Xingjian Xu

Fabrication of Z-scheme magnetic MoS2/CoFe2O4 nanocomposites with highly efficient photocatalytic activity

MoS2 thin nanosheets decorated with CoFe2O4 nanoparticles have been successfully synthesized via a simple hydrothermal method. The nanocomposites are characterized by XRD, TEM, HRTEM, BET, XPS, UV-Vis DRS, PL and magnetic property analysis. The Z-scheme mechanism at the interface of MoS2 and CoFe2O4 is formed. When the mass ratio of MoS2 and CoFe2O4 is 1:3, the MoS2/CoFe2O4 nanocomposites present excellent photocatalytic performance. The degradation rate of rhodamine B (RhB) and congo red (CR) is 93.80% and 94.43% in 90 and 50 min, respectively, under visible light irradiation. The highly photocatalytic activity could be mainly ascribed to the formed Z-scheme mechanism which facilitates the separation of photoinduced electron-hole pairs. Besides, the MoS2 thin nanosheets not only provide the most active sites for photocatalytic reactions, but also act as the backing material for CoFe2O4 nanoparticles to effectively disperse and avoid the magnetic aggregation. Moreover, the MoS2/CoFe2O4 nanocomposites present a good recyclability and the degradation rate of RhB and CR is still beyond 82% after seven runs. In addition, the nanocomposites can be easily separated by an external magnet.

High performance and prospective application of xanthate-modified thiourea chitosan sponge-combined Pseudomonas putida and Talaromyces amestolkiae biomass for Pb(II) removal from wastewater

Biosorption using microbes has been proved to be an efficient technology to remove heavy metals from wastewater, whereas the imperfections in mechanical property and separation limit their practical application. In this study, Pseudomonas putida I3 and Talaromyces amestolkiae Pb respectively combined with xanthate-modified thiourea chitosan sponge (PXTCS and TXTCS) were synthesized to investigate the Pb(II) removal ability from solutions. The prepared biosorbents possessed a three-dimensional macroporous structure convenient for separation. Experimental data indicated their biosorption behaviors well followed the pseudo-second-order kinetics and Langmuir isotherm model. The maximum biosorption capacities of PXTCS and TXTCS were 232.03 and 241.61mgg-1 with 40% P. putida I3 and 15% T. amestolkiae Pb, respectively. For the effects of co-existing metal ions on Pb(II) biosorption, the promoting degree followed the sequence: Zn(II)>Na(I)≈K(I)>Ca(II)>Mg(II)≈Al(III)≫Cd(II)>Fe(III). Both prepared biosorbents were effective in removing heavy metals from simulated industrial effluents containing various trace-level heavy metals or high concentration Pb(II).

Novel mesoporous TiO 2 @g-C 3 N 4 hollow core@shell heterojunction with enhanced photocatalytic activity for water treatment and H 2 production under simulated sunlight

A novel mesoporous TiO2@g-C3N4 hollow core@shell heterojunction photocatalyst was engineered for the first time by in situ calcining and growing of cyanamide (CY) on the surface of TiO2. The HTCN-1 possesses good structure and performance when the addition amount of CY is 1 mL. HTCN-1 shows high photocatalytic activity toward congo red (CR), rhodamine B (RhB), phenol and ciprofloxacin (CIP) with degradation efficiencies of 97%, 100%, 73%, and 74%, respectively. HTCN-1 also displays high photocatalytic activity for H2 generation at rate of 7.9 μmol h-1. A possible charger transfer mechanism and photocatalytic degradation mechanism of HTCN-1 are proposed basing on the experiment results. The enhanced photocatalytic activity may be attributed to the higher charge transfer efficiency of photogenerated electron-hole (e--h+) pairs caused by close contacts, a larger interfacial area, and the higher barrier for conduction bending. Whats more, HTCN-1 possesses relatively high stability during the entire photoreaction process. Given the unique spatial structure and superior photocatalytic characteristics of the HTCN-1, there is great potential for applications in water treatment and H2 generation.

Integration of chemical and toxicological tools to assess the bioavailability of copper derived from different copper-based fungicides in soil

Because the extensive use of Cu-based fungicides, the accumulation of Cu in agricultural soil has been widely reported. However, little information is known about the bioavailability of Cu deriving from different fungicides in soil. This paper investigated both the distribution behaviors of Cu from two commonly used fungicides (Bordeaux mixture and copper oxychloride) during the aging process and the toxicological effects of Cu on earthworms. Copper nitrate was selected as a comparison during the aging process. The distribution process of exogenous Cu into different soil fractions involved an initial rapid retention (the first 8 weeks) and a following slow continuous retention. Moreover, Cu mainly moved from exchangeable and carbonate fractions to Fe-Mn oxides-combined fraction during the aging process. The Elovich model fit well with the available Cu aging process, and the transformation rate was in the order of Cu(NO3)2 > Bordeaux mixture > copper oxychloride. On the other hand, the biological responses of earthworms showed that catalase activities and malondialdehyde contents of the copper oxychloride treated earthworms were significantly higher than those of Bordeaux mixture treated earthworms. Also, body Cu loads of earthworms from different Cu compounds spiked soils were in the following order: copper oxychloride > Bordeaux mixture. Thus, the bioavailability of Cu from copper oxychloride in soil was significantly higher than that of Bordeaux mixture, and different Cu compounds should be taken into consideration when studying the bioavailability of Cu-based fungicides in the soil.

A facile approach for surface alteration of Pseudomonas putida I3 by supplying K2SO4 into growth medium: Enhanced removal of Pb(II) from aqueous solution

A new sight of obtaining a high efficient biosorbent by supplying specific salts into bacterial growth medium was investigated in this study for Pb(II). Among a series of salts including Na2SO4, Na2S2O3, KCl, and K2SO4, the highest Pb(II) removal efficiency was observed by psychrotrophilic Pseudomonas putida I3 grown in the presence of 30g/L K2SO4 (KSI3-30) with biosorption capacity of 62.89mg/g under cold condition (15°C), which was increased by 42.35% as compared to control (without any additive, RI3). This stimulation effect was ascribed to the increase of potassium and sulfur containing groups on KSI3-30 surface via metabolic dependent ways. The probable mechanism for Pb(II) adsorption was ion-exchange and chemical complexation. The thermal and kinetic data well fitted to Langmuir adsorption model and pseudo-second order and intraparticle diffusion kinetic model. Good recyclability and effectively dealing with real wastewater suggested KSI3-30 was a promising biosorbent for Pb-contaminated wastewater treatment.