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Combining phytoremediation plants and microorganisms is a promising method of remediating heavy metal contaminated soil. In this study, two manganese-tolerant strains were isolated from Mn slag and identified as Bacillus cereus HM5 and Bacillus thuringiensis HM7. These two Bacillus spp. have the ability to dissolve phosphorus, produce IAA and iron carrier. A pot experiment of Broussonetia papyrifera was conducted to explore potential of B. cereus HM5 and B. thuringiensis HM7 to improve effect of remedying Mn pollution by B. papyrifera. The strains were inoculated under different Mn treated (5 mmol/L, 50 mmol/L, Mn slag) respectively and the growth, root structure, root activity, physiological and biochemical characteristics of the leaves and accumulation of Mn for B. papyrifera were determinated. The effects of the soil environment to remediation were observed, the results showed that the biomass, total root length, surface area, crossings, tips, forks and root activity of B. papyrifera with inoculated strain were higher than those of the control group. The inoculation of these two Bacillus spp. increased the absorption of Mn by B. papyrifera and the concentration of Mn in the aerial parts of plants, indicating that the two strains could promote the growth of B. papyrifera and the accumulation of Mn. In addition, microbes reduced malonaldehyde content and the activities of antioxidant enzymes in leaves, suggesting that the two Bacillus spp. reduced Mn-induced oxidative stress. The principal component analysis showed that the added Bacillus strain prefer to promote plant root function maintenance and improve soil environment, rather than direct adsorption of heavy metals. These observations indicated that B. cereus HM5 and B. thuringiensis HM7 were valuable microorganisms, which could improve the remediating efficiency of B. papyrifera under Mn-contaminated soil. • B. cereus HM5/ B. thuringiensis HM7 improved the accumulation of Mn by B. papyrifera. • B. cereus HM5 and B. thuringiensis HM7 could reduce oxidative stress induced by Mn. • The strains promoted the growth of plant root system and improved soil environment. [ABSTRACT FROM AUTHOR]

Abstract A novel ternary composite of graphitic carbon nitride (g-C 3 N 4)/graphene oxide (GO) sheets/BiFeO 3 (CNGB) with highly enhanced visible-light photocatalytic activity toward Cr(VI) photoreduction is prepared and characterized. The characterization and photocatalysis experiments corroborate its reasonable band gap, efficient charge separation and transfer, widened visible-light adsorption, easy solid-liquid separation, good stability and superior catalytic activity of CNGB. Three CNGB samples with different ratios of g-C 3 N 4 and BiFeO 3 (CNGB-1, -2, -3 with 2:4, 3:3, and 4:2, respectively), though possessing different adsorption ability, eventually remove all Cr(VI) ions via photocatalysis within 90 min. The catalytic efficiency of the composite is the highest at pH 2; increases in pH decrease the catalytic ability. The inorganic anions such as SO 4 −, Cl−, and NO 3 − only slightly affects the photocatalytic process. The matching of the band structure between BiFeO 3 and g-C 3 N 4 generates efficient photogenerated electron migration from the conduction band of g-C 3 N 4 to that of BiFeO 3 , which is also facilitated by the electron bridging and collecting effects of GO, and holes transfer from the valence band of BiFeO 3 to that of g-C 3 N 4 , yielding the efficient separation of photogenerated electron-hole pairs and the subsequent enhancement of photocatalytic activity. The research provides a theoretical basis and technical support for the development of photocatalytic technologies for effective application in wastewater treatment and Cr-contaminated water restoration. Highlights • g-C 3 N 4 /graphene oxide/BiFeO 3 (CNGB) ternary assembly is easily prepared. • CNGB shows excellent photocatalysis of Cr (Ⅵ) reduction and easy removal from water. • CNGB shows maximized efficiency at low pH. • CNGB have little chance of electron-hole recombination. • CNGB shows great visible-light response. [ABSTRACT FROM AUTHOR]

Developing broad-spectrum light reactions, effective charge separation, and easily recoverable photocatalysts were considered cost-effective pollution remediation methods. The ZnFe 2 O 4 /BC/ZnO composite was prepared to achieve these objectives, where biochar (BC) was used as a conductive channel and ZnFe 2 O 4 as a magnetic substance. Among them, the 0.6-ZBO composite performed the best, with photocatalytic removal of tetracycline (TC) reaching 85.6%. The photocatalytic degradation rated constant of 0.6-ZBO composite was 23.36 × 10−3 min−1, which was 7.6, 4.1, and 2.5 times higher than that of ZnFe 2 O 4 /BC, ZnO, and ZnFe 2 O 4 /ZnO samples, respectively. According to several characterization data, it was demonstrated that successful Z-scheme heterojunctions were constructed between ZnFe 2 O 4 and ZnO. The 0.6-ZBO complex increased the range of light absorption and strengthened the separation of electron-hole pairs, thus improving the redox ability of the complex. In the different water matrices, the stability of 0.6-ZBO was excellent and its ability to remove TC decreased slightly to about 11% after 5 cycles. This work provided a valuable approach to design a novel and efficient system for degrading organic pollutants in wastewater using magnetic biochar. [Display omitted] • A novel ZnFe 2 O 4 /BC/ZnO (ZBO) Z-scheme heterojunction was successfully constructed. • The ZBO heterojunction promotes the separation of electron-hole pairs. • BC as a conductive channel of ZnO and ZnFe 2 O 4. • The ZBO composite was relatively effective to remove TC from the wastewater. [ABSTRACT FROM AUTHOR]

For highly efficient photocatalytic remediation of organic pollutants, broad-spectrum light response and effective charge separation are two key goals. To achieve these goals, a novel biochar (BC) modified PbMoO 4 composite catalyst was successfully synthesized in situ by combining coprecipitation with pyrolysis treatment of poplar sawdust and the technical feasibility of degradation of tetracycline (TC) with compound photocatalyst prepared from recovered agricultural and forestry residues was preliminarily demonstrated. The characterization demonstrated that the presence of BC narrowed the bandgap, enhanced visible light absorption as well as facilitated charge separation. Three composites (with the mass ratio of PbMoO 4 to BC = 1:4; 1:1; and 4:1, respectively) displayed higher activity than pure PbMoO 4. The results showed that the composite with the PbMoO 4 to BC ratio of 1:4 exhibited the best photocatalytic activity, for 150 mg L−1 TC the removal rate was 61.0%, and the rate constant was 8.1 × 10−3 min−1, while the photocatalytic activity of PbMoO 4 was 26.0% and 3.9 × 10−3 min−1. The reactions in the presence of radical quenchers indicated that holes (h+) and superoxide radicals (O 2 −) were the dominant active species for photodegradation. In different water matrices, for 150 mg L−1 TC solution the photocatalytic activity of optimal photocatalyst decreased as follows: ultrapure water > artificial sewage > farm sewage > municipal sewage. Moreover, the catalyst exhibited good stability over five cycles. Therefore, BC doped PbMoO 4 provides a useful strategy for improving the photocatalytic ability of PbMoO 4 -based photocatalysts and offers a promising method for water purification. [Display omitted] • Using poplar sawdust as biochar source realized the rational application of waste. • In situ synthesis enhanced the adsorption and photocatalytic activity of PbMoO 4. • Superior electrical conductivity of BC helps transport of photogenerated carrier. • BC strengthened the visible light response of PbMoO 4 @BC-1. • PbMoO 4 @BC-1 showed promising visible-light photodegradation for TC degradation. [ABSTRACT FROM AUTHOR]