Institute of Fundamental Technological Research

The present paper reports on an innovative and simple route for the preparation of new hybrid materials based on TiO2 and carbonaceous supports with relatively high biochar content prepared via controlled laboratory batch pyrolysis system. Pine tar was used as a precursor for secondary char (confirmed by TGA) serving as a coating and “connecting material” between commercially available Degussa P25 TiO2 and biomass derived porous carbon support (biochar) produced from softwood or Lignin. The prepared hybrid materials were characterized by a series of physico-chemical characterization techniques such as XRD, XPS, TGA, UV–vis, XRF, SEM, COD and BET analysis. The results confirmed that the method used is viable and can be used to embed TiO2 in the structure of biochar. In aqueous phase phenol degradation, the TiO2/(secondary char-coated biochar) hybrid materials proved photocatalitically active, and especially the TiO2/secondary char-coated SWP700) showed better photocatalytic performance than the commercial TiO2 counterpart.

Biochar,Lignin,Pyrolysis,Secondary char,Water detoxification

We present a facile and green approach to produce crystalline TiO2 nanoparticles on a surface of different carbonaceous materials derived from lignocellulosic biomass such as STARBON-800® obtained by carbonization at 800 °C and biochar-SWP700 (Soft Wood Pellets (SWP) obtained by pyrolysis at 700 °C) via novel low-temperature ultrasound-promoted green methodology coupled with citric acid as a cross-linking agent. In comparison to other methods, the developed method has several significant benefits such as simplicity, great ability to get crystalline TiO2 particles (elimination of high-temperature treatment (material calcination at >300 °C) needed in the conventional sol-gel method, which is extremely important in transforming amorphous TiO2 into a photoactive crystalline phase) elimination of risky chemicals and oxidizing agent, and also ability to change some parameters (e. g. ultrasound intensity). Prepared materials were characterized by XRD, DR UV−vis, N2 physisorption, HR-XPS, XRF, HR-TEM, FT-IR and subsequently tested for their photocatalytic activities both in photocatalytic phenol degradation (in water) and oxidation of methanol (in air) under UV and visible light irradiation.

A series of new inorganic-organic hybrid materials based on TiO2 and new biochar-based supports (biochar obtained by pyrolysis of Miscanthus Straw Pellets (MSP) and Soft Wood Pellets (SWP) at 550 and 700 oC) were successfully prepared using ultrasound-assisted
methodology. The resulting composites were characterized by a wide range physicochemical techniques and investigated in water and gas phase photocatalytic test reaction. Our best composite (TiO2/SWP700) achieved phenol degradation of 64.1% (under UV light) and 33.6% (under visible light). In addition, it also showed an extraordinarily high activity (~90%) in selective oxidation of methanol to methyl formate in flow gas phase, high selectivity to
methyl formate (~80 %) and high yield of methyl formate (~88 %) after 240 minutes of illumination. It can be noticed that when TiO2 is supported on biochar, presented a superior photocatalytic ability and could be recycled at least 5 times in both photocatalytic runs tests with reproducible high photocatalytic efficiency.

Biochar,TiO2,Synthesis of composite photocatalysts,Sonication for composite preparation,Phenol degradation,Methanol oxidation