Preparation of CeO2-doped carbon nanotubes cathode and its mechanism for advanced treatment of pig farm wastewater

Applying sheet iron to enhance the treatment efficiency of digested effluent with continuous flow and the corresponding mechanism

Because of the unstable wastewater quantity and quality, the biological treatment efficiency of digested effluent was not as expected. A convenient and effective way was eagerly required to improve the efficiency of biological treatment. By sheet iron addition (R1), the COD and TN removal efficiencies under continuous flow condition increased by 59% and 37% respectively. The bulk pH maintained at around 7.5 which benefited most bacteria, while in the control (R0, without sheet iron addition) the pH decreased to 5.0. Both chemical and bio-removal of COD existed in R1, but the chemical removal dominated (63.71%). The enhanced COD removal efficiency came from the chemical oxidation by Fe3+ (47.43%) and Fe0 (10.86%). For the TN removal, the enhancement mainly came from the improvement of anammox activity by Fe3+ (14.87%), the bio-oxidation of ammonium with Fe3+ as electron acceptor (8.78%), and the bio-reduction of nitrate/nitrite with Fe2+ and H2 as electron donor (35.76%). By the first-order kinetic fitting analysis, the COD and TN removal rate in R1 was higher than that in R0. Thus, for a quick and high COD and TN removal from digested effluent, the addition of Fe0/Fe2+/Fe3+ was suggested, and the best form should be Fe0 (e.g., sheet iron). The addition of sheet iron reduces the cost of nitrogen removal and improves the efficiency of COD and TN removal. Comparing with the combined processes, this novel approach has potential advantages with simple operation and high efficiency. It endows the biological process much broader application in digested effluent treatment.

Integrating anodic sulfate activation with cathodic H2O2 production/activation to generate the sulfate and hydroxyl radicals for the degradation of emerging organic contaminants

Conventional electrocatalytic degradation of pollutants involves either cathodic reduction or anodic oxidation process, which caused the low energy utilization efficiency. In this study, we successfully couple the anodic activation of sulfates with the cathodic H₂O₂ production/activation to boost the generation of sulfate radical (SO₄^·-) and hydroxyl radical (·OH) for the efficient degradation of emerging contaminants. The electrocatalysis reactor is composed of a modified-graphite-felt (GF) cathode, in-situ prepared by the carbonization of polyaniline (PANI) electrodeposited on a GF substrate, and a boron-doped diamond (BDD) anode. In the presence of sulfates, the electrocatalysis system shows superior activities towards the degradation of pharmaceutical and personal care products (PPCPs), with the optimal performance of completely degrading the representative pollutant carbamazepine (CBZ, 0.2 mg L^-1) within 150 s. Radicals quenching experiments indicated that ·OH and SO₄^·- act as the main reactive oxygen species for CBZ decomposition. Results from the electron paramagnetic resonance (EPR) and chronoamperometry studies verified that the sulfate ions were oxidized to SO₄^·-radicals at the anode, while the dissolve oxygen molecules were reduced to H₂O₂ molecules which were further activated to produce ·OH radicals at the cathode. It was also found that during the catalytic reactions SO₄^·-radicals could spontaneously convert into peroxydisulfate (PDS) which were subsequently reduced back to SO₄^·-at the cathodes. The quasi-steady-state concentrations of ·OH and SO₄^·-were estimated to be 0.51×10^-12 M and 0.56×10^-12 M, respectively. This study provides insight into the synergistic generation of ·OH/SO₄^·- from the integrated electrochemical anode oxidation of sulfate and cathode reduction of dissolved oxygen, which indicates a potential practical approach to efficiently degrade the emerging organic water contaminants.

Evaluating the Growth of Ceria-Modified N-Doped Carbon-Based Materials and Their Performance in the Oxygen Reduction Reaction

Owning to their distinctive electronic structure, rare-earth-based catalysts exhibit good performance in the oxygen reduction reaction (ORR) and can replace commercial Pt/C. In this study, CeO₂-modified N-doped C-based materials were synthesized using salt template and high-temperature calcination methods, and the synthesis conditions were optimized. The successful synthesis of CeO₂-CN-800 was confirmed through a series of characterization methods and electrochemical tests. The test results show that the material has the peak onset potential of 0.90 V and the half-wave potential of 0.84 V, and has good durability and methanol resistance. The material demonstrates good ORR catalytic performance and can be used in Zn-air batteries. Moreover, it is an excellent catalyst for new energy equipment.

Synergistic Effect between Ni and Ce Dual Active Centers Initiated by Activated Fullerene Soot for Electro−Fenton Degradation of Tetracycline

The degradation of a high concentration of organic pollutants has long been a challenge to water restoration, and the development of electro−Fenton catalysis offers a practical approach to solving this problem. In this study, a novel electro−Fenton catalyst, activated fullerene soot−loaded NiO−doped CeO2 (0.4(0.4NiO−CeO2)−AFS) nanoparticles, was prepared through the impregnation of 0.4NiO−CeO2 particles and activated fullerene soot (AFS). When applied for the degradation of 200 mg/L of tetracycline, this catalyst demonstrated a degradation rate as high as 99%. Even after 20 cycles, the degradation rate was more than 80%. Moreover, it was concluded that AFS could initiate the synergistic effect between Ni and Ce dual active centers in the degradation of tetracycline; this can be ascribed to the extremely large specific surface area of AFS.

Multimedia fate model and risk assessment of typical antibiotics in the integrated demonstration zone of the Yangtze River Delta, China

Due to the widespread consumption of antibiotics by humans and animals, antibiotic residues from human and animal excrements are released into the environment through domestic sewage and breeding wastewater, which ultimately affect the ecological environment and human health. In this study, the concentrations of 10 antibiotics in the air, water, soil, and sediment from 2013 to 2019 in Qingpu District of the integrated demonstration zone of the Yangtze River Delta were predicated by developing a dynamic Level IV fugacity model. The influence of seasonal environmental factors (e.g., temperature, rainfall) on the distribution and migration of antibiotics in multi-media was also explored. The simulation results show that the 10 antibiotics mainly existed in water and sediment. The concentrations of antibiotics in air, water, soil, and sediment were 0-7.629 × 10^-14 ng/L, 1.187 × 10^-10-16.793 ng/L, 1.042 × 10^-14-3.500 × 10^-11 ng/g and 8.015 × 10^-12-14.188 ng/g, respectively. It was also found that the increase in temperature and rainfall can reduce the migration rate of some antibiotics into the water and sediment phases. The flux analysis of the cross-media migration and transformation of antibiotics in Qingpu District shows that advection was the prime input and output paths of antibiotics in the water. Moreover, the prime input and output paths of antibiotics in sediment were sedimentation from water to sediment and degradation. Sensitivity analysis shows that the characteristics of antibiotic emission, degradation rate, and K_oc were the most influential parameters for target chemicals. The results of risk assessment based on Monte Carlo method reveal that the overall risk level of antibiotics in sediment was relatively risk-free, and the risk of antibiotics in water decreased in the order of tetracyclines > β-lactams > fluoroquinolones > macrolides > sulfonamides.