•Chitosan/biochar hydrogel beads have great potential of easy separation and regeneration.•The uptake capacity of chitosan/biochar hydrogel beads showed about 36.72 mg/g.•The regeneration of CBHB was ...still more than 25.73 mg/g after 6th regeneration.
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Biochar is effective in water treatment but it is hard to retrieve or separate biochar powder from aqueous solutions. In this study, the removal of ciprofloxacin from aqueous solutions was investigated using chitosan/biochar hydrogel beads (CBHB). The results showed that the adsorption rate was almost independent of the temperature and occurred at the homogeneous sites of adsorbent thus obeying the Langmuir model. The equilibrium time was varying for different initial concentrations and found to be 48 h for maximum one. The maximum sorption was found to be >76 mg/g of adsorbent out of 160 mg/L as initial concentration. Adsorption obeyed the second-order mechanism with leading role of intra-particle diffusion and outer diffusion. Adsorption capacity decreased from 34.90 mg/g to 15.77 mg/g in the presence of 0.01 N Na3PO4 whereas other electrolytes such as NaCl, Na2SO4, NaNO3 with same concentration did not affect the sorption capacity. However, increased concentration of NaCl reduced the sorption capacity to some extent. CBHB showed a mixed mechanism by removing CIP through π-π electron donor-acceptor (EDA) interaction, hydrogen bonding and hydrophobic interaction. The reformation of CBHB with methanol and ethanol instead of water decreased its sorption capacity to 32.69 mg/g and 29.29 mg/g. Adsorption decreased by little after every regeneration of CBHB and was still >64 ± 0.68% (25.73 mg/g) after 6th regeneration. The efficacy of CBHB for CIP removal proved that CBHB is an economical and sustainable adsorbent.
As the most typical geological environment, limestone landforms are widespreading in the world and affect the waters that flow around them, which may also change the fate of organic contaminants in ...these waters. In this study, aquatic environment surrounding limestone was simulated with calcium carbonate, and the photolysis of tetracycline was evaluated under UV irradiation (30 μW/cm2). More tetracycline (up to 98%) was removed in 4 h in the presence of calcium carbonate while only 50% of tetracycline was eliminated in control experiment. The removal of tetracycline was greatly enhanced due to the major roles of alkaline pH and minor roles of Ca2+ and HCO3−/CO32−. In alkaline pH, tetracycline existed as TCs− with higher electronic density in the ring structures, which was more easily attacked by OH. Besides, it could also change the bond orbital energy to facilitate tetracycline absorbing more photon. Moreover, alkaline pH was beneficial to generate more OH and thus promote the indirect photolysis. In addition, alkaline pH also changed the degradation path of tetracycline and rapidly convert tetracycline to the byproducts with m/z 457 via hydroxylation and hydrogen abstraction. This work provides not only better understanding about the fate of tetracycline in aquatic environments but also new insights into the treatment of antibiotic-contaminated water.
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•Photolysis of tetracycline was greatly accelerated in waters around limestone.•Alkaline pH was major reason for the acceleration.•Both direct and indirect photolysis of tetracycline was promoted at alkaline pH.•Tetracycline was degraded via a different path at alkaline pH.
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In this study, humic acid coated biochar (HA-BC) and chitosan were combined to prepare an adsorbent with enhanced reactivity for the removal of ciprofloxacin (CIP). With initial CIP ...concentrations of 250 mg/L, the maximum adsorbed amount was 154.89 mg/g. Removal rates reached equilibrium after 12 h, obeying the pseudo second-order kinetic model. Adsorption isotherm data was better fitted to the Langmuir isotherm model. The sorption capacity of humic acid-biochar/chitosan hydrogel beads (HBCB) decreased by 11.42%, 6.66%, 9.32%, and 23.92% in the presence of NaCl, NaNO3, Na2SO4, and Na3PO4, respectively. A complex mechanism was found to be responsible for the adsorptive removal of CIP including, hydrogen bonding, π-π electron donor–acceptor (EDA) interactions and hydrophobic interactions. After four regeneration steps, sorption capacity remained sufficient (61.23 mg/g). These removal results indicate that HBCB is durable and effective for long term CIP removal.
Cadmium (Cd) is a widely distributed soil contaminant which induces oxidative damage and is therefore toxic to plants. Although selenium oxyanions such as selenite (SeO32-) and selenate (SeO42-) can ...alleviate Cd stress to plants, it is not known whether selenium nanoparticles (SeNPs) are able to do the same. The present study demonstrated the positive impact of both SeNPs and SeO32- on Brassica napus L. growth under conditions of Cd stress. Underlying mechanisms were elucidated using an oxidative stress detection assay, whole-genome RNA sequencing, and RT-qPCR. Application of selenium, especially in the form of SeNPs, decreased Cd-induced reactive oxygen species production by inhibiting the expression of NADPH oxidases (BnaRBOHC, BnaRBOHD1, and BnaRBOHF1) and glycolate oxidase (BnaGLO), thereby decreasing oxidative protein and membrane lipid damage. In addition, SeNPs improved resistance to Cd stress by decreasing Cd accumulation, maintaining intracellular calcium homeostasis, promoting disulfide bond formation, and restoring the waxy outer layer of the leaf surface. Although both forms of selenium decreased Cd toxicity, the beneficial concentration range was more extensive for SeNPs than for SeO32-.
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•SeNPs alleviated the toxic effects of Cd and improved the plant growth in B. napus.•SeNPs demonstrated superior roles in inhibiting ROS production and scavenging ROS.•SeNPs improved the basal metabolism and maintained calcium homeostasis.•SeNP is an environmental-friendly Se supplement for alleviating Cd stress.
Zn(II) is a necessary additive during antibiotic production and aquaculture, leading to the coexistence of Zn(II) and antibiotics in aquatic environment, especially in receiving waters of ...pharmaceutical and aquaculture wastewater. However, the roles of Zn(II) in the photochemical behavior of antibiotics are still not clear, which limits the understanding of the fate of antibiotic in nature. In this study, tetracycline (TC) was selected as typical antibiotic to evaluate the effect of Zn(II) on antibiotic photolysis. The removal of TC was accelerated by 22.75 % with TC:Zn(II) molar ratio at 1:5. The mechanism of Zn(II)-induced TC photolysis was explored via reactive oxygen species (ROS) analysis and density functional theory (DFT) calculation for the first time. Zn(II) could enhance the formation of TC excited states and further produce more singlet oxygen (12.54 % higher than control group) to promote indirect photolysis. Besides, Zn(II) could react with TC via complexation, and the complex was more vulnerable to attack by reactive oxygen species due to more active sites. Furthermore, the structure and toxicity of intermediates were identified with mass spectrometer, T.E.S.T. and ECOSAR software. Zn(II) hardly changed the degradation path of TC, and TC was mainly degraded via ring opening, demethylation, deamidation, and hydrogen abstraction with more toxic intermediates than the parent molecule. This work is significant to better understand the environmental fate of antibiotics, and also provides new insight into wastewater treatment in the pharmaceutical and aquaculture industry.
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•The photolysis of TC was effectively promoted in the presence of Zn(II).•Zn(II) changed the original active region of TC via complexation.•1O2 played an important role in Zn(II)-induced indirect photolysis of TC.•The generation of 1O2 were induced via the transformation of Zn-3TC⁎ and 3TC⁎.
Retinal ganglion cell (RGC) injury is one of the important pathological features of diabetes-induced retinal neurodegeneration. Increasing attention has been paid to find strategies for protecting ...against RGC injury. Long noncoding RNAs (lncRNAs) have emerged as the key regulators of many cell functions. Here, we show that Sox2OT expression is significantly down-regulated in the retinas of STZ-induced diabetic mice and in the RGCs upon high glucose or oxidative stress. SOX2OT knockdown protects RGCs against high glucose-induced injury in vitro. Moreover, Sox2OT knockdown plays a neuroprotective role in diabetes-related retinal neurodegeneration in vivo. Sox2OT knockdown could regulate oxidative stress response in RGCs and diabetic mouse retinas. Sox2OT knockdown plays an anti-oxidative role via regulating NRF2/HO-1 signaling activity. Taken together, Sox2OT knockdown may be a therapeutic strategy for the prevention and treatment of diabetes-induced retinal neurodegeneration.
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•3DG/MnO2 composites were fabricated via generating MnO2 on 3DG.•Tetracycline was removed efficiently by 3DG/MnO2 via adsorption and degradation.•Removal of tetracycline was enhanced ...due to synergistic effect of 3DG and MnO2.•The reaction of tetracycline with 3DG/MnO2 was endothermic and pH-dependent.
It is a great challenge to realize the effective removal and transform of emerging pharmaceuticals from aquatic environment. In this study, MnO2 was used as a catalyst to achieve the degradation of tetracycline (TC) in situ on the surface of three-dimensional graphene (3DG). The removal of TC were also evaluated at different temperature, pH and inorganic ions. Due to the synergistic effect of 3DG and MnO2, TC could be efficiently removed by 3DG/MnO2 composites. The removal data were fitted well with rate-retarded model, indicating that the adsorption of reaction products on the surface of 3DG/MnO2 composites could lead to saturation of surface and less reactive sites. Moreover, the reaction of TC with 3DG/MnO2 was endothermic, and reaction rate decreased with the increase of pH, due to the changes of properties of 3DG/MnO2 and TC. Inorganic ions could compete with TC for vacancy or the reactive sites on 3DG/MnO2 surface to inhibit the removal of TC. This work develops a potentially effective carbon material for simultaneous enrichment and degradation of organic pollutants and provides a new sustainable approach for wastewater treatment.
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•Graphene oxide–silver nanoparticles composite could be assembled on commercial membrane for biofouling control.•The composite membrane alleviates the biofouling process.•The ...composite membrane exhibited excellent antibacterial properties.
The removal of bacteria and other organisms from water is an important process, not only for water purification but also biofouling control in membrane filtration. In this study, we report an antibiofouling membrane by fabricating graphene oxide–silver nanoparticles (GO–AgNPs) composite onto cellulose acetate (CA) membrane. Microscopic analysis showed that the silver nanoparticles (AgNPs) retained its nanostructure morphology on the membrane surface. The contact angle results indicated that the hydrophilicity of the membrane was enhanced by the modification of modified GO–AgNPs. Under the continuous filtration test, the relative flux drop over GO–AgNPs composite membrane was only 46%, which was much lower than that the CA membrane (88%) after 24h filtration. Moreover, the flux of the GO–AgNPs composite membrane is higher than both the GO membrane and silver membrane in the filtration process. The presence of GO–AgNPs composite on the membrane exhibited a strong antibacterial activity, leading to an inactivation of 86% Escherichia coli after contacting with the membrane for 2h. This study may have great potential in developing high-performance antibiofouling membrane for membrane separation processes.
Recently, biochar is widely used as a soil amendment to improve soil properties, which might affect the fate and behavior of contaminants in soil. In this study, we investigated the effect of biochar ...on the migration of tetracycline (TC) in soil and their combined impacts on microbiome. Due to the strong interaction between soil and TC, adsorption, rather than photolysis or biodegradation, was the dominating dissipation way of TC in soil. Moreover, biochar could promote the vertical migration of TC through the decreased soil bulk density and its lower adsorption capacity. After 90-day incubation, only slight impact of TC on soil bacterial community was observed due to the rapid dissipation of TC in soil, whereas more available C supply induced by biochar significantly altered bacterial community via the enhancement of copiotrophic bacteria. Besides, biochar could decrease the soil pH and thus change the composition of fungal community. The effect of TC on fungal community was partially counteracted by biochar, which could adsorb part of TC and thus decrease the contact of TC with microorganisms. This work will improve our understanding of the fate of organic pollutants and evolution of microbiome in soil where biochar servers as soil amendment.
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•Adsorption is the dominant dissipation way for tetracycline in soils.•Biochar promoted vertical migration of tetracycline.•Biochar and tetracycline greatly shifted bacterial and fungal community composition in 90 days.
The residues of tetracycline in environment have raised increasing concern for the deleterious impact on ecological and human health. Natural organic matter (NOM), ubiquitous in natural waters, is ...unavoidable to encounter tetracycline, which might affect the fate of tetracycline in aquatic environment. In this study, we investigated the effect of natural organic matter (NOM) on the photolytic fate of tetracycline (TC). The photolysis kinetics of TC were evaluated with two representative NOM, tannic acid (TA) and gallic acid (GA). The presence of TA and GA obviously inhibited the removal of TC under UV irradiation with photolysis rate constant at 0.067 h−1 and 0.071 h−1, respectively, which were 32.3% and 28.3% less than that without TA and GA (0.099 h−1). Furthermore, NOM exhibited different impacts on both indirect photolysis and direct photolysis. NOM promoted the formation of hydroxyl radical, induced the generation of triplet-excited state NOM and thus greatly enhanced the indirect photolysis of TC. However, direct photolysis was almost completely inhibited by NOM via inner filter effect and interacting with TC to form ground-state complex with low photoreactive. Moreover, similar intermediates were detected in the presence and absence of NOM, indicating that NOM exhibited limited influence on the degradation pathways of TC. This study reveals the multiple roles of NOM on tetracycline photolysis, contributing to better understand the photolytic fate of antibiotics in natural waters.
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•The presence of NOM would slow the photolysis of tetracycline.•NOM greatly enhanced the indirect photolysis of tetracycline and almost completely inhibited the direct photolysis of tetracycline.•NOM exhibited limited influence on the degradation pathways of tetracycline.
