RESUMO
The paper describes a new method of waste polyethylene terephthalate (PET) recycling based on gas-phase treatment of the material in nitrating atmosphere. It was found that PET samples kept in the nitrating atmosphere (obtained by vaporizing 12 mol L-1 HNO3) at a temperature of 403-463 K (130-190 °C) for 5-24 h dissolve in 0.5 mol L-1 NaOH, in contrast to the untreated PET samples. Ozonation of the obtained alkaline solutions leads to a complete decomposition of the organic compounds present in the solutions. The resulting PET decomposition degree is higher than 99.9 % irrespective of the plastic color. In addition, the possibility of terephthalic acid recovery from the alkaline solutions of the conversion products was shown.
RESUMO
The kinetics of metal beta-diketonates sonolysis was studied in hexadecane solutions using a UV/VIS spectrophotometric technique. The following complexes were prepared and studied: Cu(HFAA)(2), Cu(DPM)(2), Fe(ACAC)(3), Ni(DPM)(2), Er(DPM)(3), Nd(DPM)(3), Th(DPM)(4), UO(2)(BTFA)(2).TOPO, and Np(HFAA)(4), where HHFAA is hexafluoroacetylacetone, HDPM is dipivaloylmethane, HACAC is acetylacetone, HBTFA is benzoyltrifluoroacetone, and TOPO is trioctylphosphine oxide. Sonolysis was performed under the following conditions: ultrasonic frequency 22 kHz, intensity of ultrasound 3-5 Wcm(-2), temperature 70-92 degrees C, Ar atmosphere. The kinetic behavior of the studied complexes are interpreted using a two-site model of the sonochemical processes. In the case of metal beta-diketonates with high vapor pressure the sonochemical reactions tend to occur in the gaseous phase of the cavitating bubbles. The sonolysis of less volatile complexes first occur in the liquid reaction zone surrounding the bubbles. Sonication of the studied complexes results in the formation of X-ray amorphous products consisted of a mixture of metal beta-diketonates partial degradation products. Heating of as-prepared sonication products in air yields nanocrystalline oxides of corresponding metals.
