COMPOSITES BASED ON ACTIVATED CARBON FOR THE PURIFICATION OF WASTE WATER FROM THE CHROMIUM COMPOUNDS

Abstract

Two samples of modified carbons and three samples of composite with different contents of zirconium (IV) oxide synthesized on the basis of active coal BAU. The shape and size of zirconium oxide particles formed on the carbons surface due to the homogeneous precipitation determined using electron microscopy. pH of the samples surface of synthesized composites is in the range from 6.7 to 7.2 and nonlinearly varies depending on the content of zirconium(IV) oxide. The highest value of surface pH (8.5) shows a sample of active carbon subjected to heat treatment, and less pH (6.2) shows carbon, which treated with nitric acid. The specific surface area is the smallest in the sample of initial carbon (420 m 2 /g), the largest (780 m 2 /g) is in a composite with the least content of zirconium (IV) oxide. With increasing of ZrO 2 content the surface area decreases, apparently by filling the internal volume of micro- and mesopores due its homogeneous deposition. Active carbon and composites based on it are capable of ion exchange in a wide pH range from 2 to 12. The greatest point of zero charge (9.2) has initial carbon, and the lowest (3.8) has oxidized carbon. The transition from a cationic to anionic exchange occurs at pH from 7.5 to 8.2 for composites, and does not differ significantly. Compared with the original activated carbon composites with ZrO 2 content 7 and 14 % show a greater adsorption capacity to the chromate ion, and when the content of ZrO 2 is 28 % the composites have less active.