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• Pathways of carbon-containing compounds in municipal sludge pyrolysis were Mapped. • In terms of gas pollution, most carbon was fully pyrolyzed into CO 2. • The pyrolysis liquid below 300 °C exhibited a potential for resource utilization. • The yield of CO in pyrolysis gas rapidly increased at temperature above 500 °C. • The insights hold practical implications for environmental management. Municipal sludge contains abundant amounts of carbon, with contents ranging from 14 % to 38 %. The various carbon-containing group compounds can be converted into beneficial products, but pollutants and greenhouse gases are also released through the municipal sludge pyrolysis process. Ascertaining the pathways by which carbon-containing group compounds is converted and transformed is crucial for addressing pollution concerns and promoting recycling. This study explored the transformation pathways of carbon-containing group compounds during the pyrolysis process of municipal sludge. The results showed that the three major carbon-containing group compounds including protein (61 %), cellulose (9 %), and hemicellulose (7 %), had significantly different pyrolysis temperature of 600 °C, 400 °C and 300 °C. In terms of gas pollution, most carbon was fully pyrolyzed into CO 2. While the temperature raised up to 500 °C, a part of the CO 2 converted into CO. Meanwhile, the various carbon-containing compounds exhibited distinct effects on gas production, which CH 4 was produced more with cellulose and protein presenting in the sludge. When temperature increased to 700 °C, the 60 % of the carbon-containing group compounds were transformed into liquid and solid. The pyrolysis liquid in the low-temperature stage (30–300 °C) contained a relatively high aliphatics content and lower organooxygen species (OOSs) content (at 200 °C), suggesting a potential for resource utilization. The yield of CO in the gas rapidly increased as the temperature increased in the high-temperature stage (500–700 °C). The insights from this study hold practical implications for enhancing municipal sludge pyrolysis efficiency, reducing pollution, and facilitating more sustainable and resource-efficient practices. [ABSTRACT FROM AUTHOR]

Grasslands across arid and semi‐arid regions are predicted to experience reductions in precipitation frequency. Besides, grassland degradation has become a serious problem in many of these areas. Despite increasing evidence suggesting compound effects of these synchronous alterations on biotic and abiotic ecosystem constituents, we still do not know how they will impact the coupling among ecosystem constituents and its consequences on ecosystem functioning.Here, we assessed the effects of decreased precipitation frequency and grassland degradation on ecosystem coupling, quantified based on the mean strength of pairwise correlations among multispecies communities and their physicochemical environment, individual functions and ecosystem multifunctionality, and reported their relationships within a mechanistic plant–nematode–micro‐organism–soil interactions framework.Decreased precipitation frequency led to poorly coupled ecosystems, and reduced aboveground plant biomass, soil water content, soil nutrient levels, soil biota abundance and multifunctionality. By contrast, belowground plant biomass and soil potential enzyme activities increased under decreased precipitation frequency treatment. Severe degradation resulted in decoupled ecosystems and suppressed most of individual functions and multifunctionality. Using structural equation modelling, we showed that coupling had a strong direct positive effect on multifunctionality (standardized total effect: 0.74), while multifunctionality was weakened by greater soil water variation (−0.54) and higher soil pH (−0.53).The great sensitivity of ecosystem coupling to altered precipitation regimes and degradation highlights the importance of considering interactions among biotic and abiotic components when predicting early ecological impacts under changing environments. Moreover, the positive relationship between ecosystem coupling and functioning suggests that restoration of degraded grasslands may be achieved by intensifying ecological interactions. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Purpose: Climate models predict shifts in precipitation patterns characterized by increased precipitation amount and decreased frequency for semi-arid grasslands in northeast China. However, under these novel climatic conditions, potential differences in plant biomass and its allocation among different degraded grasslands remain unclear. Methods: We conducted a mesocosm experiment to test the effects of higher precipitation amount (increased by 50% from the long-term mean) and lower frequency (decreased by 50%) on plant biomass and allocation in the lightly, moderately, and severely degraded grasslands. Results: Lower precipitation frequency promoted belowground biomass but reduced aboveground biomass through enhancing soil water variability. Higher precipitation amount enhanced aboveground biomass in the lightly and moderately degraded grasslands, but not in the severely degraded grassland due to lower soil nitrogen availability. Lower precipitation frequency weakened or ended the positive effects of higher precipitation amount on aboveground and belowground biomass, and higher precipitation amount suppressed the enhancement of lower precipitation frequency on belowground biomass, which could be attributed to temporary waterlogging. Plants in the moderately degraded grassland preferred to adjust root vertical distribution, which was impacted by the changes in plant community composition. However, adjustment of aboveground biomass vs. belowground biomass was the primary biomass allocation strategy in the other two grasslands. Conclusions: Our findings emphasized the importance of considering the degradation level of grasslands when predicting responses of ecosystem functions to the projected changes in precipitation regimes. These findings are critical for making feasible decisions for the sustainable management of degraded grasslands. Legend: + and − indicate positive and negative relationships, respectively LDG, MDG and SDG-lightly degraded, moderately degraded and severely degraded grasslands, respectively DPF-decreased precipitation frequency treatment, IPA-increased precipitation amount treatment SWC and CVSWC-mean and variation of soil water content, respectively SINC-soil inorganic nitrogen content AGB and BGB-aboveground and belowground biomass, respectively fAGB-AGB / total biomass BGB0–10 (%)-belowground biomass proportion in the 0–10 cm soil layer, BGB 0 - 10 / BGB 0 - 30 × 100 RAGB-relative aboveground biomass [ABSTRACT FROM AUTHOR]

Humic acid and arbuscular mycorrhizal fungi (AMF) in mercury (Hg) polluted paddy soil may individually induce changes of microbial community, which is essential to mercury (Hg) resistance. However, little is known regrading the effect of the combination of humic acid and AMF on the microbial community assembly in different rhizospheric zones along the growth stages of rice. In the present study, a pot experiment was conducted by applying humic acid alone (HA) or in combination with AMF (HAAM) to examine the changes in microbial community and mer A/B gene abundance. The results showed that growth stage and amendment of humic acid and AMF had important influence on the richness, diversity, and composition of bacterial and fungal communities. By contrast, a very limited rhizospheric effect on the microbial community richness and diversity was found. Diverse soil properties were responsible for the changes of bacteria, fungi, and AMF, respectively. Dissolved organic carbon (DOC) and redox potential (Eh) strongly affected fungi community, while the shift in bacterial community was mainly attributed to DOC (P < 0.05), pH (P < 0.05), and water-soluble Hg (WHg) (P < 0.05). The HAAM treatment promoted the diversity of AMF (14.0 ± 8.3 of Ace index, 15.6 ± 5.4 of Chao index) benefited from the input of organic carbon and total nitrogen (TN) along with the addition of humic acid and AMF inocula into soils. In addition, the HAAM treatment induced a much higher abundance of mer A (6.19 × 108±2.32 × 108 copy g−1) and mer B (0.52 × 107±0.09 × 107 copy g−1) genes than the HA treatment alone, suggesting the importance of a combined amendment of humic acid and AMF inocula. Our findings demonstrate the regulation of soil microbial community and the improvement of Hg-resistant genes and microbes under the combined application of humic acid and AMF with the objective to the Hg pollution control in the paddy field. [ABSTRACT FROM AUTHOR]

The dry anaerobic co-digestion of LW (livestock waste), OFHW (organic fraction of household waste), and AR (agricultural residue) was evaluated in terms of pH stability, organic removal rate, and methane yield. The total quantity of the solids involved in the digestion was adjusted to 25%. All the reactors were inoculated by 20% (in dry weight) of the municipal sludge. The dynamic changes in the pH values of the LW-AR-OFHW mixture co-digestions underwent four stages and differed from those of wet anaerobic digestion. The decrease in VS (volatile solids), volume, and weight of the LW-AR-OFHW mixtures was higher than those in AR and OFHW. The VS, volume, and weight reductions in LW-AR-OFHW co-digestion were 54.7%, 82.2%, and 72.7%, respectively. However, the VS, volume, and weight reductions in AR were only 11.1%, 20.5%, and 19.8%, respectively, and those in OFHW were only 27.4%, 45.0%, and 40.9%, respectively. The LW-AR-OFHW mixture co-digestions enhanced the methane production of the co-digester (256 m 3 /ton VS), whereas AR and OFHW produced only 12 and 93 m 3 methane/ton VS, respectively. [ABSTRACT FROM AUTHOR]

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 mono- and bimetallic nanocatalysts were synthesized from biomass tar and metal salts by ball milling combined with calcination. The synthesized catalysts were utilized for H 2 O 2 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 H 2 O 2 decomposition rate than monometallic nanocatalysts and among all the catalysts, the bimetal catalyst prepared at 300 °C (FeNi/C-300) showed the highest rate constant (10.55 × 10−3 min−1) for the decomposition of H 2 O 2. 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 °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. Image 1 • Synthesis of tar-based Fenton-like catalyst via green solvent-free method. • The metallic oxides nanoparticles were homogeneously dispersed on the catalyst. • The catalyst particles were covered with defective graphite layers. • Particle size of catalyst can be accurately controlled by the addition of tar. • The defective graphitic layers and NiO promoted the reduction of Fe3+ to Fe2+. [ABSTRACT FROM AUTHOR]

Red mud is a waste generated from the aluminum industry in large quantities. The potential of red mud as a sorbent for beneficial reuse has been the focus of research efforts. However, the limited sorption capacity of red mud has hindered its applications in the removal of environmental pollutants. In this study, the feasibility of heat treatment in improving the sorption of toxic Cd(II) by red mud was investigated in the temperature range of 200–900 °C. Heat treatment at 500 °C resulted in the highest sorption capacity (42.64 mg g−1) and the fastest sorption rate. Further analyses revealed that heat treatment at 500 °C led to significant increases in specific surface area (32.77 m2 g−1), which likely contributed to the enhanced Cd(II) sorption performance. Notably, heat treatment at 500 °C nearly doubled Cd(II) sorption stability as compared with that of raw red mud, as demonstrated by leaching experiments with simulated rainwater. Sequential extraction and XPS analyses indicated that specific sorption was the predominant mechanism involved in Cd(II) removal by red mud heat-treated at 500 °C (RM500). The strength of specific sorption following heat treatment likely contributed to the increase in sorption stability due to the formation of inner-sphere complex (–OCdOH). Metal-metal ion exchange was identified as another sorption mechanism, which, however, likely had only a limited effect on Cd(II) sorption performance. As the final pH (6.57) of the sorption system was typically lower than the pH PZC (about 10.6) of RM500, positive charges would develop on the red mud surface and impede the retention of Cd(II) cations, resulting in weak electrostatic attraction between Cd(II) cations and red mud. In summary, heat treatment at 500 °C considerably enhanced the capacity, rate and stability of Cd(II) sorption by red mud, suggesting red mud could be optimized by heat treatment as a more effective sorbent for Cd(II) removal. These findings represent the first mechanistic characterization of Cd(II) sorption by heat-treated red mud, providing much needed insights into the potential strategies to enhance the effectiveness of red mud in the sorptive removal of toxic heavy metals. Image 1 • Heat treatment at 500 °C improved the sorption performance of Cd(II) by red mud. • Enhanced sorption of Cd(II) by RM500 could be attributed to its increasing specific surface area. • Specific sorption was the predominant mechanism for Cd(II) sorption by RM500. • Metal-metal ion exchange was identified as another sorption mechanism. • Our findings highlight the considerable potential of red mud in heavy metal remediation. [ABSTRACT FROM AUTHOR]

• The pristine hydrochar was modified by H 2 O 2 and ultrasonic synergistic treatment. • The adsorption capacity of modified hydrochar was improved by more than 42 times. • Carboxyl and hydroxyl complexation and cation-π interaction were main mechanisms. • The modified hydrochar can be used as a sustainable adsorbent for water cleaning. A highly efficient modified hydrochar material by H 2 O 2 and ultrasonic synergistic treatment was prepared for Pb2+ removal in aqueous solution. The removal mechanism was investigated by a number of techniques and was provided by quantitative calculation. The maximum adsorption capacity of Pb2+ by the modified hydrochar was calculated to be 92.80 mg g−1 at pH 5.0 and 298 K, which was more than 42 times higher than pristine hydrochar (2.20 mg g−1) and much higher than the other reported modified hydrochar materials. The characterization results showed that H 2 O 2 treatment changed elemental composition, surface charge and increased oxygen-containing functional groups of the hydrochar. The mechanism study indicated that complexation with free carboxyl and hydroxyl and cation-π interaction were main mechanisms responsible for Pb2+ sorption and their corresponding contribution percentage of different mechanisms to the Pb2+ sorption was accounting for 62.12%, 27.14% and 10.74%, respectively. [ABSTRACT FROM AUTHOR]

Due to the current focus of research on ankle rehabilitation robots on structural design, there is still limited research on ankle human–machine interaction technology. In order to enable rehabilitation robots to conduct personalized rehabilitation training based on patients’ ankle movement intentions, we propose a new ankle motion recognition method based on plantar pressure. First, we designed a plantar pressure collection system based on array sensors. Then, we collected nine types of ankle joint motion pressure data from five volunteers and conducted algorithm selection, data processing, and algorithm optimization. Finally, we proposed a small sample optimization algorithm based on support vector machine, with an average recognition rate of 93.16%. The recognition method proposed in this paper can be combined with ankle rehabilitation robots to achieve active rehabilitation functions, laying the foundation for the clinical application of active rehabilitation technology. [ABSTRACT FROM AUTHOR]

Red mud as a waste material is produced in large quantities by the aluminum industry. Heat activation has been used to enhance sorption capacity of red mud for its beneficial reuse as an effective sorbent. In this study, heat-activated red mud (HARM) was investigated for its Cd(II) sorption capacity under various process conditions (Cd concentration, pH and contact time) using response surface methodology (RSM). Analysis with RSM identified pH as the most important process parameter. The positive correlation between higher pH and greater Cd(II) sorption was likely due to: (i) decreased proton competition with Cd(II) for sorption sites at higher pH; (ii) enhanced sorption via ion exchange by monovalent Cd species from hydrolysis at higher pH; and (iii) improved thermodynamics of sorption at higher pH as protons are being released as products. Further analysis indicated the sorption process was thermodynamically favorable with a negative change in Gibbs free energy. Additionally, the sorption process exhibited a positive change in enthalpy, indicative of endothermic nature of sorption; this is consistent with sorption increase at higher temperature. These findings provide needed insight into the mechanisms underlying Cd(II) sorption by HARM for more effective applications of heat-activated red mud as sorbents for Cd(II) removal. [ABSTRACT FROM AUTHOR]

Kitchen waste (KW) composting always has trouble with slow humification process and low humification degree. The objective of this study was to develop potentially efficient solutions to improve the humification of KW composting, accelerate the humus synthesis and produce HS with a high polymerization degree. The impact of Bacillus licheniformis inoculation on the transformation of organic components, humus synthesis, and bacterial metabolic pathways in kitchen waste composting, was investigated. Results revealed that microbial inoculation promoted the degradation of organic constituents, especially readily degradable carbohydrates during the heating phase and lignocellulose fractions during the cooling phase. Inoculation facilitated the production and conversion of polyphenol, reducing sugar, and amino acids, leading to an increase of 20% in the content of humic acid compared to the control. High-throughput sequencing and network analysis indicated inoculation enriched the presence of Bacillus , Lactobacillus , and Streptomyces during the heating phase, while suppressing the abundance of Pseudomonas and Oceanobacillus , enhancing positive microbial interactions. PICRUSt2 analysis suggested inoculation enhanced the metabolism of carbohydrates and amino acids, promoting the polyphenol humification pathway and facilitating the formation of humus. These findings provide insights for optimizing the humification process of kitchen waste composting by microbial inoculation. [Display omitted] • Inoculation promoted organic components degradation to form precursors of humus. • Humus and humic acids of T1 increased by 1.14 and 1.20 times compared to CK. • Inoculation changed bacterial community and enhanced positive interaction. • Microbial metabolism and humification pathway from polyphenols were promoted in T1. [ABSTRACT FROM AUTHOR]

To evaluate the longevity of the iron-activated persulfate (PS) oxidation degradation of 2,4-dinitrotoluene (2,4-DNT), zero-valent iron (ZVI), and three different micron-scale iron oxides were used as catalysts for the activation of PS. It was revealed that 2,4-DNT was degraded more effectively by ZVI and maghemite (γ-Fe2O3) compared to that of hematite (α-Fe2O3) and magnetite (Fe3O4) catalyst treatments. Denitration of 2,4-DNT and oxidation of nitro groups as nitrate occurred by Fe0/PS and γ-Fe2O3/PS. When the 2,4-DNT removal rate was 1%, the generated sulfate concentrations of Fe0/PS and γ-Fe2O3/PS were 2.08 mg/L and 1.27 mg/L, respectively. Only micron scale γ-Fe2O3 could activate PS for 2,4-DNT removal. ZVI was cycled and able to activate PS through multiple rounds. The size of the corrosion products of ZVI was more than 100 nm, and the particle size gradually increased in the cycling process. The first cycle of Fe0 resulted in 45% removal of 2,4-DNT in 360 min. The 2,4-DNT removal efficiency (68.15%) increased after the second cycle, reaching the best removal efficiency in the fourth cycle. Oxidation products formed during degradation covered the ZVI surface, forming a shell. Adsorption of organic pollutants to this shell aids in the removal efficiency of 2,4-DNT and longevity of ZVI in groundwater. [ABSTRACT FROM AUTHOR]

Aims: Terrestrial plants require relative stable stoichiometry of elements for their growth. The effects of plant species and soil phosphorus (P) concentration on P:nutrient stoichiometry in plant remains still unknown. Methods: Soil and plant samples were collected from 88 sites in a P-rich area of a subtropical portion of China to examine the linkage of soil P concentration with the concentrations and stoichiometry of 12 nutrient elements (C, N, P, S, K, Ca, Mg, Fe, Al, Zn, Mn and Na) for different plant species. Results: Soil rich in P increased the concentrations of S, P, K, Ca, Fe, Mg, Mn, Al, and Na in the plants, but induced a strong antagonism to Zn. Meanwhile, the concentrations of C and N in the leaf was restrained when the plants grew in soil under high P concentration. Clustering analysis showed that plant species were categorized according to soil P concentration into P > 2 mg g−1 and P < 2 mg g−1 groups. However, insignificant dissimilarity among plant species was noticed. Conclusions: The stoichiometry of P:nutrient in the plant organs was strongly affected by soil P concentrations and this could reflect soil nutrient status over plant species. Therefore, the difference in soil P concentration is a major driver triggering the variation in elemental stoichiometry. [ABSTRACT FROM AUTHOR]

Increased biogas residue related to the rapid development of anaerobic fermentation has become an urgent environmental problem. The pyrolysis of biogas residue into biochar is one of the most promising treatments. In this study, biochar derived from biogas residue was prepared, and the degradation efficiency of phenol by permanganate (KMnO4) increased from 25.3% to 73.4% in 60 min in the presence of biogas residue biochar (BRB). KMnO4 reacted with BRB to produce intermediate manganese dioxide (MnO2), while BRB was activated. The specific surface area increased by 132.25%, and the oxygen-containing functional groups C=O, C−O, and COOH increased after the reaction. The generated MnO2 complexed with BRB to form MnO2@BRB. The newly formed MnO2@BRB catalyzed KMnO4 to remove phenol, which explains the high removal efficiency of phenol. A significant removal rate was also observed for antibiotics and chlorophenols, which suggested that the KMnO4/BRB system has a relatively high ability to oxidize organic pollutants. In addition, the co-existing metal ions and the natural environment had little influence on the removal efficiency of the KMnO4/BRB system. This work provides a novel technology for the resource utilization of biogas residue and improved organic pollutant removal efficiency of KMnO4 in the presence of BRB. Highlights: Phenol removal was enhanced by permanganate (KMnO4) with biogas residue biochar (BRB). Manganese dioxide (MnO2) was generated and complexed with BRB to catalyze phenol removal by KMnO4. KMnO4/BRB system can be used for the removal of other organic pollutants. [ABSTRACT FROM AUTHOR]

Abstract Co-hydrothermal carbonization (co-HTC) is recognized as a promising pretreatment for upgrading fuel quality of high moisture biomass prior to further thermal conversion. The properties of the hydrochar derived from co-HTC of sewage sludge (SS) and sawdust (SD), and CO 2 gasification characteristics of the hydrochar were investigated. The results showed that the hydrochar had enhanced aromatic degree and increased metals content compared to raw sludge. The hydrochar also exhibited an enhanced gasification reactivity, resulting in high carbon monoxide content in the syngas than that from SS under identical conditions. The temperature and SD/SS mass ratio had a significant influence on the syngas composition mainly by the Boudouard reaction and water gas reaction. The gasification reactivity was strongly associated with the inorganic elements, and the KAlSi 3 O 8 inhibited while the K 2 CO 3 promoted the gasification reaction of hydrochars. Under optimal conditions, a high gasification efficiency of 77.73% was obtained, and the lower heating value of the syngas reached 8.15 MJ/Nm3. This study indicated that co-HTC of SS and SD combined with subsequent gasification had promising potential towards syngas production with high quality. Highlights • The hydrochar from co-HTC of sewage sludge and sawdust was prepared. • Hydrochar had enhanced aromatic degree, metals content and gasification reactivity. • Temperature and sawdust content had a significant influence on syngas composition. • KAlSi 3 O 8 and K 2 CO 3 had competitive effect on CO 2 gasification of the hydrochar. [ABSTRACT FROM AUTHOR]

Multicomponent nickel–iron alloy nanoparticles supported on hydrochar were synthesized by a facile one-step hydrothermal strategy. Spinel nickel ferrite (NiFe2O4) with a small crystalline size around 10 nm was uniformly dispersed on a bimetallic catalyst. The roles of the Ni/Fe doping concentration and calcination temperature in tailoring the phase, morphology and size of the Ni–Fe alloy nanoparticles were investigated. To probe the catalytic abilities of the prepared bimetallic catalysts, a two-stage reaction system was applied for steam gasification of sewage sludge. Compared to monometallic nickel nanoparticles, the synthesized bimetallic catalyst, especially Ni0.25Fe0.25/HC calcined at 700 °C, showed excellent dispersibility of the Ni–Fe alloy NPs and exhibited a strong metal–support interaction, which allowed for better suppression of carbon deposition and nanoparticle agglomeration in the reforming process. The best catalytic performance resulted in a promoted hydrogen selectivity of 113.7 g H2 per kg sludge with a low tar yield of 2.3 mg g−1 under mild gasification conditions. These shape- and size-modulated nanocatalysts harbor promising potential for their application as a highly efficient catalyst for hydrogen production via steam gasification of sewage sludge. [ABSTRACT FROM AUTHOR]

A novel, one-step synthesis strategy is proposed to fabricate γ-Fe 2 O 3 /SBA-15 nanocomposite using triblock copolymer pluronic P123 as a structure directing agent without adding acids. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses suggested that iron was mainly present as γ-Fe 2 O 3 in the composite. Transmission electron microscopy (TEM) measurement showed that this material had highly ordered hexagonal array of uniformed channels and N 2 adsorption-desorption isotherms revealed that the surface area of this material was 983–1049 m 2 /g. Vibrating sample magnetometer (VSM) measurements explained that these materials possess magnetic properties (6.23 emu/g). Batch adsorption experiments showed that low pH was beneficial for arsenic removal by γ-Fe 2 O 3 /SBA-15. The presence of NO 3 − and SO 4 2- had no influence on the uptake of arsenic, however the existence of H 2 PO 4 − and SiO 3 2- showed negative effects on arsenic removal. After five adsorption–desorption cycles, the removal rate of arsenic maintained at larger than 70.5%. The arsenic adsorption was well fitted by a pseudo second-order kinetic model. The isotherm data agrees well with the Langmuir model better than the Freundlich model. This study suggests that γ-Fe 2 O 3 /SBA-15 is promising adsorbent for efficient removal of arsenic from groundwater. [ABSTRACT FROM AUTHOR]

[Display omitted] • The surface mineral structures of biogas residue biochar and its transformance after citric acid modification was firstly detected. • A high-efficiency and stable biogas residue biochar for atrazine adsorption was prepared by citric acid modification. • The internal mechanism was analyzed for the enhanced adsorption of atrazine by citric acid modified biogas residue biochar. Atrazine is a widely used high-risk herbicide. Biogas-residue biochar (BC) is an adsorption material with low cost and great potential; however, its use is limited due to its poor surface properties. An understanding on the adsorption dynamics and mechanisms of the chemical modification of atrazine on biogas-residue biochar is very limited. Here, we examined the adsorption characteristics of atrazine on citric acid-modified BC (CA-BC) by conducting batch adsorption experiments followed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS). The results showed that citric acid modification increased the surface area from 96.60 m2/g to 266.2 m2/g, decreased the pH zpc from 8.79 to 5.64, and effectively enhanced the adsorption capacity of CA-BC from 3.67 ± 0.31 mg g−1 to 5.94 ± 0.07 mg g−1. The adsorption kinetics and isotherm dynamics of atrazine on CA-BC were effectively fitted to the Elovich and Langmuir models, indicating that the adsorption process of CA-BC jointly involved physical and chemical adsorption. The dominant surface mineral of BC was whitlockite magnesian, which was dehydrogenated after modification and caused the development of its pore structure. The peaks corresponding to the oxygen-containing groups (hydroxyl and carboxyl groups) and cyclic structures increased after modification and decreased after adsorption. Based on these results, the adsorption mechanism of atrazine included microporous filling, electrostatic interactions and functional group interactions. Citric acid modification significantly enhanced the rate, maximal capacity, and stability of atrazine adsorption on biogas-residue biochar. Therefore, CA-BC could be considered an environmentally friendly material for controlling atrazine pollution. In general, our study provides a new approach for the high-value utilization of biogas residue and establishes a theoretical basis for improving the adsorption performance of atrazine using biogas residue biochar. [ABSTRACT FROM AUTHOR]

The nitrogen content of municipal sludge is as high as 2.5～9.0 wt%, which has become an important problem in pollution control during pyrolysis. Recycling nitrogen from municipal sludge not only enables resource utilization, but also reduces the nitrogen-related pollution. In this study, the transformation pathways of nitrogen to resource material and typical pollutants during the municipal sludge pyrolysis process were analyzed. The results showed that the nitrogen species in municipal sludge were mainly protein-N (64.41%), pyridine-N (19.47%) and inorganic-N (16.13%). After pyrolysis at 300 °C, the peptide bond of protein-N was gradually broken down, resulting in the formation of three nitrogenous intermediates (amine-N, nitrile-N and heterocyclic-N) were produced. These intermediates can be transformed to NH 3 for resource recovery or to HCN pollutants. Moreover, the full nitrogen transformation pathways of municipal sludge pyrolysis were constructed by the method of Spearman's correlation coefficient and experiment analysis. It was found that NH 3 and HCN were mostly generated from the cracking of three nitrogenous intermediates at 600–800 °C. In addition, there was a prominent effect on the transformation of HCN to NH 3 with co-presence of calcium minerals in raw sludge. By adding inorganic calcium minerals, NH 3 as a recyclable component was prominently improved by 10.30% at 700 °C, while HCN yield was decreased by 53.02% accordingly under the inhibitory effect. The results systematically provided a theoretical support to the possibility of nitrogen recycling for utilization during municipal sludge pyrolysis, as well as to control the transformation of nitrogen elements into pollutants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biogas residue biochar (BRB) was used as an additive in dry anaerobic fermentation. • Methane production and hydrolysis was enhanced by BRB. • Microbial diversity increased by BRB. • Fastidiosipila , Proteiniphilum and Methanosarcina enriched by BRB. Kitchen wastes (KW) dramatically increasing with population and economy enhancing, and dry anaerobic fermentation was used to treat it. However, the large amount of biogas residue severely restricted the application of dry anaerobic fermentation, because the high total solid might lead to the system failure. Therefore, it is urgent to find appropriate way to improve the efficiency of dry anaerobic fermentation and reduce the great amount of biogas residue. In this study, a tentative experiment was conducted to investigate the effect of biochar prepared from biogas residue on the performance of dry anaerobic fermentation system. The results showed that almost half of the biogas residue was reduced and converted into biochar. At the presence of biochar, methane yield was 308.6 mL/gVS, which was 10.5% higher than that of control. Compared to the system without biochar, the highest volatile fatty acid (VFA) concentration was 19.3% higher and the percentage of acetate and valerate was 25.3％ and 12.8％, while it was 16.3% and 22.0% in the control, suggesting that biochar accelerated the degradation of VFA. Bacteria community diversity increased, Fastidiosipila and Proteiniphilum enriched at the presence of biochar, which might accelerate the hydrolysis and acidification of KW. Hydrogenotrophic methanogens was dominated and syntrophic acetate oxidation was the primary pathway to produce methane. This study developed a new recycle route for improving the efficiency of dry anaerobic fermentation while reducing the large amount of biogas residue generated from dry anaerobic fermentation. [ABSTRACT FROM AUTHOR]

Clogging generally happens to the leachate piping system, which poses a risk to the environment. A low surface energy nanocomposite is prepared to mitigate the cloggings, by adding the fluorinated acrylate polymer and hydrophobically modified nano-silica into high-density polyethylene (HDPE) substrate. The best addition of the fluorinated acrylate polymer and the nano-silica is given as 15% and 5%, to produce the composite with a low surface energy of 29.4 mJ/m2. Through the characterization of contact angle (CA), electrochemical corrosion, scanning electron microscopy (SEM) with energy dispersive X-ray spectrometer (EDS), atomic force microscope (AFM) and thermogravimetry (TG), the composite shows low wettability, good corrosion resistance and thermal stability. The surface hydrophobic property of the composite remains unchanged after being immersed in an acidic (pH = 2) and an alkaline (pH = 12) solution, indicating that the prepared composite has strong adaptability to the extreme environments. In addition, the composite shows better anti-scaling performance than that of the commercial high-density polyethylene (HDPE) and polyvinyl chloride (PVC) pipe materials by application of a dispensing leachate immersion test. The results provide insights into engineering practice for the design and manufacture of pipe materials for leachate collection and transport. • A low surface energy fluorinated acrylate copolymer with short perfluoroalkyl groups is prepared by bulk polymerization. • An organic/inorganic cross-linked HDPE/PFA/SiO2 composite is fabricated. • The anti-scaling performance of the composite is better than that of the typical commercial HDPE and PVC pipes. • The composite has good thermal stability, abrasion resistance, and acid-alkali resistance. • The composite has application potentials in pipe design and manufacture. [ABSTRACT FROM AUTHOR]

• Precipitation events trigger the pulse N 2 O emissions. • All sizes of precipitation events significantly increase cumulative N 2 O emissions. • Cumulative N 2 O emission after precipitation events parabolically varied with precipitation event sizes. • N addition amplifies the response of cumulative N 2 O emissions to precipitation events. • Precipitation event size plus long-term N addition led to substantial differences in N 2 O emissions. Precipitation events and nitrogen (N) addition play important roles in regulating nitrous oxide (N 2 O) emissions in semi-arid grassland ecosystems. The effects of precipitation events, long-term N addition, and their interaction on N 2 O emissions, however, remain largely unclear. We conducted a mesocosm experiment to examine how long-term N addition (0 and 10 g N m−2 yr−1, from 2011 to 2020) affects N 2 O emission responses to a gradient of manipulated precipitation events (0, 5, 10, 20, and 50 mm). The precipitation events had pulsing effects on N 2 O emissions due to the stimulation of microbial activity and substrate availability. Precipitation events significantly parabolically increased cumulative N 2 O emissions. Long-term N addition substantially enhanced cumulative N 2 O emissions response to precipitation events. The precipitation events and long-term N addition synergistically improved cumulative N 2 O emissions. The water-filled pore space and ammonium nitrogen content were the most important factors driving the temporal dynamics and accumulation of N 2 O emissions following the precipitation events and long-term N addition. Our study indicates that N addition affects the N 2 O emissions responses to precipitation events, which are essential for understanding the response of N 2 O emissions to global change. [ABSTRACT FROM AUTHOR]

Zero valent iron (Fe0) can reduce Cr(VI) in water, where Fe0 and Fe(Ⅱ) are possible electron donors, but passivation and aggregation easily occur to Fe0. To improve the performance of Fe0, a new hybridization strategy of Fe/Cu bimetal and silica-based mesoporous molecular sieve MCM-41 for the removal of Cr(VI) from water has been proposed. The results show that the two-dimensional mesoporous structure of MCM-41 can provide skeleton support for Fe0, improve the mass transfer rate, and overcome the aggregation bottleneck of Fe0. The Cr(VI) removal rate reached 98.98% (pH = 2) after 40 min. The analytical results revealed Cr(VI) removal process: Cr(VI) adsorbed onto Fe/Cu-MCM-41 by electrostatic attraction and other molecular inter-atomic forces. The second metal, Cu, can inhibit the passivation of Fe0 and promote Fe(Ⅱ)through the formation of Fe/Cu battery, thereby promoting the electron transfer. The resulting Cr(Ⅲ) is precipitated as FeCr 2 O 4 and Cr x Fe 1−x (OH) 3. [Display omitted] • Nano bimetallic Fe/Cu-loaded mesoporous silica Fe/Cu-MCM-41 was synthesized. • Cu acts as catalytic metal could provide active sites for electron transfer. • pH has been found to be an important factor affecting the removal rate of Cr(VI). • Bimetallic-nanomaterial supported system can reduce passivation. [ABSTRACT FROM AUTHOR]

Antibiotics are emerging pollutants and increasingly present in aquaculture and industrial wastewater. Due to their impact on the environment and health, their removal has recently become a significant concern. In this investigation, we synthesized nano zero-valent iron-loaded magnetic mesoporous silica (Fe-MCM-41-A) via precipitation and applied the adsorption of oxytetracycline (OTC) from an aqueous solution. The effects of competing ions such as Na+, Ca2+ and Cu2+ on the adsorption process under different pH conditions were studied in depth to providing a theoretical basis for the application of nanomaterials. The characterization of the obtained material through transmission electron microscopy demonstrates that the adsorbent possesses hexagonal channels, which facilitate mass transfer during adsorption. The loaded zero-valent iron made the magnetic, and was thus separated under an applied magnetic field. The adsorption of OTC onto Fe-MCM-41-A is rapid and obeys the pseudo-second-order kinetic model, and the maximum adsorption capacity of OTC is 625.90 mg g−1. The reaction between OTC and Fe-MCM-41-A was inner complexation and was less affected by the Na+. The effect of Ca2+ on the adsorption was small under acidic and neutral conditions. However, the promotion effect of Ca2+ increased by the increase of pH. Cu2+ decreased the removal efficiencies continuously and the inhibitory effects decrease varied with the increase of pH. We propose that surface complexing, ion-exchange, cationic π-bonding, hydrogen bonding, and hydrophobicity are responsible for the adsorption of OTC onto Fe-MCM-41-A. [ABSTRACT FROM AUTHOR]

• LMW DOM was gradually transformed into HMW DOM during composting. • Core microorganisms associated with DOM transformation were identified. • Chemoheterotrophy was the major function of microorganisms during composting. • T, moisture and pH were key physicochemical factors affecting DOM stabilization. Transformation of DOM fractions with different molecular weights during composting of chicken manure (CM), garden waste (GW) and municipal solid waste (MSW) was evaluated in this study. The results revealed that DOM concentrations decreased by 49.8%, 53.9% and 86.4% during CM, GW and MSW composting, respectively. Meanwhile, low molecular weight (<650 Da) DOM was visibly transformed into high molecular weight (>10 kDa) DOM for enhancing their stability during composting. Core microorganisms promoting DOM stabilization were identified by network analysis, such as Prosthecobacter , Paenalcaligenes and Solibacillus. In addition, DOM composition was also related to the relative abundance of microbial metabolic function, such as chemoheterotrophy and aerobic chemoheterotrophy. Moreover, temperature, moisture and pH were identified as the key physicochemical factors affecting the DOM stabilization mediated by core microorganisms during composting. These above findings are helpful to regulate the DOM stabilization during composting and improve the quality of final composts. [ABSTRACT FROM AUTHOR]

• Adding amino acids promote humification process of lignocellulosic composting. • Assess the degradation and transformation of organic components during composting. • Reveal mechanism of organic components transformation with amino acids addition. • Propose a regulation method for improving carbon sequestration of lignocellulose. The aim of this study is to assess the effectiveness of protein-like precursors addition on promoting humification process during lignocellulose-like biomass composting through adding amino acids to compost. The humification indexes of R1 and R2 was significantly higher than that of CK (P < 0.05). The decreasing ratio of Maillard precursor concentration of R2 and R1 was higher than CK. Amino acids addition affected the bacteria community and environmental factors during composting. Variance partitioning analysis showed that humification process was strengthened with environmental factors, bacteria community, Maillard precursors. Structural equation model (SEM) analysis showed that amino acids had substantial impact on promoting humic acid (HA) formation. The combined application of protein-like wastes and lignocellulose-like wastes was suggested to improve carbon sequestration. This study lays a foundation for economically and effectively managing different types of straws by composting. [ABSTRACT FROM AUTHOR]

Irrigation with treated wastewater (TWW) has become a prevailing agricultural practice due to the scarcity of fresh water resources, which may have a significant impact on the microbial communities that are critical to many biogeochemical processes in soils. However, it is unclear whether there are links between soil microbial responses to long-term irrigation with different sources of wastewater and soil depth. Here we assess the influence of treated domestic (DTWW), leather industry (LTWW) and pharmaceutical (PTWW) wastewater on microbial communities in vertical soil profiles using high-throughput sequencing based on 16S rRNA and internal transcribed spacer (ITS) gene profiling. We found that microbial α-diversity in the vertical profiles of soils was significantly influenced by TWW irrigation. Bacteria and fungi in different soil depths showed distinct responses to TWW; irrigation with TWW markedly increased abundance of bacterial OTUs and inhibited abundance of fungal OTUs. β-diversity analysis showed that the effect of TWW irrigation on microbial communities was greater than the effect of soil depth, and microbes in subsurface soil were more sensitive to different sources of irrigation water. We also found that, based on β-diversity analysis, irrigation with treated industrial wastewater, including LTWW and PTWW, had a greater impact on microbial community structures than DTWW. TWW irrigation significantly affected the composition of indigenous soil microbial communities at different depths and might introduce exogenous microbes into the soil environment. Our work explicitly demonstrates the vertical responses of bacterial and fungal communities in soils to irrigation with TWW from different sources, which can provides insights into the microbial-dominated geochemical processes from the perspective of the entire soil profile under the context of wastewater irrigation. Unlabelled Image • Significant effect of treated wastewater (TWW) on microbial diversity, community structure and composition. • TWW exerted positive impact on bacterial abundance of OTUs and negative impact on fungal abundance of OTUs. • Microbial community structures were more markedly affected by industrial TWW irrigations than domestic TWW irrigation. • Effects of TWW irrigation on microbial communities were greater than that caused by soil depth. [ABSTRACT FROM AUTHOR]

• The microbial community dynamics could affect the phytoavailability of heavy metals. • The organic function group could affect bioaccessibility of heavy metals. • The phytoavailability of heavy metal of key factor is the total N, total C and NO 3 −-N. Municipal sludge compost contains residual heavy metals (HMs), which could limit the utilization of compost as a resource. Studies have revealed that the availabilities of HMs in composting system are affected by microbial-driven organic matter and physicochemical indices. However, how the microbial community dynamics affect the availability of HMs during municipal sludge composting remains unclear. In this study, high-throughput sequencing technology was applied to investigate the response relationship between microbial dynamics and different availability of HMs. A total of 31 main genera within 5 phyla were identified. The concentrations of the most available HMs increased, and the increasing rates varied from 102% to 240%. Proteobacteria, Firmicutes, and Chloroflexi could affect organic matter to control the phytoavailability of Cr and Pb, whereas Proteobacteria, Bacteroidetes, and Actinobacteria could affect the phytoavailability of Cu and Zn. The bioaccessible HMs are only affected by organic functional groups, whereas the leachable HMs are not affected by organic matter or microorganisms. The "physicochemical index-microorganisms-available heavy metal" response pathway and principal component analysis showed that the increase in total C and N and the decreasing content of NO 3 −–N reduce the phytoavailable HMs. We finally proposed a regulation method to improve the resource utilization of municipal sludge composting and provide theoretical support for the harmlessness of municipal sludge composting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Existence of PLA decreased the relative abundance of Bacillus at mesophilic phase. • PLA granule in composting negatively affected seed germination. • PLA degradation could stimulate core genes related to lactide metabolism. • PLA interfered TCA cycle especially at thermophilic and mature phases. The aim of this study was to assess the effect of polylactic acid (PLA) on microbial community composition and core metabolism pathways in food waste (FW) composting. The presence of PLA negatively influenced microbial community richness and decreased respectively the abundance of Bacillus , Halocella and Cellvibrio at mesophilic, thermophilic and mature phases. Analysis of microbial metabolism at the gene level help to understand the mechanism in co-composting with FW and PLA. The expression of core functional genes related to lactide metabolism was stimulated by PLA degradation at thermophilic and mature phases. The sum of absolute abundance of functional genes that involved in first and second carbon oxidation of tricarboxylic acid cycle was decreased due to the existence of PLA. The transformation between 2-Oxoglutarate and Succinyl-CoA were interfered in thermophilic phase, which might result in the lower germination index in PLA group (115%) than that in control (186%). [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe0@NC-0.8–0.6–800 featured high reusability, stability and adaptability. • Fe0@NC-0.8–0.6–800 could effectively treat real groundwater contamination. • N-doped defects improved PS activation through non-radical pathways. • Contribution to four removal paths was studied by quenching and EPR. • Possible Ph degradation pathways in the Fe0@NC-0.8–0.6–800 system was proposed. Zero valent iron (Fe0)-based biochar prepared using Fe salts as the Fe source has low yield and is readily oxidized, which limit its practical applications. In this study, a Tangyuan-like structure N-doped C shell Fe0 composite (Fe0@NC-0.8–0.6–800) was prepared via a "hydrothermal coating-pyrolysis reduction" strategy using glucose, ferroferric oxide (Fe 3 O 4), and urea as raw materials to activate persulfate (PS) for organic contaminant degradation. The results revealed that Fe0@NC-0.8–0.6–800, prepared by pyrolyzing 0.8 g Fe 3 O 4 and 0.6 g urea at 800 °C, removed 100% phenol within 20 min with 0.204 min−1 reaction rate constant (k obs), which was 2.4 times higher than that of Fe0@C-0.8–0-800 without N-doping (0.0866 min−1). The primary Fe0@NC-0.8–0.6–800 facilitation mechanisms include enhanced adsorption capacity, increased number of active sites on the C surface, electron transfer, and Fe2+ regeneration. Moreover, the synergistic effect between Fe0 and N defects (graphitic N and pyridinic N) in Fe0@NC-0.8–0.6–800 is the main reason for promoting non-radical pathway (1O 2) generation. Based on the intermediates detected, five possible phenol degradation pathways were identified. The toxicity of phenol and degradation byproducts was evaluated by ECOSAR program. Through recycling experiments, and application in real groundwater, Fe0@NC-0.8–0.6–800 was found to show promising potential and offers a new strategy for treating organic matter-contaminated groundwater. [ABSTRACT FROM AUTHOR]

Abstract High humidity and potential threat of pathogen of anaerobic digestates are unfavorable to the environment by direct utilization. To achieve the sustainable utilization of digestates, composting might be a good choice. Meanwhile, the aeration rate of composting has been optimized. Co-composting of digestates and chicken manure was performed under different aeration conditions (0.05, 0.1 and 0.15 L·min−1·kg−1·organic matter (OM)). During composting, internal transformation of humic substance (HS) has been studied for obtaining the potential application value of the co-composting products. Results suggested that the HS concentration was increased by 21.1%, 26.4% and 22.4% with the aeration rates were 0.05, 0.1 and 0.15 L·min−1·kg−1·OM, respectively. The aeration rate of 0.15 L·min−1·kg−1·OM was more conducive to germination. Parallel factor analysis and dimensional correlation spectra (2DCOS) have been combined to reveal the conversion relationships of HS components for understanding the compost application pattern. Hetero-2DCOS indicated that aeration of 0.05 min−1·kg−1·OM and 0.1 L·min−1·kg−1·OM contributed to the formation of complex compounds at long wavelength, and aeration of 0.15 L·min−1·kg−1·OM was beneficial for labile compounds formation at short wavelength. In views of the aeration of 0.1 L·min−1·kg−1·OM was more beneficial to improve HS concentration than 0.05 L·min−1·kg−1·OM, 0.1 L·min−1·kg−1·OM and 0.15 L·min−1·kg−1·OM were consider as the most important aeration rate to conduct digestates composting. Overall, the aeration affected the HS composition which, in turn, might affect the application ways of composting products. This study could provide a reference for industrial composting production and applications. Graphical abstract Unlabelled Image Highlights • Difference in ventilation affects humic substance (HS) structure during composting. • Lower ventilation contributes to complex compounds accumulation. • Higher ventilation promotes labile compounds formation. • Appropriate land use pattern can be selected based on the structure feature of HS. • Composting significantly improves the economic value of digestates. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe-AnGS was prepared by a biologically induced mineralization method. • The effect of Fe-AnGS on performance and microbial community was studied. • Genes abundance for carbon dioxide reduction pathway increased by 29.40-43.54 %. • Inoculation of Fe-AnGS in MEC with glucose improved TMP CE by 11.83–29.30 %. • Fe-AnGS inoculation was an efficient strategy to establish and enhance DIET pathway. The magnetite nanoparticle-anaerobic granular sludge complex (Fe-AnGS) was formed by a biologically induced mineralization method, then applied in microbial electrolysis cells (MEC) to enhance the direct interspecies electron transfer (DIET) pathway via selective enriched electrogenic microorganisms for biogas production. Results showed with the highest Fe loading amount of 325.03 ± 8.40 mg/gVS, the magnetization and conductivity of Fe-AnGS were improved by 30.94 % and 29.16 %, respectively. The MEC with Fe-AnGS enriched the specific electrogenic microorganisms in the anode and cathode chambers. Simultaneously, genes coding for carbon dioxide reduction [M00567] increased by 29.40–43.54 % and 34.29–43.43 %, respectively. Inoculation of Fe-AnGS in MEC with glucose as substrate enhanced the experimental methane production of the cathode chambers (EMP C), and theoretical methane production of the cathode chamber (TMP CE) by 8.00–14.10 %, and 11.83–29.30 %, respectively. Consequently, inoculation of Fe-AnGS in MEC could establish and enhance the DIET pathway for methane production. [ABSTRACT FROM AUTHOR]

Enriched phosphate-solubilizing bacteria (PSB) agent were acquired by domesticated cultivation, and inoculated into kitchen waste composting in different stages. The effect of different treatments on organic acids production, tricalcium phosphate (TCP) solubilization and their relationship with bacterial community were investigated during composting. Our results pointed out that inoculation affected pH, total acidity and the production of oxalic, lactic, citric, succinic, acetic and formic acids. We also found a strong advantage in the solubilization of TCP and phosphorus (P) availability for PSB inoculation especially in the cooling stage. Redundancy analysis and structural equation models demonstrated inoculation by different methods changed the correlation of the bacterial community composition with P fractions as well as organic acids, and strengthened the cooperative function related to P transformation among species during composting. Finally, we proposed a possible mechanism of P solubilization with enriched PSB inoculation, which was induced by bacterial community and organic acids production. [ABSTRACT FROM AUTHOR]

The aim of this work was to identify the factors which can affect humic substance (HS) formation. Composting periods, HS precursors, bacteria communities and environment factors were recognized as the key factors and few studies explored the potential relationships among them. During composting, HS precursors were mainly formed in the heating and thermophilic phases, but HS were polymerized in the cooling and mature phases. Moreover, bacterial species showed similar classification of community structure in the same composting period of different materials. Furthermore, structural equation model showed that NH 4 − -N and NO 3 − -N were the indirect environmental factors for regulating HS formation by the bacteria and precursors as the indirect and direct driver, respectively. Therefore, both environmental factors and HS precursors can be the regulating factors to promote HS formation. Given that, a new staging regulating method had been proposed to improve the amount of HS during different materials composting. [ABSTRACT FROM AUTHOR]

The treatment of biogas residue with complex composition from anaerobic bog has gradually become a challenge for energy utilization of solid waste. However, biogas residue rich in cellulose hemicellulose and lignin can be employed to prepare biochar. In this study, biogas residue biochar (HBC800) activated persulfate(PS) was prepared by a two-step method of 800 ℃ calcination and acid modification, which has the characteristics of large specific surface area, rich functional groups. HBC800 had excellent activated PS degradation efficiency of phenol (91.6 %). The effect of common ions was weak and showed good environmental adaptability in groundwater on phenol degradation. Electron Paramagnetic Resonance (EPR) and quenching tests were employed to find that electron transfer and singlet oxygen (1O 2) were the main mechanisms for phenol degradation in the HBC800/PS system. This result is mainly attributed to the important role played by surface oxygen-containing functional groups, defects and graphite nitrogen as active sites. HBC800 has good recycling efficiency and practical ability to treat coking wastewater. This study provides an alternative to biogas residue biochar utilization and better support for the closed-loop utilization of agroforestry waste resource. [Display omitted] • HBC800 was prepared by a two-step method of 800 ℃ calcination and acid modification. • HBC800 had excellent activated PS degradation efficiency of phenol. • The presence of phenol was more favorable for singlet oxygen generation in the HBC800/PS. • This work provides an alternative to the closed-loop utilization of agroforestry waste. [ABSTRACT FROM AUTHOR]

The reactivity of potassium persulfate (PP) in the degradation of 2,4-dinitrotoluene (2,4-DNT), with when iron and carbon as activators, is investigated. Effects of pH, persulfate concentration, and ionic strength on the degradation efficiency of 2,4-DNT by persulfate are studied in batch experiments, with simulated groundwater environmental conditions of no light, neutral pH and low temperatures (15 °C). The degradation of 2,4-DNT heightens and follows the pseudo-first-order kinetic model in the system comprising Fe/AC and S 2 O 8 2− . Addition of activated carbon (AC) increases the release of Fe 2+ to activate PP. When the concentration of persulfate is 100 mg/L, the 2,4-DNT degradation is the best at an initial pH of 2. The 2,4-DNT removal efficiency increases in the order of pH 2 > pH 9 > pH 3 > pH 5 > pH 11 > pH 7 in the Fe/AC + PP system. 2,4-DNT degradation in the presence of Cl − is slower in the first 100 min, but there is no obvious difference in degradation efficiency further on. This is most likely due to persulfate activation and Fe/AC reduction in this system. Meanwhile, the presence of bicarbonate ions inhibits the degradation of 2,4-DNT. A possible mechanism is proposed based on the reasons for the degradation of 2,4-DNT in the Fe/AC + PP system. Iron–carbon micro-electrolysis promotes micronmeter-sized iron to generate Fe 2+ . This study provides the design for an advanced, refractory organic matter-based oxidation technique for improved groundwater pollution remediation. [ABSTRACT FROM AUTHOR]

The aim of this work was to put forward a method to improve HS amount by studying the formation regularity of HS. Five precursors have been detected and few researches combined them with bacteria to study HS formation. During composting, the polyphenols, carboxyl and amino acids concentration decreased by 75.8%, 63.2% and 68.3% on average, respectively. However, the polysaccharides, reducing sugars and HS concentration increased by 61.2%, 47.1% and 37.33% on average. Relationships between precursors and HS concentration showed that the HS formation were significantly affected ( p < 0.05). The key bacteria community and physical–chemical parameters which affected HS formation have also been identified by redundancy analysis. Twelve key bacteria communities have been selected, which were significantly affected by physical–chemical parameters ( p < 0.05). Accordingly, we proposed an adjusting method to promote HS amount during composting based on the relationship between the key bacteria communities and the precursors as well as physical–chemical parameters. [ABSTRACT FROM AUTHOR]

Humic acids (HAs) coupled with humic-reducing microorganisms (HRMs) can facilitate contaminants reduction. Molecular-weight (MW) of HA governs the chemical and HRMs behavior. However, MW of HAs with chemical characteristics linking to HRMs in different wastes composting have never been investigated. Results from the HPSEC-UV analysis showed that composting significantly increased weight-average molecular weight (M w) of HA with a broad range from 675 Da to 27983 Da, and governing heterogeneous chemical characteristics. In proteinaceous composts, MW< 4000 Da of HAs were greatly related to alkyl and carbonyl, while MW> 20000 Da of HAs were presented by oxygen–nitrogenous functional groups, methyl, and alkyl groups. For cellulosic composts, MW< 1500 Da and 4000–10000 Da of HAs were characterized by aliphatic ethers and aromatic groups. MW> 20000 Da of HAs were constructed by phenols, methoxy and nitrogen functional groups. In lignocellulosic composts, MW> 20000 Da of HAs were only characterized by aromatic groups. Furthermore, seven groups of HRMs adapted to the heterogeneous chemical characteristics within HAs ranked by MW were recognized. Consequently, the possible routes that composting properties response to the connections of HRMs-chemical structures-MW of HAs in proteinaceous, cellulosic and lignocellulosic composts were constructed, respectively. Our results can help to develop the fine classification-oriented approach for recycling utilization of organic wastes. [Display omitted] • Composting significantly increased Mw of HA with a broad range from 675 Da to 27982 Da. • MW governed their unique chemical structures within HAs in different composts. • Seven groups of HRMs were identified linking to the ranked MW of HA. • Composting properties-key HRMs-chemical structures with MW of HAs were constructed.a [ABSTRACT FROM AUTHOR]

In this study, PCR-DGGE method was applied to investigate the impact of multi-stage inoculation treatment on the community composition of bacterial and fungal during municipal solid wastes (MSW) composting process. The results showed that the high temperature period was extended by the multi-stage inoculation treatment, 1 day longer than initial-stage inoculation treatment, and 5 days longer than non-inoculation treatment. The temperature of the secondary fermentation increased to 51 °C with multi-stage inoculation treatment. The multi-stage inoculation method improved the community diversity of bacteria and fungi that the diversity indexes reached the maximum on the 17 days and 20 days respectively, avoided the competition between inoculations and indigenous microbes, and enhanced the growth of dominant microorganisms. The DNA sequence indicated that various kinds of uncultured microorganisms with determined ratios were detected, which were dominant microbes during the whole fermentation process. These findings call for further researches of compost microbial cultivation technology. [ABSTRACT FROM AUTHOR]

Converting sewage sludge (SS) into biochar via pyrolysis is proposed as a prospective strategy for recycling nutrients and reducing environmental risks. Yet, from the perspective of carbon (C) balance the viability of pyrolyzing SS still remains unclear. Here we quantified the C footprint of the whole process from raw SS pyrolysis to final disposal of SS-derived biochar (SSB) using life cycle assessment based on a 20-tonne industrial pyrolysis furnace and field experiments. Results indicated that about 0.101 tonnes of direct CO 2 equivalent (CO 2e) (from N-containing organic compounds in SS) plus 1.506 tonnes of indirect CO 2e (from energy consumption and dewatering agents) were emitted for each tonne of dry SS treated during its dewatering and pyrolysis processes, and at least 0.252 tonnes of CO 2e were sequestered as stable C in SSB, depending on the final application route of SSB. In contrast, the net C emissions from traditional SS treatments amounted to at least 2.432 tonnes of CO 2e per tonne of dry SS under the similar scenarios. Converting SS into SSB thus showed great advantages in C balance over the traditional treatments of SS. Sensitivity analyses indicated that the moisture and C contents of SS and the usage of dewatering agents were the key factors affecting C balance in the SSB-to-soil system. These findings highlight the C sequestration potential of pyrolysis and provide important support for the optimization and management of SS treatment. [Display omitted] • Carbon balance in the whole life cycle of sewage sludge biochar (SSB) was assessed. • Pyrolysis has great advantages in C balance over traditional sewage sludge treatments. • Key factors affecting carbon balance for SSB were discussed using sensitivity analysis. • Sewage sludge dewatering process constitutes the largest C emissions in the system. [ABSTRACT FROM AUTHOR]

Anaerobic co-digestion (A co-D) performance of Phragmites australis , feces and kitchen waste with addition of clinoptilolite (one main kind of zeolite) was investigated to evaluate the improvement of biogas/methane production and internal mechanism of nitrogen and organics control. A better biogas/methane production was observed by 10% clinoptilolite (v/v) than bentonite and diatomite, with the shortest lag phase of 0.070 d −1 , the max rate of 15.89 L/(kg VS day) and ultimate biogas production of 308.2 L/kg VS as the modified Gompertz equation predicted. Accordingly, the content of methane in the biogas was increased from 44.10% to 65.30%. Furthermore, the clinoptilolite inhibited the acidification of digestion liquid (optimum pH 7.0–7.5) and enhanced the VFAs (acetic acid, propionic acid and butyric acid) destruction. Moreover, 10% of clinoptilolite optimally enhanced the microbial utilization of Ca 2+ /Mg 2+ , controlled the C/N ratio, and improved the biogas production as well as NH 3 -N/NO 3 -N inhibition efficiency. [ABSTRACT FROM AUTHOR]

Nanofiltration (NF) membrane configuration for fluoride and arsenic removal from groundwater has a key role in controlling operation performances and membrane fouling. Some bench-scale contrast experiments using commercial NF membranes were done to obtain the optimum arrangement performances. The NF membrane arrays included one-stage, two-stage, and three-stage systems. The NF membrane surface was negatively charged above its isoelectric point (approximately at pH 5.9–6.4). Accordingly, the raw groundwater was initially adjusted to a neutral or alkaline pH to enhance the effect of electrical charge repulsion and improve the ion removal efficiencies by NF. The encouraging results indicated that a membrane in a parallel-linear arrangement with staging 2:1 was the preferable arrangement to remove fluoride and arsenic from low-salinity groundwater in rural areas of China. With this optimal arrangement, the NF system obtained fluoride and arsenic removal efficiencies of 70˜73% and 92˜94% respectively, a preferable permeate flux of 73.37 L h−1m2and acceptable water flux recovery rate of 65% at 16°C. This optimal arrangement can further limit the potential membrane fouling by lowering the interstage Reynolds number. Moreover, the water product cost was lowest by the NF system with this optimal arrangement. [ABSTRACT FROM AUTHOR]

Low transparency of the wastewater as one of the limitations weakens photocatalyst activity. Herein, a self-floating melamine foam/polyaniline (PANI)/N,O,P-containing covalent organic polymer (MF/PANI/NOP–COP) photocatalyst was successfully synthesized to achieve in-situ H 2 O 2 production and boost Fe(Ⅱ)/Fe(Ⅲ) cycle, exhibiting a strong catalytic activity for treating high chroma wastewater. Compared with the PANI/NOP–COP powder, the Rhodamine B degradation and mineralization efficiencies were enhanced by 3.5 and 6.6 times in the presence of the self-floating MF/PANI/NOP–COP, respectively. The enhanced catalytic activity was derived from the satisfied visible light harvest performance (4.8%) and the high surface charge injection efficiency (96.4%) in the high chroma environment. Meanwhile, 179 ± 29.5 μM H 2 O 2 was generated and the stabilized Fe(Ⅱ) concentration was increased from 0.21 mM to 0.45 mM, reducing the additive dosages of Fe(Ⅱ) and H 2 O 2. Moreover, the self-floating MF/PANI/NOP–COP exhibited an easy-to-recycle property and a broadened range of pH application (2–6). The high-efficiency degradation performance was owing to the sustainable generation of •OH at the Fenton/photocatalysis dual reaction activity centres in the photocatalysis-self-Fenton system. [Display omitted] • A self-floating MF/PANI/NOP–COP photocatalyst is synthesized for treating high chroma wastewater. • The H 2 O 2 production and Fe(Ⅱ)/Fe(Ⅲ) cycle processes are boosted by MF/PANI/NOP–COP. • Dual reaction activity centres are constructed to maintain good degradation performances. [ABSTRACT FROM AUTHOR]

• Decreased precipitation frequency suppressed nematode abundance, especially for bacterivores. • Nematode community structure was not affected by the altered precipitation frequency. • Responses of nematodes to the altered precipitation were divergent in different degraded grasslands. Rainfall patterns in arid and semi-arid regions are characterized by a reduction in rainfall frequency. However, under this novel climatic condition, potential changes in soil nematode community among different degraded grasslands remain unclear. We conducted a mesocosm experiment to test the effects of lower precipitation frequency (decreased by 50% from the long-term mean) on nematodes in the lightly degraded (LDG), moderately degraded (MDG) and severely degraded grasslands (SDG). The decreased precipitation frequency treatment significantly reduced the total abundance of nematodes by reducing soil moisture and enhancing moisture variability. Compared with other trophic groups of nematode, bacterivores were more sensitive to the altered precipitation and were significantly suppressed by higher soil moisture variation caused by lower precipitation frequency in the degraded grasslands. The decreased precipitation frequency treatment promoted plant belowground biomass through increasing soil moisture variation, which promoted plant parasites in LDG. However, in MDG and SDG, plant parasites were mainly suppressed by higher soil moisture variation under the altered precipitation frequency treatment, and were less impacted by the aforementioned stimulation in plant belowground biomass. The nematode community structure was not affected by the altered precipitation frequency treatment. This study provides experimental data for predicting responses of ecosystem functions to the projected changes in precipitation regimes. These findings are critical for making feasible decisions for the sustainable management of degraded grasslands. [ABSTRACT FROM AUTHOR]

Scaling commonly occurs at pipe wall during landfill leachate collection and transportation, which may give rise to pipe rupture, thus posing harm to public health and environment. To prevent scaling, this study prepared a low surface energy nanocomposite by incorporating silicone-acrylate polymer and hydrophobically modified nano-SiO2 into the high-density polyethylene (HDPE) substrate. Through the characterization of contact angle, scanning electron microscopy and thermogravimetry, the results showed that the prepared composite has low wettability and surface free energy, excellent thermal stability and acid-base resistance. In addition, the prepared composite was compared with the commercial HDPE pipe material regarding their performance on anti-scaling by using an immersion test that places their samples into a simulated landfill leachate. It was apparent that the prepared composite shows better scaling resistance. The study further expects to provide insight into pipe materials design and manufacture, thus to improve landfill leachate collection and transportation. [ABSTRACT FROM AUTHOR]

In this study, Ni nanoparticles supported on renewable porous carbon were prepared using hydrochar as a carbon precursor via in situ formation and self-reduction. The structure properties of the prepared nanocatalysts were characterized by multiple techniques, including XRD, SEM, and HR-TEM, and the dry reforming of methane (DRM) performance of the nanocatalysts in terms of conversion efficiency and reactivity stability was evaluated. The results revealed that the Ni2+ was uniformly anchored on the surface of the hydrochar, and subsequently the Ni nanoparticles were well dispersed in the composite with a diameter of less than 8 nm and had a narrow particle size distribution at a temperature lower than 800 °C. With an increased temperature from 800 to 900 °C, the significant sintering and agglomeration of nickel particles and the transformation from amorphous carbon to graphitic structure were observed in the composite. The nanocatalysts prepared at a temperature of 700 °C (Ni@C-700) and 800 °C (Ni@C-800) exhibited a high reforming conversion rate and catalytic stability of CH4 by CO2 (around 52% for Ni@C-700 and 70% for Ni@C-800 after 800 min of run-time, respectively). As for the composite obtained at 900 (Ni@C-900), the highly graphitic degree was coupled with the significantly increased nickel particle size, and this resulted in a remarkably decreased conversion efficiency. The present study offers a valuable application of the hydrochar and a facile and green approach to prepare highly active and cost-efficient Ni nanoparticles on porous carbons towards the dry reforming of methane. [ABSTRACT FROM AUTHOR]

• MnO 2 facilitated humin formation, especially in lignocellulose-rich materials. • Degradation of organic components was accelerated by the addition of MnO 2. • The formation mechanism of humin was identified. • The role of MnO 2 in the formation of humin content was identified. The study aims to accelerate the formation of humin (HM) with the addition MnO 2 to achieve carbon sequestration during different material composting. The results indicated that the addition of MnO 2 could improve the concentration of HM by increasing of the content in functional groups during corn straw (CS) and chicken manure (CM) composting. With the addition of MnO 2 , non-aromatic functional groups were responsible for the increase of the HM concentration in CM, while aromatic functional groups were dominating for CS. Although the formation mechanism of HM varied significantly across different materials, the MnO 2 promoted more abundant functional groups to participate the formation of recalcitrant fluorescence components in CS and CM. In addition, the aromatization of HM structure was improved by adding the MnO 2. Therefore, the addition of MnO 2 not only increase carbon sequestration but also increase the compost product resilience during the decompose of agricultural organic wastes. [ABSTRACT FROM AUTHOR]