Сhlorophenols Removal From Solution Using Adsorption and Oxidation in Presence of Activated Carbon Fiber

Abstract

Adsorption and catalytic decomposition of 3- and 4-chlorophenols in the presence of hydrogen peroxide were studied for estimation of efficiency of the adsorption and catalytic methods for purification of solutions from chlorophenols related to special group of the priority toxic water pollutants. Activated carbon fiber and fiber modified with iron/iron oxide having highly developed surface and porous structure were used as the adsorbents. It was shown that adsorption of chlorophenols on the initial carbon fiber was higher as compared to the modified one and equaled to 309 mg/g for 3-chlorophenol and 301 mg/g for 4-chlorophenol. The sorption isotherm of 4-chlorophenol on the initial fiber is described by Langmuir equation with constant equals to 0.065 L/mg, while for composite sorbent constant equals to 0.037 L/mg. It was discovered that removal of chlorophenols from aqueous solutions in the processes of catalytic oxidation in the presence of a heterogeneous catalyst was more efficient than that in the adsorption process. Experimental data have been obtained on the dependence of the concentration of 3-and 4-chlorophenols on the time of destruction at specified pH values and the ratios of the pollutant and hydrogen peroxide. With an increase in the 4-chlorophenol: H2O2 ratio from 1:1 to 1:6, the degree of chlorophenol destruction increases from 75% to 88% (pH 3); when the pH changes from 1 to 9, the greatest degree of destruction is 70% (3-CP) and 87% (4-CP) was achieved at pH 3 (chlorophenol: H2O2 1:4). It was shown that in the system chlorophenol / H2O2 / catalyst there are optimal parameters (pH is 3 and chlorophenol : H2O2 ratio is 1:6), which provide the most complete removal of chlorophenol from solution. The results of chromatography-mass spectrometry analysis show that during contact with the modified fiber, the content of 4-CP decreases dramatically and degradation products are formed (for example, maleic acid), which is consistent with the known schemes for the oxidative destruction of chlorophenols.