Treatment Of Harbor Oily Wastewater By Modified Semi-coke

The harbor plays important roles in the urbanization and the national economic development. However, serious environmental pollution is also coming with the opportunities brought by harbor construction to economic stimulation. Oil sewage, trash, sanitary sewage from heavy harbor traffic are among those wastes which create a huge pressure to harbor environment. Oily wastewater is especially difficult to treat, posing a great threaten to ecosafety of the marine system. It is therefore of great significance, for improving the water quality and harbor sustainable development, to conduct researches on eliminating oil pollution.The thesis focuses on the modification of semi-coke for the purpose of improving its adsorption efficiency in treating harbor oily wastewater. The influence of modification method on the surface morphology and adsorption performance of semi-coke was inspected. The HNO3-high temperature N2 activated semi-coke was chosen as an example to inspect the influence of operating parameters on adsorption capacity by using a static experiment, in which dispersed and emulsified oils in artificial sea water were adsorbed on modified semi-cokes.It was shown that the surface morphology and adsorption performance of semi-coke changed greatly after the modification. Hydrothermal treatment seriously scratched the surface of semi-coke, reduced both of its surface area and proportion of micropore. However, a further H2O2 processing increased the surface area of semi-coke, while the surface area and the pore volume decreased after a futher stearin modification. The pore size and surface area of semi-coke increased after either a HNO3 or a high-temperature N2 activation, while a better result could be obtained by combining the two methods. As far as the oil removing efficiency is concerned, the hydrothermal, hydrothermal-H2O2 and HNO3 treatment make the performance worse, while hydrothermal-stearin modification, high-temperature N2 and HNO3-high-temperature N2 treatment improve it. A removal rate of 34.81% was obtained for the raw semi-coke used for a oily wastewater at a certain concentration. The value increased to 49.67% and 55.09% for hydrothermal-stearin modification and high–temperature N2 treatment, respectively. The highest value of 76.53% was achieved for HNO3-high-temperature N2 treatment, suggesting a great potential for the treatment of oily wastewater.The equilibrium was reached in 20 minutes for adsorption of dispersed oil by HNO3-high-temperature N2 modified semi-coke, compared to 90 minutes for the emulsified oil adsorption. It was justified that the adorption at 20℃followed a pesudo-secondary Lagergren kinetics in both cases. It was also indicated that the adsorption of dispersed oil could be described by using a BET formula at lower temperatures, while a Freundlich isotherm was better for describing the adsorption of emulsified oil. The oil-adsorbing process by modified semi-coke from oily artificial sea water is exothermic, and an enhanced temperature is then unfavorable for the treatment process. The effects of pH value and salinity of the sea water were similar for the two cases.A field harbor oily wastewater was used to validate the usefulness of the modified semi-coke for oil removal performance. The oil-removal rate of raw semi-coke for the field wastewater was 33.67%, and those of hydrothermal treated-stearin modified, high-temperature N2 treated and HNO3-high- temperature N2 treated semi-cokes were 46.89%, 52.93% and 72.15%, respectively. They are potentially excellent materials for harbor wastewater oil removal.