The detection methods and generation mechanisms of the intrinsic reactive oxygen species (ROS), i.e., superoxide anion radical (•O2–), hydrogen peroxide (H2O2), singlet oxygen (1O2), and hydroxyl radical (•OH) in photocatalysis, were surveyed comprehensively. Consequently, the major photocatalyst used in heterogeneous photocatalytic systems was found to be TiO2. However, besides TiO2 some representative photocatalysts were also involved in the discussion. Among the various issues we focused on the detection methods and generation reactions of ROS in the aqueous suspensions of photocatalysts. On the careful account of the experimental results presented so far, we proposed the following apprehension: adsorbed •OH could be regarded as trapped holes, which are involved in a rapid adsorption–desorption equilibrium at the TiO2–solution interface. Because the equilibrium shifts to the adsorption side, trapped holes must be actually the dominant oxidation species whereas •OH in solution would exert the reactivity...

Generation and Detection of Reactive Oxygen Species in Photocatalysis

The rapid depletion of conventional fossil fuels and day-by-day growth of environmental pollution due to use of extensive use of fossil fuels have raised concerns over the use of the fossil fuels; and thus search for alternate renewable and sustainable sources for fuels has started in the last few decades. In this context biomass derived fuels seems to be the promising path; and various routes are available for the biomass processing such as pyrolysis, transesterification, hydrothermal liquefaction, steam reforming, etc.; and the hydrothermal liquefaction (HTL) of wet biomass seems to be the promising route. Therefore, this article briefly enlightened a few concepts of HTL such as the elemental composition of bio-crude obtained by HTL, different types of feedstock adopted for HTL, mechanism of HTL processes, possible process flow diagrams for HTL of both wet and dry biomass and energy efficiency of the process. In addition, this article also enlisted possible future research scope for concerned researchers and a few of them are setting up HTL plant suitable for both wet and dry biomass feedstock; analysing influence of parameters such as temperature, pressure, residence time, catalytic effects, etc.; deriving optimized pathways for better conversion; and development of theoretical models representing the process to the best possible accuracy depending on nature of feedstock.

A review on hydrothermal liquefaction of biomass

The continuous combustion of non-renewable fossil fuels and depletion of existing resources is intensifying the research and development of alternative future energy options that can directly abate and process ever-increasing carbon dioxide (CO2) emissions. Since CO2 is a thermodynamically stable compound, its reduction must not consume additional energy or increase net CO2 emissions. Renewable sources like solar energy provide readily available and continuous light supply required for driving this conversion process. Therefore, the use of solar energy to drive CO2 photocatalytic reactions simultaneously addresses the aforementioned challenges, while producing sustainable fuels or chemicals suitable for use in existing energy infrastructure. Recent progress in this area has focused on the development and testing of promising TiO2 based photocatalysts in different reactor configurations due to their unique physicochemical properties for CO2 photoreduction. TiO2 nanostructured materials with different morphological and textural properties modified by using organic and inorganic compounds as photosensitizers (dye sensitization), coupling semiconductors of different energy levels or doping with metals or non-metals have been tested. This review presents contemporary views on state of the art in photocatalytic CO2 reduction over titanium oxide (TiO2) nanostructured materials, with emphasis on material design and reactor configurations. In this review, we discuss existing and recent TiO2 based supports, encompassing comparative analysis of existing systems, novel designs being employed to improve selectivity and photoconversion rates as well as emerging opportunities for future development, crucial to the field of CO2 photocatalytic reduction. The influence of different operating and morphological variables on the selectivity and efficiency of CO2 photoreduction is reviewed. Finally, perspectives on the progress of TiO2 induced photocatalysis for CO2 photoreduction will be presented.

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Review of material design and reactor engineering on TiO2 photocatalysis for CO2 reduction

Contents: Variety and Quality. Variability loss and tolerance. Determining tolerances. Tolerance design and experimental design. Offline and online quality control. Parameter design and tolerance design: case study. Experimental design for smaller is better characteristics. Experimental design for larger is better characteristics. Bypassing the S/N ratio: spring experiment. Experimental design for dynamic characteristics.

Introduction to quality engineering. designing quality into products a

Fabrication and photocatalytic activity enhanced mechanism of direct Z-scheme g-C 3 N 4 /Ag 2 WO 4 photocatalyst

The photocatalytic methods for nitrogen oxides removal were recently very intense areas of scientific research. Photo-deNOx processes offer interesting ways for abatement of these harmful gases. This review describes several methods for removing NO by photocatalytic reactions. These methods can be classified into three major groups: photo selective catalytic reduction (photo-SCR), photo-oxidation and photo-decomposition. The application of photocatalysts and photo-processes for NOx abatement in real-scale cases are presented. The fast-growing development of these methods is revealed by the large number of issued patents in photo-deNOx applications. The mechanism of NO creation and the traditional methods (primary and secondary) of NOx removal are summarized and discussed. A cooperative system that combines the traditional (thermal) process and a photo-process is then proposed for improving NOx removal efficiency.

Removal of NOx by photocatalytic processes

CO2 biofixation was investigated using tubular bioreactors (15 and 1.5 l) either in the presence of green algae Chlorella vulgaris or Nannochloropsis gaditana. The cultivation was carried out in the following conditions: temperature of 25 °C, inlet-CO2 of 4 and 8 vol%, and artificial light enhancing photosynthesis. Higher biofixation were observed in 8 vol% CO2 concentration for both microalgae cultures than in 4 vol%. Characteristic process parameters such as productivity, CO2 fixation, and kinetic rate coefficient were determined and discussed. Simplified and advanced methods for determination of CO2 fixation were compared. In a simplified method, it is assumed that 1 kg of produced biomass equals 1.88 kg recycled CO2. Advance method is based on empirical results of the present study (formula with carbon content in biomass). It was observed that application of the simplified method can generate large errors, especially if the biomass contains a relatively low amount of carbon. N. gaditana is the recommended species for CO2 removal due to a high biofixation rate—more than 1.7 g/l/day. On day 10 of cultivation, the cell concentration was more than 1.7 × 107 cells/ml. In the case of C. vulgaris, the maximal biofixation rate and cell concentration did not exceed 1.4 g/l/day and 1.3 × 107 cells/ml, respectively.

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CO2 Biofixation and Growth Kinetics of Chlorella vulgaris and Nannochloropsis gaditana

Oxy-fuel combustion of selected solid fuels under atmospheric and elevated pressures

The co-combustion of hard coal with raw and torrefied biomasses (willow (Salix viminalis), olive oil residue and waste wood from furniture manufacturing)

Oxy-fuel combustion is a potential low-emission technique for energy conversion. This paper presents the results of oxy-fuel experiments under high-pressure conditions. The influence of process parameters, such as reactor pressure and temperature, on the emission of NOx, N2O, and other compounds was tested. A new oxy-fuel experimental setup is presented. The experiments were conducted using a laboratory-scale (fuel input of up to 3 kg/h) pressurized fluidized-bed combustor. The feedstock used was “Ziemowit” coal, and the tests were carried out under oxy-fuel and air-fired conditions. The temperature inside the reactor was in the range of 750–900 °C. Generally, NOx emission decreases significantly under higher pressure; however, the details of this trend depend upon the experimental conditions. The effects of pressure and temperature on NOx and N2O emissions are discussed.

Janusz Lasek

Papers

Removal of NOx by photocatalytic processes

CO2 Biofixation and Growth Kinetics of Chlorella vulgaris and Nannochloropsis gaditana

Oxy-fuel combustion of selected solid fuels under atmospheric and elevated pressures

The co-combustion of hard coal with raw and torrefied biomasses (willow (Salix viminalis), olive oil residue and waste wood from furniture manufacturing)

Pressurized Oxy-fuel Combustion: A Study of Selected Parameters