利用三步法（热溶剂还原法,硅烷化和氨基功能化）制备了Fe3O4@SiO2-NH2磁性纳米复合材料用于水体中全氟化合物的萃取,结合超高效液相色谱-串联三重四极杆质谱（UPLC-MS/MS）技术,建立了水体中7种典型全氟化合物的检测方法。通过扫描电镜...利用三步法（热溶剂还原法,硅烷化和氨基功能化）制备了Fe3O4@SiO2-NH2磁性纳米复合材料用于水体中全氟化合物的萃取,结合超高效液相色谱-串联三重四极杆质谱（UPLC-MS/MS）技术,建立了水体中7种典型全氟化合物的检测方法。通过扫描电镜（SEM）、透射电镜（TEM）和傅立叶红外光谱（FT-IR）等手段对材料进行表征,详细研究了解析溶剂、解析溶剂体积、解析时间、吸附时间和p H值等因素对萃取效率的影响。结果表明：氨基被成功修饰在Fe3O4@SiO2纳米粒子的表面,Fe3O4@SiO2-NH2磁性纳米材料对目标全氟化合物有较好的萃取效果,在萃取时间为20 min,解析溶剂为3 m L×4含0.28%氨水的甲醇,解析时间为5 min,p H 5.0时,萃取效率最佳。在最优实验条件下,全氟化合物的检出限为0.2~0.5 ng/L,线性范围为1~500 ng/L。方法用于实际水体中目标全氟化合物的检测,样品的加标回收率不低于82.0%。展开更多
This paper is focused on the cascade refrigeration cycle using natural refrigerant CO 2-NH 3. The properties of refrigerants CO 2 and NH 3 are introduced and analyzed.CO 2 has the advantage in low stage of cascade ref...This paper is focused on the cascade refrigeration cycle using natural refrigerant CO 2-NH 3. The properties of refrigerants CO 2 and NH 3 are introduced and analyzed.CO 2 has the advantage in low stage of cascade refrigeration cycle due to its good characteristics and properties. The thermodynamic analysis results of the CO 2-NH 3 cascade refrigeration cycle demonstrates that the cycle has an optimum condensation temperature of low stage and also has an optimum flow rate ratio.By comparing with the R13-R22 and NH 3-NH 3 cascade refrigeration cycles, the mass flow rate ratio of CO 2-NH 3 is larger than those of R13-R22 and NH 3-NH 3, the theoretical COP of CO 2-NH 3 cascade refrigeration cycle is larger than that of the R13-R22 cascade cycle and smaller than that of the NH 3-NH 3 cascade cycle. But the real COP of CO 2-NH 3 cascade cycle will be higher than those of R13-R22 and NH 3-NH 3 because the specific volume of CO 2 at low temperature does not change much and its dynamic viscosity is also small.展开更多
In this paper, the laccase immobilized on Fe304@SiO2-NH2 nanoparticles was successfully prepared by the glutaraldehyde cross-linking method. The degradations of 2,4-diehlorophenol （2,4-DCP） catalyzed by laccase and ...In this paper, the laccase immobilized on Fe304@SiO2-NH2 nanoparticles was successfully prepared by the glutaraldehyde cross-linking method. The degradations of 2,4-diehlorophenol （2,4-DCP） catalyzed by laccase and immobilized laccase were carried out. The optimal conditions regarding degradation efficiency were also discussed, which include reaction time, pH value, temperature, concentration of 2,4-DCP and laccase. When laccase was immobilized on Fe304@SiO2-NH2 carrier by crosslinking with glutaraldehyde, the stability and repetition were im- proved significantly. The removal efficiency of 2,4-DCP by immobilized laccase still remained over 59% after six cycles of operation. Degradation of 2,4-DCP is a first-order reaction and the activation energies of 2,4-DCP catalyzed by laccase and immobilized laccase are 51.93 kJ·mol-1 strate the immobilized laccase had a faster degradation Fe304@MSS-NH2 can promote the degradation reaction. and 44.12 kJ·mol-1, respectively. The results demonrate than the free laccase; the magnetic carrier展开更多
文摘利用三步法（热溶剂还原法,硅烷化和氨基功能化）制备了Fe3O4@SiO2-NH2磁性纳米复合材料用于水体中全氟化合物的萃取,结合超高效液相色谱-串联三重四极杆质谱（UPLC-MS/MS）技术,建立了水体中7种典型全氟化合物的检测方法。通过扫描电镜（SEM）、透射电镜（TEM）和傅立叶红外光谱（FT-IR）等手段对材料进行表征,详细研究了解析溶剂、解析溶剂体积、解析时间、吸附时间和p H值等因素对萃取效率的影响。结果表明：氨基被成功修饰在Fe3O4@SiO2纳米粒子的表面,Fe3O4@SiO2-NH2磁性纳米材料对目标全氟化合物有较好的萃取效果,在萃取时间为20 min,解析溶剂为3 m L×4含0.28%氨水的甲醇,解析时间为5 min,p H 5.0时,萃取效率最佳。在最优实验条件下,全氟化合物的检出限为0.2~0.5 ng/L,线性范围为1~500 ng/L。方法用于实际水体中目标全氟化合物的检测,样品的加标回收率不低于82.0%。
文摘This paper is focused on the cascade refrigeration cycle using natural refrigerant CO 2-NH 3. The properties of refrigerants CO 2 and NH 3 are introduced and analyzed.CO 2 has the advantage in low stage of cascade refrigeration cycle due to its good characteristics and properties. The thermodynamic analysis results of the CO 2-NH 3 cascade refrigeration cycle demonstrates that the cycle has an optimum condensation temperature of low stage and also has an optimum flow rate ratio.By comparing with the R13-R22 and NH 3-NH 3 cascade refrigeration cycles, the mass flow rate ratio of CO 2-NH 3 is larger than those of R13-R22 and NH 3-NH 3, the theoretical COP of CO 2-NH 3 cascade refrigeration cycle is larger than that of the R13-R22 cascade cycle and smaller than that of the NH 3-NH 3 cascade cycle. But the real COP of CO 2-NH 3 cascade cycle will be higher than those of R13-R22 and NH 3-NH 3 because the specific volume of CO 2 at low temperature does not change much and its dynamic viscosity is also small.
基金support from the National Natural Science Foundation of China （Grant No. 20971043 and No. 20577010）, the Open Project Program of State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University.
文摘In this paper, the laccase immobilized on Fe304@SiO2-NH2 nanoparticles was successfully prepared by the glutaraldehyde cross-linking method. The degradations of 2,4-diehlorophenol （2,4-DCP） catalyzed by laccase and immobilized laccase were carried out. The optimal conditions regarding degradation efficiency were also discussed, which include reaction time, pH value, temperature, concentration of 2,4-DCP and laccase. When laccase was immobilized on Fe304@SiO2-NH2 carrier by crosslinking with glutaraldehyde, the stability and repetition were im- proved significantly. The removal efficiency of 2,4-DCP by immobilized laccase still remained over 59% after six cycles of operation. Degradation of 2,4-DCP is a first-order reaction and the activation energies of 2,4-DCP catalyzed by laccase and immobilized laccase are 51.93 kJ·mol-1 strate the immobilized laccase had a faster degradation Fe304@MSS-NH2 can promote the degradation reaction. and 44.12 kJ·mol-1, respectively. The results demonrate than the free laccase; the magnetic carrier
