Study On Treatment Of Nitrogen Heterocyclic Compounds Wastewater By Fuel Ash Adsorption-Regeneration

As a kind of solid waste being produced by fuel combustion, Fuel ash (FA) is used as a good adsorbent considering the advantages of its’ large output, low cost and active group and porous structure. It can be used to deal with the biological refractory organic compounds in the water. FA becomes a poisonous and harmful substances after adsorption saturation, it needs to be carried on the regeneration process, instead of being directly discarded.In this article, the washed FA was used as the adsorbents to deal with the typical nitrogen heterocyclic compounds (indole, pyridine and quinoline) water. The process was reached in balance in a relatively short period of time. Within5mins, the adsorption has already been almost saturated, with the increase of time, the increasing adsorption rate gradually slows down. So, this study selected30mins as the adsorption time. Under the conditions(30℃150r/min and30min), the adsorption kinetics and thermodynamic properties of three typical NHCS onto the FYA and FLA were investigated. The results showed that the rate of adsorption of three compounds onto FYA and FLA followed the first order better, the adsorptions followed Freundlich isotherms better. The rate of FYA’s adsorption is superior to that of the FLA’s, but the adsorption’s effect is inferior. The indole’s adsorption capacity onto FYA and FLA’s reached0.628mg/g and1.5135mg/g respectively in5mins; the pyridine’s adsorption capacity onto FYA and FLA’s reached0.2044mg/g and0.6186mg/g respectively in5mins; the quinoline’s adsorption capacity onto FYA and FLA’s reached0.44185mg/g and1.09752mg/g respectively in5mins.The Fenton oxidation method was adopted to regenerate the FYA and FLA after adsorption saturation, and the best regeneration conditions were investigated. The results showed that the best H2O2dosing quantities were6.4,9.2,1.6,16,22.4and9.2mmol/L; the best Fe24dosing quantities were1,3.2,0.6,2.6,7.6and3.2mmol/L; the best initial pH value were3,4,4.3,3and4. The multiple cyclic adsorption-regeneration process were studied under the best regeneration conditions. Negative correlation can be found between the fuel ashes regeneration percentage and regeneration times as a whole, despite its ups and downs. In the regeneration process, the initial regeneration rate of indole onto FYA and FLA is the lowest, and the continuous adsorption-regeneration effects were the worst. Then the BET, IR, SEM and XRD methods were used to investigate the raw and saturated FA’s physicochemical properties and surface morphology, explaining the FYA’ worse adsorption capacity and better regeneration capacity when compared to FLA to some extent.