Prediction of the Removal Efficiency of a Novel Two‐Stage Hybrid Scrubber for Flue Gas Desulfurization

Emission of SO₂ from various industrial sources occurs in varying concentrations and quantities. The operation of scrubbers as SO₂ control devices is getting more and more attention as pollution control regulations are tightened. Experimental investigations on the scrubbing of SO₂ in a novel two‐stage hybrid (spray‐cum‐bubble column) scrubber using water and dilute sodium alkali are reported. Empirical and semi‐empirical correlations are developed for the prediction of the performances of the bubble and the spray sections in terms of various pertinent variables of the system for water and alkaline scrubbing, respectively. The contribution of the mass transfer enhancement factor towards the removal of SO₂ has been exploited while developing the semi‐empirical correlation for the prediction of performance in alkaline scrubbing. The predicted values are in excellent agreement with the experimental values. Finally, the operating features of the scrubber and design aspects are discussed in order to develop our understanding for practical applications.     

Electrical conductivity of poly(vinyl alcohol)/carbon nanotube multilayer thin films: Influence of sodium polystyrene sulfonate mediated carbon nanotube dispersion

This investigation was aimed to enhance the dispersibility of multi-walled carbon nanotubes (MWCNT) using sodium polystyrene sulfonate (Na-PSS) polyelectrolyte. Subsequently, electrically conducting, multi-layer thin films are prepared utilizing layer by layer assembly method with poly(vinyl alcohol) as a host matrix. The highest extent of MWCNT dispersion was observed in MWCNT:Na-PSS ratio of 1:9 (wt/wt), which was estimated from UV-Vis spectroscopic analysis. Zeta potential measurements of Na-PSS modified MWCNT dispersion showed large negative potentials ranging from −52 to −64 mV in the most stable pH range of 4 to 10, suggesting the colloidal stability is due to the long-range repulsive nature of electrostatic interactions from negatively charged sulfonate groups. Complementary molecular dynamics simulations showed that adsorption of Na-PSS imparts a large negative potential to the carbon nanotube surface, which increases with an increase in Na-PSS concentration. The multi-layer thin film of (1:9) MWCNT:Na-PSS exhibited a DC electrical conductivity of 2.96 × 10² S/m.     

Highly accessible SnO2 nanoparticle embedded SBA-15 mesoporous silica as a superior photocatalyst

We address the accessibility of tin oxide (SnO₂) nanoparticles synthesized inside the pores of mesoporous silica (SBA-15) host. On using a low-temperature route for in situ synthesis of SnO₂ and hence eliminating interparticle aggregation, SnO₂ nanoparticles of diameter much smaller (3.5 nm) than the cylindrical pore diameter (6.3 nm) of the SBA-15 could be synthesized. This enables molecules diffusing into the SBA-15 pores to access the very high specific surface area of SnO₂; enabling the diffusing species to react easily with the latter. This is demonstrated by an enhanced photocatalytic degradation rate constant of an aqueous solution of rhodamine B dye, on contacting the latter with the SnO₂-SBA-15 composite.     

Aerosol dynamics and the synthesis of fine solid particles

Aerosol dynamics (AD) is the discipline that deals with changes in particle size distributions in space and time. AD is based on (1) certain fundamental principles embodied in a set of equations, (2) experimental methods and instrumentation and (3) numerical and computational methods. Over the last few decades, AD has emerged as an enabling discipline in the design of aerosol reactors employed in the gas phase synthesis of fine powders, the characterization of particle emissions from sources such as coal-fired power plants and the atmospheric aerosol. The development of basic AD concepts since early in the 20th century is traced to the present. Major gaps that remain in the field and likely advances over the next few years are discussed. Although accurate predictions of particle size from first principles are difficult to make in practical applications, AD principles can be used to explain trends in product properties for flame and laser ablation reactors that operate under very different temperatures and quench rates.     

Synthesis of CuInS2 films by sulphurization of Cu/In stacked elemental layers

CuInS₂ films were synthesized by sulphurization of In/Cu stacked elemental layers (SEL) deposited onto glass and Mo-coated glass substrates by graphite box annealing at temperatures of 620–880 K. The films thus synthesized were characterized by measuring electrical, optical, microstructural and photoluminescence properties. The microstructure and hence the physical properties of the films depended critically on the amount of sulphur incorporation. Nature of charge carriers depended on both Cu/In and S/(Cu+In) ratio and the carrier concentration varied between 10¹⁴ and 10¹⁸ cm⁻³. Grain boundary scattering effects were critically studied by measuring the electrical conductivity and Hall mobility simultaneously on the same sample. The shape of the grains depended critically on the sulphur content. The PL spectra were dominated by the excitonic peak 788 nm followed by another peak at 892 nm which may be ascribed to the DA transition.