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The graphene oxide was prepared via one step under low-temperature with natural flake graphite as raw material. Factors affecting oxidation degree and layer spacing of graphene oxide were discussed in the process of low-temperature oxidation, such as the dosage of oxidant and oxidation time in system. The results indicate that high C-O bond and low defect structure (ID:IG=0.63) graphene oxide with the carbon and oxygen atom ratio of 1.98 can be prepared in the condition of the potassium permanganate with natural flake graphite mass ratio of 1:3, oxidation temperature of 0℃, oxidation time of 48h.This way avoids the increase of graphene oxide defects in the process of Hummers preparation due to the formation of CO2, which leads to the hexagon fracture and the absence of carbon atoms. After microwave reduction, the reduced graphene oxide with low defect is obtained, which the distance between defects(LD)is 12nm,the defect density(nD) is 2.21×1011cm-2 and the ratio of ID:IG is only 0.85 (ΓG=32.1cm-1).

The effects of process conditions on preparation of U 3 O 8 by calcination from ammonium uranyl carbonate in microwave fields were assessed and optimized for maximizing the total uranium as well as calcination temperature, adopting as Central Composite Design (CCD) methodology. The process variables assessed were calcination temperature, calcination duration and mass of sample. A quadratic model relating the process variables and the total amount of uranium and U 3 O 8 was proposed eliminating the insignificant parameters. The optimal calcination conditions were estimated to be a calcination temperature of 942.75 K, calcination duration of 8.78 min, with the corresponding total uranium and U 3 O 8 to be 82.07% and 31.33%, respectively. [ABSTRACT FROM AUTHOR]

Crofton weed was converted into a high-quality activated carbon (CWAC) via microwave-induced CO2 physical activation. The operational variables including activation temperature, activation duration and CO2 flow rate on the adsorption capability and activated carbon yield were identified. Additionally the surface characteristics of CWAC were characterized by nitrogen adsorption isotherms, FTIR and SEM. The operating variables were optimized utilizing the response surface methodology and were identified to be an activation temperature of 980 °C, an activation duration of 90 min and a CO2 flow rate of 300 ml/min with a iodine adsorption capacity of 972 mg/g and yield of 18.03%. The key parameters that characterize quality of the porous carbon such as the BET surface area, total pore volume and average pore diameter were estimated to be 1036m²/g, 0.71 ml/g and 2.75 nm, respectively. The findings strongly support the feasibility of microwave heating for preparation of high surface area porous carbon from Crofton weed via CO2 activation. [ABSTRACT FROM AUTHOR]