Removing Environmentally Harmful Substances

Dioxins or environmental endocrine disruptors (environmental hormones) are emitted to environment which are too toxic and harmful and induce deformities or deaths, even with a very small quantity of these chemicals.

Dioxin is a collective name for chlorinated compounds including two benzene rings combined with ether linkage. The toxicity depends on the number and the substituted positions of chlorine on benzene rings. The optimum specification of the porous carbons for this purpose is as follows: pore size: 2-5 nm; specific surface area: >500 m2/g; pore volume: >0.2 ml/g; particles size about 20 /m.

Catalyst metal

Figure 36. The concept of spillover of hydrogen in metal/carbon systems.

Catalyst metal

Figure 36. The concept of spillover of hydrogen in metal/carbon systems.

There are many chemical substances that are listed as environmental endocrine disruptors. Their removal by an adsorption technique is studied. Abe et al. studied the adsorption of 4-nonylphenol and bisphenol A on four types of activated carbons from different origins [176]. The porous carbons used there were particularly excellent adsorbents for bisphenol A by adsorbing up to saturation uptake even at concentrations as high as several mg/L.

In the practical situation for removing toxic substance from our environment, the concentration of the target molecules is very low as in the case of dioxin and furthermore the kinds of the suspicious molecules are various, which make the design of suitable porous carbon materials difficult. However, it is necessary to develop a design method for suitable porous carbon materials in order to protect our lives.

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