Potential Valorization of Waste Tires as Activated Carbon-Based Adsorbent for Organic Contaminants Removal.

The present study investigates the potential of waste tires to produce a valuable adsorbent material for application in wastewater treatment. In the first stage, the pyrolysis of ground rubber tire was explored using non-isothermal and isothermal thermogravimetric analysis experiments. The effect of operating parameters, such as heating rate and pyrolysis temperature, on the pyrolysis product yields was considered. The slow pyrolysis of ground rubber tire was taken up in a large-scale fixed-bed reactor for enhanced char recovery. Four pyrolysis temperatures were selected by thermogravimetric data. The product yields were strongly influenced by the pyrolysis temperature; at higher temperatures, the formation of more gases and liquid was favored, while at lower pyrolysis temperatures, more char (solid fraction) was formed. The produced chars were characterized in terms of mineral composition, textural properties, proximate analysis, and structural properties to identify the relationships between the pyrolysis temperature and the char properties. In a second step, a series of activated chars were prepared, starting from the pyrolytic chars via chemical and/or physical activation methods. Then, the activated chars were characterized and tested as adsorbents for atrazine and ibuprofen. Adsorption experiments in aqueous media were carried out in a small-scale batch reactor system. Chemical activation seems appropriate to significantly reduce the inorganic compounds initially present in ground rubber tire and contribute to an important increase in the surface area and porosity of the chars. Adsorption experiments indicated that chemically activated chars exhibit high aqueous adsorption capacity for atrazine.

Synthesis, Characterization and Catalytic Activity of Ternary Oxide Catalysts Using the Microwave-Assisted Solution Combustion Method.

Ni-Co-Al, Ni-Cu-Al and Co-Cu-Al ternary oxide catalysts, with a fixed 5 wt% transition metal loading, were prepared by the microwave-assisted solution combustion method and tested in CO oxidation. The bulk and surface properties of the catalysts were investigated, using XRD, N2 adsorption-desorption, SEM, XPS and TEM techniques. XRD, XPS and TEM results revealed that nickel and cobalt were present as spinels on the surface and in the bulk. Differently, copper was preferentially present in "bulk-like" CuO-segregated phases. No interaction between the couples of transition metal species was detected, and the introduction of Cu-containing precursors into the Ni-Al or Co-Al combustion systems was not effective in preventing the formation of NiAl2O4 and CoAl2O4 spinels in the Ni- or Co-containing catalysts. Copper-containing catalysts were the most active, indicating that copper oxides are the effective active species for improving the CO oxidation activity.

Binary Oxides Prepared by Microwave-Assisted Solution Combustion: Synthesis, Characterization and Catalytic Activity.

Three different alumina-based Ni, Cu, Co oxide catalysts with metal loading of 10 wt %, and labeled 10Ni⁻Al, 10Co⁻Al and 10Cu⁻Al, were prepared by microwave-assisted solution combustion. Their morphological, structural and surface properties were deeply investigated by complementary physico-chemical techniques. Finally, the three materials were tested in CO oxidation used as test reaction for comparing their catalytic performance. The 10Cu⁻Al catalyst was constituted of copper oxide phase, while the 10Ni⁻Al and 10Co⁻Al catalysts showed the presence of "spinels" phases on the surface. The well-crystallized copper oxide phase in the 10Cu⁻Al catalyst, obtained by microwave synthesis, allowed for obtaining very high catalytic activity. With a CO conversion of 100% at 225 °C, the copper containing catalyst showed a much higher activity than that usually measured for catalytic materials of similar composition, thus representing a promising alternative for oxidation processes.