Treatment Of Oily Wastewater By Modified Semi-coke

This thesis focuses on the application of semi-coke to treat oily wastewater. The influences of several parameters about the oily wastewater treatment by semi-coke are observed. Based on the properties of semi-coke and oily wastewater, suitable modification methods are explored, so that the adsorption capacity of semi-coke to oily wastewater could be improved by modification.The results show that, the application of semi-coke as a kind of sorbent in oily wastewater treatment is advisable. At 20℃, the equilibrium adsorption capacity of semi-coke is about 12mg/g, close to half of the adsorption capacity of activated carbon in the same condition. And the adsorption capacity of semi-coke is slightly affected by the pH of oily wastewater, as the discrepancy of adsorption capacity of semi-coke is about 0.4mg/g. With the increase of solution salinity, the adsorption ability of semi-coke is obviously improved, the difference of which could get 41% at most, and shows little change with the increase of solution salinity. The adsorption dynamics and thermodynamics on the treatment of oily wastewater with semi-coke are discussed tentatively. The process of treatment of oily wastewater is exothermic, attribute to physical adsorption. So, the accretion of solution temperature is unfavorable to treatment of oily wastewater by semi-coke.Several modification methods of semi-coke are explored, physical and chemical properties of the surface of modified semi-coke are analyzed. The effects of modified semi-coke on the treatment of oily wastewater are studied. The surface area of raw semi-coke is 103.21m²/g. Thereinto, the surface area of modified semi-coke by N₂ at high temperature could attain nearly 2.5 times more. There is a slight influence of modification on the pore size of semi-coke, which changes between 2.2-2.0nm. The surface of raw semi-coke basically presents neutral. The modification of KOH, H₂O₂ and N2 at high temperature can improve the concentration of basic group on the surface of semi-coke. The adsorption ability of most modified semi-coke is improved at different extent. The semi-cokes modified by KOH and H₂O₂ are better than others. Under the appropriate condition, the capacity of modified semi-coke by KOH and H₂O₂ could be 20mg/g, which increases nearly one time compared to that of raw semi-coke.In addition, the adsorption column experiments of semi-coke are carried out. The results indicate that: low flow velocity and low concentration of oily wastewater are beneficial to the treatment of oily wastewater with semi-coke. The oil removal rate of modified semi-coke by KOH could get 90%. While the adsorption ability of modified semi-coke by H₂O₂ and Cu(NO₃)₂-N₂ are comparative, both the oil removal rate are about 80%. There is a gap between the effect of the treatment of practical and simulative oily wastewater by semi-coke. The average oil removal rate of raw semi-coke, modified semi-coke by KOH and H₂O₂ are respectively at 33%, 66% and 60%.Furthermore, the pilot study of the regeneration process of semi-coke by vapor is carried out. With the increase of vapor temperature and regeneration time, the effect of semi-coke regeneration is improved. After the first time regeneration, the effect of oily wastewater treatment with semi-coke is better than raw semi-coke, however, with the increase of regeneration times, the adsorption ability of semi-coke continually decline.