Abstract:

As a kind of inexpensive materialbiochar, the function of soil restoration and other aspects has caused wide public concern, but its catalytic role has been studied rarely. The feasibility of persulfate (PS) catalyzed by biochar(BC) to decolor an azo dye (acid orange (AO7)) was studied. Some factors influencing the decolorizing efficiency of PS/BC system were evaluated, including pH, concentration of biochar and PS/AO7 mole ratio. What’s more, the recycle effect and characteristics of biochar were studied.Results showed that the decolorizing effect of the PS/BC system was obviously better than the only PS system. The decoloration of AO7 by both reaction systems followed first order reaction kinetics. The optimum pH of PS/BC system was nearneutral. The higher the biochar concentration, the better the decolorizing effect was. Similar trend was observed for the PS/AO7 mole ratio, whereas the catalytic effect did not increase accordingly. The reused biochar could still decolor AO7. The BC holes were mostly located on the surface of the layered structure, and most of them were blocked after repeated use. Excluding ash and oxygen, content of elements (C, N, H, S) reduced at a certain degree. Many different surface functional groups of BC were mainly C=O, C=C, C-O, C-H, aromatic C=C and C-H and -OH. The absorption peak of -OH disappeared after repeated use. All the above, pine biochar could catalize persulfate to decolorize azo dye -AO7, and the principle was that, the sulfate free radical which was produced by the reaction of -OH function group on the surface of biochar and persulfate could remove AO7.

Key words: biochar, persulfate, azo dye, acid orange 7