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We evaluated the effects of the number of years of restoration of vegetation on soil microbial community structure and biomass in degraded ecosystems. We investigated the microbial community structure by analyzing their phospholipid fatty acids then examined microbial biomass carbon and nitrogen by chloroform fumigation extraction of restoration soils over several years. The data were compared with those of highly degraded lands and native vegetation sites. The results show that the duration of vegetation on the sites substantially increased microbial biomass and shifted the microbial community structure even after only 4 years. However, microbial communities and biomass did not recover to the status of native vegetation even after 35 years of vegetation cover. A redundancy analysis and Pearson correlation analysis indicated that soil organic carbon, total nitrogen, available potassium, soil water content, silt content and soil hardness explained 98.4% of total variability in the microbial community composition. Soil organic carbon, total nitrogen, available potassium and soil water content were positively correlated with microbial community structure and biomass, whereas, soil hardness and silt content were negatively related to microbial community structure and biomass. This study provides new insights into microbial community structure and biomass that influence organic carbon, nitrogen, phosphorus and potassium accumulation, and clay content in soils at different stages of restoration.

Soil erosion is a type of land degradation caused by the interactive interaction of numerous factors, such as natural and socioeconomic conditions of a particular watershed. In this study, a comprehensive integrated methodology was used to evaluate the water erosion hazard in the Zhuxi watershed in Southern China, which is greatly affected by eroded soil. Ten indicators were selected, and a thematic layer map was generated for each indicator using Geographic Information System (GIS). The weight of each evaluation indicator was determined by combining analytic hierarchy process (AHP) with entropy method. Results show that the east and west sections of the Zhuxi watershed have very low and low grades of soil erosion hazards, respectively, and the middle part has the highest hazard. More than 60% of the area has high erosion hazard (moderate to very high). The intensity of soil erosion is lower than its hazard level, especially in high-grade hazard. The obtained results for erosion hazard level can be used to develop conservation strategies for the Zhuxi watershed. This study evaluates soil erosion hazard and offers reference for soil erosion control.

Loss of soil nutrients in runoff accelerates eutrophication of surface waters. This study found out the critical of rainfall intensity and slope angles of total nitrogen and phosphorus in surface runoff for degraded Ferralsols in southern China. We established plots (1.5 m × 0.5 m × 0.3 m; length × width × height) to investigate the effects of rainfall intensity (1.0, 1.5, 2.0 mm min−1) and slope gradients (10°, 15°, 20°) on runoff rate, total nitrogen and total phosphorus loss rates and dynamic factors. Our results indicated that a slope gradient of 15° is suitable for controlling TN and TP losses in degraded Ferralsols, 1.5 mm min−1 is the critical rainfall intensity of nitrogen and phosphorus loss in runoff in our study, runoff rate determines runoff-associated TN and TP losses, and runoff shear force is the dynamic factor for nitrogen and phosphorus losses. Our study might also be helpful for predicting water erosion and non-point source pollution in large scales and natural slope scales and building a model of soil erosion watershed scales.

This study investigated the effects of polyvinyl chloride (PVC) addition on low-rank coal’s pyrolysis characteristics, especially the products distribution and chlorine migration. Hailar lignite (HLE) with different industrial, pure, PVC-content additions were prepared (the mass percentage of PVC addition was from 5% to 25%), and the co-pyrolysis characteristics of HLE and PVC were performed on a fixed-bed reactor and thermogravimetric analyzer. The chars were characterized with X-ray diffraction (XRD), X-ray fluorescence (XRF), and Fourier-transform infrared (FT-IR) spectroscopy analysis. The gas and tar compositions were analyzed by using gas chromatography (GC) and a gas chromatography–mass spectrometry (GC–MS) system, respectively. The results indicate that the addition of PVC can increase the release amounts of CH4, C2H4, and C2H6, simultaneously reducing the release amount of CO2 and CO; the quality of pyrolysis tar was also improved, especially the alkane content in tar, which increased by 6.9%. The migration of chlorine in PVC was analyzed with the different PVC additions and terminal pyrolysis temperatures. It showed that the content of chlorine in the gas phase first increased with the increasing pyrolysis temperature, but at the terminal temperature of 600 °C, the chlorine in the gas phase began to decrease. The results of the co-pyrolysis char characterization show that the content of the alkali metal oxide gradually decreases in the char, and metal chloride appears during the pyrolysis process. In the co-pyrolysis reaction of coal and PVC, chlorine was fixed in the char, thereby reducing the distribution of chlorine in the gas phase. This also proves that the PVC pyrolysis process, with the participation of low-rank coal, can enrich chlorine into the solid phase, thus reducing the emission of chlorine in the gas phase.

The study aims to explore the kinetics of coal char during high temperature gasification by thermogravimetric analyzer and in situ heating stage microscope. Yangchangwan coal (YCW) and Shenfu coal (SF) were selected as the feedstock. The kinetics was fitted by using shrinking core, random pore, and homogeneous models, respectively. The in situ heating stage microscope was used to observe the ash morphology change of coal char. The results show that the random pore model was optimal for fitting the kinetics of coals. At 1273–1673 K, the range of apparent activation energy of YCW and SF chars were 82.27–90.74 kJ mol−1 and 89.78–91.42 kJ mol−1, respectively. Most of the YCW and SF chars were observed to participate in gasification by random pore mode and amorphous ash was formed. A few of YCW char particles were observed to undergo gasification by both homogeneous and shrinking core modes. The area shrinkage ratio of YCW char involved in the gasification by shrinking core mode was reduced by 58% after 20 min of reaction. At 1573–1673 K, the char gasification was controlled by ash layer diffusion. Compared with the reactivity at 1273–1473 K, SF char gasification reactivity at higher temperatures was reduced for that SF coal ash could agglomerate into sphere to wrap the residual carbon, while YCW char reactivity was increased since YCW ash was agglomerated into sphere, the sphere were melting and flowing with each other, so the residual carbon was exposed on YCW char surface.

The concept of treating waste with waste is of great significance to realize the sustainable development of human society. In this work, the high metals-containing coal gasification fine slag (CGFS) from the coal gasification industry is directly transformed into an excellent adsorbent for malachite green wastewater adsorption. CGFS exhibits a rough and porous structure, which is mainly composed of SiO 2 and various metal compounds. Numerous spherical structures which are generated by the melting of inorganic substances are distributed on the surface of CGFS with a large number of flocculent carbon structures covering the substrate or interspersed. Experiments confirm that CGFS is a competitive adsorbent for the removal of malachite green due to its low cost and high adsorption performance. The theoretical maximum adsorption capacity of CGFS at 298 K predicted by the Langmuir model reached as high as 1787 mg/g and the capacity increases with the temperature. The removal efficiency reached 100% for CGFS at a solid–liquid ratio of 0.05 g/100 mL and a malachite green concentration of 100 mg/L. A dominant role of chemisorption was confirmed by the analytical results of the pseudo-second-order model and the Freundlich model combined with the characterization results. The metal oxides and carbon structures in CGFS are presumed to be the main active adsorption sites. From the fitting of the intraparticle diffusion model, the adsorption rate was limited first by membrane diffusion and then by intraparticle diffusion as the adsorption process proceeded. Graphical Abstract

Propylene epoxidation by oxygen over Cu-based catalysts is a most ideal and economical process. The unsupported CuO x nanoparticles were synthesized by liquid phase reduction method. The crystalline phase and size of CuO x nanoparticles were characterized by XRD and TEM, respectively. The catalytic performances of CuO x with different pretreatment temperatures and atmospheres were also investigated. The as prepared unsupported CuO x nanoparticles were composed of Cu and Cu 2 O. With elevating the pretreatment temperatures under N 2 atmosphere, the size of CuO x nanoparticles increased gradually from 25 nm to 58 nm. However, the relative content between Cu and Cu 2 O remained almost unchanged, indicating that the valence state of Cu species in CuO x was kept nearly constant. The C 3 H 6 epoxidation activities showed a first increases and then decreases trend with enhancing the particle size of CuO x . The highest activity of propylene epoxidation was achieved when the particle size of CuO x was 41 nm. The conversion of propylene was 0.14% and the selectivity of propylene oxide was 30% respectively under the reaction temperature of 150 °C. The results indicated that the appropriate CuO x particle size was a key factor for propylene oxide formation on Cu-based catalysts. Graphic Abstract The C 3 H 6 epoxidation activities showed a first increases and then decreases trend with enhancing the particle size of CuO x . When the CuO x particle size was 41 nm, the formation rate of PO reached maximum. The appropriate particle size of Cu species with low valence state was crucial to the generation of PO for C 3 H 6 epoxidation reaction by O 2 on Cu-based catalysts.

The co-gasification of biomass and coal is helpful for achieving the clean and efficient utilization of phosphorus-rich biomass. A large number of alkali and alkaline earth metals (AAEMs) present in the ash system of coal (or biomass) cause varying degrees of ash, slagging, and corrosion problems in the entrained flow gasifier. Meanwhile, phosphorus is present in the slag in the form of PO43−, which has a strong affinity for AAEMs (especially for Ca2+) to produce minerals dominated by calcium phosphates or alkaline Ca-phosphate, effectively mitigating the aforementioned problems. To investigate the changing behavior of the slag flow temperature (FT) under different CaO/P2O5 ratios, 72 synthetic ashes with varying CaO/P2O5 ratios at different Si/Al contents and compositions were prepared, and their ash fusion temperatures were tested. The effects of different CaO/P2O5 ratios on the FT were analyzed using FactSage thermodynamic simulation. A model for predicting slag FT at different CaO/P2O5 ratios was constructed on the basis of the average molar ionic potential (Ia) method and used to predict data reported from 19 mixed ashes in the literature. The results showed that Ia and FT gradually increased with a decreasing CaO/P2O5 ratio, and the main mineral types shifted from anorthite → mullite → berlinite, which reasonably explained the decrease in ash fusion temperatures in the mixed ash. The established model showed good adaptability to the prediction of 19 actual coal ash FTs in the literature; the deviation of the prediction was in the range of 40 °C. The model proposed between FT and Ia based on the different CaO/P2O5 ratios can be used to predict the low-rank coal and phosphorus-rich biomass and their mixed ashes.

The synergy effect of high K-low Ca-high Si biomass ash-based model system (BAMS) on the synthesis gas output and reaction characteristics of petroleum coke (PC) steam gasification process was studied using three biomass ash (BA) components, KCl, SiO2, and CaCO3, which were used as the model compounds. In the ternary model system, the steam gasification experiment of PC was conducted using a fixed bed reactor and gas phase chromatography. The synergistic effects of binary and ternary components in the ternary model system on the gasification of PC were obtained. These investigations were based on the data from the gas analysis and examined the gasification reaction process, syngas release behavior, and reaction characteristics. This study examined the effects of binary and ternary components in the ternary model system on the evolution of semi-char structure during PC gasification. This correlation revealed the synergistic effect of the model system on PC gasification. Scanning electron microscope (SEM) and Raman spectroscopy were used to characterize the structure and surface microstructure of the gasification semi-char. The results showed that the yields of different gases in the ternary model system were in H2 > CO > CO2. Compared with single PC gasification, the yields of H2, CO, syngas, and carbon conversion were increased by 29.42 mmol/g, 20.40 mmol/g, 56.68 mmol/g, and 0.35, respectively. All other components in the ternary model system with high K-low Ca-high Si demonstrated catalytic effect, except for SiO2 and the Ca-Si system, which showed inhibitory effects on syngas release and reaction features. Integrating SEM and Raman spectroscopic analyses, it was elucidated that CaCO3 and KCl diminished the degree of graphitization in semi-char through interactions with the carbonaceous matrix. This phenomenon facilitated the gasification process and exhibited a synergistic effect. Secondly, SiO2 will react with CaCO3 and KCl, producing inert silicates and inactivating these compounds, leading to the decline of catalysis.

Co-thermal chemical conversion of coal and biomass is one of the important ways to realize efficient and clean utilization of coal. In this study, a typical Ningdong coal-Yangchangwan bituminous coal and cow manure were used to study the synergistic effect of intrinsic alkali, alkaline earth metals (AAEM) and organic matter on the co-gasification of coal and biomass by thermogravimetry analyzer (TG). The results showed that AAEM had obvious synergistic promotion effect on the gasification of a bituminous coal-cow manure mixture in the isothermal gasification (1000 ℃), whereas the organic matter will show the opposite effect on the process. To further investigate the effect of organic matter on the gasification process, the influence of organic matter on non-isothermal (25-1000 ℃) gasification reaction was investigated with heating rate of 10 ℃ /min, the kinetic parameters of the gasification reaction were obtained by Coats-Redfern method. The increase of biomass mass fraction in the sample facilitates the migration of alkali metals from the material to the solid phase. The possible mechanism of the synergistic effect of intrinsic AAEM/organic matter on the co-gasification process was proposed.