Formation and Transformation of Typical Pollutant from MSW by Hydrothermal Carbonization towards Biofuel Hydrochar Production

An unprecedented increase in municipal solid waste (MSW) is increasingly attractive in response to waste-to-energy. MSW pretreatment is an essential step due to the inherent properties of MSW. Hydrothermal carbonization (HTC) offers an efficient approach for converting MSW into carbonaceous hydrochars. In this chapter, the formation and transformation of heavy metals and polycyclic aromatic hydrocarbons (PAHs) during HTC of MSW were determined. The results indicated that HTC can homogenize the density and size of MSW and also increase carbon content. Moreover, the concentrations of heavy metals in the leachates of the hydrochars were lower than the United States Environmental Protection Agency (US EPA) maximum limits. Compared to MSW, the concentrations of Cr, Cd, Hg, and Zn in the hydrochars were low and the concentrations of Pb, As, Ni, and Cu were high. The concentrations of PAHs in the hydrochars increased with increasing temperature in the range of 1298.71–177698.20 μg/kg, which were much higher than that in MSW, except for H-160. The dominant PAH rings in MSW and the hydrochars were four-ring PAHs and three-ring PAHs, respectively. These findings suggest that 180°C is an appropriate hydrothermal temperature to reduce heavy metals and the toxicity PAHs of MSW

Multi-modal knowledge graph inference via media convergence and logic rule

Media convergence works by processing information from different modalities and applying them to different domains. It is difficult for the conventional knowledge graph to utilise multi-media features because the introduction of a large amount of information from other modalities reduces the effectiveness of representation learning and makes knowledge graph inference less effective. To address the issue, an inference method based on Media Convergence and Rule-guided Joint Inference model (MCRJI) has been proposed. The authors not only converge multi-media features of entities but also introduce logic rules to improve the accuracy and interpretability of link prediction. First, a multi-headed self-attention approach is used to obtain the attention of different media features of entities during semantic synthesis. Second, logic rules of different lengths are mined from knowledge graph to learn new entity representations. Finally, knowledge graph inference is performed based on representing entities that converge multi-media features. Numerous experimental results show that MCRJI outperforms other advanced baselines in using multi-media features and knowledge graph inference, demonstrating that MCRJI provides an excellent approach for knowledge graph inference with converged multi-media features

Wave propagation of bending jet in electrospinning process

The electrospinning process features bending jets in space and solidified nanofibers on a collector. Although electrospun nanofibers have been widely applied, the wave characteristics, especially the first jet bend and tapered envelope cone profile, of bending jets are not fully comprehended. In this work, a spatial normal mode k− is true to characterize the convective instability of a bending jet. Some real wave variables are measured and calculated. It is observed that the first jet bend occurs at the jet end. The instability grows quickly at the early stage of a wave. Underdeveloped dispersive waves are temporally and spatially unstable. When dispersive waves develop to a mature stage, the instability grows slowly, and developed dispersive waves are only spatially unstable. Furthermore, the energy ratio of electric energy to kinematic energy accounts for the wave characteristics of a bending jet. A high energy ratio may stabilize the jet, and a very low energy ratio destabilizes the jet. The stabilizing effect of the high energy ratio suppresses the growth of dispersive waves at the jet source. Once residual charges within the jet trigger small perturbations to the electric field near the plate owing to the Coulomb repulsive effect of like charges, the destabilizing effect of the low energy ratio causes the rapid development of small perturbation first at the jet end. The inhomogeneous distribution of electric energy contributes to the tapered envelope cone profile of a bending jet. Numerically and experimentally, the wave speed is in the order of 1 m/s, and the growth rate is in the order of 102 m−1. The numerical results are in accordance with the experimental results

Perceptions of Different Stakeholders on Reclaimed Water Reuse: The Case of Beijing, China

Public involvement is critical to the successful implementation of reclaimed water reuse programs. Based on the participatory research method, we studied the attitudes of the stakeholders who are involved in reclaimed water reuse in Beijing, China. Results showed that the general public’s knowledge on water resources was poor, while their awareness on reclaimed water reuse was high. The general public showed a strong acceptance of non-contact and non-potable reclaimed water reuse, but their acceptance of the three major water reuse types of river water supplement, park water supplement, and agriculture irrigation was not high. The beneficial use of reclaimed water was admired by water resource managers, industrial sectors, and researchers, and these stakeholders strongly supported the advancement of reclaimed water reuse. However, some of the stakeholders showed concerns about the potential risks from reclaimed wastewater reuse. Among them, risks from waste water treatment facilities were the biggest concern. Stakeholders’ perception of reclaimed water was influenced by their social-economic attributes. This study will enrich the current survey findings on public perception of reclaimed water reuse, particularly in developing countries

The Stability of U(VI) and As(V) under the Influence of pH and Inorganic Ligands

Uranium and arsenic are two pollutants commonly found in groundwater near uranium mines. However, the reactivity of U(VI) and As(V) need to be carefully investigated to better understand their fate and transport in the environment. In this study, the reactivity of U(VI) and As(V) were studied under various pH, bicarbonate, and Ca2+ levels. In air-equilibrated systems, the reactivity of U(VI) and As(V) generally decreased with the increase in pH, as evidenced by the solubility of U(VI) and As(V) increasing along with the elevation of pH. At pH = 8, 44.70% and 37.81% of initially added U(VI) and As(V) remained soluble. The addition of 1 mM of bicarbonate increased the reactivity of U(VI) and As(V) at mild acidic to neutral pH; however, the presence of bicarbonate significantly increased the solubility of U(VI) at mild alkaline condition, as nearly all U(VI) remained soluble at pH values of 8 and 9. After the addition of Ca2+, the solubility of both U(VI) and As(V) decreased at mild acidic to neutral pH ranges; however, the addition of Ca2+ markedly increased the soluble percentages of U(VI) at neutral pH, in which the condition 97.81 ± 2.95% of U(VI) remained soluble. Comparatively, only 36.13 ± 4.98% and 1.69 ± 1.08% of U(VI) were soluble at the same pH in air-equilibrated and bicarbonate systems. Our study demonstrated that U(VI) and As(V) are less reactive at neutral to alkaline conditions. Furthermore, the addition of bicarbonate and Ca2+ can further reduce the reactivity of U(VI) and As(V) at neutral to alkaline conditions. The findings of this study contribute to a deeper understanding of the fate and transport of U(VI) and As(V) in groundwater and could aid in better designing of U(VI) and As(V) removal processes

Formation and toxicity of polycyclic aromatic hydrocarbons during CaO assisted hydrothermal carbonization of swine manure

The effects of temperature and Ca0 introduction on polycyclic aromatic hydrocarbons (PAHs) contents, distribution patterns and toxicity of the products from hydrothermal carbonization (HTC) of swine manure (SM) were investigated in this study for the first time. The results indicated that increasing temperature decreased total PAHs content of the hydrochar, while the PAHs toxicity firstly decreased and then increased during HTC of SM. For the aqueous product, the total PAHs content and toxicity gradually decreased with increasing temperature. CaO introduction during HTC of SM significantly suppressed the PAHs formation and promoted the transformation from higher molecular weight PAHs into lower molecular weight PAHs in HTC products, resulting in the remarkably decreased content and toxicity of PAHs. The lowest total PAHs content (1428.57 mu g/kg) and TEQ value (21.33 mu g/kg) of the hydrochar were obtained by 15% CaO introduction at 200 degrees C and 180 degrees C, respectively, and compared to SM, they were decreased by 73.73% and 79.51%, respectively. Moreover, 3-ring PAHs were the predominant PAHs in HTC products regardless of CaO introduction. The present study demonstrated that CaO assisted HTC at temperature lower than 220 degrees C was effective to reduce the total content and toxicity of PAHs in SM, and the prepared hydrochar was a promising soil amendment in view of the elimination of PAHs toxicity. (C) 2019 Elsevier Ltd. All rights reserved

Age-Effect Radial Growth Responses of Picea schrenkiana to Climate Change in the Eastern Tianshan Mountains, Northwest China

The climate changed from warm-dry to warm-wet during the 1960s in northwest China. However, the effects of climate change on the response of radial growth from different age-class trees have been unclear. We assessed the age-effect radial growth responses in three age-classes (ml-old: ≥200 years, ml-middle: 100–200 years and ml-young: <100 years) of Schrenk spruce (Picea schrenkiana Fisch. et Mey.) in the eastern Tianshan Mountains. The primary conclusions were as follows: the developed chronologies of the three age-class trees contained significant climate information and exhibited high similarity as shown by calculating the statistical parameter characteristics and Gleichlaufigkeit index. The three age-class trees were consistent for annual variation trends of radial growth under climate change, showing similar fluctuations, tree-ring width chronology trends, time trends of cumulative radial growth, and basal area increment. In addition, the old and middle trees were found to be more sensitive to climate variability by analyzing Pearson correlations between radial growth from three age-class trees and climate factors. As a result, the drought caused by reduced total precipitation and higher mean temperature was a limiting factor of tree radial growth, and the trees with ages of up to 100 years were more suitable for studies on the growth-climate relationships. Thus, the studies on age-effect radial growth responses of Schrenk spruce can help not only in understanding the adaptive strategies of different-age trees to climate change, but also provide an accurate basis for climate reconstruction

Facile and green synthesis of highly dispersed tar-based heterogeneous Fenton catalytic nanoparticles for the degradation of methylene blue

Thermochemical conversion of biomass produces tar, as an inevitable byproduct, which was a potentially precursor for carbon material preparation. This study provided an approach of preparation of tar-based Fenton-like catalytic nanoparticles from waste biomass tar via green solvent-free approach. The monoand bimetallic nanocatalysts were synthesized from biomass tar and metal salts by ball milling combined with calcination. The synthesized catalysts were utilized for H2O2 decomposition and subsequent methylene blue (MB) degradation in aqueous solution. The results showed that the presence of tar resulted in the porous structure and defective graphite layers on the surface of resultant catalysts. The bimetallic nanocatalysts had higher H2O2 decomposition rate than monometallic nanocatalysts and among all the catalysts, the bimetal catalyst prepared at 300 degrees C (FeNi/C-300) showed the highest rate constant (10.55 x 10(-3) min(-1)) for the decomposition of H2O2. This high catalytic activity of FeNi/C-300 was attributed to the promotion of Fe3+ reducing to Fe2+ due to accelerated electron exchange by the introduction of nickel and the formation of defective graphite layers. For MB degradation, the monometal nanocatalyst prepared at 300 degrees C (Fe/C-300) and FeNi/C-300 showed high removal efficient in the degradation of methylene blue, and the highest removal efficiency reached 100% and 98%, respectively. This study offered a promising approach for the preparation of heterogeneous Fenton catalytic nanoparticles for organic pollutant removal using waste biomass tar and by green synthesis method. Most importantly, this approach has the potential to be extended for other metal based Fenton catalytic nanoparticles synthesis. (C) 2019 Elsevier Ltd. All rights reserved