Biochar Catalyzed Persulfate Oxidation Of Azo Dye Wastewater

Biochar is a hot topic in recent years, and shows an infinite potential in theimprovement of soil, C stock enhancement、emission reduction of greenhouse gasesand environmental pollution control. Persulfate advanced oxidation technology, whichhas good prospects for development in the field of organic wastewater treatment thatis difficult to be removed by biochemistry, is a new technology based on the sulfateradicals. Persulfate oxidation degradation of organic wastewater catalyzed byactivated carbon is a kind of new catalytic method, which has just started in recentyears but obvious effect, is also the research focus.In this paper, PS directly heterogeneously catalyzed oxidative degradation oforganic pollutants (azo dye wastewater: AO7) was studied in the presence of biochar.Thus, a kind of new AOPs—biochar catalyzed PS oxidation was found. Then, thecatalytic properties and other properties such as surface structure were compared andlead to develop a new kind of organic wastewater treatment technology. Specificstudies and results are as follows:(1)The adsorption of AO7by AC and Biochar: The AO7adsorption effect by thealone AC and biochar system and we found that AC had a good adsorption effect onAO7, the12h decolorization rate was100%and there is almost no AO7in thesolution. While there is hardly any adsorption by biochar and the color of the solutionafter48h didn’t change.(2)The degradation of AO7by the AC/PS and Biochar/PS systems: Thefeasibility of PS oxidation catalyzed by biochar and the comparison of catalytic effectby AC and biochar and the influence of the biochar concentration、PS/AO7molarratio and the repeat utilization were studied. Compared with the only PS oxidativesystem (the48h degradation of AO7was60%) and the only AC adsorption system(the48h degradation of AO7was10%), the AC/PS combined system remove AO7fast, and the36h degradation rate was100%, while the48h degradation rate by theBiochar/PS combined system was80%. This suggested that AC/PS system andBiochar/PS system had synergy effect, and biochar also has a catalytic PS degradation function of biochemical organic pollutants AO7in water. By increasing the biocharconcentration from0.5g/L to5g/L, the results showed that the36h degradation rate ofbiochar/PS system was95.4%, and the48h one was100%,46%and34.1%higherthan that of the only PS system. Therefore, high concentration of biochar may nothave better catalytic effect. Increasing the PS/AO7molar ratio could accelerate theremoval rate. When the molar ratio improved from50:1to500:1, the48h degradationrate by the combined system increased from47.4%to100%. However, that by theonly PS system also increased greatly, from34.6%to99.7%. This suggested thatwhen the initial PS concentration increased to a certain degree, it would reachsaturation and the catalytic effect wouldn’t improve. AC could be reused in the AC/PSsystem; the degradation of AO7by the combined system was still98.42%and33.07%higher than the only PS system and only0.97%lower than the initial combinedsystem when AC was used once. And for Biochar/PS system, the first removal ratewas79.14%, the second one was52.44%and the last one was39.29%after beingused twice. And the degradation efficiency of AO7was inferior to the only PS system,so the recycle of biochar was bad.(3)The differences of AC and Biochar: The structure of biochar was flake, whilethat of AC was block; biochar was obviously less than AC in the quantity and depth ofthe holes; almost all the holes were blocked after being used for the third time thoughthe first change was not so big and that of AC had no change. In terms of elements,the element content of AC and biochar decreased both. What’s more, the C、N、Scontent of AC was significantly higher than that of biochar, while the H content wasrelatively lower. Biochar had higher H/C atomic ratio and contained more originalorganic matter, while the carbonization degree of AC was relatively higher. Theinfrared spectrum adsorption peak of biochar was more than AC.