[Compositional Variation of Spent Mushroom Substrate During Cyclic Utilization and Its Environmental Impact].

Nutrition components and elements analysis of spent mushroom substrates/composts (SMS/SMC) during a cyclic utilization were performed to state the compositional variation during reutilization and composting process. Environmental risk assessment of heavy metals and other pollutants were also taken into consideration. The results showed that the water consumption during reutilization reached 13.8%; while the protein and polysaccharide contents increased by 32.9% and 20.4%, respectively, suggesting that SMS still had a lot of nutrients. After composting disposal, however, the protein and polysaccharide contents decreased by 50% and 79%, respectively, while the lignin, cellulose and hemicellulose contents didn't show a significant difference; the C/N ratio decreased; the total humic acid content increased by 18.6%, all of which means that the composting process made great contributions to organic degradation. The heavy metal analysis showed that As, Hg, Pb, Cd, Cr concentrations in organic compost met the requirement of limit standard (NY525-2012). In addition, the results of column leaching test showed that N, P and organics in both SMS and SMC had a possibility of leaching loss, and the accumulation of TN and COD in SMC leachate decreased by 15.0% and 62.8%, respectively, compared to SMS group.

Fe3O4 and MnO2 assembled on honeycomb briquette cinders (HBC) for arsenic removal from aqueous solutions.

In this study, a novel composite adsorbent (HBC-Fe3O4-MnO2) was synthesized by combining honeycomb briquette cinders (HBC) with Fe3O4 and MnO2 through a co-precipitation process. The purpose was to make the best use of the oxidative property of MnO2 and the adsorptive ability of magnetic Fe3O4 for enhanced As(III) and As(V) removal from aqueous solutions. Experimental results showed that the adsorption capacity of As(III) was observed to be much higher than As(V). The maximum adsorption capacity (2.16 mg/g) was achieved for As(III) by using HBC-Fe3O4-MnO2 (3:2) as compared to HBC-Fe3O4-MnO2 (2:1) and HBC-Fe3O4-MnO2 (1:1). The experimental data of As(V) adsorption fitted well with the Langmuir isotherm model, whereas As(III) data was described perfectly by Freundlich model. The pseudo-second-order kinetic model was fitted well for the entire adsorption process of As(III) and As(V) suggesting that the adsorption is a rate-controlling step. Aqueous solution pH was found to greatly affect the adsorption behavior. Furthermore, co-ions including HCO3(-) and PO4(3-) exhibited greater influence on arsenic removal efficiency, whereas Cl(-), NO3(-), SO4(2-) were found to have negligible effects on arsenic removal. Five consecutive adsorption-regeneration cycles confirmed that the adsorbent could be reusable for successive arsenic treatment and can be used in real treatment applications.

[Removal of Cr(VI) by iron filings with microorganisms to recover iron reactivity].

The reduction of Cr(VI) by iron filings and microorganisms was carried out during our investigation. Effects of factors (e. g. temperature, initial pH, iron filings loadings, inoculum size, initial concentration of Cr(VI) and other ions) on Cr(VI) reduction were studied, and the X-ray photoelectron spectroscopy (XPS) was applied to explore elements composition on the surface of iron filings. Experimental results revealed a promotion of Cr(VI) reduction by iron filings with the presence of microorganisms, and the Cr(VI) removal was complete within 18 h. Results showed the Cr(VI) reduction preferred a higher temperature within the range of 25-42 degrees C and the optimum initial pH was supposed to be 5.8. The efficiency of Cr(VI) reduction was increased with increasing amounts of iron filings and microorganisms, and was decreased with the increasing initial concentration of Cr( VI). Mn2+, Zn2+, Co2+, Cu2+ and Ni2+ ions could cause varying degrees of inhibition of Cr(VI) reduction, and among these ions, the effect of Mn2+ was the smallest and that of Ni2+ was the highest. Characterizations with XPS indicated the deposition of Cr element on iron filings surface in forms of Cr(III) and Cr(VI), as the Cr2p3/2 region could be decomposed into two peaks at (576.8 +/- 0.1) eV and (578.1 +/- 0.1) eV. Furthermore, Cr(III) was most likely to be in the form of Cr(OH)3 or Fe(x)Cr(1-x)(OH)3.