study, NixFe3−xO4 catalysts with variable compositions (x = 0.2, 0.6 and 1.0) were synthesized. The physical and chemical characteristics of NixFe3−xO4 catalysts were investigated systematically. NixFe3−xO4 catalysts have sheet-like morphology and spinel type structure. In NixFe3−xO4/PS system, sulfate radical (SO4−) and hydroxyl radicals (HO) produced by PS activation degraded TC efficiently. In the comparation of different NixFe3−xO4 catalysts, Ni0.6Fe2.4O4 presented superior catalytic activity performance. The optimum degradation rate in 86% was obtained at Ni0.6Fe2.4O4 = 350 mg/L, PS = 42.0 µM and pH = 7 after 35 min reaction. The main radicals (SO4− and HO) were identified by scavengers and the electron spin resonance (ESR) experiment. Meanwhile, possible activation and degradation mechanism were analyzed thoroughly. The high catalytic efficiency and short degradation period of Ni0.6Fe2.4O4 catalyst indicate that it has great potential in TC wastewater disposal and environmental protection.
•Micro-fiber grids effectively capture fog droplets with a peak efficiency of 21.4%•Interception of fog droplets occurs on waterdrops that clog the grid.•A dimensionless relation determines the ...effect of clogging on collection efficiency.•Large waterdrops deflect fog flow to small drops to effectively intercept fog.
Fog collectors can mitigate water scarcity by capturing droplets from fog streams. Previous research focuses on improving aerodynamic design and surface characteristics to enhance collection efficiency. However, limited attention has been given to micro-meter level fog-intercepting structures and the impact of waterdrop clogging. This study investigates the fog collection process on microfiber grids with varying fiber spacings and diameters. Waterdrops clog the grid openings with a pattern that small waterdrops satelliting large ones. Due to the small fiber diameter, the waterdrops are “visible” to incoming airflow and strongly affect fog droplet interception. The large waterdrops deflect incoming fog flow towards the small ones, and the small waterdrops efficiently capture the fog droplets. Consequently, the fog collectors based on microfiber grids demonstrated an exceptional water collection efficiency of up to 21.4%. The micro-fiber grids require minimal material usage and no special surface treatment, highlighting a great potential in fog water collection. Additionally, this work provides a novel design strategy of fog collector, i.e., reducing the size of the fog-intercepting structure to directly capture fog droplets by waterdrops.
•Two controversial mechanisms for pyrrole chemical polymerization are compared.•Kinetics of the Pyrrole in-situ polymerization on electrospun template are studied.•Pyrrole In-situ polymerization ...enhances reactions between oligomers and monomers.•The fabricated PPy composite membrane is a conductive material for many applications.
Polypyrrole (PPy) is a conductive polymer that can be fabricated into various structures via in-situ polymerization for different applications. However, a kinetics study of its in-situ polymerization is needed for a better understanding of the mechanisms of pyrrole polymerization. This paper develops two different kinetics models based on existing PPy polymerization mechanisms. The most suitable mechanism is first identified by comparing the model results with experimental data. Then, in-situ polymerizations of PPy on electrospun fibrous polyacrylonitrile (PAN) templates were produced at temperatures ranging from 273 to 285 K. The results show that the overall reaction rate of the in-situ polymerization process in the presence of electrospun fibrous template is faster than that without the template. Further investigation confirms that the increase in the overall reaction rate is attributed to the enhanced reactions between oxidized pyrrole oligomers and neutral pyrrole monomers, as the corresponding reaction rate constant and activation entropy increased by 158.2–209.6% and 37.7%, respectively. The reason is that the considerable number of available reaction sites between oxidized oligomers and neutral monomers are created by the fibrous template. In addition, the composite membrane obtained from the in-situ polymerization exhibited well-developed fibrous nanostructure, good electrical conductivity (0.29 ± 0.04 S∙m−1), sufficient mechanical strength (UTS of 8.7 MPa) and relatively stable thermal properties (up to 250 °C).
•Fe(II)/UHP process was developed to improve sludge dewatering••OH from Fe(II)/UHP liberated the EPSs-bound and cells-bound water••OH from Fe(II)/UHP reduced centrifugal liquor viscosity and ...electronegativity•Fe(II)/UHP reduced solid-liquid interface interaction of WAS•Fe(II)/UHP increased hydrophobicity, flocculation, and flowability of WAS
The treatment and disposal of sludge is a complex environmental problem because of the high moisture content. Herein, We reported the process of Fe(II) activating Urea hydrogen peroxide (UHP) to improve waste activated sludge (WAS) dewaterability for the first time. Fe(II)/UHP was proven to significantly improve WAS dewaterability. Specifically, under the optimal conditions with 60/35-Fe(II)/UHP mg/g TSS, the CST, SRF, and WCSC of WAS reduced from 215.3 ± 7.5s, 9.2 ± 0.32 (× 1012 m/kg), and 92.2 ± 0.7% (control) to 62.3 ± 4.3s, 2.8 ± 0.09 (× 1012m/kg), and 70.4 ± 0.4%, respectively. Further analysis revealed that •OH was generated in the Fe(II)/UHP system and played the dominant role in enhancing WAS dewaterability. •OH was found to attack extracellular polymeric substances (EPSs) and cells, causing EPSs fragmentation and decomposition part of EPSs into micro-molecule organics or even inorganics, and leading to cell destruction, thus liberating the EPSs-bound and cells-bound water. •OH also degraded the protein in centrifugal liquor (CL) into micro-molecule organics such as amino acids, which could reduce the viscosity and electronegativity of CL. The above facts ultimately reduced solid-liquid interface interaction but increased hydrophobicity, flocculation, and flowability of WAS. Meanwhile, the broken WAS flocs were then re-flocculated via adsorption bridging and charge neutralization induced by Fe(II) and Fe(III). Moreover, Fe(II)/UHP treatment achieved the reduction and stabilization of heavy metals of dewatered sludge, which further enabled its land application. Finally, the Fe(II)/UHP process was found to be more attractive than the Fe(II)/persulfate, classical Fenton processes, and cPAM in terms of cost savings and practical implementation.
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Modeling the relationships between the quality response variables and process settings or in situ sensing variables is a fundamental problem in quality engineering. Such relationships are important ...for product quality prediction, process monitoring, and optimization. Data collected from a single system often only carry limited information, making modeling one system at a time challenging. Multi-task learning (MTL) jointly models similar-but-non-identical systems and utilizes the similarities among systems for better performance. However, existing MTL becomes much less effective if important variables are missing or unmeasurable in the underlying process (latent variables). More importantly, commonly shared latent variables across systems often reflect important process patterns/behaviors, deserving more investigations. We proposed an MTL framework for multivariate or profile responses by explicitly decomposing the variation among systems into explainable variation and latent variation. Specifically, the explainable variation is from variables observed in data, while the latent variation is from the latent basis functions automatically generated from model residuals. The proposed method improves the prediction accuracy and interpretability of modeling. The simulation and a case study in a silicon ingot manufacturing network demonstrate that the proposed method can improve the quality modeling performance and recover critical process knowledge for silicon ingot manufacturing based on Czochralski (CZ) process. Note to Practitioners-This research is motivated by quality modeling of a semiconductor manufacturing network consisting of multiple furnaces (systems) producing silicon ingots. An accurate quality model in manufacturing is essential for downstream tasks such as process monitoring and optimization. As data collected from a single system often only carry limited information, aggregating data from multiple systems in quality modeling can significantly improve the performance. However, different systems in a network are often similar-but-non-identical to each other due to different degradation statuses, usage history, product receipts. As a result, data from different systems are heterogeneous, making combining all data for modeling inappropriate. Multi-task learning (MTL) solves this problem and recovers the similar-but-non-identical nature of systems. However, existing MTL is much less effective if important latent factors/variables are missing or unmeasurable in the underlying process. More importantly, such latent factors can reflect important process patterns/behaviors. This work improves the MTL framework by explicitly explaining the unexplained variations using the latent factors automatically generated from model residuals. The simulation and the case study in a silicon ingot manufacturing network demonstrate that the proposed method improves the quality modeling performance and recovers critical process knowledge for silicon ingot manufacturing based on Czochralski (CZ) process.
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•Efficient catalytic OE composites were synthesized for persulfate activation.•The main radicals (SO4− and HO) on tetracycline degradation were identified.•The Co dispersion affect ...the catalytic performance of OE composites.
The performance of pure cerium oxide (CeO2) and cobalt oxide (Co3O4) in advance oxidation processes cannot meet the growing pursuit of superior catalytic efficiency. In this study, efficient heterogeneous Co3O4/CeO2 (OE) composites were fabricated by a calcination method to activate persulfate (PS) for tetracycline (TC) degradation. Results showed that OE-2/PS system exhibited the highest TC degradation efficiency (79%), while that of CeO2/PS system and Co3O4/PS system was only 22% and 14%, respectively. Co dispersion and turn over frequency demonstrated the superiority of OE-2 composite. Oxidative sulfate radicals (SO4−) and hydroxyl radicals (HO) generated in the process contributed to the efficient degradation of TC, which was proved by radical scavenging experiment and electron spin resonce experiment. In addition, the high stability and recycling ability of OE-2 composite were proved by the detection of leaching of Co and Ce ions and cycling test.
