In case of accidents at the industrial facilities, where there are devices that are a source of ionizing radiation, a significant part of the fission products is in a vaporous and aerosol state. There is no sharp drop in the radiation levels, which means that the terrain can be damaged for a long time and become uninhabitable. To assess the damage and eliminate the consequences of exposure to a hard radiation pulse, it is required to have such systems that register the dose fields in real time with a high temporal resolution and do not require regular verification and reference to the reference fields. To solve the problem, it is proposed to measure the dose rate of pulsed radiation by the induced conductivity in the air. This makes it possible to obtain the absolute values of the dose rate without reference to the reference fields, with a time resolution of 1·108 per second. The relationship between conductivity of the ionized air and the dose rate is given by means of experimentally determined constants: mobility of the electrons in the air and the lifetime of electrons before they stick to oxygen molecules in the air considering participation of the third particle. Proposed method is based on the microwave sounding of the highly ionized air. This allows to significantly expand the range of application of the ionization methods up to 1·108 Sv/s for photon radiation and to provide nanosecond time resolution. In the present experiments, the time dependence of the dose rate on time obtained by high-frequency probing was measured, and the dose per pulse was found by integrating over time. Measurement results were compared with the readings of a certified integral thermoluminescent dosimeter based on LiF. Measurement results indicate agreement within 20–30 %. High-frequency detectors can be used as part of information and measurement systems to alert about possible emergencies. The method allows obtaining final information in real time and forming management teams on mitigation of emergency situations consequences.
Изучены адсорбция типичного гербицида 2,4-дихлорфеноксиуксусной кислоты (2,4-Д) из его водного раствора на гранулированном активированном угле (ГАУ), кинетика адсорбции 2,4-Д на ГАУ, а также его порометрические характеристики и микроструктура. Показана высокая адсорбционная способность 2,4-Д на ГАУ.
The adsorption of a typical herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), from its aqueous solution on granular activated carbon (GAC) was studied. The kinetics of adsorption of 2,4-D on GAC and its porosimetric characteristics and microstructure were studied. A high adsorption capacity of GAC for 2,4-D was found.
The kinetics of adsorption of the typical herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and phenoxyacetic acid (the product of 2,4-D decay in the natural environment) on the activated carbon Sibunit was studied in an aqueous medium. The porosity and surface structure of the carbon were studied. The orders of 2,4-D and phenoxyacetic acid adsorption were determined. The high adsorption capacity of Sibunit for these substances was found.
Landfills in Germany are currently approaching stabilization phase; as a result removal of inert organics and potentially toxic elements in the leachate is becoming a primary concern. Dissolved air floatation (DAF) at the secondary stage reduces only 27% of the residual chemical oxygen demand (COD) in the investigated treatment systems; downstream granular activated carbon (GAC) units are required to further reduce COD concentration by 40-56% to meet indirect discharge or direct discharge limits respectively. Therefore, in this study performance in terms of COD and trace metals adsorption of different types of granular activated carbon were compared over different contact times and dosages. GAC 1 with Brunauer-Emmett-Teller (BET) surface area of 719.5 +/- 2.1 m(2)/g and average pore diameter (D) of 4.81 nm was identified to be inappropriate for treatment of leachate from this landfill. GAC 2 (with BET of 1513.7 +/- 6.4 m(2)/g and D of 3.50 nm) was feasible for COD reduction from DAF-pretreated leachate, while GAC 3 (with BET of 644.5 +/- 2.6 m(2)/g and D of 5.65 nm) can be coupled either with biological step alone, or as a tertiary step after the DAF unit. Moreover, as COD is the primary remaining contaminant of interest after secondary and tertiary treatment, spectrometer probes provide a close estimation of COD concentration for use in online monitoring. Beside COD removal, GAC 3 also confirmed the effectiveness of trace metals adsorption even at trace level, as it removed 66, 64, 48, 47, 43, and 25% of copper, cobalt, chromium, manganese, nickel, and zinc, respectively.