Characterisation of ashes from waste biomass power plants and phosphorus recovery

Biowastes, such as meat and bone meal (MBM), and poultry litter (PL), are used as energy sources for industrial combustion in the UK. However, the biomass ashes remaining after combustion, which contain nutrients such as phosphorus, are landfilled rather than utilised. To promote their utilisation, biomass ashes from industries were characterised in terms of their elemental and mineral compositions, phosphorus extractability, and pH-dependent leachability. These ashes were highly alkaline (pH as high as 13), and rich in calcium and phosphorus. The P bio-availabilities in the ash evaluated by Olsen\u27s extraction were low. Hydroxyapatite and potassium sodium calcium phosphate were identified by X-ray powder diffraction (XRD) as the major phases in the MBM and PL ashes, respectively. The leaching of P, Ca, and many other elements was pH dependent, with considerable increase in leaching below about pH 6. P recovery by acid dissolution (e.g., with H SO ) seems feasible and promising; the optimized acid consumption for ~90% P recovery could be as low as 3.2–5.3 mol H /mol P. 2 4

Products distribution and heavy metals migration during catalytic pyrolysis of refinery oily sludge

The reclamation disposal of oily sludge, which is a hazardous waste from the extraction, transportation, storage, and refining of crude oil, is a paramount challenge for environmental protection and resource recycle. Herein, a catalytic pyrolysis approach with the participation of CaO was adopted for oil resource recovery. The results show that the optimal pyrolysis temperature for recovering oil was 500 °C, in which the pyrolysis oil yield was 44.37%. CaO could act as a catalyst during the pyrolysis process, thus promoting the formation of light components in the pyrolysis oil. The light components in pyrolysis oil increased from 5.08% to 16.67% with the participation of CaO. Meanwhile, the addition of CaO immobilized As, Cr, Pb and Zn into the pyrolysis slag, thus decreasing their migration into pyrolysis oil and gas. The migration of Ni displayed a different trend, and part of Ni entered into the pyrolysis oil and gas. The BCR continuous extraction experiments display that the highly biological-activity heavy metals (i.e., F1, F2 and F3 form) was transformed to a more stable state (i.e., F4 form). These results demonstrate that the catalytic pyrolysis approach with the participation of CaO not only improve the yield and quality of pyrolysis oil, but also reduce the emission and mobility of heavy metals

Effective removal of high-chroma rhodamine B over Sn0.215In0.38S/reduced graphene oxide composite : synergistic factors and mechanism of adsorption enrichment and visible photocatalytic degradation

The highly visible light active Sn0.215In0.38S/reduced graphene oxide (SIS/RGO) composites with hierarchical porous were prepared by a facil solvothermal in-situ growth method for rhodamine B (RhB) removal coupling adsorption with photocatalysis. The morphology, composition and photocurrent response of the adsorptive photocatalysts were systematically characterized. The investigation results showed that both adsorption and photocatalytic processes were affected by pH, ionic strength and so on. The RhB adsorption process complied with pseudo-second order kinetics equation and Langmuir isotherm model, and the SIS/RGO-2.5% showed the optimum adsorption-photocatalytic performance. The maximum adsorption capacity of SIS/RGO-2.5% was 173.97 mg·g−1 mainly attributing to the electrostatic attraction, π − π interaction and surface complexation. Due to efficient mass transfer efficiency, dye self-sensitization and effective transfer of photogenerated carriers, the photodegradation efficiency of RhB over SIS/RGO-2.5% was as high as 96.25% under visible light irradiation for 25 min and the corresponding reaction rate constant is 3.98 times of Sn0.215In0.38S. The results of free radical capture and electron spin resonance experiments indicated that the [rad]O2− and h+ were the main active species attacking RhB. Furthermore, cyclic experiments showed the considerable reusability and stability of photocatalysts for the RhB degradation

Metal-free efficient photocatalyst for stable visible-light photocatalytic degradation of refractory pollutant

The photocatalytic performance of the star photocatalyst g-C3N4 is restricted by the insufficient solar light absorption, low surface area and the fast recombination of photogenerated electron-hole pairs. The present study developed a facile in situ method to construct hexagonal boron nitride (h-BN) decorated g-C3N4 metal-free heterojunction with the aim to greatly enhance the surface area and promote the charge separation. The physical, chemical and optical properties of the resulted samples were thoroughly characterized. The photocatalytic performance of h-BN/g-C3N4 composites were evaluated under visible light irradiation using antibiotic tetracycline (TC) and rhodamine B (RhB) as target pollutants. Results showed that h-BN/g-C3N4 composites exhibited much higher photocatalytic activity than pure g-C3N4 and h-BN. The optimum photocatalytic efficiency of BC-3 sample for the degradation of TC was about 2.3 and 60.3 times higher than that of individual g-C3N4 and h-BN, respectively. Meanwhile, it was about 7.3 and 11.8 times higher than that of individual g-C3N4 and h-BN for RhB degradation, respectively. The enhanced photocatalytic activity of h-BN/g-C3N4 composite is mainly attributed to the larger surface area and the unique physicochemical properties of h-BN nanosheet which acts as a promoter for photoexcited holes transfer. This work indicates that the metal-free h-BN/g-C3N4 hybrid photocatalyst is a promising material in wastewater control