Carbon microspheres with diameter of 1–10 μm were prepared by treatment of waste oil in a supercritical carbon dioxide (scCO2) system. The structure and morphology of the products were characterized by X-ray diffraction, field-emission scanning electron
microscopy, and Raman spectrometry. It is shown that the products consist of graphite microspheres with relatively low graphitization.
The yield of solid products increased from 26.8 wt% to 42.2 wt% as the reaction temperature was raised from 530°C to 600°C.
Spheres with multilayer structure could be obtained by means of subsequent vacuum annealing of the carbon microspheres at
1500°C. The formation mechanisms of carbon microspheres in the scCO2 system and the influence of vacuum annealing on the structure are discussed in detail. 相似文献
A high-swelling superabsorbent was synthesized with biodegradable N-maleyl chitosan as cross-linker, acrylic acid (AA) and acrylamide (AM) as the monomers, ammonium peroxodisulfate–sodium bisulfite
(NaHSO3) as redox initiation system, by means of aqueous solution polymerization. The best reaction condition was based on the orthogonal
experiment design. The optimal conditions on distilled water absorbency and on 0.9 wt% NaCl solution absorbency were monomer
concentration 20 wt%, mole ratio of AA to (AA + AM) 60%, the neutralization degree of AA 40%, cross-linker concentration 2%
and monomer concentration 25 wt%, mole ratio of AA to (AA + AM) 60%, neutralization degree of AA 50% and cross-linker concentration
1%, respectively. Factors influencing the water absorbency of superabsorbent also were investigated, by single factor experiment
method. The absorbency of superabsorbents in distilled water and 0.9 wt% NaCl solution increased and then decreased with the
increasing of monomer concentration, mole ratio of AA to (AA + AM) and degree of neutralization of AA. With the increasing
of cross-linker concentration, the absorbency in distilled water increased and then decreased, but it decreased all the time
in 0.9 wt% NaCl solution. In enzymatic degradation tests, the weight loss of superabsorbent was related to the content of
cross-linker. 相似文献
As a heavy industrial city, Liuzhou has been facing a serious pollution problem. It is necessary to take steps to control and prevent environmental pollution wherever possible. Surface soil samples were collected from four communities in Liuzhou City, to determine the concentrations, distributions, sources, and toxicity potential of polycyclic aromatic hydrocarbons (PAHs) present. The mean concentrations of total PAHs in the surface soil are 756.43 ng/g for the heavy industrial area, 605.06 ng/g for the industrial area, 481.24 ng/g for the commercial–cum–residential area, and 49.93 ng/g for the rural area. Both the isomer ratio and principal component analyses for the PAHs prove that these pollutants originate mainly from coal, diesel, gasoline, and natural gas combustion. The pollution hierarchies and toxic equivalency factor of BaP prove that the city is subject to heavy pollution caused by industry, transportation, and daily human activities. 相似文献
The concentration levels of 36 airborne heavy metals and atmospheric radioactivity in total suspended particulate (TSP) samples were measured to investigate the chemical characteristics, potential sources of aerosols, and health risk in Beijing, China, from September 2016 to September 2017. The TSP concentrations varied from 6.93 to 469.18 μg/m3, with a median of 133.97 μg/m3. The order for the mean concentrations of heavy metals, known as hazardous air pollutants (HAPs), was as follows: Mn > Pb > As > Cr > Ni > Se > Cd > Co > Sb > Hg > Be; Non-Designated HAPs Metals: Ca > Fe > Mg > Al > K > Na > Zn > P > Ba > Ti > Cu > Sr > B > Sn > I > V > Rb > Ce > Mo > Cs > Th > Ag > U > Pt. The median concentration of As was higher than China air quality standard (6 ng/m3). The gross α and β concentration levels in aerosols were (1.84?±?1.59) mBg/m3 and (1.15?±?0.85) mBg/m3, respectively. The enrichment factor values of Cu, Ba, B, Ce, Tl, Cs, Pb, As, Cd, Sb, Hg, Fe, Zn, Sn, I, Mo, and Ag were higher than 10, which indicated enriched results from anthropogenic sources. Pb, As, and Cd are considered to originate from multiple sources; fireworks released Ba during China spring festival; Fe, Ce, and Cs may come from stable emissions such as industrial gases. The health risks from anthropogenic metals via inhalation, ingestion, and dermal pathway were estimated on the basis of health quotient as well as the results indicated that children faced the higher risk than adults during the research period. For adults, the health risk posed by heavy metals in atmospheric particles was below the acceptable level.