Search

FeMn bimetallic nanoparticles coated with nitrogen-doped graphene shells (FeMn@NG) were prepared by calcination of cellulose supported Prussian blue analogs under N 2 flow, and used as catalysts to activate peroxymonosulfate (PMS) for the degradation of 2,4,6-trichlorophenol (2,4,6-TCP). The addition of cellulose during the formation of Prussian blue analogs reduced the agglomeration of metal particles in the subsequent carbonization process, thus increasing the specific surface area and enhancing the catalytic efficiency of the obtained catalyst. 1O 2 and the electron transfer pathway were proved to be the main mechanisms by radical quenching experiment, electron paramagnetic resonance and chronoamperometry analysis. The metal leaching of lower than 0.1 mg L−1 and high catalytic stability were attributed to the stable core-shell structure that the metals were encapsulated and protected by graphene shells. The XPS analysis implied that a Fe/Mn redox cycle existed and played a role in balancing electrons during the PMS activation. This study shows that the PMS activator with high catalytic activity can be obtained for the degradation of pollutants by combining Prussian blue analogs with cellulose. [Display omitted] • Core-shell FeMn@NG was fabricated from celluose supported Prussian blue analogs. • The addition of cellulose significantly enhanced the catalytic efficiency. • Low metal leaching observed was attributed to the core-shell structure. • A non-radical dominated mechanism was illustrated in FeMn@NG/PMS/2,4,6-TCP system. [ABSTRACT FROM AUTHOR]

The recycling of solid waste is of increasing economic and environmental significance. Herein, a low-cost and environmentally friendly catalyst was prepared by simple pyrolysis using warm paste residue as raw material and urea as nitrogen source. The prepared WPR-N-700 catalyst exhibited high catalytic activity for the degradation of bisphenol A (BPA) by activation of peroxymonosulfate (PMS). The removal of 99% BPA in 20 mg L−1 solution was achieved within 30 min in WPR-N-700/PMS system by adding 0.3 g L−1 catalyst and 0.2 g L−1 PMS. The systematic experiments showed that the catalyst exhibited good catalytic versatility and adaptability in many types of refractory organic pollutants and coexisting inorganic ionic systems. The catalyst still had good magnetic properties and could be easily separated under the external magnetic field. The free radical quenching test and electron paramagnetic resonance (EPR) test revealed that sulfate radical (SO 4 •−), radicals (•OH), superoxide radical (O 2 •−) and singlet oxygen (1O 2) were the primary reactive oxygen species for the degradation of BPA in the WPR-N-700/PMS system. Thus, this study provides an economical and effective method for the recycling of solid waste, and innovatively proposes a new idea of using solid waste to prepare catalysts. [Display omitted] • A low-cost peroxymonosulfate activator was prepared from warm paste residue. • N-doping of raw material achieved using urea nitrogen source by simple pyrolysis. • The primary reactive oxygen species for BPA degradation were SO 4 •−, •OH, O 2 •−, 1O 2. • Many types of refractory organic pollutants can be degraded. [ABSTRACT FROM AUTHOR]

In the present study, based on the currently used deep-buried coaxial double-pipe heat exchange systems for closed loop heat extraction, the influence of several inner pipe types on the heat transfer performance of buried pipe systems is analyzed. The deep-buried coaxial double-pipe with a smooth inner pipe used in current practice was taken as an example, and a full-scale three-dimensional (3D) numerical model coupling the heat transfer processes inside and outside the pipe was established by using a depth of 50 m and taking into account the modeling workload. Based on this model, full-scale 3D numerical models of coaxial double-pipes with spiral and corrugated pipes as the inner pipe types were established, and numerical analysis of heat transfer was performed. The results indicated that the heat transfer capacity of the buried pipe system can be improved by changing the shape of the inner pipe. However, the influence of the inner pipe type on heat transfer was far lower than that of the water flow rate circulating inside the buried pipe system and the initial ground temperature. • 3D numerical models of coaxial double-pipes at a depth of 50 m were established. • The models included smooth, spiral, and corrugated inner pipe types. • The effect of inner pipe types on heat transfer enhancement was calculated and compared. • The effect of ground temperature, flow rate, and pipe type on heat transfer was compared. [ABSTRACT FROM AUTHOR]