Abstract
Based on the increasingly serious formaldehyde pollution, effective degradation of formaldehyde has become a practical problem that humans urgently need to solve. Among many treatment methods, activated carbon has the advantages of large specific surface area, high adsorption efficiency, and uniform pore size distribution. As a kind of clean photocatalytic material for formaldehyde degradation, titanium dioxide supported by activated carbon has become a research hotspot to develop adsorption-catalytic materials for formaldehyde degradation. In this paper, the research progress of activated carbon and its modification, the photocatalytic principle and modification of titanium dioxide, and TiO2/AC materials are reviewed. The results show that the pore size distribution gradient and acidic oxygen-containing functional groups of activated carbon play key roles in the formaldehyde adsorption process. TiO2 doped with metal ions and nonmetal ions can significantly improve the photocatalytic activity. The TiO2/AC material can greatly improve the photocatalytic rate and achieve the technical goal of efficient and clean degradation for formaldehyde.
Highlights
Relevant research shows that, with the rapid development of economic society, decoration materials are emerging one after another, and most of these materials contain pollutants such as formaldehyde [1, 2] which is known as ant aldehyde, chemical formula HCHO, molecular weight 30.03, formaldehyde gas relative density 1.067, liquid density 0.815 g/cm3 (-20°C), melting point -92°C, and boiling point -19.5°C
Formaldehyde can form hydrogen bonds with functional groups and oxidize with carboxyl and phenolic hydroxyl groups in pore size. It can be seen from the previous studies that the content of functional groups on the surface of activated carbon determines the degree of chemical adsorption and oxidation reaction, the large specific surface area of micropores provides sufficient physical adsorption sites for pollutants, and the pore size distribution affects the internal diffusion ability of formaldehyde molecules
Zhu et al [62] studied the effect of Au/TiO2 photocatalytic removal for gaseous formaldehyde, and the results showed that when the relative humidity and blue light intensity were 13% and 38.5 MW/cm2, respectively, the degradation rate of formaldehyde under light reaction was 77%, much higher than the conversion rate under dark reaction
Summary
With the rapid development of economic society, decoration materials are emerging one after another, and most of these materials (such as manmade panels and glue paint) contain pollutants such as formaldehyde [1, 2] which is known as ant aldehyde, chemical formula HCHO, molecular weight 30.03, formaldehyde gas relative density 1.067, liquid density 0.815 g/cm (-20°C), melting point -92°C, and boiling point -19.5°C. Due to the long release cycle of formaldehyde and being affected by the season, it is not applicable to take ventilation to remove formaldehyde in some cold areas Green plants such as cactus, Chlorophytum, and aloe [16] can remove low concentration of formaldehyde; its normal growth will be affected or even withered in high concentration of indoor, so it has little effect on absorption of formaldehyde. Photocatalytic degradation technology uses light of a certain wavelength to irradiate photocatalyst materials to produce active species, which participate in the reaction to degrade formaldehyde into carbon dioxide and water, and so produces the effect of air purification [20]. TiO2, the principle of photocatalytic reaction, and the load and modification treatment were reviewed, and the adsorption and degradation properties of activated carbon and TiO2/AC for formaldehyde were analyzed and compared, providing scientific guidance for the degradation of formaldehyde
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