High-Efficiency Photo-Fenton-like Catalyst of FeOOH/g-C3N4 for the Degradation of PNP: Characterization, Catalytic Performance and Mechanism Exploration.

The composite photocatalyst FeOOH/g-C3N4 was prepared through thermal polycondensation and co-precipitation methods, followed by XRD, SEM and UV-vis characterization. The stability of FeOOH/g-C3N4 was explored by the recycling test. The active species in the reaction system were investigated by the capture experiment. The results indicated that the optimal preparation condition for g-C3N4 involved calcination at 600 °C for 4 h. XRD analysis revealed that g-C3N4 exhibits a high-purity phase, and Fe in FeOOH/g-C3N4 exists in a highly dispersed amorphous state. SEM analysis showed that FeOOH/g-C3N4 has a rough surface with an irregular layered structure. Element composition analysis confirmed that the content of elements in the prepared catalyst is consistent with the theoretical calculation. FeOOH/g-C3N4 possesses the largest specific surface area of 143.2 m2/g and a suitable pore distribution. UV-vis DRS analysis showed that the absorption intensity of FeOOH/g-C3N4 is stronger than that of g-C3N4. When the catalyst dosage was 1.0 g/L, the H2O2 dosage was 4 mmol/L, the PNP initial concentration was 10 mg/L and the initial pH value was 5, the PNP removal could reach 92% in 120 min. Even after 5 cycles, the efficiency of PNP removal by FeOOH/g-C3N4 remains nearly 80%. The capture experiment indicated that both •OH and •O2- play roles in the photocatalytic degradation of PNP, with •OH being more significant. These findings affirm that FeOOH has been successfully incorporated into g-C3N4, resulting in a conspicuous catalytic effect on the degradation of PNP in the visible light-assisted Fenton-like reaction.

Microbial characteristics of landfill leachate disposed by aerobic moving bed biofilm reactor.

An aerobic moving bed biofilm reactor (MBBR) was applied to treat landfill leachate generated from a domestic waste incineration plant. Pollutant removal efficiency of this reactor under stable operating condition was studied. The biomass, bacteria species, and microbial metabolism in this reactor were investigated. These results showed that the average removal efficiency of chemical oxygen demand (COD) and ammonia nitrogen in the aerobic MBBR achieved 64% and 97% in the optimum conditions, respectively. The three-dimensional fluorescence spectrum revealed that the content of soluble microbial byproducts from extracellular polymeric substances extraction in suspended sludge was much higher than that on biofilm, and the types of pollutants were various in different regions of the reactor. It also indicated that the MBBR system had a stable, rich and regular microorganism community, including large amounts of nitrifying bacteria and denitrifying bacteria. Scanning electron microscopy suggested that biofilm attached to the packing provided a good anoxic-aerobic micro environment system to achieve a high metabolic activity, which favored COD and ammonia removal.

Efficient degradation of cellulosic ethanol wastewater by perovskite activation of Sr element A-site doped lanthanide copper chalcogenide materials.

The degradation of cellulosic ethanol wastewater by peroxymonosulfate (PMS) is one of the important methods to solve the environmental problems caused by it. In order to improve the degradation efficiency of cellulosic ethanol wastewater, the design of more catalytically active and stable chalcogenide catalysts has become a problem that needs to be solved nowadays. The application of foreign cations to replace the A- or B-site to increase the oxygen vacancy of the chalcocite catalyst to improve the efficiency of chalcocite catalytic degradation of wastewater has received much attention. In this work, the perovskite material LaCuO3 was synthesized using a citric acid-sol-gel method, and the novel material La1-xSrxCuO3 was prepared by doping of Sr element at the A position. In order to prepare catalytic materials with better performance, this study carried out performance-optimized degradation experiments on the prepared materials and determined that the catalytic efficiency of La0.5Sr0.5CuO3 prepared under the conditions of the complexing agent dosage of 1:2, the gel temperature of 80 °C, and the calcination temperature of 700 °C was better than that of the catalytic materials prepared under other conditions. The prepared material has good recycling function; after four times recycling, the removal rate of pollutant COD is still more than 85%. This work provides a new synthesis method of perovskite material with good recycling function and high catalytic efficiency for the degradation technology of cellulosic ethanol wastewater.

Impurity removal with highly selective and efficient methods and the recycling of transition metals from spent lithium-ion batteries.

The use of lithium-ion batteries (LIBs) is skyrocketing since they are widely applied in portable consumer devices and electric vehicles. However, at the end of their lifetime, large amount of spent LIBs will result in a negative environmental impact and aggravate the problem of resource shortage without proper disposal. Therefore, recycling is an effective solution, which will be enforced in the near future. Herein, the purification, recovery and reuse of transition metals from spent LIBs were thoroughly studied. First, the target impurities in a solution were effectively removed individually. Iron(iii) and aluminum(iii) impurities were removed by adjusting the pH value, whereas copper(ii) was purified using highly selective electrodeposition technology and solvent extraction. Second, Ni0.41Co0.21Mn0.38(OH)2 was co-precipitated by adjusting the pH value of the purified metal solution, containing nickel(ii), cobalt(ii) and manganese(ii) ions to 11 with NaOH and a proper amount of NH3·H2O. The comprehensive loss in nickel(ii), cobalt(ii) and manganese(ii) was only 0.37% in the purification and co-precipitation procedures. Finally, LiNi0.41Co0.21Mn0.38O2 (marked as LNCM-R) synthesized with the recycled materials was tested and compared with LiNi0.41Co0.21Mn0.38O2 (marked as LNCM-N) synthesized with new materials as the control group. The XRD, SEM and TEM results indicate that both samples have the same structure and morphology. Furthermore, the charge-discharge tests, initial dQ/dV curves, EIS and GITT results indicate a similar electrochemical performance of the LNCM-R and LNCM-N samples. The purification and recycling strategies in our research have high efficiency and comparatively low cost, which provide great guidance for the industrial recycling of spent Li-ion batteries.