Liyuan Chai

The anaerobic granular sludge from an Internal Circulation (IC) reactor of a paper mill wastewater treatment plant were seeded in an Anammox upflow anaerobic sludge blanket reactor. After 185 days operation, the reactor was finally started up by increasing the influent ammonium and nitrite concentrations to 224 mg/L and 255 mg/L, respectively, with volumetric nitrogen removal rate increasing to 3.76 kg/(m3·d). The physicochemical characteristics of the cultivated Anammox granules were observed by scanning electron microscope, transmission electron microscope and Fourier Transform infrared spectroscopy (FTIR). Results suggested that during the start-up course, the granular sludge initially disintegrated and then re-aggregated. FTIR spectra results revealed that the Anammox granular sludge contained abundant functional groups, indicating that it may also possess good adsorption properties. The ecological structure of the granular sludge, analyzed by the metagenomic sequencing methods, suggested that the relative abundance of the dominant bacterial community in the seeding sludge, i.e., Proteobacteria, Firmicutes, Bacteroidetes, significantly reduced, while Planctomycetes which contains anaerobic ammonium oxidation bacteria remarkably increased from 1.59% to 23.24% in the Anammox granules.

Kraft lignin (KL) is the major pollutant in black liquor. The bacterial strain Pandoraea sp. B-6 was able to degrade KL without any co-substrate under high alkaline conditions. At least 38.2 % of chemical oxygen demand and 41.6 % of color were removed in 7 days at concentrations from 1 to 6 g L⁻¹. The optimum pH for KL degradation was 10 and the optimum temperature was 30 °C. The greatest activities of 2,249.2 U L⁻¹ for manganese peroxidase and 1,120.6 U L⁻¹ for laccase were detected on the third and fifth day at pH 10, respectively. Many small molecules, such as cinnamic acid, ferulic acid, 2-hydroxy benzyl alcohol, and vanillyl methyl ketone, were formed during the period of KL degradation based on GC–MS analysis. These results indicate that this strain has great potential for biotreatment of black liquor.

This work described a novel method for the synthesis of high-ferromagnetism nanoparticles (Fe₃O₄/CNTs) to efficiently remove Cr(VI) from aqueous solution. The Fe₃O₄/carbon nanotubes (CNTs) were prepared by in situ reduction with post-oxidation method by using cheap and environmentally friendly precursor under mild condition. Magnetic hysteresis loops revealed that Fe₃O₄/CNTs had superior saturation magnetization (152 emu/g), enabling the highly efficient recovery of Fe₃O₄/CNTs from aqueous solution by magnetic separation at low magnetic field gradients. FTIR, Raman, XPS, and TEM observations were employed to characterize the physical–chemical properties of Fe₃O₄/CNTs, demonstrating that CNTs were successfully coated with iron oxide matrix. The adsorption equilibrium of Cr(VI) on Fe₃O₄/CNTs was reached within 30 min. Langmuir, Freundlich, and Dubinin–Radushkevich isotherm were chosen to analyze the equilibrium data. The results indicated that Langmuir model can well describe the equilibrium data with the maximum adsorption capacity of 47.98 mg/g at room temperature and 83.54 mg/g at 353 K. The adsorption capacity of Fe₃O₄/CNTs for Cr(VI) was greatly improved as compared to raw CNTs and other similar adsorbents reported. The pseudo-second-order kinetic model provided the best description of Cr(VI) adsorption on Fe₃O₄/CNTs. Most importantly, possible synthesis mechanism and Cr(VI) removal mechanism were explored. The results suggest that large amounts of Cr(VI) were adsorbed on Fe₃O₄/CNTs surface by substituting the surface position of –OH and then reducing it to Cr(OH)₃ and Cr₂O₃.

Background: Lignin materials are abundant and among the most important potential sources for biofuel production. Development of an efficient lignin degradation process has considerable potential for the production of a variety of chemicals, including bioethanol. However, lignin degradation using current methods is inefficient. Given their immense environmental adaptability and biochemical versatility, bacterial could be used as a valuable tool for the rapid degradation of lignin. Kraft lignin (KL) is a polymer by-product of the pulp and paper industry resulting from alkaline sulfide treatment of lignocellulose, and it has been widely used for lignin-related studies. Results: Beta-proteobacterium Cupriavidus basilensis B-8 isolated from erosive bamboo slips displayed substantial KL degradation capability. With initial concentrations of 0.5–6 g L^-1, at least 31.3% KL could be degraded in 7 days. The maximum degradation rate was 44.4% at the initial concentration of 2 g L^-1. The optimum pH and temperature for KL degradation were 7.0 and 30°C, respectively. Manganese peroxidase (MnP) and laccase (Lac) demonstrated their greatest level of activity, 1685.3 U L^-1 and 815.6 U L^-1, at the third and fourth days, respectively. Many small molecule intermediates were formed during the process of KL degradation, as determined using GC-MS analysis. In order to perform metabolic reconstruction of lignin degradation in this bacterium, a draft genome sequence for C. basilensis B-8 was generated. Genomic analysis focused on the catabolic potential of this bacterium against several lignin-derived compounds. These analyses together with sequence comparisons predicted the existence of three major metabolic pathways: β-ketoadipate, phenol degradation, and gentisate pathways. Conclusion: These results confirmed the capability of C. basilensis B-8 to promote KL degradation. Whole genomic sequencing and systematic analysis of the C. basilensis B-8 genome identified degradation steps and intermediates from this bacterial-mediated KL degradation method. Our findings provide a theoretical basis for research into the mechanisms of lignin degradation as well as a practical basis for biofuel production using lignin materials.

Traditional chemical oxidative polymerization, with the procedure of gradually adding the oxidant, generally produces amine-containing conjugated polymer (NCP) microparticles. In this paper, an improved method has been developed through using a small amount of Cu²⁺ prior to the polymerization for large-scale synthesis of poly(m-phenylenediamine) (PmPD, one typical NCP) nanoparticles. The Cu-monomer/oligomer complex nanoparticle structures formed before the polymerization are suitable intermediates to activate the polymerization and induce the morphology evolution of the PmPD nanostructures. A possible mechanism is that Cu ions at the centre of the complex mediate the electron transfer from ligand to persulfate oxidant, as analyzed by comparative experiments; Fourier transform infrared spectrometry (FTIR) and open-circuit potential of the polymerization. During the growth of macromolecular chains, the Cu ions are gradually released into the bulk solution from the complex. The nano-sized PmPD was used to adsorb a dye (Orange G) and showed high adsorbance of 387.6 mg g⁻¹, which is on average 200 mg g⁻¹ more than that of the microparticles.

A hexavalent chromium [Cr(VI)] reducing bacterial strain was isolated from chromium-containing slag. It was identified as Pannonibacter phragmitetus based on physiological, biochemical characteristics and 16S rRNA gene sequence analysis. This bacterium displayed great Cr(VI) reduction capability. The Cr(VI) could be completely removed in 24 h under anaerobic condition when the initial concentration was 1,917 mg L⁻¹, with the maximum reduction rate of 562.8 mg L⁻¹ h⁻¹. The Cr(VI) reduction rate increased with the increase of Cr(VI) concentration. P. phragmitetus was able to use many carbon sources such as lactose, fructose, glucose, pyruvate, citrate, formate, lactate, NADPH and NADH as electron donors, among which the lactate had the greatest power to promote the reduction process. Zn²⁺, Cd²⁺ and Ni²⁺ inhibited, while Cu²⁺, Pb²⁺, Mn²⁺ and Co²⁺ stimulated the reduction. The optimum pH and temperature for reduction were 9.0 and 30 °C, respectively. The results indicated that this strain had great potential for application in the bioremediation of chromate-polluted soil and water systems.