Implementing a completely autotrophic nitrogen removal over nitrite process using a novel umbrella basalt fiber carrier.

The completely autotrophic nitrogen removal over nitrite (CANON) process is significantly hindered by prolonged start-up periods and unstable nitrogen removal efficiency. In this study, a novel umbrella basalt fiber (BF) carrier with good biological affinity and adsorption performance was used to initiate the CANON process. The CANON process was initiated on day 64 in a sequencing batch reactor equipped with umbrella BF carriers. During this period, the influent NH4+-N concentration gradually increased from 100 to 200 mg·L-1, and the dissolved oxygen was controlled below 0.8 mg L-1. Consequently, an average ammonia nitrogen removal efficiency (ARE) and total nitrogen removal efficiency (TNRE) of ∼90 and 80% were achieved, respectively. After 130 days, ARE and TNRE remained stable at 92 and 81.1%, respectively. This indicates a reliable method for achieving rapid start-up and stable operation of the CANON process. Moreover, Candidatus Kuenenia and Candidatus Brocadia were identified as dominant anammox genera on the carrier. Nitrosomonas was the predominant genus among ammonia-oxidizing bacteria. Spatial differences were observed in the microbial population of umbrella BF carriers. This arrangement facilitated autotrophic nitrogen removal in a single reactor. This study indicates that the novel umbrella BF carrier is a highly suitable biocarrier for the CANON process.

Effect of Wet-Dry Cycles on the Mechanical Performances and Microstructure of Pisha Sandstone.

The effects of the wet-dry cycles on the chemical compositions, microstructure, and mechanical properties of Pisha sandstone were experimentally investigated in the current study. A series of uniaxial compression tests were conducted to validate the deterioration of the mechanical property of specimens after wet-dry cycles. In addition, the evolutions of the mineral compositions and microstructure characteristics were confirmed by X-ray diffraction (XRD) and scanning electron microscope (SEM). Experimental results indicated that with the increase of wet-dry cycles, the mechanical properties of Pisha sandstone gradually decrease. After five wet-dry cycles, the uniaxial compressive strength, elastic modulus, and fracture energy of specimens were reduced by 41.06%, 62.39%, and 31.92%, respectively. The failure mode of the specimen changes from inclined shear failure to peel failure. Compared to the initial specimens, the relative content of primary minerals after five wet-dry cycles declined by 5.94%, and the relative content of clay minerals after five wet-dry cycles increased by 54.33%. Additionally, the porosity of samples exhibits a positive correlation with wet-dry cycles. Compared to the initial specimens, the porosity of specimens after five wet-dry cycles increased by 176.32%. Finally, a prediction model of the correlation between uniaxial compressive strength and porosity is proposed and verified.

Rapid cultivation of anammox sludge based on Ca-alginate cell beads.

Current gel entrapment technology has certain advantages for the enrichment of anammox sludge. In this study, the optimal preparation conditions and cultivation equipment of Ca-alginate cell beads for the culturing anammox sludge were proposed. The preparation parameters of the Ca-alginate cell beads were as follows: 3% sodium alginate, 4% CaCl2, VSA:Vcell = 1:1, a drop height of 9 cm, stirring speed of 300 rpm, and cross-linking time of 24 h. The prepared cell beads were regular spheres with a uniform size and hard texture. Throughout the 9 days of cultivation, the number of anammox bacteria in the Ca-alginate cell beads was 4.3 times that of the initial sludge, and the color of the cell beads changed from yellowish-brown to reddish-brown. Scanning electron microscopy (SEM) analysis showed that the SA gel beads had a good microporous structure. The fluorescence in situ hybridization (FISH) results illustrated that the bacteria were mostly dispersed inside the Ca-alginate cell beads. Additionally, the qPCR results implied that only a relatively small amount of anammox biomass (2.74×106 copies/gel-bead) was required to quickly start the anammox process. The anammox bacteria in the Ca-alginate cell beads grew with a fast growth rate in a short period and exhibited high activity due to diffusion limitations. In addition, the anammox bacteria cultivated in the Ca-alginate cell beads could adapt to the increase in substrate concentration in a short period. The optimal incubation time of this gel entrapment method for anammox sludge was no more than 17 days under the experimental conditions of this work. Therefore, this simple and practicable gel entrapment method may serve as a suitable pre-culture means for the rapid enrichment of anammox bacteria.

The removal of Cu(II)-EDTA chelates using green rust adsorption combined with ferrite formation process.

Classical adsorbents such as activated carbon are inefficient to remove Cu(II)-EDTA in solution. Moreover, the heavy metals in the generated sludge can easily be dissolved back into solution. In this research, a novel strategy developed by coupling green rust adsorption and ferrite formation technology was proposed for Cu(II)-EDTA chelate removal. At the adsorption stage, green rust sulfate (GRME(SO42-)) showed a high adsorption efficiency of chelated copper, with a capacity of 126.41 mg g-1, compared to other classical adsorbents. During the ferrite formation stage, GRME(SO42-)-based precipitate with high moisture content and slow settling rate could be transformed into ferrite-based precipitate with low moisture content and rapid settling rate. The volume and moisture content of ferrite were 2.20 and 1.45 times lower than those of GRME(SO42-) and the sedimentation velocity of ferrite was also 1.23 times higher than that of GRME(SO42-), which strongly demonstrated the necessity of the ferrite formation process. Toxicity characteristic leaching procedure (TCLP) test results showed that the metallic copper of GRME(SO42-) sludge could be more easily dissolved back into solution than that of ferrite precipitate under weak-acid conditions, indicating the stability of ferrite. In addition, after the ferrite process, the generated sludge exhibited soft magnetism and could be quickly separated within few seconds using an external magnetic field. All these results showed that the combined green rust adsorption with ferrite formation method was an efficient, recyclable and eco-friendly method for the treatment of wastewater containing Cu(II)-EDTA.

SIKVAV promotion proliferation of vascular endothelial cells and related mechanisms.

BACKGROUND: Vascular endothelial injury, a key factor in diabetic foot ulcers (DFUs) pathogenesis, is linked to the impaired proliferation and migration of vascular endothelial cells, modulated by hypoxia-inducible factor, growth factors, and inflammatory elements. OBJECTIVE: The present study assesses the role of SIKVAV (Ser-Ile-Lys-Val-Ala-Val), a peptide shown to enhance cell proliferation and migration, on mouse aortic endothelial cell (MAEC) and the corresponding molecular mechanisms. METHODS: MAEC were treated with SIKVAV at 0, 100, 200, 400, and 600 µg/mL for 0, 24, 48, and 72 h. Cell viability was tested using the CCK-8 assay. Proliferating cell nuclear antigen (PCNA), extracellular signal-regulated kinase 1/2 (ERK1/2), and protein kinase B (Akt) levels were measured by qRT-PCR and western blot. RESULTS: SIKVAV augmented PCNA mRNA expression and stimulated vascular endothelial cell proliferation in a concentration and time-dependent fashion. Furthermore, it amplified the expression of p-ERK1/2 and p-Akt, pivotal components of the mitogen-activated protein kinase (MAPK)/ERK1/2 and phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathways. The inhibition of these pathways suppressed PCNA mRNA expression, cell proliferation rate, and decreased p-ERK1/2 and p-Akt levels, highlighting SIKVAV's role in promoting vascular endothelial cell proliferation via these pathways. CONCLUSION: The results of this study confirmed that SIKVAV grafted onto scaffolds can accelerate the proliferation of vascular endothelial cells for the therapy of skin wounds, and provide a theoretical basis for its application in ischemic disease as synthesized biomaterials scaffolds of tissue engineering.

Removal and kinetics of cadmium and copper ion adsorption in aqueous solution by zeolite NaX synthesized from coal gangue.

Zeolite can remove the heavy metals in wastewater, but the removal efficiency was determined by the types of zeolites and the treatment conditions. In this study, a kind of zeolite NaX synthesized from the coal gangue, a by-product of coal production, was used and the removal efficiency of Cd2+ and Cu2+and the kinetic models were studied. The effects of its dosage, initial pH value of wastewater, and adsorption temperature on its adsorption of heavy metals Cd2+ and Cu2+ in the simulated wastewater were studied through the indoor experiments in laboratory, and the adsorption mechanism was analyzed by the adsorption kinetic model based on its adsorption efficiency and its structures. The results show that the zeolite NaX synthesized from coal gangue has a good adsorption effect on Cd2+ and Cu2+. The adsorption reaches the best effect when the dosage of zeolite is 2 g/L, the initial pH of simulated wastewater is 5, the adsorption temperature is room temperature (25 ℃), and the removal efficiency of Cd2+ and Cu2+ (100 mg/L) is more than 90%. Additionally, the Langmuir, Freundlich, and Temkin isothermal adsorption models were used to compare and analyze the adsorption effects. The equilibrium data was better fitted by the Langmuir model with the maximum adsorption capacities of 100.11 mg/g (Cd2+) and 95.29 mg/g (Cu2+), and both separation coefficients were 0-1, which shows that the process was the favorable adsorption. Weber Morris diffusion model shows that the adsorption process at 120 min was more consistent with the pseudo-second-order kinetics model, and the adsorption efficiency was simultaneously controlled by the liquid diffusion step and intraparticle diffusion step. Moreover, the removal mechanism of Cd2+ and Cu2+ mainly includes physical adsorption and ion exchange. Therefore, the adsorption effect of zeolite synthesized from coal gangue is remarkable, which will provide a feasible and potential alternative for its resource application.

Heterotrophic nitrification and aerobic denitrification process: Promising but a long way to go in the wastewater treatment.

The traditional biological nitrogen removal (BNR) follows the conventional scheme of sequential nitrification and denitrification. In recent years, novel processes such as anaerobic ammonia oxidation (anammox), complete oxidation of ammonia to nitrate in one organism (comammox), heterotrophic nitrification and aerobic denitrification (HN-AD), and dissimilatory nitrate reduction to ammonium (DNRA) are gaining tremendous attention after the discovery of metabolically versatile bacteria. Among them, HN-AD offers several advantages because individual bacteria could achieve one-stage nitrogen removal under aerobic conditions in the presence of organic carbon. In this review, besides classical BNR processes, we summarized the existing literature on HN-AD bacteria which have been isolated from diverse habitats. A particular focus was given on the diversity and physiology of HN-AD bacteria, influences of physiological and biochemical factors on their growth, nitrogen removal performances, as well as limitations and strategies in unraveling HN-AD metabolic pathways. We also presented case studies of HN-AD application in wastewater treatment facilities, pointed out forthcoming challenges of HN-AD in these systems, and presented modulation strategies for HN-AD application in engineering. This review may help improve the existing design of wastewater treatment plants by harnessing HN-AD bacteria for effective nitrogen removal.

Mixotrophic denitrification processes in basalt fiber bio-carriers drive effective treatment of low carbon/nitrogen lithium slurry wastewater.

Lithium battery slurry wastewater was successfully treatedby using basalt fiber (BF) bio-carriers in a biological contact oxidation reactor. This resulted in a significant reduction of COD (93.3 ± 0.5 %) and total nitrogen (77.4 ± 1.0 %) at 12 h of HRT and dissolved oxygen (DO) of 0-1 mg/L. The modified Stover-Kincannon model indicated that the total nitrogen removal rate was 4.462 kg/m3/d in R-BF while the substrate maximum specific reaction rate (qmax) in the Monod model was 0.323 mg-N/mgVSS/d. A stable internal environment was established within the bio-nest. Metataxonomic analysis revealed the presence of denitrification and decarbonization bacteria, combined heterotrophic nitrification-aerobic denitrification bacteria, nitrite-oxidizing bacteria, and ammonia-oxidizing bacteria. Functional analysis displayed changes related to (aerobic)chemoheterotrophy, nitrogen respiration, nitrate reduction, respiration/denitrification of nitrite, and nitrate in R-BF. The study proposes a novel approach to achieve denitrification for the treatment of lithium slurry wastewater at low C/N conditions.

The treatment of electroplating wastewater using an integrated approach of interior microelectrolysis and Fenton combined with recycle ferrite.

Heavy metal ions in chelated forms have aroused great concerns because of their high solubility, poor biodegradation and extreme stability. In this research, an efficient strategy, interior microelectrolysis-Fenton-recycle ferrite (IM-Fenton-RF), was developed to treat simulated electroplating wastewater containing chelated copper at room temperature. The decomplexation of chelated copper was carried out by both interior microelectrolysis and Fenton reactions. IM process can not only partly degrade the complexes of chelated copper via the microelectrolysis reaction but also it produces Fe2+ ions for the Fenton reaction. After decomplexation, the IM-Fenton effluent directly flowed into the RF reactor for copper ions removal. Under optimum reaction conditions (reflux ratio = 0.37, Fe2+ concentration = 9.20 g/L at pH 10.18), 99.9% copper was removed by the IM-Fenton-RF system. The produced IM-Fenton-RF sludge is based on ferrite precipitate and has several advantages over metal hydroxides sludge. Ferrite sludge is stable owing to the stability of ferrite's crystal structure, while the toxicity characteristic leaching procedure (TCLP) test meets relevant standards. The sedimentation rate and volume of ferrite sludge were 3.86 times faster and 11.0 times lower than those of metal hydroxides sludge. Furthermore, the yielding sludge of ferrite can be recovered and utilized for the synthesis of Fe-C metallic species, the main compound of IM packing for interior microelectrolysis reaction. All these results show that a combination of IM-Fenton and RF is an effective approach to treat wastewater containing chelated copper, showing great potential for industrial applications.

Organic and inorganic nitrogen removals by an ureolytic heterotrophic nitrification and aerobic denitrification strain Acinetobacter sp. Z1: Elucidating its physiological characteristics and metabolic mechanisms.

Although heterotrophic nitrification-aerobic denitrification (HN-AD) is promising in nitrogen removal, it remains unclear for most HN-AD strains in physiological characteristics and metabolic mechanisms. In this study, a newly isolated strain Acinetobacter sp. Z1 converted not only inorganic nitrogen, but also organic nitrogen to N2. Among them, urea was the preferential nitrogen substrate. Single-factor experiments showed that efficient HN-AD process occurred with acetate as carbon source, C/N ratios of 12 for NH4+-N and 15 for NO3--N, pH 8, 30 °C, DO of ∼5.8 mg/L and salinity less than 1.5 %. Subsequently, response surface analysis was applied to predict the optimal growth conditions. Its complete genome annotation in combination with enzymatic activity assay and nitrogen balance calculation showed that at least four pathways involved in nitrogen metabolism. This work indicates that ureolytic strain Z1 could be prepared as bacterial agents with other HN-AD strains to treat urea-containing wastewater like urine from urban community.

Low carbon-to-nitrogen ratio digestate from high-rate anaerobic baffled reactor facilitates heterotrophic/autotrophic nitrifiers involved in nitrogen removal.

In this study, baffled anaerobic-aerobic reactors (AOBRs) with modified basalt fiber (MBF) carriers and felt were used to treat domestic wastewater (DWW). The influent was first treated in anaerobic compartments, with the NH4+-N containing digestate refluxed into aerobic compartment for nitrification. The nitrified liquid was channeled to the anaerobic compartments for further denitrification. Under optimal conditions, AOBR with MBF carriers could remove 91% chemical oxygen demand (COD) and 81% total nitrogen (TN), with biomass production increased by 7.6%, 4.5% and 8.7% in three successive anaerobic compartments compared to the control. Biological viability analysis showed that live cells outnumbered dead cells in bio-nests. Metagenomics analysis showed that multiple metabolic pathways accounted for nitrogen conversion in anaerobic and aerobic compartments. More importantly, low COD/TN ratio digestate facilitated heterotrophic nitrification-aerobic denitrification (HN-AD) species growth in aerobic compartment. This study provides a promising strategy to source treatment of DWW from urban communities.

Calcium modified basalt fiber bio-carrier for wastewater treatment: Investigation on bacterial community and nitrogen removal enhancement of bio-nest.

Modified basalt fiber (MBF) is a sustainable material studied as novel wastewater treatment bio-carrier recently. This work studied the effects of calcium modification on the bacterial affinity of modified fiber (Ca-MBF), bacterial community, and nitrogen removal performance. Results showed that Ca-MBF with hydrophilic (62.66°) and positively-charged (7.80 mV) surface accelerated bacterial attachment. Volatile suspended solids on Ca-MBF (5.46 g VSS/g fiber) were increased by 2.61 times after modification, with high bacterial activity when bio-carriers were cultured in activated sludge. Extracellular polymeric substances on Ca-MBF was 4.35 times higher and consisted of more protein. Bio-nests with unique aerobic/anaerobic structure formed on the ultrafine carriers in bioreactor. Ca-MBF bioreactor exhibited total nitrogen removal efficiency above 72.2% and COD removal efficiency above 94.2% with more stable performance than unmodified carrier in long-term treatment using synthetic domestic wastewater.16S rRNA gene sequencing revealed enhanced abundance of nitrifying and denitrifying bacteria in Ca-MBF bio-nest.

The role of gel wound dressings loaded with stem cells in the treatment of diabetic foot ulcers.

Diabetic foot ulcers (DFUs) are a serious complication of diabetes and the main cause of nontraumatic lower limb amputations, resulting in a serious economic burden on society. The main causes of DFUs include peripheral neuropathy, foot deformity, chronic inflammation, and peripheral artery disease. There are many clinical approaches for the treatment of DFUs, but they are all aimed at addressing a single aetiological factor. Stem cells (SCs), which express many cytokines and a variety of nerve growth factors and modulate immunological function in the wound, may accelerate DFU healing by promoting angiogenesis, cell proliferation, and nerve growth and regulating the inflammatory response. However, the survival time of SCs without scaffold support in the wound is short. Multifunctional gel wound dressings play a critical role in skin wound healing due to their ability to maintain SC survival for a long time, provide moisture and prevent electrolyte and water loss in DFUs. Among the many methods for clinical treatment of DFUs, the most successful one is therapy with gel dressings loaded with SCs. To accelerate DFU healing, gel wound dressings loaded with SCs are needed to promote the survival and migration of SCs and increase wound contraction. This review summarizes the research advancements regarding multifunctional gel wound dressings and SCs in the treatment of DFU to demonstrate the effectiveness and safety of this combinational therapeutic strategy.

Enhancement of nitrogen removal in hybrid wastewater treatment system using ferric citrate modified basalt fiber biocarrier.

Developing biofilm carriers is of great significance for efficient wastewater treatment. In this work, ferric citrate was used to modify inorganic basalt fiber (BF) biocarrier, thus improving its surface properties and the nitrogen removal in hybrid wastewater treatment system. The results showed that the iron element on modified basalt fiber (Fe-MBF) existed in the forms of ferric citrate, Fe(OH)3, Fe2O3, and FeO. The ferric deposition increased the surface roughness, hydrophilicity and reduced the electronegativity of BF. The water contact angle of BF and Fe-MBF was 117.46° and 64.85°, respectively. The surface zeta potential of BF was -17.64 mV, but shifted positively (-8.67 mV) after deposition modification. The microorganism adhesion tests showed that the attached biomass and extracellular polymeric substances (EPS) content on Fe-MBF biocarrier significantly increased and the attached bacteria had also high viability. The Fe-MBF biocarrier showed good nitrogen removal performance in the hybrid bioreactor, with total nitrogen removal efficiency up to 95.35±0.82%, increasing by about 16% compared to that with unmodified BF biocarrier. This work also provided a green modification strategy to enhance biofilm carrier in wastewater treatment.

Treatment of high-load organic wastewater by novel basalt fiber carrier media.

The carrier medium plays a key role in improving existing remediation potential of conventional biological contact oxidation reactors. In this study, a biological contact oxidation reactor was constructed using basalt fiber (R-BF) as a biological carrier. The bioreactor performance was investigated in terms of reduction in chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), and total nitrogen (TN) at organic loadings rate of 15.243 kg/m3·d and nitrogen loading rate of 1.068 kg/m3·d. We found that COD, NH4+-N, and TN were reduced to 99.1%, 97.9%, and 97.8%, respectively. Within the R-BF, a bio-nest was developed which had abundant pores and channels and supported successful movement of nutrients, resulting in high biological activity (55.78%). The microbial communities within the bio-nest were diverse and rich and sludge production during operation was minimal. This makes BF a promising application for wastewater treatment. This research might be useful in the construction of integrated bioreactors that can operate under high organic and nitrogen loadings rates with reduced energy consumption, i.e. 75% in this study.

Improving the consolidation properties of hydrophilic polyurethane for feldspathic sandstone water erosion prevention.

Feldspathic sandstone is a type of sandstone that is severely eroded by wind, rainfall, and gravity forces. The land surface in feldspathic area is degraded and covered with extremely low vegetation coverage. In this study, we propose a type of hydrophilic polyurethane (W-OH) to control its erosion and conduct the experiment to evaluate the consolidation performances. The results showed that the cementing materials (such as montmorillonite) are the main reason for the vulnerability of feldspathic sandstone to erosion, which expands by absorbing water. Additionally, the organic content is extremely low and is not suitable for vegetation growth. However, when the different concentrations of W-OH solution were sprayed on the feldspathic sandstone surface, the solution could penetrate in several minutes and form a flexible and porous consolidation layer. The anti-scourability index (K) of the layer could increase from approximately 0.2 to 1.0 which significantly increased the water resistance. The water retention benefit increased by 50%. In the simulated rainfall test, the sediment yield reduction in the treated slopes sprayed with the W-OH solution could reach 99% compared with that on the control slopes. The SEM images indicated that the W-OH solution enveloped the feldspathic sandstone particles and connected them tightly together. Therefore, the consolidation layer could decrease water erosion rate and reduce evaporation.

Effects of rainfall intensity, slope angle, and vegetation coverage on the erosion characteristics of Pisha sandstone slopes under simulated rainfall conditions.

The water loss and soil erosion in the Pisha sandstone region in the middle reaches of the Yellow River are extremely severe, leading to extremely harmful effects on the ecological environment and safety of the lower reaches. In this paper, the effects of the slope angle (20, 30, and 40°), rainfall intensity (20, 50, and 80 mm/h), and vegetation coverage (10, 30, and 50%) on the erosion characteristics of the Pisha sandstone slopes are studied using indoor-simulated rainfall tests. The results show that the infiltration into the Pisha sandstone is only 10~15%. It is found that rainfall intensity has the most significant effect on runoff, which gradually increases with increasing rainfall intensity. Vegetation significantly affects runoff reduction when the rainfall intensity is low (approximately 20 mm/h), but this effect decreases with increasing rainfall intensity. Rainfall intensity has an extremely significant effect (P < 0.01) on the sediment yield, followed by vegetation coverage, and slope angle. When the vegetation coverage is approximately 50%, the reduction in sediment yield reaches approximately 70%. Additionally, the sediment reduction benefit is more significant than the runoff reduction benefit. The presence of the eroded gullies on slopes with vegetation is less compared to that on the bare slopes. Therefore, relatively high vegetation coverage (≥ 50%) is required for soil and water conservation in Pisha sandstone area. The findings will provide some reference for Pisha sandstone conservation.

Reactive oxygen species generation in FeOCl nanosheets activated peroxymonosulfate system: Radicals and non-radical pathways.

Iron oxychloride (FeOCl) is utilized as a activator of peroxymonosulfate (PMS) for the degradation of paracetamol (APAP) and phenacetin (PNCT) in response to the water pollution by persistent pharmaceuticals. The degradation process was well fitted with a pseudo-first order kinetic pattern, and the excellent catalytic performance towards APAP (100 % removal) and PNCT (86.5 % removal) was obtained in the presence of 0.2 g/L FeOCl and 2.0 mM PMS at pH 7.0 in 30 min. In-situ electron spin resonance (ESR) and scavenging tests revealed the generation of a series of ROS (·OH, SO4-, O2-, 1O2), which was highly dependent on pH. Besides, the non-radical pathways process involved 1O2 was dominant in APAP oxidation, while both ·OH and 1O2 are significant in PNCT removal. Furthermore, the formation of disinfection by-products (DBPs) during post-chlorination showed neglectable increment at neutral and alkaline condition with FeOCl/PMS pre-oxidation, and the calculated cytotoxicity would experience a continuous deterioration with pH increase. These results displayed high efficiency of FeOCl/PMS system in micropollutants degradation and a relatively comprehensive activation process of PMS, which may promote practical application in environmental remediation.

Performance Evaluation of the Polyurethane-Based Composites Prepared with Recycled Polymer Concrete Aggregate.

Currently the investigation on recycled cement concrete aggregate has been widely conducted, while the understanding of the recycled polymer concrete aggregate is still limited. This study aims to fill this knowledge gap through the experimental investigation on mechanical and durability performance. Specifically, the remolded polyurethane stabilized Pisha sandstone was collected as the recycled polymer concrete aggregate. The remolded Pisha sandstone was then applied to re-prepare the polyurethane-based composites. After that, the mechanical performance of the prepared composites was first examined with unconfined and triaxial compressive tests. The results indicated that the Pisha sandstone reduces the composite's compressive strength. The reduction is caused by the remained polyurethane material on the surface of the remolded aggregate, which reduces its bond strength with the new polyurethane material. Aiming at this issue, this study applied the ethylene-vinyl acetate (EVA) to enhance the bond performance between the polyurethane and remolded sandstone. The test results indicated both the unconfined and triaxle compressive strength of the polyurethane composites were enhanced with the added EVA content. Furthermore, the durability performance of the EVA-modified composites were examined through freeze-thaw and wet-dry cycle tests. The test results indicated the EVA could enhance the polyurethane composites' resistance to both wet-dry and freeze-thaw cycles. Overall, the modification with EVA can compensate for the strength loss of polyurethane composites because of the applied remolded aggregate and enhance its sustainability.

Remediation of phenanthrene contaminated soil by g-C3N4/Fe3O4 composites and its phytotoxicity evaluation.

This work is a premier demonstrating the technical feasibility of remediation of PAHs-contaminated soil by g-C3N4/Fe3O4. g-C3N4/Fe3O4 has been synthesized by typical two steps involved the synthesis of g-C3N4 and the subsequent in situ co-precipitation of Fe3O4 nanoparticles. g-C3N4/Fe3O4 exhibits excellent visible-light-driven photocatalytic activity for the degradation of phenanthrene in soil at circumneutral pH. The enhanced photocatalytic activity of g-C3N4/Fe3O4 should be attributed to the hybrid of Fe3O4 and g-C3N4 and appropriate Fe3O4 loading amount can improve not only the visible light absorption ability but also the separation of the photo-induced electron-hole pairs. The phytotoxicity evaluation, a preliminary ecological risk assess, was conducted on lettuce cultivation experiments. Base on the data of growth indexes including seeds germination percentage, root length, leaf length, and fresh weight of lettuce, it can be conclude that photocatalytic oxidation based on g-C3N4/Fe3O4 provide a mild oxidation process to degrade the phenanthrene from contaminated soil and there is no negative impact on the growth of lettuce. This work definitely demonstrates that this soil remediation method based on g-C3N4/Fe3O4 is technologically feasible and has immense potential in the application of remediation of organic pollutant contaminated soils.