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•EL/EC and ZVI activated persulfate had synergetic effect on sludge dewatering.•EZP conditioning effectively enhanced different types of sludge dewaterability.•EZP oxidation destroyed ...the EPS and cells, releasing bound water in sludge flocs.•Degradation of protein-like substances contributed to sludge dewatering.•Cost of EZP conditioning saving up to 41.9% in comparison with Fenton method.
Waste activated sludge (WAS) is difficult to be dewatered due to the highly water bounded in sludge flocs, and the extracellular polymeric substances (EPS) was the major factor affecting sludge dewatering performance. In this study, the hybrid process of electrolysis/electrocoagulation and zero-valent iron activated persulfate oxidation (EZP) showed a significant synergetic effect in enhancing municipal sludge dewaterability, and has the potential for enhancing industrial sludge dewaterability. The optimal dewatering conditions for municipal sludge were voltage 40V and 4.15g/L Na2S2O8 when zero-valent iron induced electrodes were applied. After EZP pretreatment, the municipal sludge specific resistance to filtration (SRF) and capillary suction time (CST) decreased by 87.4% and 49.1% respectively. The effects of EZP pretreatment on zeta potential, EPS property, viscosity and dewaterability of different sludge were analyzed to unravel the underlying mechanism of sludge conditioning. Results showed that the EZP oxidation was capable to effectively disrupt the EPS, crack the entrapped cells, and degrade the protein-like substances, reducing the viscosity and negative zeta potential, releasing bound water inside EPS and cells and thus improving sludge dewaterability. According to the analysis of Three-dimensional excitation emission matrix (3D-EEM), the EZP technology greatly decomposed tryptophan and aromatic protein-like substances in EPS. Scanning electron microscope (SEM) analysis further revealed that the disrupted EPS and cells were coagulated after EZP conditioning and reinforced sludge dewatering. The preliminary economic analysis showed that the optimized EZP was economically favorable.
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•Sludge dewatering and minimization can be achieved by H2O2 based AOP.•Methane yield in sludge anaerobic digestion can be improved prominently by H2O2 based AOP.•Pollutants retained ...in sludge can be degraded effectively via strong oxidative hydroxyl radical.•Cost estimation of H2O2 based AOP in sludge treatment has been materialized.
The disposal of excessive activated sludge by advanced oxidation processes (AOP) to avoid its potential environmental risk has received extensive attention. As an efficient and clean oxidant, hydrogen peroxide (H2O2) has been used widely in AOP. In H2O2 based AOP, strong oxidative hydroxyl radical (HO) produced by different kinds of activation methods plays an important role in sludge treatment for sludge reduction, recycling and risk relief. This review summarizes current studies and breakthroughs of H2O2 based AOP in sludge treatment. Meanwhile, the possible mechanisms of H2O2 based AOP in sludge dewatering, sludge minimization, anaerobic digestion and the removal of pollutants are clarified systemically. Furthermore, the cost estimation of H2O2 based AOP in sludge treatment is materialized. Finally, the possible focus of future study in sludge treatment via H2O2 based AOP is present. This review can provide a theoretical basis for applying H2O2 based AOP in sludge reduction, recycling and risk relief.
Aconitine (ACO) is a classic drug of arrhythmogenic agents for establishment of arrhythmias in animal models. We used a two-microelectrode voltage-clamp technique analysis of Kv1.5 and HERG channels ...expressed in
Xenopus laevis oocytes to characterize the blocking activity of ACO.
Aconitum has been widely used to treat various diseases in China for a long time. However, improper use of this drug results in severe intoxication. Aconitine (ACO), a diterpenoid alkaloid from aconitum, mainly contributes to cardio-toxic effects of aconitum and has also been commonly known to induce arrhythmias in animal models. However, its pro-arrhythmic mechanisms are not clear.
The effects of ACO on HERG and Kv1.5 channels were investigated.
HERG and Kv1.5 channels were expressed in
Xenopus laevis oocytes, and the resulting currents were recorded using a two-microelectrode voltage clamp technique.
In HERG channels, ACO exhibited a blockade in a voltage- and time-dependent manner. The blockade was enhanced by further activation of currents, which were consistent with an open-channel blockade. In Kv1.5 channels, ACO produced a voltage-, time-, and frequency-dependent inhibition. The blockade was enhanced by higher rates of stimulation, consistent with preferential binding of the drug to the open state. In addition, ACO blocked Kv1.5 and HERG channels in a concentration-dependent manner with an IC
50 of 0.796
±
0.123 and 1.801
±
0.332
μM, respectively.
ACO blocks HERG and Kv1.5 potassium channels in the open state. Blockade of potassium channels, particular the HERG channel, may be one of the important mechanisms of how ACO induces arrhythmias.
Application of MIVM for Pb-Sn System in Vacuum Distillation Kong, Lingxin; Yang, Bin; Li, Yifu ...
Metallurgical and materials transactions. B, Process metallurgy and materials processing science,
12/2012, Letnik:
43, Številka:
6
Journal Article
Recenzirano
The activity coefficients of components of the Pb-Sn binary alloy system were calculated based on the molecular interaction volume model (MIVM). A significant advantage of this model lies in its ...ability to predict the thermodynamic properties of liquid alloys using only two binary infinite activity coefficients. Based on the MIVM, the vapor-liquid phase equilibrium of the Pb-Sn alloy system in vacuum distillation has been predicted using the activity coefficients of Pb and Sn. The results showed that the content of tin in the vapor phase was 0.008 wt pct, while in the liquid phase, it was 83 wt pct at 1173 K (900 °C); it reached 0.022 wt pct in the vapor phase, while in the liquid phase, it was 92 wt pct at 1223 K (950 °C); and it was 0.052 wt pct in the vapor phase, while in the liquid phase, it was 97.88 wt pct at 1273 K (1000 °C). The content of tin in the vapor phase increased with the distillation temperature increasing. Experimental investigations into the separation of Pb and Sn from the Pb-Sn alloy by vacuum distillation were carried out for the proper interpretation of the results of the model. The influence of the distillation time (20 to 80 minutes) and the distillation temperatures of 1173 K, 1223 K, and 1273 K (900 °C, 950 °C, and 1000 °C) on the separating effect was also studied. The experimental results showed that the content of tin in the vapor phase was 0.085 wt pct, while in liquid phase, it was 83 wt pct under the operational conditions of distillation temperature of 1173 K (900 °C), evaporation time of 20 minutes, and chamber pressure of 20 Pa; it reached 0.18 wt pct in the vapor phase, while in the liquid phase, it was 92 wt pct at 1223 K (950 °C), 20 minutes, and 20 Pa; and it was 0.35 wt pct in the vapor phase, while in the liquid phase, it was 97.88 wt pct at 1273 K (1000 °C), 20 minutes, and 20 Pa. In all these experiments, it was observed that the content of tin in the vapor phase increased as the distillation time and temperatures were increased. The experimental results are in good agreement with the predicted values of the MIVM for the Pb-Sn binary system.
In this work, Fe(II) catalyzing sodium percarbonate (Fe(II)/SPC) was managed to facilitate waste activated sludge (WAS) dewatering for the first time. The results showed that after WAS was treated by ...20 mg/g total suspended solids (TSS) Fe(II) and 50 mg/g TSS SPC, the water content of sludge cake (WCSC) by press filtration and capillary suction time (CST) dropped from 90.8% ± 1.6% and 96.1 ± 4.0 s (the control) to 55.6% ± 1.4% and 30.1 ± 2.5 s, respectively. The mechanism investigations indicated that four intermediates or products (i.e., •OH, H2O2, Fe(II), and Fe(III)) generated in the Fe(II)/SPC process were responsible for the improved WAS dewaterability, and •OH and Fe(III) were the two major contributors. It was found that •OH collapsed and fragmented extracellular polymeric substances, damaged cell wall and permeabilized cytoplasmic membrane, and transformed conformation of the extracellular proteins secondary structure via both affecting the hydrogen bond maintaining α-helix and cracking disulfide bond in cysteine residues while Fe(III), the oxidization product of Fe(II), decreased the surface electronegativity and water-affinity surface areas of WAS flocs. As a result, the bound water release, flocculability, surface hydrophobicity, drain capability, and flowability of WAS flocs were strengthened whereas the compact surface structure, colloidal forces, network strength, gel-like structure, and apparent viscosity of WAS flocs were weakened. In addition, Fe(II)/SPC process also reduced the recalcitrant organics and fecal coliforms in sludge, which facilitated land application of dewatered sludge. The findings acquired in this work not only deepens our understanding of Fe(II)/SPC-involved WAS treatment process but also may guide engineers to develop both effective and promising strategies to better condition WAS for dewatering in the future.
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•Fe(II)/SPC was firstly developed to dewater sludge and the mechanism was uncovered.•Thixotropic and viscoelastic behaviors of sludge were modified by Fe(II)/SPC.•Bound EPS of sludge were collapsed and fragmented by Fe(II)/SPC.•Conformation of extracellular proteins structure was altered by Fe(II)/SPC.•Fe(II)/SPC damaged cell wall and permeabilized cytoplasmic membrane in sludge.
•Sludge EPSs are affected by micelles formed by surfactant molecules.•Water is released from sludge by surfactants that promote the dissolution of EPSs.•VFA and methane yields improved via surfactant ...enhancement of hydrolase activity.•Pollutants contained in sludge can be removed effectively by surfactants.
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Proper treatment of waste-activated sludge (WAS) involves three pivotal processes, dewatering, anaerobic digestion, and pollutants removal, which need to be re-assessed urgently. Although many traditional sludge treatments have been developed, it is prudent to enhance the efficiency of sludge treatment using multifunctional, flexible, and environmentally friendly surfactants. With regard to sludge dewatering, surfactants can weaken the binding interaction between sludge flocs and promote the dissolution of extracellular polymeric substances (EPSs), resulting in the release of bound water. Using surfactants in anaerobic digestion promotes the release of enzymes trapped in sludge and improves the activity of enzymes during hydrolysis. Owing to their characteristic encapsulation of hydrophobes into self-assembled aggregates (micelles), surfactants can form host-guest complexes with polycyclic aromatic hydrocarbons (PAHs). Additionally, surfactants can enhance the desorption of heavy metals and prevent the emergence of heavy metal residue. This review summarizes the current surfactant-based sludge treatment technologies according to their roles in sludge disposal solutions. Then, possible mechanisms of surfactants in sludge dewatering, anaerobic digestion, and the removal of organic pollutants and heavy metals are analysed systemically. Finally, changes to sludge treatment via the aid of surfactants are highlighted. This review presents the comprehensive advances in the use of surfactants in WAS reduction, recycling, and risk relief, underscoring their roles in increasing economic efficiency and ensuring environmental quality.
•A systematic DFT study was carried out to analyze the various Sn–As cluster.•During vacuum distillation, As introduced Sn into the volatiles as AsSn compounds.•The removal As of crude Sn via ...multistage vacuum distillation.
In the realm of high–tech industries, Sn has emerged as an indispensable strategic metal. However, the pyrometallurgical refining process of crude Sn is marred by the production of a substantial amount of hazardous solid waste, notably As–Al slag, posing a direct threat to the ecological safety of the production areas. This study delineates a novel process for the removal of As from crude Sn, employing vacuum gasification–directional condensation, corroborated by theoretical calculations and laboratory experimental research. Theoretically, at a system pressure ranging from 1–10 Pa, the initial volatilization temperatures of Sn and As exhibit significant variance. However, the formation of intermetallic compounds can induce Sn volatilization. Experimentally, the condensation temperature for As was predominantly within 331.7–484.7 K. During the vacuum gasification–directional condensation process, the presence of Sn4As3 intermetallic compounds impeded As volatilization. And under optimal conditions, the As content in the Sn product was recorded at 0.0053 %. Inspired from the calculations, a multistage vacuum distillation method was successfully proposed and achieved to remove As from crude tin. Typically, the total material recovery rate is 99.96 %, and the direct rate of Sn is 93.02 %. The total power consumption and emission of this process are better than the corresponding parameters of other treatment processes, which is a promising solution for the cleaning and effective removal of As.
Zero valent iron (ZVI) activating peroxydisulfate (PDS) was demonstrated to be effective in improving the dewaterability of anaerobically digested sludge (ADS). However, details of how ZVI/PDS ...enhances the dewaterability remain largely unknown. This work therefore aims to reveal the facts of what happen in ZVI/PDS involved ADS systems. Experimental results showed that ZVI/PDS treatment remarkably improved the dewaterability of ADS, with the minimal normalized capillary suction time of 8.6 ± 0.5 s L/g·VSS being obtained at the dosages of 2 g/g TSS ZVI and 0.5 g/g TSS PDS, which was 42.5% of that in the control. In this case, 71.2% ± 1.8% of water content (press filtration) was measured, which was 16.9% lower than that determined in the control. The mechanism investigations showed that ZVI activating PDS produced substantially reactive species, i.e., SO4•- and •OH, and these strong oxidative radicals decreased surface negative charges of ADS flocs, caused disruption of extracellular polymeric substances (EPS) and release of intracellular substances, and changed the secondary structure of proteins. Additionally, the products of ZVI oxidation, i.e., Fe2+ and Fe3+, were effective flocculants, thus their generation benefited the coagulation of ADS flocs through compressing double electric layers and neutralizing negative charges of sludge colloidal particles. As a result, the flocculability, hydrophobicity, and flowability of ADS were enhanced, but the bound water content, fractal dimension, and viscosity of ADS were decreased, which were responsible for the improvement of dewaterability. Further analyses exhibited that the contributions of these major contributors were different, and their contributions to the dewaterability improvement were in the order of SO4·- > ·OH > Fe2+/Fe3+. It was also found that ZVI/PDS treatment enhanced the degradation of recalcitrant organics, inactivation of the fecal coliforms, and mitigation of the toxicity of heavy metals in the dewatered sludge, which were beneficial to its land application.
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•ZVI/PDS treatment improved the dewatering of ADS.•ZVI/PDS treatment disrupted EPS fractions and induced intracellular matter release.•ZVI/PDS treatment changed protein secondary structure of EPS fractions.•ZVI/PDS treatment facilitated the re-flocculation of oxidated ADS.
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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.
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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.
