Adsorption of lead ions by activated carbon doped sodium alginate/sodium polyacrylate hydrogel beads and their in-situ recycle as sustainable photocatalysts.

In this study, sodium alginate (SA), sodium polyacrylate (PAAS) and powdered activated carbon (PAC) were cross-linked by calcium ions [(Ca(II)] to form SA/PAAS/PAC (SPP) hydrogel beads. The hydrogel-lead sulfide (SPP-PbS) nanocomposites were successfully synthesized by in-situ vulcanization after the lead ions [(Pb(II)] adsorption. SPP showed an optimal swelling ratio (600% at the pH value of 5.0) and superior thermal stability (206 °C of heat-resistance index). The adsorption data of Pb(II) was compatible with the Langmuir model, and the maximum adsorption capacity of SPP was 391.65 mg/g after optimizing the mass ratio of SA to PAAS (3:1). The addition of PAC not only enhanced the adsorption capacity and stability, but also promoted photodegradation. The significant dispersive capacity of PAC and PAAS resulted in PbS nanoparticles with particle sizes of around 20 nm. SPP-PbS showed good photocatalysis and reusability. The degradation rate of RhB (200 mL, 10 mg/L) was 94% within 2 h and maintained above 80% after 5 cycles. The treatment efficiency of SPP was more than 80% in actual surface water. The results of quenching experiments and electron spin resonance (ESR) experiments revealed that the superoxide radicals (O2-) and holes (h+) were the main active species in the photocatalytic process.

Impacts of PFOAC8, GenXC6, and their mixtures on zebrafish developmental toxicity and gene expression provide insight about tumor-related disease.

Concerns about per- and polyfluoroalkyl substances (PFASs) have grown in importance in the fields of ecotoxicology and public health. This study aims to compare the potential effects of long-chain (carbon atoms ≥ 7) and short-chain derivatives and their mixtures' exposure according to PFASs-exposed (1, 2, 5, 10, and 20 mg/L) zebrafish's (Danio rerio) toxic effects and their differential gene expression. Here, PFOAC8, GenXC6, and their mixtures (v/v, 1:1) could reduce embryo hatchability and increase teratogenicity and mortality. The toxicity of PFOAC8 was higher than that of GenXC6, and the toxicity of their mixtures was irregular. Their exposure (2 mg/L) caused zebrafish ventricular edema, malformation of the spine, blood accumulation, or developmental delay. In addition, all of them had significant differences in gene expression. PFOAC8 exposure causes overall genetic changes, and the pathways of this transformation were autophagy and apoptosis. More importantly, in order to protect cells from PFOAC8, GenXC6, and their mixtures' influences, zebrafish inhibited the expression of ATPase and Ca2+ transport gene (atp1b2b), mitochondrial function-related regulatory genes (mt-co2, mt-co3, and mt-cyb), and tumor or carcinogenic cell proliferation genes (laptm4b and ctsbb). Overall, PFOAC8, GenXC6, and their mixtures' exposures will affect the gene expression effects of zebrafish embryos, indicating that PFASs may pose a potential threat to aquatic biological safety. These results showed that the relevant genes in zebrafish that were inhibited by PFASs exposure were related to tumorigenesis. Therefore, the effect of PFASs on zebrafish can be further used to study the pathogenesis of tumors.

Enhanced removal of diclofenac via coupling Pd catalytic and microbial processes in a H2-based membrane biofilm reactor: Performance, mechanism and biofilm microbial ecology.

Diclofenac (DCF) is a most widely used anti-inflammatory drug, which has attracted worldwide attention given its low biodegradability and ecological damage, especially toxic effects on mammals including humans. In this study, a H2-based membrane biofilm reactor (H2-MBfR) was constructed with well-dispersed Pd nanoparticles generated in situ. The Pd-MBfR was applied for catalytic reductive dechlorination of DCF. In batch tests, DCF concentration had significantly effect on the rate and extent DCF removal, and NO3- had negative impact on DCF reductive dechlorination. Over 67% removal of 0.5 mg/L DCF and 99% removal of 10 mg/L NO3--N were achieved in 90 min, and the highest removal of 97% was obtained at 0.5 mg/L DCF in the absence of NO3-. Over 78 days of continuous operation, the highest steady-state removal flux of DCF was 0.0097 g/m2/d. LC-MS analysis indicated that the major product was 2-anilinephenylacetic acid (APA). Dechlorination was the main removal process of DCF mainly owing to the catalytic reduction by PdNPs, microbial reduction, and the synergistic reduction of microbial and PdNPs catalysis using direct delivery of H2. Moreover, DCF reductive Dechlorination shifted the microbial community in the biofilms and Sporomusa was responsible for DCF degradation. In summary, this work expands a remarkable feasibility of sustainable catalytic removal of DCF.

Long-term effects of Cu(II) on denitrification in hydrogen-based membrane biofilm reactor: Performance, extracellular polymeric substances and microbial communities.

Divalent copper (Cu(II)) frequently coexists with nitrate (NO3-) in industrial wastewater and the effect of Cu(II) on the autotrophic denitrification system using H2 as the electron donor remains unknown. In this study, the hydrogen-based membrane biofilm reactor (H2-MBfR) was operated continuously over 150 days to explore the effect of Cu(II) on the performance of autotrophic denitrification system and understand the key roles of EPS and microbial community. More than 95% of 20 mg-N/L NO3- was removed at 1-5 mg/L Cu(II), and the removal rate of NO3--N was stabilized to 82% at 10 mg/L Cu(II) after a short period, while NH4+ and NO2- in effluent were hardly detected, indicated that high concentration of Cu(II) did not permanently inhibit the denitrification performance in H2-MBfR. Colorimetric determination showed that Cu(II) stimulated the secretion of EPS, in which the protein (PN) content was much higher than polysaccharide (PS). The PN/PS ratios increased from 0.93 to 1.99, and the PN was more sensitive to copper invasion. The results of three-dimensional excitation-emission matrix illustrated that tryptophan was the main component of EPS chelating Cu(II) to reduce toxicity. The results of Fourier-transform infrared demonstrated that hydroxyl, carboxyl, and protein amide groups bound and reduced Cu(II). Furthermore, Cu(II) was effectively removed (>80%), and the results of distribution and morphology analysis of Cu(II) show that the electron-dense deposits of monovalent copper (Cu(I)) were found in EPS and biofilms and the reduction of Cu(II) to Cu(I) was an obvious self-defense reaction of biofilm to copper stress. The microbial richness and diversity decreased with the long-term exposure to Cu(II), while the relative abundance of denitrifiers Azospira and Dechloromonas increased. This study provides a scientific basis for the optimal design of treatment system for removal of nitrate and recovery of heavy metals simultaneously.

Microbe-mediated transformation of metal sulfides: Mechanisms and environmental significance.

Microorganisms play a key role in the natural circulation of various constituent elements of metal sulfides. Some microorganisms (such as Thiobacillus ferrooxidans) can promote the oxidation of metal sulfides to increase the release of heavy metals. However, other microorganisms (such as Desulfovibrio vulgaris) can transform heavy metals into metal sulfides crystals. Therefore, insight into the metal sulfides transformation mediated by microorganisms is of great significance to environmental protection. In this review, first, we discuss the mechanism and influencing factors of microorganisms transforming heavy metals into metal sulfides crystals in different environments. Then, we explore three microbe-mediated transformation forms of heavy metals to metal sulfides and their environmental applications: (1) transformation to metal sulfides precipitation for metal resource recovery; (2) transformation to metal sulfides nanoparticles (NPs) for pollutant treatment; (3) transformation to "metal sulfides-microbe" biohybrid system for clean energy production and pollutant remediation. Finally, we further provide critical views on the application of microbe-mediated metal sulfides transformation in the environmental field and discuss the need for future research.

Effects of perfluoroalkyl substances on root and rhizosphere bacteria: Phytotoxicity, phyto-microbial remediation, risk assessment.

BACKGROUND: Per- and polyfluoroalkyl substances (PFAS) is easily sink into soil, affecting plants growth and microenvironment. However, the impacts of PFAS-related risk assessment on root and rhizosphere microbiomes are still poorly understood. OBJECTIVE: Researched on Arabidopsis thaliana and Nicotiana benthamiana growing in contaminated with perfluorooctanoic acid (PFOA), hexafluoropropylene oxide-dimer acid (HFPO-DA) and their mixtures. RESULTS: (i) Bioaccumulation of PFAS in roots was positively correlated with carbon chain length, contamination levels and exposure time, the phytotoxicity was as follows: HFPO-DA < (PFOA + HFPO-DA) < PFOA; (ii) Both short-term and long-term accumulation of PFAS would affect the changes in root antioxidant system and physiological metabolism; (iii) Single or mixed contamination of PFAS had unique influences on rhizosphere microbial diversity, community composition and interspecies interaction, and mixture was more complex. More importantly, the performance of Sphingomonadaceae and Rhizobiaceae microbial communities could contribute to the practice of phyto-microbial soil remediation. FUTURE DIRECTION: Pay more attention on novel pollution pathway in cultivation, exposure levels for different plants (especially crops), as well as more exact and scientific risk assessments. Establish a new PFAS grouping strategy and ecotoxicity life cycle assessment framework.

Carboxymethyl cellulose stabilized ferrous sulfide@extracellular polymeric substance for Cr(VI) removal: Characterization, performance, and mechanism.

Iron-based materials, especially ferrous sulfide (FeS), effectively remediate chromium pollution. However, the agglomeration of FeS reduces its reactivity to chromium. Herein, carboxymethyl cellulose stabilized ferrous sulfide@extracellular polymeric substance (CMC-FeS@EPS) was developed to remove hexavalent chromium (Cr(VI)) from water. CMC-FeS@EPS (98.00%) exhibited excellent removal efficiency of 40 mg/L Cr(VI) than those of FeS (57.35%) and CMC-FeS (68.60%). CMC-FeS@EPS showed good removal efficiency of Cr(VI) in wide pH range (from 4 to 9) and the co-existence of ions. FTIR and XPS results demonstrated that EPS functional group accelerated the process of adsorption and precipitation. Electrochemical results showed that CMC-FeS@EPS transferred electrons to Cr(VI) faster than CMC-FeS. In total, this study started from a new idea of using EPS to improve the performance of CMC-FeS, and provided a simple and effective way to remediate chromium pollution without secondary pollution.

Do perfluoroalkyl substances aggravate the occurrence of obesity-associated glucolipid metabolic disease?

BACKGROUND: Since 2016, more and more studies have been conducted to explore the combination of obesity and perfluoroalkyl substances (PFASs) exposure, and the results indicate that PFASs may be connected with the occurrence of obesity-associated glucolipid metabolic disease (GLMD). OBJECTIVES: This article summarizes the epidemiological studies on PFASs and obesity-related GLMD, as well as relevant experimental evidence. RESULTS: (i) Both obesity and PFASs exposure can cause disorder of glucose and lipid metabolism (GLM). (ii) Obesity is a pivotal factor in the high incidence of GLMD induce by PFASs. (iii) PFASs are aggravating the occurrence of obesity-associated GLMD [e.g., diabetes, cardiovascular disease (CVD), and liver disease]. CONCLUSION: The paper fills the gaps among environmental chemistry/epidemiology/toxicology area research. More importantly, PFASs should be taken into account to explain the high-prevalence of obesity-related GLMD. FUTURE DIRECTION: Three research programs are proposed to explore the synergistic mechanism of PFASs and obesity. In addition, three suggestions are recommended to solve the harm of PFASs pollutants to human beings.

Insight the roles of loosely-bound and tightly-bound extracellular polymeric substances on Cu2+, Zn2+ and Pb2+ biosorption process with Desulfovibrio vulgaris.

The aim of this study is to explore the fate and mechanism of metal cations of biosorption in the Desulfovibrio vulgaris system (including bacterial cells and secreted loosely-bound extracellular polymeric substances (LB-EPS) and tightly-bound extracellular polymeric substances (TB-EPS)). The relative contribution of EPS (TB-EPS and LB-EPS) to the adsorption of three metal cations is much greater than that of bacterial cells, and the adsorption capacity of Pb2+ on EPS (TB-EPS and LB-EPS) is much greater than that of Cu2+ and Zn2+ (Pb2+ > Cu2+ > Zn2+). The order of absorption capacity was as follows: LB-EPS > TB-EPS > bacterial cells, the adsorption contribution of EPS (including TB-EPS and LB-EPS) to Cu2+, Zn2+ and Pb2+ accounted for total adsorption capacity was 82%, 83% and 86%, respectively. It was suggested that LB-EPS was the first reaction barrier of immobilization metal cations before metal cations was able to pass through EPS and react with cells. The adsorption process was dominated by complexation and electrostatic interaction. The three-dimensional excitation-emission matrix (3D-EEM) identified two main fluorescence peaks of the aromatic and tryptophan protein-like substances in EPS. According to the synchronous fluorescence spectra, the tryptophan protein-like substances were gradually quenched with increased metal cations concentrations, which the quencher mechanism is dynamic quenching. The findings of this work are significant to reveal the fate of Cu2+, Zn2+ and Pb2+ during its sorption process onto Desulfovibrio vulgaris, and provide useful information of the interaction between Desulfovibrio vulgaris and its secreted EPS with metal cations.