One-step self-assembly of Fe-biochar composite for enhanced persulfate activation to phenol degradation: Different active sites-induced radical/non-radical mechanism.

Persulfate (PS) activation by nanoscale zerovalent iron (nZVI) is promising for water purification, while is limited due to its easy agglomeration and oxidation. Herein, nZVI encapsuled in carbon matrix shell was synthesized via one-step carbothermal reduction. The core-shell structure effectively inhibited oxidation and agglomeration of nZVI core, and graphitized porous structures facilitated phenol binding with maximal adsorption capacity of 117.10 mg/g achieved by nZVI0.6-BC800. Both reactive oxygen species (SO4•-, O•H, O2•- and 1O2) and electron transfer process resulted in phenol decomposition. Owing to diversified active sites, the nZVI0.6-BC800/PS system could completely degrade phenol degradation within short time, and exhibited great adaptation to extensive pH range (3.0-9.0) and coexisting substances. Additionally, the nZVI0.6-BC800/PS system could maintain over 85% removal of phenol after three recycles or 50 days of storage, and was highly-efficient to different water environments, thus proposing rational design of iron-carbon catalyst with potential in water treatment.

Exogenous application of Bradyrhizobium japonicum AC20 enhances soybean tolerance to atrazine via regulating rhizosphere soil microbial community and amino acid, carbohydrate metabolism related genes expression.

Atrazine is used to control broad-leaved weeds in farmland and has negative impacts on soybean growth. Legume-rhizobium symbiosis plays an important role in regulating abiotic stress tolerance of plants, however, the mechanisms of rhizobia regulate the tolerance of soybean to atrazine based on the biochemical responses of the plant-soil system are limited. In this experiment, Glycine max (L.) Merr. Dongnong 252, planted in 20 mg kg-1 of atrazine-contaminated soil, was inoculated with Bradyrhizobium japonicum AC20, and the plant growth, rhizosphere soil microbial diversity and the expression of the genes related to soybean carbon and nitrogen metabolism were assessed. The results indicated that strain AC20 inoculation alleviated atrazine-induced growth inhibition via increasing the contents of leghemoglobin and total nitrogen in soybean seedlings. The psbA gene expression level of the soybean seedlings that inoculated strain AC20 was 1.4 times than that of no rhizobium inoculating treatments. Moreover, the inoculated AC20 increased the abundance of Acidobacteria and Actinobacteria in soybean rhizosphere. Transcriptome analysis demonstrated that strain AC20 regulated the genes expression of amino acid metabolism and carbohydrate metabolism of soybean seedlings. Correlation analysis between 16S rRNA and transcriptome showed that strain AC20 reduced Planctomycetes abundance so as to down-regulated the expression of genes Glyma. 13G087800, Glyma. 12G005100 and Glyma.12G098900 involved in starch synthesis pathway of soybean leaves. These results provide available information for the rhizobia application to enhance the atrazine tolerate in soybean seedlings.

A novel PEI-grafted N-doping magnetic hydrochar for enhanced scavenging of BPA and Cr(VI) from aqueous phase.

Herein, polyethyleneimine (PEI)-grafted nitrogen-doping magnetic hydrochar (PEIMW@MNHC) was synthesized for hexavalent chromium (Cr(VI)) and bisphenol A (BPA) elimination from water. Characterizations exhibited that abundant amino functional groups, intramolecular heterocyclic N, azo and Fe-NX structures were successfully introduced into the inherent structure of hydrochar. The obtained PEIMW@MNHC presented maximum uptake of 205.37 and 180.79 mg/g for Cr(VI) and BPA, respectively, and was highly tolerant to various co-existing ions. Mechanism investigation revealed that the protonated amino, intramolecular heterocyclic N and Fe(II) participated in Cr(VI) reduction, and the N/O-containing groups and Fe(III) fixed Cr(III) onto PEIMW@MNHC by the formation of complexes and precipitates. On the other hand, azo, Fe-NX and graphitic N structures contributed to the removal of BPA via pore filling, hydrogen bonding and π-π interactions. Additionally, PEIMW@MNHC maintained over 85.0% removal efficiency for Cr(VI) and BPA after four cycles, manifesting that PEIMW@MNHC was an ideal adsorbent with outstanding practical application potential.

Pinecone-derived magnetic porous hydrochar co-activated by KHCO3 and K2FeO4 for Cr(VI) and anthracene removal from water.

Herein, magnetic porous pinecone-derived hydrochar (MPHCMW) co-activated by KHCO3 and K2FeO4 through one-step microwave-assisted pyrolysis was innovatively synthesized for hexavalent chromium (Cr(VI)) and anthracene (ANT) removal from water. The analyses of characterization consequences and co-activation mechanisms not merely proved the high specific surface area (703.97 m2/g) and remarkable microporous structures of MPHCMW caused by the synergistic chemical activation of KHCO3 and K2FeO4, but also testified successful loading of Fe0 and Fe3O4 on MPHCMW by the process of carbothermal reduction between K2FeO4 and carbon matrix of hydrochar. The resultant MPHCMW possessed pH-dependence for Cr(VI), while adsorption for ANT was hardly impacted by the pH of solution. Moreover, the adsorption processes of MPHCMW could attain equilibrium within 60 min for Cr(VI) and 30 min for ANT with multiple kinetics, and the corresponding adsorption capacity for Cr(VI) and ANT was 128.15 and 60.70 mg/g, respectively. Additionally, the adsorption percentages of MPBCMW for Cr(VI)/ANT was maintained at 87.87/82.64% after three times of adsorption-desorption cycles. Furthermore, pore filling, complexation, electrostatic interaction, reduction and ion exchange were testified to enhance the removal of Cr(VI), while the ANT removal was achieved via π-π stacking, complexation, pore filling and hydrogen bonding force.