Microwave heating is rapidly emerging as an effective and efficient tool in various technological and scientific fields. A comprehensive understanding of the fundamentals of microwave-matter ...interactions is the precondition for better utilization of microwave technology. However, microwave heating is usually only known as dielectric heating, and the contribution of the magnetic field component of microwaves is often ignored, which, in fact, contributes greatly to microwave heating of some aqueous electrolyte solutions, magnetic dielectric materials and certain conductive powder materials,
This paper focuses on this point and presents a careful review of microwave heating mechanisms in a comprehensive manner. Moreover, in addition to the acknowledged conventional microwave heating mechanisms, the special interaction mechanisms between microwave and metal-based materials are attracting increasing interest for a variety of metallurgical, plasma and discharge applications, and therefore are reviewed particularly regarding the aspects of the reflection, heating and discharge effects. Finally, several distinct strategies to improve microwave energy utilization efficiencies are proposed and discussed with the aim of tackling the energy-efficiency-related issues arising from the application of microwave heating. This work can present a strategic guideline for the developed understanding and utilization of the microwave heating technology.
•Biomass wastes-derived activated carbon were prepared by one-step method.•The properties of precursors were characterized by thermogravimetric analysis.•The surface acidic functional groups were ...determined by NH3-TPD.•The characterization and adsorption properties of both carbons were compared.
As biomass wastes, Arundo donax Linn and pomelo peel were used as precursors for activated carbons (ALAC and PPAC) preparation by phosphoric acid activation. The pore structure and surface acidic functional groups of both carbons were characterized by nitrogen adsorption/desorption experiment, NH3-temperature-programmed desorption (NH3-TPD) and Fourier transform infrared spectroscopy (FTIR). A batch of experiments was carried out to investigate the adsorption performances of ciprofloxacin under different conditions. Results showed that PPAC exhibited larger surface area (1252m2/g) and larger portion of mesoporous, while ALAC was typical of microporous materials. Results from NH3-TPD suggested that ALAC was characteristic of more acidic functional group than PPAC. The maximum monolayer adsorption capability was 244mg/g for ALAC and 400mg/L for PPAC. Kinetics studies showed intra-particle diffusion was not the unique rate-controlling step. Boundary layer resistance existed between adsorbent and adsorbate.
Carbon-based single-atom catalysts (SACs) with atomic sizes of active sites have become the promising candidates for a variety of catalytic systems because of their high atom utilization, and unique ...electronic structures. Different types of single-atom sites can be fabricated via multiple preparation strategies, which would demonstrate distinct different coordination configurations and electronic features, and ultimately affected the structure-catalysis relationship of SACs in targeted reactions. As a result, it is necessary to identify the active sites of SACs and understand the structure-catalysis relationship of SACs at the atomic scale. In this review, a variety of preparation strategies of carbon-based SACs were documented. Then, the recent development on versatile characterization techniques and computational achievements were summarized regarding in understanding the electronic and geometric characteristics of carbon-based SACs. Finally, major challenges and development directions concerning single-atom sites identification and advanced tools development are discussed to shed light on future research of carbon-based SACs.
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Understanding the coordination configurations and electronic features of the SACs help to understand their structure-catalysis relationship in targeted reactions at the atomic scale
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•Novel sludge ceramic and SFC were separately filled into BAF and Fe-C micro electrolysis reactor.•Configuring Fe-C micro electrolysis greatly improved the controlling of residual TP ...and CIP.•Four main degradation pathways were proposed according to the LC–MS analysis.•The richness and diversity of the microbial community increased a lot with CIP pressure.
A modified biological aerated filter (BAF) system configured Fe-C micro electrolysis was applied to enhance phosphorus and ciprofloxacin (CIP) removal. A novel sludge ceramic and sintering ferric-carbon ceramic (SFC) were separately packed into a lab-scale BAF and Fe-C micro electrolysis reactor. The BAF and Fe-C micro electrolysis coupled system was operated about 230days. The enhancement of phosphorus and ciprofloxacin removals by Fe-C micro electrolysis, the degradation mechanisms of CIP and the variations of microbial population were investigated. The removal efficiencies of chemical oxygen demand (CODcr), ammonia (NH4-N), total phosphorus (TP) and CIP reached about 95%, 95%, 80% and 85% in the combined process, respectively. Configuring Fe-C micro electrolysis significantly enhanced phosphorus and CIP removal, whereas had no promotion on N removal. Four main degradation pathways were proposed according to the LC–MS analysis. More than 12 degradation products were detected through the treatment of Fe-C micro electrolysis and only 3 biodegraded products with low concentration were identified in BAF effluent. The high-throughput sequencing analysis showed that the microbial community changed a lot under CIP pressure. The relative abundance of Sphingomonadaceae, Xanthomonadaceae, Bradyrhizobium, Helicobacter and Pseudomonas increased with CIP influent. This study provides a promising process in CIP wastewater treatment.
•The lignin-based activated carbon was prepared by physical activation with steam.•The influences of various process parameters were investigated.•The optimum preparation conditions were ...determined.•The lignin-based carbon prepared by steam activation exhibited a mesoporous structure.•The static adsorption experiment and adsorption isotherms were studied.
Black liquor lignin obtained from pulp and paper industry was employed as the precursor for preparing activated carbon by physical activation with steam. The preparation was carried out with a two-step approach, firstly carbonized in an oxygen-free atmosphere and subsequently activated with steam. Experiments were performed to investigate the influences of different preparation parameters such as carbonization temperature, activation temperature and activation time on the pore texture characteristics of the products in detail by nitrogen adsorption analysis. The analysis results demonstrated that the optimized lignin-based activated carbon (LAC) obtained at a carbonization temperature of 450°C, carbonization time of 60min, activation temperature of 725°C and activation time of 40min. The microstructures of the raw lignin, the carbonized lignin and LAC were examined by SEM, whereas, surface chemistry was probed through FTIR. In the adsorption study, LAC was applied to remove methylene blue (MB) from aqueous solution. In the isotherms study, the Langmuir and Freundlich isotherms were applied to analyze the equilibrium data for the adsorption of MB onto LAC. It was found that the equilibrium data could be fit well by the Langmuir equation, and the maximum adsorption capacity was 92.51mg/g. The considerable maximum adsorption capacity indicated that the LAC could afford a noteworthy potential for dye wastewater treatment. Consequently, the procedure of physical activation with steam demonstrated its environmental and practical value for producing lignin-based adsorbent.
•Fabricate the stable PVP-NZVI/Cu bimetallic particles for CIP degradation.•Explore the catalytic activity of PVP-NZVI/Cu for CIP.•Quantitative analysis of PVP-NZVI/Cu in the CIP removal ...process.•Identify the degradation process of CIP by the mass spectrometry (MS).
A combined system of polyvinylpyrrolidone (PVP) and nanoscale zerovalent iron (NZVI) with copper (Cu) bimetallic particles (PVP-NZVI/Cu) was designed for ciprofloxacin (CIP) reduction under weak magnetic field (WMF) condition. The surface morphology and physicochemical properties of the novel catalytic materials were further characterized. In addition, the catalytic reactivity of PVP-NZVI/Cu was determined in the presence or absence of WMF. Experimental results demonstrated that the catalytic performance of PVP-NZVI/Cu system was enhanced by the introduction of WMF with maximum removal rate of CIP reaching 95.6% (120 min). Kinetic analysis exhibited that the degradation of CIP in compliance with pseudo-first-order kinetics. Eventually, the degradation products of CIP after reacting with the PVP-NZVI/Cu nanocomposites were determined by the mass spectrometry (MS). Quantitative analysis of PVP-NZVI/Cu adsorption and Fenton oxidation during the CIP removal process were also evaluated. The roles of PVP-NZVI/Cu adsorption/Fenton oxidation were dynamically changed and the Fenton oxidation was observed to be greatly strengthened as the removal process proceeded. The study provided a new insight into the removal of CIP by NZVI, which has prospect for the practical application of NZVI.
In this work, four alkaline lignin (AL) based flocculants with distinct molecular weight, chain architectures and charge densities (denoted as AL-g-DMC1, AL-g-DMC2, AL-GTA1 and AL-GTA2) were prepared ...from paper mill sludge, which were designed via graft copolymerization of dimethyl diallyl ammonium chloride (DMC) or etherification of 2, 3-epoxypropyl trimethyl ammonium chloride (GTA). The characteristics of the aforementioned flocculants were evaluated by a series of analysis technologies, which essentially confirmed the successful introduction of quaternary ammonium groups onto the AL. The flocculation performances of the four synthesized lignin-based polymers as the coagulant aids for PAC were investigated in disperse dye (DY) wastewater treatment, and the effects of dosages, initial pH, coexisting ions, humic acid (HA) or kaolin particles were also studied. The results indicated that branched copolymers with high molecular weight like AL-g-DMC1 and AL-g-DMC2 exerted excellent color removals and satisfactory floc properties in comparison with linear polymers with low molecular weight (AL-GTA1 and AL-GTA2). Furthermore, AL-g-DMC1 and AL-g-DMC2 exhibited remarkable tolerance on pH alteration and coexisting ions owing to their strong bridging action.
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•Four lignin-based flocculants were prepared from paper mill sludge.•Flocculants with distinct molecular weight and charge densities were designed.•Branched copolymers with high molecular weight exerted excellent color removals.•Flocculants with same chain architectures but higher charge density performed well.•The synergetic mechanisms and structure-activity relationships were discussed.
In this work, Co/Fe and Co/Al layered double oxides (Co/Fe-LDO and Co/Al- LDO)ozone catalysts were obtained from Co/Fe and Co/Al layered double hydroxides intermediates (Co/Fe-LDH and Co/Al-LDH). ...Firstly, the optimal preparation parameters of the two intermediates were determined, then the morphology and mineralogy microstructure of the derived Co/Fe-LDO and Co/Al- LDO ozone catalysts were systematically studied. Finally, the reaction kinetics of the two ozone catalysts for the deep degradation of aniline wastewater in catalysts/ozone systems were established. The results showed that the optimal preparation conditions were set as pH 12, temperature 60 °C, cobalt‑iron ratio 3:1 for Co/Fe-LDH intermediate, and pH 12, temperature 70 °C, cobalt‑aluminum ratio 3:1 for Co/Al-LDH intermediate. During calcination treatment, the dehydration and recrystallization effect impelled LDH intermediate to form LDO catalyst. The derived ozone catalysts Co/Fe-LDO and Co/Al-LDO possess layered structure, and Co species was mainly based on Co3O4 as the main mineral phase of the two ozone catalysts. The addition of catalyst can realize the deep ozonation catalysis of aniline wastewater. The kinetic models established on the aniline oxidized by ozone or catalyst/ozone systems were both fitted the first-order reactions, and the reaction activation energy for CODCr and TOC degradation were significantly reduced in catalyst/ozone system.
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•Co/Fe and Co/Al-LDO catalysts were obtained by coprecipitation-calcination methods.•Co/Fe and Co/Al-LDO catalysts have typical lamellar structures.•The aniline kinetics model by the bimetallic ozone catalysts was established.
The adsorption of methyl orange and methyl violet from aqueous solutions by
Phragmites australis activated carbon (PAAC) was studied in a batch adsorption system. The adsorption studies include both ...equilibrium adsorption isotherms and kinetics. Several isotherm models were investigated and the adsorption isotherm data were best represented by the Temkin isotherms. The kinetic data were well described by the pseudo-second-order kinetic model. The mechanism of the adsorption process was determined from the intraparticle diffusion model. The results indicate that PAAC could be employed as a low-cost alternative for the removal of the textile dyes from effluents.
Schematic model for removing CIP by GT-nZVI/Cu bimetallic particles under oxic conditions
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•Compare the reactivity of nZVI/Cu and GT-nZVI/Cu composites.•Explore the influence of ...initial concentration, initial pH, temperature and magnetic flux intensity on the reactivity of GT-nZVI/Cu towards CIP.•Identify the remanence effect of the material.•Identify the degradation process of CIP by the mass spectrometry (MS).
In this study, nanoscale zerovalent iron (nZVI) with copper (Cu) bimetallic particles, whichare applied for degradation of Ciprofloxacin (CIP) under weak magnetic field (WMF), were synthesized using green tea extracts (GT-nZVI/Cu). The surface morphology and physicochemical properties of the novel catalytic materials were characterized. It was found that GT-nZVI was more stable and performed better in oxidation resistance than the nZVI synthesized by traditional chemical methods. Besides, the catalytic reactivity of GT-nZVI/Cu was measured with and without WMF, it is obvious from the experimental results the performance of GT-nZVI/Cu system was enhanced significantly with WMF. Moreover, WMF still had a certain effect even after being removed, which is called remanence effect. The mass spectrometry (MS) was utilized to analyze the degradation products of CIP, and the contribution of adsorption and Fenton/Fenton-like oxidation of GT-nZVI/Cu during CIP removal process was further evaluated. It was found that as the removal process progressed, the contribution ratio of Fenton/Fenton-like oxidation rose rapidly and exceeded adsorption after 20 min. Eventually, attempts have been made to regenerate GT-nZVI/Cu, in which physical recovery (ultrasonic) was the main route, and the CIP removal rate decreased as the regeneration times increased. This research provides new insights into the green synthesis and regeneration of nZVI and is expected to realize the practical application of nZVI.
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