2015 年 2015 巻 270 号 p. 241-249
The adsorptive removal of pollutants from water by activated carbons (ACs) and activated carbon fibers (ACFs) and related studies are briefly reviewed based on our own studies and a literature survey. AC and ACF can be derived from various carbonaceous precursors using physical and chemical activation. Pretreatment of raw bamboo with an alkali to remove hemicellulose and lignin resulted in an AC with wide pores that can accommodate bulky large molecules. Adsorption of organic pollutants from water was principally governed by the surface area and pore size of the AC and ACF, and a hydrophobic surface was desirable, although ionic pollutants preferentially adsorbed on a hydrophilic AC and ACF surface containing hetero atoms of oxygen and nitrogen. Cationic pollutants in water such as heavy metal ions could be effectively removed by negatively charged pyridine, pyrrole and especially carboxy groups of a Brønsted acid on the AC surface, whereas anionic pollutants of nitrate, phosphate, fluoride and arsenic, for instance, adsorb on positively charged species such as quaternary nitrogen (N-Q), aliphatic amine, quinone, and a lactone of Lewis acid. Since an AC surface contains a large number of different nitrogen and oxygen species, one must tailor the surface so that the desired species are dominant in order to prepare an adsorbent for a particular purpose.
