Resource utilization of MSWI fly ash supporting TiO2/BiOCl nanocomposite for enhanced photocatalytic degradation of sodium isopropyl xanthate: Mechanism and performance evaluation.

The removal of organic pollutants in water environments and the resource utilization of solid waste are two pressing issues around the world. Facing the increasing pollution induced by discharge of mining effluents containing sodium isopropyl xanthate (SIPX), in this work, municipal solid waste incineration fly ash (MSWI FA) was pretreated by hydrothermal method to produce stabilized FA, which was then innovatively used as support for the construction of FA/TiO2/BiOCl nanocomposite (FTB) with promoted photocatalytic activity under visible light and natural sunlight. When the content of FA was 20 wt% and the mass ratio of TiO2 to BiOCl was 4:6, a remarkable performance for the optimal FTB (20-FTB-2) was achieved. Characterizations demonstrated that TiO2 and BiOCl uniformly dispersed on FA contributing to high surface area and broad light adsorption of FTB, which exhibits excellent adsorption capacity and light response ability. Build in electric field formed in the interface of TiO2/BiOCl heterojunction revealed by density functional theory calculations accelerated the separation of photoinduced e- and h+, leading to high efficiency for SIPX degradation. The synergetic effect combined with adsorption and photocatalytic degradation endowed 20-FTB-2 superior SIPX removal efficiency over 99% within 30 min under visible light and natural sunlight irradiation. The photocatalytic degradation pathways of SIPX were determined through theoretical calculations and characterizations, and the toxic byproduct CS2 was effectively eliminated through oxidation of •O2-. For 20-FTB-2, reusability of photocatalyst was showed by cycle tests, also the concentrations of main heavy metals (Pb, Zn, Cu, Cr, and Cd) in the liquid phases released during photocatalyst preparation process (< 1 mg/L) and photodegradation process (< 8.5 µg/L) proved the satisfactory stability with low toxicity. This work proposed a novel strategy to develop efficient and stable support-based photocatalysts by utilizing MSWI FA and realize its resource utilization.

First Report of Ilyonectria coprosmae Causing Root Rot of Bletilla striata in Yunnan province of China.

Bletilla striata is a valuable medicine in China, belonging to the Orchidaceae family, and is used for treating various ailments such as hemoptysis, pyocutaneous disease, and anal fissure by preventing blood flow, reducing swelling, and promoting granulation. In June 2022, a disease with symptoms similar to root rot was observed on B. striata in the pineland (the area was 0.4 hectare) of Lancang County (22°48'17" N, 99°46'58"22 E), Yunnan Province, China. The root rot incidence rate reached 16% (Table S1). The root rot incidence was calculated as follows: root rot incidence (%) = (number of root rot seedlings/total number of seedlings investigated) × 100. In May 2023, the similar symptoms were observed in the field, and the disease incidence was 17% (Table S1). Initially, there were no obvious symptoms on the leaves. Subsequently, the leaves wilted and brown spots appeared. Later, the entire leaf browned, withered and eventually died (Fig. S1A, B). The roots were brown and the browning spread from the root edge to the center, causing vascular bundle browning and dead lignified fibers in the cortex (Fig. S1C, D). To isolate the causal pathogen, 20 symptomatic root tissues were collected from 20 plants. Cutting the diseased tissues into small pieces (0.5 × 0.5 cm). After surface sterilization (30s with 75% ethanol and 3 min with 2% sodium hypochlorite, rinsed three times with sterile water), the disinfected root tissues were plated onto potato dextrose agar (PDA) and incubated at 25℃ for 4 to 6 days with 12 h light/dark photoperiod. A total of 10 single-spore isolates with similar morphology and conidial characteristics were obtained. one representative isolate BJG6 was selected for identification and further study. The fungal colony was reddish-brown or orange-white on PDA after 8 days of incubation at 25℃. The mycelium was like carpet or cotton, and the edge of colony was uniform (Fig. S1E). Large conidia were formed on simple conidial peduncles (Fig. S1F, G). The conidia with 1~3 septates and 1 mostly, with cylindrical shapes and narrow tops but sharp bases (Fig. S1H-J). Conidia with 1 septate measured as 5.5 (4.3-6.7) × 20.7 (16.0-25.4) µm (n=30), while those with 2 septates measured as 6.6 (5.8-7.4) × 26.5 (21.7-31.3) µm (n=30), and those with 3 septates was 6.9 (6.2-7.8) × 31.8 (29.3-34.3) µm (n=30). Ellipsoidal microconidia could be formed on conidiophore and measured as 2.4 (1.9-2.9) × 4.9 (5.9-3.9) µm to 2.7 (2.2-3.2) × 5.4 (4.3-6.5) µm (n=30). Spherical or subspherical chlamydospores were produced on low-nutrient agar, with an average size of 5.8(5.0-6.6) µm×5.3 (4.4-6.2) µm (n=30) (Fig. S1K, L). According to the morphology and conidial features, the pathogen was consistent with the description of Ilyonectria coprosmae (Cabral et al. 2012). The total genomic DNA was extracted, and primer pairs ITS4/ITS5 were used to amplify and sequence the rDNA-ITS region (ITS1-5.8 S rRNA-ITS2 gene regions) (White et al. 1990). The sequences were deposited in GenBank (SUB13905750 for ITS). BLAST searches revealed BJG6 showed 98% homology with corresponding sequences of Ilyonectria coprosmae in GenBank (JF735260). A phylogenetic tree (MEGA 7.0) was constructed using maximum-likelihood methods (Fig. S2). To identify pathogenicity, a cultured medium in a size of 6mm containing isolate BJG6 was inoculated onto ten healthy roots of B. striata, PDA plugs alone were used as the uninoculated controls. All samples were placed in a dark inoculation chamber at 25℃. The pathogenicity test was replicated three times. After two weeks, all inoculated roots appeared similar symptoms identical to those observed on field plants (Fig. S1M, N-P), while control plants remained healthy (Fig. S1Q, R). The same pathogenic fungus was reisolated from the symptomatic root rot, and the characteristics of colony and conidia were the same as the original isolates (Fig. S1S, T). These results confirmed I. coprosmae as the causal pathogen of root rot disease on B. striata in China by Koch's postulates tests for the first time. Further exploration should be conducted to understand the occurrence and migration of this disease, so as to develop specific and efficient disease management strategies in the future.

Enhancement of catalytic detoxification of polycyclic aromatic hydrocarbons in fly ash from municipal solid waste incineration via magnetic hydroxyapatite-assisted hydrothermal treatment.

The emission of carcinogenic, teratogenic, and mutagenic polycyclic aromatic hydrocarbons (PAHs) during municipal solid waste incineration (MSWI) of fly ash (FA) has attracted significant attention. Hydrothermal treatment (HT) has emerged as a practical approach for degrading PAHs during MSWI of FA by utilizing magnetite (Fe3O4) as a catalyst and hydrogen peroxide (H2O2) as an oxidizing agent. In this study, as an alternative to traditional hydroxyapatite (HAP), eggshell-derived magnetic hydroxyapatite (MHAP) was synthesized and applied in the hydrothermal catalytic degradation of PAHs in MSWI FA in an H2O2 system for the first time. The degradation efficiency of the PAHs is influenced not only by H2O2 but also by the choice of hydroxyapatite. Adding HAP or MHAP during hydrothermal treatment with H2O2 substantially reduced the overall PAH concentration and toxicity equivalent quantity (TEQ), superior to that without H2O2. MHAP demonstrated superior catalytic activity compared to HAP in the presence of H2O2 in the hydrothermal system. The hydrothermal detoxification of the PAHs increased with increasing MHAP dosage. By employing 0.5 mol/L H2O2 as the oxidant and 15 wt% MHAP as the catalyst, a total PAH degradation rate of 88.9 % was achieved, with a remarkable TEQ degradation rate of 98.3 %. Notably, the level of 4-6-ring PAHs, particularly benzo(a) pyrene (BaP) and dibenz(a,h)anthracene (DahA), with a TEQ of 1.0, was significantly reduced (by 69.4 % and 46.0 %, respectively). MHAP remained stable during the hydrothermal catalytic process, whereas H2O2 was effectively activated by MHAP and decomposed to produce strongly oxidizing hydroxyl (•OH) under hydrothermal conditions. •OH produced from the decomposition of H2O2 and metals on the surface of MHAP act as catalytically active centers, efficiently converting high-ring PAHs to low-ring PAHs. These findings provide valuable insights and a technological foundation for PAH detoxification in MSWI FA via hydrothermal catalytic oxidation.

Rapid Analysis of Compounds from Piperis Herba and Piperis Kadsurae Caulis and Their Differences Using High-Resolution Liquid-Mass Spectrometry and Molecular Network Binding Antioxidant Activity.

There is a serious mixing of Piperis Herba and Piperis Kadsurae Caulis in various parts of China due to the similar traits of lianas, and there is a lack of systematic research on the compound and activity evaluation of the two. Likewise, the differences in compounds brought about by the distribution of origin also need to be investigated. In this study, high-resolution liquid-mass spectrometry (UPLC-Q-Zeno-TOF-MS/MS) was used to analyze samples of Piperis Herba from five origins and Piperis Kadsurae Caulis from five origins, with three batches collected from each origin. The compounds were identified based on precise molecular weights, secondary fragments, and an online database combined with node-to-node associations of the molecular network. The t-test was used to screen and analyze the differential compounds between the two. Finally, the preliminary evaluation of antioxidant activity of the two herbs was carried out using DPPH and ABTS free radical scavenging assays. The results showed that a total of 72 compounds were identified and deduced in the two Chinese medicines. These compounds included 54 amide alkaloids and 18 other compounds, such as flavonoid glycosides. The amide alkaloids among them were then classified, and the cleavage pathways in positive ion mode were summarized. Based on the p-value of the t-test, 32 differential compounds were screened out, and it was found that the compounds of Piperis Herba were richer and possessed a broader spectrum of antioxidant activity, thus realizing a multilevel distinction between Piperis Herba and Piperis Kadsurae Caulis. This study provides a preliminary reference for promoting standardization and comprehensive quality research of the resources of Piperis Herba using Piperis Kadsurae Caulis as a reference.

Improving mesophilic anaerobic digestion of food waste by side-stream thermophilic reactor: Activation of methanogenic, key enzymes and metabolism.

Anaerobic digestion (AD) is a favorable way to convert organic pollutants, such as food waste (FW), into clean energy through microbial action. This work adopted a side-stream thermophilic anaerobic digestion (STA) strategy to improve a digestive system's efficiency and stability. Results showed that the STA strategy brought higher methane production as well as higher system stability. It quickly adapted to thermal stimulation and increased the specific methane production from 359 mL CH4/g·VS to 439 mL CH4/g·VS, which was also higher than 317 mL CH4/g·VS from single-stage thermophilic anaerobic digestion. Further exploration of the mechanism of STA using metagenomic and metaproteomic analysis revealed enhanced activity of key enzymes. The main metabolic pathway was up-regulated, while the dominant bacteria were concentrated, and the multifunctional Methanosarcina was enriched. These results indicate that STA optimized organic metabolism patterns, comprehensively promoted methane production pathways, and formed various energy conservation mechanisms. Further, the system's limited heating avoided adverse effects from thermal stimulation, and activated enzyme activity and heat shock proteins through circulating slurries, which improved the metabolic process, showing great application potential.

Conductive materials enhance microbial salt-tolerance in anaerobic digestion of food waste: Microbial response and metagenomics analysis.

Previous studies have shown that high salinity environments can inhibit anaerobic digestion (AD) of food waste (FW). Finding ways to alleviate salt inhibition is important for the disposal of the growing amount of FW. We selected three common conductive materials (powdered activated carbon, magnetite, and graphite) to understand their performance and individual mechanisms that relieve salinity inhibition. Digester performances and related enzyme parameters were compared. Our data revealed that under normal and low salinity stress conditions, the anaerobic digester ran steady without significant inhibitions. Further, the presence of conductive materials promoted conversion rate of methanogenesis. This promotion effect was highest from magnetite > powdered activated carbon (PAC) > graphite. At 1.5% salinity, PAC and magnetite are beneficial in maintaining high methane production efficiency while control and the graphite added digester acidified and failed rapidly. Additionally, metagenomics and binning were used to analyze the metabolic capacity of the microorganisms. Some species enriched by PAC and magnetite possessed higher cation transport capacities and were to accumulate compatible solutes. PAC and magnetite promoted direct interspecies electron transference (DIET) and syntrophic oxidation of butyrate and propionate. Also, the microorganisms had more energy available to cope with salt inhibition in the PAC and magnetite added digesters. Our data imply that the promotion of Na+/H+ antiporter, K+ uptake, and osmoprotectant synthesis or transport by conductive materials may be crucial for their proliferation in highly stressful environments. These findings will help to understand the mechanisms of alleviate salt inhibition by conductive materials and help to recover methane from high-salinity FW.

Enhanced phosphorus release from waste activated sludge using ascorbic acid reduction and acid dissolution.

Due to the widespread application of various iron (Fe)-derived substances used in phosphorus (P) removal during wastewater treatment, Fe-P species generated in this process constitute an important part of P speciation in non-digested sludge. SEM-EDS and sequential extraction methods were utilized to analyze the speciation, distribution, and spatial variation of P contained in the sludge. Inorganic P accounted for 91.3% of the total P, and Fe(III)-P represented the greatest percentage (68.5%) in the inorganic P fraction. Ascorbic acid, also known as vitamin C (VC), performed well in releasing P from sludge, especially in combination with subsequent pH adjustment to 3.0 using HCl. Fe(III)-P in sludge was first reduced to Fe(II)-P by VC, then dissolved in acidic conditions to release Fe2+ and PO43-. Other metal-P compounds were also partially dissolved and released. VC disrupted the sludge floc structure, releasing organic P via organic efflux. There was a positive correlation (R2>0.97, p<0.05) between the amount of released P and the amount of reductant (VC). There was a synergistic effect between 120 mmol/L VC and acidity, producing the greatest P release of 67.1% of total sludge P. The P release efficiency achieved in this study was higher than other reported methods. Additionally, VC provides a more sustainable option due to its natural biodegradability. Released P and Fe2+ can be recovered as vivianite with recovery rates of 88% and 99%, respectively. This finding provides a new direction for effective, sustainable sludge P recovery and utilization.

Adsorption behaviors of three antibiotics in single and co-existing aqueous solutions using mesoporous carbon.

The residual antibiotics detected frequently in aquatic environment may pose a potential threat to human health and ecosystem. Exploring a possible way to remove them from antibiotic polluted-water is a key problem demanding prompt solution. To investigate their adsorption characteristics, three antibiotics including tetracycline (TC), ciprofloxacin (CIP), and sulfadiazine (SDZ) have been removed using sucrose-based mesoporous carbon (SMC) in single and co-existing systems. Characterization revealed that the SMC had a high Brunauer-Emmett-Teller (BET) surface area (1215.48 m2/g), large mesoporous pore size (6.36 nm), and abundant oxygen-containing functional groups, which might offer sufficient adsorption sites for antibiotics. The process of antibiotics adsorption was described well using pseudo-second-order model. The rate constant K2 at various temperatures followed the order 308 K > 298 K > 288 K. This finding suggesting the increase in temperature could promote the removal of antibiotics. The maximum adsorption capacities for TC (232.10 mg/g), CIP (257.30 mg/g), and SDZ (204.28 mg/g) of SMC were obtained using Langmuir isotherm (pH = 4-6, T = 308K, SMC dosage = 10 mg, C0 = 30-40 mg/L). These data implied SMC had the excellent adsorptive property and affinity to antibiotics. In binary systems, SMC offers efficient removal percentages (>90%) for each of the target antibiotic. While the removal efficiencies of TC, CIP, and SDZ by SMC in the ternary system were 90.40, 72.99, and 80.46%, respectively. These results suggested the competition on active sites of SMC happened among the three antibiotics. The affinities of SMC to three antibiotics followed the order TC > SDZ > CIP. The removal of antibiotics by SMC were mainly attributed to the mechanisms including electrostatic interactions, hydrophobic interactions, hydrogen bonding and so on. This study will provide a technical support for antibiotic wastewater treatment.

Evaluation of iron-loaded granular activated carbon used as heterogeneous fenton catalyst for degradation of tetracycline.

To optimize the efficiency of general adsorption-Fenton oxidation treatment, iron-loaded granular activated carbon (Fe-GAC) was prepared, characterized, and used as a catalyst in the heterogeneous Fenton oxidation of tetracycline (TC). Characterization revealed that the Fe(II) was successfully introduced onto the original granular activated carbon (GAC) and diversified the materials' surface morphology and elemental compounds. Under an initial pH of 3.0, the Fe-GAC/Fenton system obtained a maximum removal rate of 92.6%, with hydrogen peroxide (H2O2) dosages of 9 mmol g-1. And the GAC/Fenton without iron supplementation was 89.5%, with H2O2 dosages of 8 mmol g-1. Additionally, the Fe-GAC/Fenton system consumed a lower Fe(II) dosage than GAC/Fenton, with Fe(II)/H2O2 molar ratios of 0.007:1 and 0.04:1, respectively. Analysis of total organic carbon demonstrated higher mineralization efficiency in the Fe-GAC/Fenton system (67.2%), which was approximately 1.3 times of GAC/Fenton. Desorption experiments showed that the adsorption and degradation accounted for 19.22% and 80.78% of the total TC removal by GAC/Fenton, and 10.58% and 89.42% in the Fe-GAC/Fenton system, respectively. Electron paramagnetic resonance (EPR) technique and quenching experiments demonstrated that the dominant reactive oxygen species (ROS) in synergistic treatments were hydroxyl (•OH) and hydroxy peroxyl (HO2•) radicals. In addition, three potential degradation pathways for TC were proposed according to the detected fourteen intermediates. Catalyst regeneration treatments were evaluated over six cycles, and the regeneration was 6.5% higher with the iron-supplemented carbon granules. Overall, the Fe-GAC can be used as an efficient catalyst in practical water treatment, and this study demonstrated a promising method to develop adsorption-Fenton technology.

Occurrence of per- and polyfluoroalkyl substances (PFAS) in municipal solid waste landfill leachates from western China.

Landfill leachate has been documented as a significant source of trace organic pollutants, comprising an expansive family of per- and polyfluoroalkyl substances (PFAS). This study presents the findings on the distribution of 13 perfluoroalkyl carboxylates (PFCAs) and 4 perfluoroalkyl sulfonates (PFSAs) in leachates from 6 municipal solid waste (MSW) landfills in western China. The total concentrations of 17 PFAS in sampled leachates ranged from 1805 to 43,310 ng/L, and 15 compounds were detected in all samples. The short-chain compounds perfluorobutane sulfonate (PFBS, mean mass fraction 23.1%) and perfluorobutyric acid (PFBA, mean mass fraction 20.6%) were dominant. There were higher PFAS concentrations in leachates from operating landfills (mean: 12,194 ng/L) compared to closed landfills (mean: 2747 ng/L), but there was no significant difference between young (< 10 years) and old landfills (> 10 years). Moderate to weak correlations were observed between PFAS concentrations and leachate properties, e.g., TN, NH4+-N, TOC, and pH. This is the first report on the distribution of PFAS in landfill leachates from western China. The results have identified landfill leachate as an underestimated source of PFAS in the environment and have contributed to a more comprehensive evaluation on PFAS presence across China.

Correction: Antimicrobial peptide modification enhances the gene delivery and bactericidal efficiency of gold nanoparticles for accelerating diabetic wound healing.

Correction for 'Antimicrobial peptide modification enhances the gene delivery and bactericidal efficiency of gold nanoparticles for accelerating diabetic wound healing' by Song Wang et al., Biomater. Sci., 2018, 6, 2757-2772, DOI: 10.1039/C8BM00807H.

Constructed wetlands for rural domestic wastewater treatment: A coupling of tidal strategy, in-situ bio-regeneration of zeolite and Fe(â ¡)-oxygen denitrification.

Constructed wetlands (CWs) offer a promising method to treat domestic wastewater in rural areas, but CWs usually limiting in nitrogen removal and large area. In this study, zeolite and pyrite were used to construct tidal wetlands to address the problems of insufficient oxygen supply and carbon source. The results show that the fully drained wetland achieved the highest ammonia removal load of 34.67 ± 1.72 g/(m2·d) with 8.57 ± 1.13 mg/L of effluent. Pyrite was found to compensate for the lack of carbon source in the denitrification process in half-drained wetland, which achieved a 78.36 ± 5.3% TN removal rate with 7.09 ± 1.85 mg/L effluent concentration. Pyrite released Fe(II) to promote nitrate reduction for denitrification in the subsequent flooded period. Microbial community analysis indicates that the tidal flow constructed wetlands simultaneously achieved nitrification and denitrification by the coupling of in-situ zeolite regeneration and Fe(II) oxidation denitrification.

Effect of magnetite on the catalytic oxidation of polycyclic aromatic hydrocarbons in fly ash from MSW incineration: A comparative study of one-step and two-step hydrothermal processes.

Polycyclic aromatic hydrocarbons (PAHs), many of which are carcinogenic, teratogenic, and mutagenic, exist in fly ash (FA) produced from municipal solid waste incineration (MSWI). Hydrothermal treatment (HT) is an efficient approach to remove PAHs from MSWI FA. Here, magnetite (Fe3O4) was used as the catalyst and hydrogen peroxide (H2O2) as the oxidant for one-step and two-step catalytic hydrothermal methods. When the magnetite dosage increased to 15 wt%, the maximum degradation rates of PAHs were 84.36% and 92.51%, respectively; however, the toxicity equivalent quantity (TEQ) degradation rates of the PAHs both increased upon increasing the magnetite dose. At 20 wt% Fe3O4, the maximum TEQ degradation rates of the PAHs were 93.29% and 97.76%, respectively. The reaction between OH and PAHs is non-selective, which means that LMW, MMW, and HMW PAHs were all degraded. The decrease in TEQ was mainly due to the degradation of HMW PAHs, i.e., those with five rings. Under the same Fe3O4 dose, oxidant dose, and reaction time, the detoxification of PAHs by the two-step method was significantly better than that of the one-step method, possibly because the two-step method more effectively produced OH. The first step degraded more than 90% of PAHs, and the residual PAHs in the HT products of the first step limited the utilization of the oxidant during the second step. The minerals in the HT products implied that the two-step hydrothermal method not only produced more OH, which reacted with PAHs, but also generated metal-magnetite substitution, which affected its surface reactivity during heavy metal adsorption and catalysis. These results revealed that both magnetite and the two-step hydrothermal treatment degraded PAHs. 20 wt% magnetite was the optimal amount during the two-step hydrothermal catalytic oxidation of MSWI FA.

Removal of diclofenac and oxytetracycline from synthetic urine by furfuryl alcohol-derived mesoporous carbon.

In this study, using furfuryl alcohol as the precursor carbon and mesoporous silica as the template, and furfuryl alcohol-derived mesoporous carbon (FMC) was prepared. The specific surface area of FMC was 1022.61 m2/g, the pore volume was 1.71 cm3/g, and the mesoporous volume was 98.8%. Based on the adsorption kinetics of pharmaceuticals onto the FMC in synthetic urine, equilibrium adsorption was reached in 120 min, and it followed a pseudo-second-order model. The adsorption isotherms were well-fitted by the Sips isotherm model, and the saturated adsorption capacities of diclofenac and oxytetracycline in fresh urine were 411.8 mg/g and 465.9 mg/g, respectively. Batch experiment results showed that pharmaceutical removal was strongly influenced by urine components such as sodium chloride, urea, and ammonium hydroxide. The adsorption of diclofenac and oxytetracycline was influenced by many factors including π-π interactions, hydrogen bonds, and electrostatic forces. FMC exhibited excellent reusability and retained urine nutrients during pharmaceutical adsorption.

Mechanism study of improving anaerobic co-digestion performance of waste activated sludge and food waste by Fe3O4.

A large amount of waste activated sludge (WAS) and food waste (FW) are produced every year in China. Anaerobic co-digestion is considered to be an effective way to solve this problem. This study applied FW/WAS mixture as co-substrate to create different digestive environment, aiming to understand the mechanism of Fe3O4 particles in promoting AD performance. The results showed that the addition of Fe3O4 presented various performances when facing different digestive acidification stress brought by different mixing ratios of WAS and FW. Methanogenic pathways and microbial communities varied with substrates' properties. For group A (WAS mono-digestion), the acetoclastic methanogens dominated, 20 mg/g VS (according to the iron element) Fe3O4 could promote methane production, while 200 mg/g VS Fe3O4 would inhibit microbial activity. The promoted methane production by Fe3O4 was attributable to the promotion of sludge hydrolysis. For group B (WAS: FW = 1:0.5, based on VS addition, similarly hereinafter), Fe3O4 triggered direct interspecific electron transfer (DIET) between bacteria and methanogens. For group C (WAS: FW = 1:1), the hydrogenotrophic methanogens dominated, bacteria excreted more non-conductive polysaccharides in EPS to resist unfavorable environment, thereby it prevented their contact with Fe3O4 particles. So, it was difficult for Fe3O4 to trigger DIET and promote the digestive performance of batch experiments in such condition.

Optimization of hydrothermal synthesis of hydroxyapatite from chicken eggshell waste for effective adsorption of aqueous Pb(II).

Proper disposal of the millions of tons of eggshell waste generated around the world every year is a significant environmental challenge. However, eggshell waste can be converted into new materials that may be useful for a wide range of applications. In this study, four methods, including the conventional subcritical hydrothermal method (CSHM), microwave-assisted subcritical hydrothermal method (MSHM), conventional low-temperature hydrothermal method (CLHM), and ultrasonic-assisted low-temperature hydrothermal method (ULHM) were used to convert eggshell waste into hydroxyapatite (HAP). For each hydrothermal method, increasing the reaction temperature increased production efficiency and improved the degree of crystallinity of HAP. X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the preferred eggshell-derived HAP, which was produced by the MSHM at 180 °C in a period of only 1 h. For the MSHM, the HAP yield was 75.3%, the degree of HAP crystallinity was as high as 0.78, and pure, rod-like, nano-sized HAP particles with high specific surface area were produced. For the preferred HAP produced by the MSHM, the adsorption capacity of Pb2+and pH were positively related in the range of pH 1-6. Consequently, the HAP produced by the MSHM showed relatively high maximum adsorption (qm= 505.05 mg/g) of Pb2+ in aqueous solution. The adsorption process followed a pseudo-second-order reaction model, and the equilibrium adsorption was well fit by the Langmuir model.

Aged landfill leachate enhances anaerobic digestion of waste activated sludge.

Anaerobic digestion (AD) is considered as a sustainable pathway to recover energy from organic wastes, but the digestive efficiency for waste activated sludge (WAS) is not as expected due to the limitations in WAS hydrolysis. This study proposes an effective strategy to simultaneously treat WAS and landfill leachate, aiming to promote WAS hydrolysis and enhance organics converting to methane. The effects of landfill leachate on the four stages (i.e., solubilization, hydrolysis, acidogenesis, and methanogenesis) of AD of WAS, as well as the effect mechanisms were investigated. Results showed that adding appropriate amounts of landfill leachate could promote the steps of solubilization, hydrolysis and acidogenesis of WAS, but had no-effect on methanogenesis. The hydrolysis and acidogenesis efficiency in the leachate added digesters were 2.0%-8.4% and 35.2%-72.7% higher than the control digester. Mechanism studies indicated that humic acid (HA) contained in the leachate was conducive to the processes of both hydrolysis and acidogenesis, but detrimental to the methanogenesis. Effects of heavy metals (HMs) on AD of WAS was also dose-dependent. Digestive performance was inhibited by excessive HMs but promoted by moderate dosages. Humic acid and metal ions tend to interact to form complexes, and thus relieve their each inhibition effects. It is also found that the stability of sludge flocs was reduced by the leachate through reducing both apparent activation energy (AAE) and median particle size (MPS) of the sludge. Microbial community and diversity results revealed that the relative abundance of microbes responsible for hydrolysis and acidogenesis increased when landfill leachate was present. This research provides a more technically and economically feasible approach to co-treating and co-utilizing WAS and landfill leachate.

Co-digestive performance of food waste and hydrothermal pretreated corn cob.

Anaerobic co-digestion of lignocellulosic biomass and food waste (FW) has been extensively applied. However, whether hydrothermal pretreatment (HTP) of lignocellulosic biomass can enhance the performance in co-digestion deserves further investigation. In this study, corn cob (CC) was adopted as a typical lignocellulosic biomass for co-digestion with FW at different VS ratios of 1:3 (S1-S4) and 1:6 (S5-S8), attempting to evaluate the effect of HTP of CC at different temperature gradients (125, 150 and 175 °C) on the co-digestion performance. The emphasis was placed on hydrolysis, acidification and methanogenesis for different feedstock conditions. Results illustrated that the HTP had a certain destroying effect on the lignocellulose structure in CC and the crystallinity of cellulose decreased, significantly facilitating its co-digestion with FW. For FW/CC co-digestion at the VS ratio of 1:3, the S3 group (CC was pretreated at 150 °C) reached the maximum cumulative biogas yield (CBY) of 4660 mL and the maximum specific methane yield (SMY) of 316.9 mL/g·VS. Moreover, at 1:6, S7 group (pretreated at 150 °C) exhibited the optimal CBY of 4100 mL while achieving the SMY of 277.6 mL/g·VS among the digesters, indicating that the co-digestion of pretreated CC and FW could achieve higher methane production, and 150 °C refers to the optimal pretreatment temperature. Moreover, the peak values of the accumulated VFAs in digesters S1-S4 (2000-3000 mg/L) is higher than that in digesters S5-S8 (800-1500 mg/L). As suggested from microbial community and diversity date, the HTP expedited the enrichment of system hydrolyzing and acidogenic bacteria. These results are significant and provide certain guidance for optimizing the co-digestion of FW and CC in actual engineering.

Effects of green waste addition on waste activated sludge and fat, oil and grease co-digestion in mesophilic batch digester.

Anaerobic digestion (AD) is regarded as an effective method to treat waste activated sludge (WAS) and fat, oil and grease (FOG). Co-digestion of WAS/FOG could promote the methane yield but it will cause acid and salinity inhibition. Green waste (GW) was added into the digesters, and its effects on co-digestion of WAS and FOG in the mesophilic batch digester were investigated. Digestive performances (such as hydrolysis, acidogenesis and methanogenesis) were studied emphatically. The results showed that digester L6 (WAS:FOG:GW = 1:2:1, VS basis) presented the highest specific methane yield (SMY, 341.5 mL/g VS). The results of kinetics study verified that there was a slower hydrolysis rate when GW was applied as a co-substrate, which could reduce the potential of acid inhibition. Volatile fatty acid (VFA) and electrical conductivity analysis showed that GW addition could keep moderate VFA concentrations and alleviate the negative effects of high-salinity substrates on the digestive systems. The microbial community and diversity analysis proved that GW addition was beneficial to keep the balance of hydrolytic bacteria, acidogens and acetogens. The results of this study indicated that GW addition could enhance the energy recovery and system stability in the WAS/FOG co-digestive system.