RESUMO
Nanoplastics (NPs) are usually formed by the decomposition of large plastics, which will cause water pollution after entering the water body. Carbon filter column is used to adsorb and remove polystyrene nanoparticles (PSNPs). The influence of experimental conditions on adsorption was investigated and fitted by kinetic model. The results show that increasing the height of carbon filter column and decreasing the initial concentration of PSNPs and water flow rate can prolong the breakthrough time of carbon filter column. When the initial concentration of PSNPs is 0.8â mgâ L-1, the influent flow rate is 4â mLâ min-1 and the height of carbon filter bed is 8.5â cm, the removal effect is the best, and the depletion point of carbon filter column is extended to 48â h. Adams-Bohart model is suitable for describing the initial stage of adsorption. Thomas and Yoon-Nelson models can well describe the whole dynamic adsorption process of PSNPs, and Yoon-Nelson model can accurately predict the time required for 50% PSNPs to penetrate the carbon column. The adsorption mechanism of NPs by carbon filter column is mainly through the attachment sites and pore retention provided by particles on the surface of activated carbon. This study can provide new technical and theoretical support for the removal of NPs.
RESUMO
Micro/nano plastics ï¼M/NPsï¼ are widely dispersed in the soilï¼ atmosphereï¼ and water environment due to their small particle sizeï¼ easy adsorptionï¼ and strong migrationï¼ and have been detected in all major water bodies in recent years. As a type of emerging pollutantï¼ the physiological toxicity of M/NPs has a great impact on human health. The current bottleneck in this research field lies in the precise detection and efficient removal of M/NPs. Electrochemical technologyï¼ owing to its advantages of simple portabilityï¼ sensitivityï¼ and low cost in the detection of M/NPsï¼ has the advantages of environmental friendlinessï¼ controllable reactionï¼ and high efficiency in the removal of M/NPsï¼ demonstrating enormous application potential. Based on the pollution status of M/NPsï¼ the application of electrochemical technology to the detection and removal of M/NPs in the water environment was elaborated and summarized. The electrochemical sensing methods of M/NPs and the principles and characteristics of sensor recognition of M/NPs were analyzed. The removal efficiency and influencing factors of M/NPs in water by electro-flocculationï¼ electro-adsorptionï¼ electro-oxidationï¼ and electro-reduction technologies were also discussed. The results indicated that the detection of M/NPs particles using electrochemical sensing methods exhibited good characterization performanceï¼ and M/NPs could be efficiently removed through electrochemical techniques such as electrocoagulationï¼ electro-adsorptionï¼ electro-oxidationï¼ and electro-reduction. The influencing factors of electrochemical technology on the detection and removal of M/NPs were mainly related to sensor devicesï¼ electrode materialsï¼ material interface regulationï¼ parameter conditionsï¼ and reactor systems. In the futureï¼ researchers should focus on the design of sensorsï¼ the development of electrode materialsï¼ and the optimization of reaction processesï¼ which are expected to realize the application of M/NPs from laboratory detection and removal to actual water bodies.
RESUMO
Microplastics have been identified as an emerging pollutant that poses a risk to the aquatic environment, and it is a challenge to find a suitable removal process. Electrocatalytic oxidation (ECO) technology has shown promising performance in removing various persistent organic pollutants. In this study, we prepared a new anode for removing polystyrene microplastics (PS MPs) by ECO. Ti/La-Sb-SnO2 electrodes doped with the rare earth element La as the active layer were synthesized to enhance the electrocatalytic activity. The lifespan of the electrode was improved by doping Mn, Co, or Ru as an intermediate layer modification between the titanium (Ti) substrate and the La-Sb-SnO2 active layer, respectively. The experimental results indicated that the addition of three types of intermediate layers led to different degrees of decrease in the catalytic activity of the electrode and the degradation performance of PS MPs. The addition of the Co intermediate layer had a negligible effect on the catalytic activity and performance of the Ti/La-Sb-SnO2 anode for PS degradation. In addition, the electrode lifespan with Co intermediate layer was significantly prolonged, which was 4.54, 2.38, and 1.19 times higher than the electrode without intermediate layer and the electrode with Ru and Mn intermediate layer, respectively. Therefore, Co was determined to be the optimal choice as the intermediate layer, and the production technique for the Ti/La/Co-Sb-SnO2 anodes was carefully adjusted. The degradation efficiency of PS MPs was optimized at a heat treatment temperature of 400 °C and a Sn: Co material ratio of 5:1, with a removal rate of 28.0 %. The ECO treatment also resulted in more pronounced changes in the structure and functional groups of the MPs. Various alkyl cleavage and oxidation products were detected after the treatment, suggesting that the oxidant (hydroxyl radicals) strongly interacted with the MPs, leading to their degradation. Overall, this work provided a new insight into removing MPs in water through the use of modified electrodes.