Tetracycline Adsorption Performance and Mechanism Using Calcium Hydroxide-Modified Biochars.

Tetracycline is frequently found in various environments and poses significant ecological risks. Calcium hydroxide-modified biochar has shown potential as a material for removing multiple classes of pollutants from wastewater streams. The tetracycline-adsorption performance and mechanism of alkali-modified biochars derived from nine wastes (corn straw, rice straw, swine manure, cypress powder, wheat straw, peanut shell, walnut shell powder, soybean straw, and corncobs) were investigated in the study. Among the four alkalis tested, calcium hydroxide exhibited the most effective modification effects at a pyrolysis temperature of 500 °C. Straw biomass was most suitable to be modified by calcium hydroxide, and calcium hydroxide-modified biochar showed the highest adsorption performance for tetracycline. The maximum adsorption capacities were 8.22 mg g-1 for pristine corn straw biochar and 93.46 mg g-1 for calcium hydroxide-modified corn straw biochar. The tetracycline adsorption mechanism by calcium hydroxide-modified corn straw biochar involved hydrogen bonding, oxygen-containing functional groups, Ca2+ metal complexation, and electrostatic attraction. Consequently, calcium hydroxide-modified corn straw biochar emerges as an environment-friendly, cost-effective, and efficient tetracycline adsorbent.

Phytoremediation of fluoroalkylethers (ether-PFASs): A review on bioaccumulation and ecotoxilogical effects.

Fluoroalkylethers (ether-PFASs), as alternatives to phased-out per- and perfluoroalkyl substances (PFASs), have attracted mounting attention due to their ubiquitous detection in aquatic environment and their similarity to legacy PFASs in terms of persistence and toxicity. In this review, the sources and distribution of ether-PFASs in soil ecosystem as well as their toxic impacts on soil microbial community are summarized. The plant uptake and bioaccumulation potential of ether-PFASs are presented, and a wide range of the influencing factors for their uptake and translocation is discussed. In response to ether-PFASs, the corresponding phytotoxic effects, such as seed germination, plant growth, photosynthesis, oxidative damage, antioxidant enzymes activities, and genotoxicity, are systematically elucidated. Finally, the current knowledge gaps and future research prospective are highlighted. The findings of this review will advance our understanding for the environmental behavior and implications ether-PFASs in soil-plant systems and help explore the strategies for ether-PFASs remediation to minimize their adverse toxicity.

Insight into radical-nonradical coupling activation pathways of peroxymonosulfate by CuxO for antibiotics degradation.

In this work, a heterogeneous catalyst of CuxO was rationally designed by using Cu-based metal organic frameworks (marked Cu-BDC) as the template, and was used to degrade tetracycline (TC) via activation of peroxymonosulfate (PMS). The optimal CuxO-350 showed excellent catalytic efficiency for TC degradation, and the reaction rate constant (0.104 min-1) was 8 times higher than that (0.013 min-1) of raw Cu-BDC. The characterization observations confirmed that CuxO-350 possessed multiple valence states (CuO and Cu2O) and oxygen vacancies (Ov), both of which were favorable for the activation of PMS, resulting in promoting the generation of active species in the CuxO-350 + PMS system. Different from the free radical pathway in Cu-BDC + PMS system, a radical-nonradical coupling process was detected in the CuxO-350 + PMS system, which was confirmed by quenching experiments and EPR measurements. Moreover, the toxicity prediction showed that the toxicity of degradation intermediates declined compared with TC. This work not only opened up a new strategy for the rational design and preparation of high-efficient catalysts by employing metal organic frameworks precursors, but also offered an insight into the reaction mechanism of PMS activation through a radical-nonradical coupling process catalyzed by CuxO-350 derived from Cu-BDC.

Transformation of sulfamethoxazole by sulfidated nanoscale zerovalent iron activated persulfate: Mechanism and risk assessment using environmental metabolomics.

The threat caused by the misuse of antibiotics to ecology and human health has been aroused an extensive attention. Developing cost-effective techniques for removing antibiotics needs to put on the agenda. In current research, the degradation mechanism of sulfamethoxazole (SMX) by sulfidated nanoscale zerovalent iron (S-nZVI) driven persulfate, together with the potential risk of intermediates were studied. The degradation of SMX followed a pseudo-first order kinetics reaction with kobs at 0.1176 min-1. Both SO4•- and •OH were responsible for the degradation of SMX, and SO4•- was the predominant free radical. XPS analysis demonstrated that reduced sulfide species promoted the conversion of Fe (III) to Fe (II), resulting in the higher transformation rate of SMX. Six intermediates products were generated through hydroxylation, dehydration condensation, nucleophilic reaction, and hydrolysis. The risk of intermediates products is subsequently assessed using E. coli as a model microorganism. After E.coli exposure to intermediates for 24 h, the upmetabolism of carbohydrate, nucleotide, citrate acid cycle and downmetabolism of glutathione, sphingolipid, galactose by metabolomics analysis identified that SMX was effectively detoxified by oxidation treatment. These findings not only clarified the superiority of S-nZVI/persulfate, but also generated a novel insight into the security of advanced oxidation processes.

Effects of aging on surface properties and endogenous copper and zinc leachability of swine manure biochar and its composite with alkali-fused fly ash.

Biochar aging is a key factor leading to the decline of biochar stability and the release of endogenous pollutants. This study investigated the effects of five artificial and simulated aging processes on the surface properties and endogenous copper (Cu) and zinc (Zn) leachability of swine manure biochar and its composite with alkali-fused fly ash. Aging obviously reduced carbon (C) content on the surface of swine manure biochar and increased oxygen (O) content. Among all the aging treatments, high-temperature aging had the greatest effect on C content. Following the aging treatments, the C-C bond contents on the surfaces of swine manure biochar decreased significantly, whereas the C-O bonds increased significantly; however, there were less changes in the amounts of C-C and C-O bonds on the surfaces of modified biochar than on swine manure biochar. Aging significantly enhanced the leaching toxicity of Cu and Zn, and Zn availability and bioaccessibility in swine manure biochar and modified biochar. However, it minimized Cu availability and bioaccessibility, especially under high-temperature aging. Greater amounts of Zn than Cu were extracted from swine manure biochar and modified biochar. However, under all the aging treatments, the leaching toxicity, availability, and bioaccessibility of Cu and Zn in modified biochar were significantly lower than in swine manure biochar. This implies that modified biochar application poses lower environmental risks than swine manure biochar.

Synthesis of silica-composited biochars from alkali-fused fly ash and agricultural wastes for enhanced adsorption of methylene blue.

Two types of silica-composited biochars were prepared by mixing swine manure or rice straw with alkali-fused fly ash (AFFA) followed by pyrolysis. A 10% (w/w) AFFA modification improved the specific surface area, pore volume, and average pore size of the biochars. Certain surface oxygen-containing functional groups (i.e., -OH and CO) in the biochars were protected, and silicon-oxygen bonds (i.e., O-Si-O and OSi) were strengthened considerably by AFFA modifications during high-temperature pyrolysis. The adsorption capacity of biochar for methylene blue (MB) was enhanced after AFFA modification, and a modified biochar with the highest adsorption capacity was prepared at a pyrolysis temperature of 700 °C, pyrolysis holding time of 2 h, and an AFFA proportion of 10%. The MB adsorption capacity of the modified biochars significantly increased when the pH of the solution increased (from 3 to 13). The adsorption data were well described by a pseudo-second-order model and Langmuir isotherms. The maximum MB adsorption capacities of the modified swine manure and rice straw biochars were 143.76 mg/g and 131.58 mg/g, respectively. The adsorption capacities of the AFFA-modified biochars were 10.7-112.3% higher than those of the unmodified biochars. The enhanced MB adsorption capacities of the former appear to be attributed to their increased specific surface areas, increased porosities, strong oxygen-containing functional groups, and high contents of exchangeable sodium ions. These results indicate that industrial and agricultural wastes can be reused to produce novel silica-composited biochars with high MB removal capacity. Accordingly, these biochars could be effectively used to treat wastewater and thus to mitigate solid waste disposal-related problems.

Ternary Monolithic ZnS/CdS/rGO Photomembrane with Desirable Charge Separation/Transfer Routes for Effective Photocatalytic and Photoelectrochemical Hydrogen Generation.

Highly efficient and easy recyclable monolithic photocatalysts with ideal separation/transport route for photogenerated charge carriers are much desired. In this work, a ZnO seed-induced growth approach is developed to fabricate a ternary monolithic photomembrane, that is, ZnS/CdS heterojunction nanorods in situ grow into the interspaces of multilayer reduced graphene oxide (rGO) sheets (denoted as ZnS/CdS/rGO). The monolithic ZnS/CdS/rGO photomembrane can serve as an efficient visible-light photoactive membrane for photocatalytic (PC) or photoelectrochemical (PEC) hydrogen generation. The fast electron transport of 1D CdS nanorods, the excellent electronic conductivity of multilayer stacked rGO sheets, the intense visible-light absorption of CdS, the unique hierarchical structure, and double heterojunctions (ZnS/CdS and CdS/rGO) efficiently boost the photogenerated electron-hole pairs separation and transfer across the interfacial domain of the photomembrane under visible-light irradiation. Furthermore, the superior stability and reusability of the photomembrane is achieved by the ideal process of photogenerated electron-hole pair separation/transfer, i.e., holes transfer to ZnS and electrons transfer to rGO to inhibit CdS from photocorrosion.

Experimental study on radon exhalation behavior of heap leaching uranium ore column with dilute sulfuric acid.

In order to study the radon release behavior when heap leaching uranium ores with dilute sulfuric acid, unleached uranium ores from a uranium mine in southern China were selected as test samples. Adopting parameters from leaching processes commonly used in uranium mines, a laboratory experiment was carried out for 21 days with a one-dimensional acid heap leaching experimental column. The surface radon exhalation rate of uranium ore column was determined by static accumulation method while spraying with deionized water and dilute sulfuric acid. The uranium leaching rate and ore column height for all 21 days of the experiment were also measured. The results show that (1) when sprayed with a leaching agent, the surface radon exhalation rate of uranium ore column initially increased with time sharply. After a maximum value was reached, the rate gradually decreased and stabilized. When the spraying stopped, the surface radon exhalation rate of uranium ore column initially decreased, before increasing until it tended to stabilize. (2) During the entirety of the 21-day leaching experiment, the cumulative leaching rate of uranium increased gradually with time. On the other hand, the surface radon exhalation rate of uranium ore column fluctuated, but the leaching of uranium from uranium ores had almost no effect on the radon exhalation rate. (3) There was no linear correlation between the surface radon exhalation rate and the residual height of ore column during leaching, but the collapsing event of ore column was the direct inducing factor of the fluctuation of surface radon exhalation rate.

Earth-abundant NiS co-catalyst modified metal-free mpg-C3N4/CNT nanocomposites for highly efficient visible-light photocatalytic H2 evolution.

In the present work, the earth-abundant NiS co-catalyst modified mesoporous graphite-like C3N4 (mpg-C3N4)/CNT nanocomposites were prepared via a two-step strategy: the sol-gel method and the direct precipitation process. The mpg-C3N4/CNT/NiS composite photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectroscopy, photoluminescence spectroscopy (PL), photoelectrochemical (PEC) and electrochemical impedance spectra (EIS) experiments. The photocatalytic H2-production activity over the composite catalysts was also evaluated by using an aqueous solution containing triethanolamine under visible light (λ≥ 420 nm). The results showed that the loading of earth-abundant NiS co-catalysts onto metal-free mpg-C3N4/CNT nanocomposites can remarkably enhance their photocatalytic H2-production activity. The optimal loading amount of NiS on metal-free mpg-C3N4/CNT nanocomposites was about 1 wt%. The as-obtained mpg-C3N4/CNT/1% NiS ternary composite photocatalyst exhibits the best H2-evolution activity with the highest rate of about 521 µmol g(-1) h(-1) under visible light (λ≥ 420 nm), which is almost 148 times that of a pure mpg-C3N4/CNT sample. The enhanced photocatalytic activity can be mainly attributed to the synergistic effect of effectively promoted separation of photo-generated electron-hole pairs and enhanced H2-evolution kinetics. The co-loading of nanocarbon materials and earth-abundant co-catalysts onto metal-free mpg-C3N4 photocatalysts offers great potential for practical applications in photocatalytic H2 evolution under visible light illumination.

[Effects of leukemia bone marrow stromal cells on resistance of co-cultured HL-60 to idarubicin].

To study the role of hematopoietic microenvironment abnormality in development of minimal residual disease and its mechanism, the viability of HL-60 cells was investigated by means of bone marrow stromal cell culture system or co-culture system of bone marrow stromal cell with HL-60 cells and idarubicin (IDA), flow cytometry and ELISA. The results showed that viability of HL-60 cells gradually decreased along with the increase of IDA dose and prolongation of culture time. Amount of HL-60 cells co-cultured with leukemia bone marrow stramal cells was significantly increased as compared with that of the control (P < 0.05). Bone marrow stromal cells or stromal cell conditioned medium reduced the effect of IDA on HL-60 cells in culture. In conclusion, leukemia bone marrow stromal cells contribute to increasing resistance of HL-60 cells to chemotherapeutic agents, and play some role in developing minimal residual disease.