Heterogeneous catalytic ozonation by amorphous boron for degradation of atrazine in water

As one of the most promising and practical advanced oxidation processes(AOPs),the catalytic ozonation is triggered by the active components of catalyst,which are usually derived from metals or metal oxides.To avoid the metal pollution from catalyst,here the amorphous boron(A-boron)is used as a metalfree catalyst for catalytic ozonation to produce free radicals for effective degradation of atrazine(ATZ),the world-widely used herbicide and also a widespread pollutant in environment.A-boron exhibits an outstanding performance for catalytic ozonation to remove ATZ from water.As A-boron is introduced into ozonation,the degradation efficiency in 10 min is promoted to 97.1%,much higher than that of 15.1%under ozonation.The mechanism is that the B-B bonds and internal suboxide B in A-boron serve as the main active sites to donate electrons to accelerate ozone decomposition to produce reactive oxygen species(ROS),including·O_(2)^(-)and^(1)O_(2),and further enhance ATZ degradation via ROS reactions.Moreover,the A-boron is still highly active with a degradation efficiency of ATZ over 95%in 10 min even after four successive cycles.This work shows A-boron could be an alternative for the active components of metal or metal oxide in catalytic ozonation.

Effect of carbon dioxide concentration on the combustion characteristics of boron agglomerates in oxygen-containing atmospheres

In ramjet combustion chambers,carbon dioxide(CO_(2))produced by the combustion of carbonaceous fuel enters the chamber together with boron agglomerates.In order to investigate the effect of CO_(2)concentration present in an oxygen-containing atmosphere on the combustion characteristics and oxidation mechanisms of boron agglomerates,we used a laser ignition system,an X-ray diffractometer(XRD),and a thermogravimetric-differential scanning calorimetry(TG-DSC)combined thermal analysis system.Single-particle boron was tested in the laser-ignition experiments as the control group.The ignition experiment results showed that with a fixed O2 concentration of 20%,when the particle temperature reaches the melting point of boron,increasing CO_(2)content causes the combustion process of boron agglomerates to transition from single-particle molten droplet combustion to porous-particle combustion.Furthermore,XRD analysis results indicated that the condensed-phase combustion products(CCPs)of boron particles in a mixed atmosphere of O2 and CO_(2)contained B4C,which is responsible for the porous structure of the particles.At temperatures below 1200℃,the addition of CO_(2)has no obvious promotion effect on boron exothermic reaction.However,in the laser-ignition experiment,when the oxygen concentration was fixed at 20%while the CO_(2)concentration increased from 0%to 80%,the maximum temperature of boron agglomerates rose from 2434 to 2573 K,the self-sustaining combustion time of single-particle boron decreased from 396 to 169 ms,and the self-sustaining combustion time of boron agglomerates decreased from 198 to 40 ms.This study conclusively showed that adding CO_(2)to an oxygen-containing atmosphere facilitates boron reaction and consumption pathways,which is beneficial to promoting exothermic reaction of boron agglomerates at relatively high temperatures.