Petrochemical Waste Research Paper

The petrochemical plants are among those industries which create some kinds of deleterious wastes that must be treated. Sodium hydroxide (Caustic) scrubbing solutions are commonly used in petrochemical (such as olefin units) for the elimination of impurities and acid constituents such as all kinds of mercaptans, CO2 and H2S [1]. The strong caustic solutions (20 wt % NaOH) are used to extract low molecular weight mercaptans from the naphtha stream. Once these components react with the NaOH, a waste solution becomes known as a spent caustic [2]. Average pH value of spent caustic typically is greater than 12, depending on the origin this waste contains high levels of hydrogen sulfide, mercaptan and phenol respectively [3]. Spent caustic is a highly odorous waste due to the high concentration of toxic constituents like thiophene, mercaptans contents. According to the US EPA under the RCRA definition spent caustic is categorized hazardous waste [4], thus

5, 6 indicated contour and surface plot based on the experimental design at 8.5 L/min air flow. The contour and surface figures were applied to specify the optimum level of each variable for the most response [25]. It has been found that the optimal temperature for treatment and regeneration of spent caustic is 85 to 95 ºC. As well as is obvious from Fig. 5 which the process efficiency will be reduced after the present temperature. Fig. 5 demonstrated, the reaction time was not too long and it is in the interest of process. The surface plots indicate the effects and interaction of two independent variables (temperature and reaction time) on the response. As well as 3D surface plots (Fig. 6) show, the best conditions for this process. As a consequence of temperature effect, the caustic regeneration will be reduced in lower than 85 ºC and more than 95 ºC. The COD and S2- Results will depend on the regeneration of caustic. In this temperature range, the optimal results will be achieved for sulfide and