8. In developed society, most people spend more than 80% of their time in closed environments like
modern office buildings, shopping centers, schools and newly built houses and even at home or inside
vehicles.1–4 Moreover, it is possible that the concentration of many indoor pollutants is higher than
those outside. This is caused by a quick release of contaminants of which the concentration builds up.1
Formaldehyde already was classified as a known human carcinogen (cancer-causing substance) by the
International Agency for Research on Cancer and as a probable human carcinogen by the U.S.
Environmental Protection Agency.6 Among the many chemical contaminants usually found in polluted
indoor air, formaldehyde (HCHO) is one of the major species.
A number of studies have been made for removing formaldehyde from gas and liquid streams,
including adsorption,8–10 biological,11 catalytic12–14 and photocatalytic oxidation processes.15
The adsorption, biological and catalytic methods have drawbacks such as the need to operate at high
temperature, the use of costly materials and the lacking efficiency of the catalysts
use of efficient catalytic materials to remove formaldehyde in indoor or outdoor environment.
Semiconductor heterogeneous photocatalysis is a widespread technique that has the great potential
to remove organic contaminants in air or water.15 This process which is in the group of “Advanced
Oxidation Processes (AOPs)” is suitable for the oxidation and degradation of organic pollutants.
9. CONCEPT OF POLLUTION AND TOXIC POLLUTANTS
INSIDE THE HUMAN BODY AND EATING
CONTAMINATED FOOD AS AN OPEN MOUTH
INGESTING INDUSTRIAL TOXINS OR CLIMATE
CHANGE AFFECTS WITH 3D ILLUSTRATION
ELEMENTS.
10. It is accepted that the initial step for photocatalytic degradation is the formation
of an extremely reactive but short–lived hydroxyl radical (OH•) by hole trapping
(Eqs. (5) and (6)). The OH• is formed on the highly hydroxylated semiconductor
surface. Hydroxyl species are formed when water interacts with bridging oxygen
atoms on the surface, or when coordinating to oxygen vacancies.35 This process is
immediately followed by the reduction of adsorbed oxygen species, derived either
from
dissolved oxygen molecules, or by other electron acceptors available. The main
reactions governing the photocatalysis process are as follows:
Electron–hole pair formation:
TiO
2 +h → TiO2 +ecb − +h+ b (1
11.
12.
13.
14. USAGE
formaldehyde-based resins in wood panel and board
products also enables the sustainable use of forest
resources and minimizes waste, as composite wood
panels, such as particleboard, are typically made from
recovered wood waste that would otherwise be burned or
disposed of in a landfill.
15. • Nail polish, nail glue, eyelash glue, hair gel, hair-smoothing products, baby
shampoo, body soap, body wash, color cosmetics.
16. Formaldehyde is classified as a carcinogen by the world health organization (who) and ranks second on the list
of toxic chemicals under priority control in china. most indoor formaldehyde comes from man-made panel
boards. many countries have placed formaldehyde off-gassing restriction on man-made panel boards. the
F★★★★ standard from japan has the strictest regulations. wanhua has received formaldehyde-free certification
through japan's F★★★★ certification program for its products.
In accordance with F★★★★ standards, the tested formaldehyde content should not be higher than 0.3mg/l
(0.5mg/l under E0 standards).
