Study On Treatment Of Wastewater Produced By DDNP Production With Coagulation And Adsorption

As a typical representative of all detonating explosives in the nitro-diazotized category, DDNP has been widely used, especially in the mass manufacture of industrial blasting detonators, due to its excellent performance, abundant raw materials, low cost and relatively safe production. The liquid effluents from DDNP, containing diazodinitrophenol, nitro-compound, sulfide and phenolic compounds, etc, is a toxic organic wastewater, which would pollute the environment and pose a threat on the health of the neighborhood residents if not properly handled. Although scholars have developed a variety of technology-based wastewater treatments, these treatments do not survive in the real operation because of their poor effect, or technical problems, or economic reasons. As a result, some enterprises have been forced to abandon the production of DDNP. Since the wastewater of DDNP production has brought about a series of problems to people and the social at large, this study took it as the subject and succeeded in ameliorating the status quo by adopting a combination of coagulation and adsorption technologies. The result of the study is an initial establishment of a new treatment of DDNP wastewater, with which the treated water reaches corresponding national wastewater discharge standards. Besides, this method can be used for reference in nitro-phenolic organic wastewater treatment.In the beginning, the paper examined the coagulation pretreatment of DDNP wastewater. By experimenting and observing the effects of different coagulants in treating DDNP wastewater, the study selected polyferric sulphate(PFS) as best. Then by employing the single-factor method, the study further investigated the effects of different technological parameters, including the dose of coagulant, pH value, rapid stirring speed and time, and slow stirring speed and time. Finally, through orthogonal test, the study ascertained the optimized technological conditions of coagulation pretreatment. The result of the study showed that the removal rate of COD, nitro-phenolic compounds, and chrome should be 53%, 34.9% and 65.4% respectively when the adding dose of PFS was 450mg/L, the pH value 8, the rapid stirring speed 200r/min, the rapid stirring time 60s, and the slow stirring time 20min.After that, the paper studied the static adsorption/desorption process of the pretreated wastewater. By experimenting with three different adsorption resins in this process, the study decided type XDA-1 as best. In addition, having changed the pH values, the study found that pH 3-4 was optimal. Then by referring to adsorption thermodynamics and kinetics of the system, this study expected to seek a more in-depth understanding of the process and guidance for the optimization and enhancement of the process. The result presents that the process of XDA-1 resins absorbing the nitro-phenolic compounds corresponded to the Freundlich absorption isotherm model, and it was a physical absorption resulting in uneven surface. Further, the kinetic data showed the adsorption progress fit the pseudo-first-order models and that particle diffusion predominated in the whole adsorbing procedures. The studies also demonstrated that at room temperature, ethanol had the best desorption effect for already-saturated resins.Finally, by using the adsorbent and desorption selected in static experiments, the study examined the dynamic adsorption and desorption processes of pretreated DDNP wastewater. The paper studied the effects of different flow rates and initial concentration of DDNP wastewater for dynamic adsorption. The study found out that the flow rate of 2BV/h was most appropriate, and the higher the initial concentration of DDNP wastewater was, the greater the treatment capacity of DDNP wastewater would be. In addition, the dynamic desorption tests studied the effects of different flow rates and initial concentration in the desorption process. The results showed that the desorption flow rate from 0.5BV/h to 1.5BV/h was favorable. Diluted ethanol wasn't suitable as a desorption for the renewal of resin-beds.