Coupling Iron Sludge Addition and Intermittent Aeration for Achieving Simultaneous Methanogenesis, Feammox, and Denitrification in a Single Reactor Treating Fish Sludge.

An integrated anaerobic digestion system for the simultaneous removal of carbon and nitrogen from fish sludge was developed by coupling iron sludge supplementation with intermittent aeration. In terms of nitrogen removal, Fe(III) in iron sludge could trigger Feammox reactions and intermittent aeration could drive the Fe(II)/Fe(III) cycle to sustain continuous ammonia removal. Mass balance analysis suggested that nitrate was the main product of Feammox, which was subsequently removed through heterotrophic denitrification. In terms of carbon removal, the Fe(III)-induced dissimilatory iron reduction (DIR) process significantly promoted fish sludge hydrolysis and provided more simple organics for methanogens and denitrifiers, but aeration showed a negative impact on methanogenesis. To promote nitrogen removal and avoid serious methanogenesis inhibition, different aeration intensities were studied. Results showed that compared with the control without aeration or iron sludge addition, aeration for 5 min every 3 days (150 mL/min) contributed to a 29.0% lower NH4+-N concentration and a 12.1% lower total chemical oxygen demand level on day 28, and the decline in methane yield was acceptable (only 13.5% lower). Simultaneous methanogenesis, Feammox, and denitrification in a single reactor treating fish sludge were achieved, which provides a simple and low-cost strategy for the treatment of organic wastewater.

Synergistic oxygen vacancy-rich CuO/visible light activation of peroxymonosulfate for degradation of rhodamine B: fast catalyst synthesis and degradation mechanism.

This work outlines the synthesis of copper oxide nanoparticles (CuO-SC) loaded with a number of oxygen vacancies by a fast sodium citrate assisted precipitation method with no need of calcination. X-ray diffraction, scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy, time-resolved fluorescence lifetime and electrochemical impedance spectra were used to characterize the as-synthesized nanocomposites. The results indicated that the CuO-SC nanoparticles had regular fusiform shape with high surface area, wide light harvesting window, fast charge transport and high carrier concentration. As a result, the catalytic activity of the CuO-SC/peroxymonosulfate (PMS)/visible light (Vis) system for the degradation of rhodamine B (RhB) was much higher than that of as-prepared CuO nano powder in the absence of sodium citrate. Almost 98.0% of the initial RhB dyes was decomposed in 20 min with 0.12 g L-1 PMS and 0.3 g L-1 catalyst. Meantime, it exhibited high catalytic stability with little deactivation after four runs and a wide application range of pH. Moreover, RhB can be readily degraded with backgrounds of Cl-, NO3 -, SO4 2-, HCO3 - and low concentration of humic acid in a CuO-SC/PMS/Vis system. Combined with the results of electron spin resonance paramagnetic spectroscopy, X-ray photoelectron spectroscopy and radical quenching experiments, holes, superoxide radicals and a small amount of sulfate radicals, hydroxyl radicals and singlet oxygen were involved in the CuO-SC/PMS/Vis system. Furthermore, a possible degradation mechanism based on the synergistic effect of radical reaction and non-radical reaction was proposed based on the above results.

Fly ash derived calcium silicate hydrate as a highly efficient and fast adsorbent for Cu(ii) ions: role of copolymer functionalization.

The environmental issues caused by heavy metal accumulation from polluted water are becoming serious and threaten human health and the ecosystem. The adsorption technology represented by calcium silicate hydrate has attracted much attention, but suffers from high manufacturing costs and poor stability bottlenecks. Here, we have proposed a "trash-to-treasure" conversion strategy to prepare a thin sheet calcium silicate hydrate material (ACSH) using solid waste fly ash as silicon source and a small amount of Acumer2000 as modifier. The obtained materials showed fast adsorption rates, superior adsorption capacities and remarkable long-term stability for Cu(ii) removal. Under the conditions of 0.5 g L-1 adsorbent concentration and 100 mL Cu(ii) solution with a concentration of 100 mg L-1, ACSH can adsorb 95.6% Cu(ii) within 5 min. The adsorption isotherms conformed to Langmuir models and the maximum adsorption capacity was 532 mg g-1. Using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, specific surface area and pore structure analysis, it was found that the excellent adsorption performance could be attributed to the ultrahigh surface area (356 m2 g-1), abundant pores and multiple active sites induced by Acumer2000 modification. Moreover, the encapsulation effect from carboxylate and long carbon chains in Acumer2000 endowed modified samples with strong corrosion resistance to CO2, which effectively inhibited the formation of by-product CaCO3 and retained the remarkable adsorption performance for more than 100 days. Interestingly enough, the advantages of ACSH in economy and performance could been maintained in ACSH based adsorptive membranes. This work is of great significance for solid waste utilization as well as the preparation of high quality, cost-effective and long-term stability calcium silicate hydrate materials.

Solvent Effect on the Solvothermal Synthesis of Mesoporous NiO Catalysts for Activation of Peroxymonosulfate to Degrade Organic Dyes.

In this work, we successfully prepared three different mesoporous NiO nanostructures with preferential (111) planes using three different solvents-water, a water-ethanol mixture, and a water-ethylene glycol mixture. The NiO nanosheets prepared from the water-ethylene glycol mixture and denoted as NiO-EG showed a nanosheet morphology thinner than 10 nm, whereas the water-ethanol and water samples were 30-40 nm and above 100 nm thick, respectively. The NiO-EG catalyst was found to exhibit a high catalyzing ability to activate peroxymonosulfate (PMS) for decoloring dyes, by which 94.4% of acid orange 7 (AO7) was degraded under the following reaction conditions: AO7 = 50 mg/L, catalyst = 0.2 g/L, PMS = 0.8 g/L, pH = 7, and 30 min reaction time. The dye degradation rate was investigated as a function of the catalyst dosage, pH, and dye concentration. According to quenching experiments, it was found that SO4 •-, HO•, and O2 •- were the dominant radicals for AO7 degradation, and oxygen vacancies played a significant role in the generation of radicals. High surface area, thin flaky structure, rich oxygen vacancies, fast charge transport, and low diffusion impedance all enhanced the catalytic activity of NiO-EG, which exhibited the highest degradation ability due to its abundant accessible active sites for both adsorption and catalysis.

Highly conductive and flexible paper of 1D silver-nanowire-doped graphene.

A novel architecture of graphene paper is proposed to consist of "1D metallic nanowires/defect-free graphene sheets". Highly conductive and flexible papers of 1D silver nanowires (Ag NWs) and chemical vapor deposition (CVD) graphene sheets as an example were fabricated by a simple filtration method. CVD graphene paper possesses much higher electrical conductivity of 1097 S/cm, compared with other reported carbon-related papers (graphene, carbon nanotube, etc.). With the addition of Ag NWs to form Ag NWs/graphene paper, the electrical conductivity is further improved up to 3189 S/cm, even higher than ∼2000 S/cm of bulk graphite. Ag NWs/graphene papers have very good flexibility with the only <5% loss of electrical conductivity over 500 times mechanical bending. Highly conductive composite papers have potential in high-performance, flexible energy conversion and storage devices.