NOx storage and reduction over copper-based catalysts. Part 2: Ce0.8M0.2O�� supports (M = Zr, La, Ce, Pr or Nd)

5% copper catalysts with Ce0.8M0.2O�� supports (M = Zr, La, Ce, Pr or Nd) have been studied by rapid-scan operando DRIFTS for NOx Storage and Reduction (NSR) with high frequency (30 s) CO, H2 and 50%CO + 50%H2 micropulses. In the absence of reductant pulses, below 200���250 ��C NOx was stored on the catalysts as nitrite and nitro groups, and above this temperature nitrates were the main species identified. The thermal stability of the NOx species stored on the catalysts depended on the acid/basic character of the dopant (M more acidic = NOx stored less stable ��� Zr4+ < none < Nd3+ < Pr3+ < La3+ ��� M more basic = NOx stored more stable). Catalysts regeneration was more efficient with H2 than with CO, and the CO + H2 mixture presented an intermediate behavior, but with smaller differences among the series of catalyst than observed using CO alone. N2 is the main NOx reduction product upon H2 regeneration. The highest NOx removal in NSR experiments performed at 400 ��C with CO + H2 pulses was achieved with the catalyst with the most basic dopant (CuO/Ce0.8La0.2O��) while the poorest performing catalyst was that with the most acidic dopant (CuO/Ce0.8Zr0.2O��). The poor performance of CuO/Ce0.8Zr0.2O�� in NSR experiments with CO pulses was attributed to its lower oxidation capacity compared to the other catalysts.

Synthesis of denim waste-based adsorbents and their application in water defluoridation

This study evaluates the application of denim fiber scraps as a precursor for the synthesis of adsorbents for water treatment via pyrolysis and their application in water defluoridation. The best pyrolysis conditions for the synthesis of this novel adsorbent have been identified and a metal doping route with different salts of Al3 +, La3 + and Fe3 + was proposed to improve its fluoride adsorption behavior. Different spectroscopic and microscopic techniques (i.e., FTIR, XPS, XRF, SEM) were used to characterize the precursor and adsorbents, and to analyze the surface interactions involved in the fluoride removal mechanism. Experimental results showed that these adsorbents were effective for fluoride adsorption showing uptakes up to 4.25 mg/g. The Si-O���metal���F interactions appear to be highly relevant for the fluoride removal. This study highlights the potential of denim textile waste as a raw material for the production of added-value products, thus minimizing their associated disposal cost. It also shows the performance of denim textile waste as a precursor of adsorbents for addressing relevant environmental concerns such as fluoride pollution.