Pore structure engineering for carbon foams as possible bone implant material.

In this study authors aim to produce carbon foams with controllable pore size and distribution with high ratio of open porosity and to determine the cytotoxicity, and the bio-compatibility of the carbon foams by controlled experiments on the Dawley rats. Carbon foams are produced from Mitsubishi AR pitch at different pressures, temperatures, pressure release times, and additives for the purpose of using it as a bone implant material. Carbon foams with controllable range of pore sizes and distribution by using temperatures between 283 and 300 degrees C, pressures between 38 and 78 bar, and pressure release times between 5 and 600 s. The highest total porosity was found to be 86%. This porosity level was also complemented by the highest density, and compressive strength. Addition of isotropic pitch, graphite powder and THF, toluene and xylene solvents resulted in higher pore volumes compared with no additives. In the case of exploiting this result, it should be noted that higher pore volumes are realized with drastic drop in porosity and strength. The ability of porous foam to provide scaffold to tissue in vivo was finally investigated after 3 months of implantation in adequate pockets in the nude mice for insertion. Histological examination of the engineered constructs revealed that the tissue adaptation and bone compatibility of the carbon foam material studies on rats was found to be satisfactory. Progression of connective tissue formation into the carbon implant was observed without any sign of cytotoxicity and incompatibility during the postoperative follow-ups.

Thermal treatment of landfill leachate and the emission control.

The main aim of this study was to develop an appropriate system for the thermal treatment of landfill leachate. In the initial phase of this study, characterization studies were conducted both for the waste disposed and leachate generated. For the thermal treatment of the landfill leachate two different incineration systems, namely a double-phase liquid waste incineration system and a new pilot-scale incineration system, were tested. During the experimental study, the capability of the new pilot-scale incineration system was proven to treat the landfill leachate. However, high concentrations of NOx were recorded. On the other hand, the experimental data, obtained during the testing period of the double-phase liquid waste incineration system, indicated that the fluidized bed incinerator provided an extra unit sufficient to complete the oxidation of partial products of combustion and organics carried from the initial incinerator. Therefore, lower gaseous emissions were noted. However, an agglomeration problem has occurred, due to the high concentrations of Na, Ca and K. It was concluded that considering the flexibility of the thermal processes, thermal treatment of leachate could successfully be applied to Odayeri landfill, as well as to many landfills, if proper gas treatment systems are applied.

Pyrolysis of virgin and waste polypropylene and its mixtures with waste polyethylene and polystyrene.

A comparison of waste and virgin polypropylene (PP) plastics under slow pyrolysis conditions is presented. Moreover, mixtures of waste PP with wastes of polyethylene (PE) and polystyrene (PS) were pyrolyzed under the same operating conditions. Not only the impact of waste on degradation products but also impacts of the variations in the mixing ratio were investigated. The thermogravimetric weight loss curves and their derivatives of virgin and waste PP showed differences due to the impurities which are dirt and food residues. The liquid yield distribution concerning the aliphatic, mono-aromatic and poly-aromatic compounds varies as the ratio of PP waste increases in the waste plastic mixtures. In addition to this, the alkene/alkane ratio of gas products shows variations depending on the mixing ratio of wastes.