The Degradation Of Amines Organic Wastewater And Detection And Treatment Of Its Main Byproduct

With the rapid growth of population and the development of economy, emissions of amines organic wastewater increase every year. The amines organic compounds are widely used as important chemical raw materials, which are toxic and hazardous, non-biodegradable, and producing a series of intermediate products. They will be harmful to the environment and human health if they are directly discharged without any treatment. In this paper, the amine organic wastewater was studied mainly including ammonia nitrogen causing eutrophication, unsymmetrical dimethylhydrazine ?UDMH? as the principal component of liquid rocket propellant and N-Nitrosodimethylamine ?NDMA? as the intermediate of degrading UDMH and potential carcinogen. The method of ion exchange resin and photocatalysis are more promising treatment techniques of amines wastewater with the advantages of simplicity of operation, mild reaction conditions, high efficiency and no secondary pollution. In this study a series of experiments were conducted to verify the feasibility of these two technologies, and obtained the optimum operating conditions.Through investigating removing effect of 001x7, D001 and HD-8 resin for low concentration of ammonia nitrogen wastewater, the results showed that HD-8 resin has better removal efficiency. And then, the tests of removing ammonia nitrogen on HD-8 resin were carried out through four factors such as the resin dosage, temperature, pH and stirring time, the results showed that when the amount of resin is 3g, the removal efficiency of ammonia nitrogen reached 95%, which attained the primary discharging standard ?<15mg/L? of the industrial ammonia nitrogen wastewater. The equilibrium time was 5min, the resin static saturation capacity was Q=6.3mg/g. The removal efficiency increases firstly and then decreases with increasing pH value, affected by the resin sulfonic acid group ?-SO3H?, the optimal value of pH is 6. The removal rate increases with increasing temperature as a result of endothermic reaction. Using NaCl, HCl, H₂SO4 and NaOH four kinds of desorbent on resin desorption test results showed that the desorption efficiency of HCl is best. After consecutive exchange and desorption experiments for five times, the exchange capacity of the resin remains almost unchange, indicating its good stability. Under these optimum conditions, the degradation efficiency of using HD-8 resins and modified HD-8 resin to treat UDMH wastewater is as low as 70%. The kinetics and thermodynamics properties are studied on HD-8 resin to remove ammonia nitrogen, the results showed that this process follows the Freundlich model equations and second-order kinetics equation, cooperativly controlled by the liquid film diffusion and particle diffusion. The apparent activation energy is 7.82kJ/mol, which is less than 40kJ/mol, revealing that the reaction is easy. The adsorption process is spontaneous process ??G<0? and endothermic reaction ??H> 0?.The photocatalyst TiO₂ and ZnO were prepared by Sol-gel method, which were applied into the degradation of UDMH wastewater, the results showed that TiO₂ has a better catalytic performance. The catalyst was used to remove ammonia nitrogen, the removal efficiency reached more than 95%. The tests of the modification of TiO₂ photocatalysts and optimization of the reaction conditions on the removal of UDMH wastewater were carried out through nine aspects including respectively catalyst dosage, the active component element ?Cu, Fe? and the amount of doping, auxiliary elements ?Zn, Zr, Nd? and the amount of doping, H₂O₂ dosage, pH, temperature, the initial concentration of UDMH wastewater, exposure time and reusability of the catalyst, the results showed that when the catalyst?1%Zr-5%Cu/TiO₂? dosage is 0.1g, the amount of H₂O₂ is 0.75mL, the illumination time is 1h, pH is 7 and the temperature of 35?, the degradation rate of UDMH was nearly 100%, COD removal rate reached 93.1%, meeting the national emission standards, NDMA content was as low as 0.02mg/L, almost negligible. After reused for 5 times, the activity of the catalyst remained high, indicating that the catalyst has a good stability. TiO₂ photocatalyst was structurally characterized by UV-Vis DRS, XRD, SEM and EDX, the results confirmed that the maximum absorption wavelength ?254nm?, crystalline ?anatase?, structural morphology ?spherical? particle size ?10-20nm? and the actual mass fraction of element. Under the optimum conditions, the degradation process was traced by ultraviolet-visible full wavelength scanning, the detection of the concentration of total carbon, total nitrogen, ammonia, byproduct NDMA and formaldehyde, the results showed that the composition of the reaction solution first become complicated and then become simple with the increase of time, illustrating that UDMH was firstly converted to some refractory intermediate products ?such as NDMA?, then slowly degraded until the products disappeared, and ultimately achieved the purpose of degradation, proving the thoroughness of this degradation reaction. To explore the degradation mechanism of removing UDMH with photocatalysis, LC-MS chroma to graphy was used to detect and analysis the intermediate products, the reaction mechanism is that the photocatalyst produced electron-hole under illumination, which make H₂O produce·OH, and catalyzed H₂O₂ to generate ·OH simultaneously,·OH mainly attack the amino of UDMH, UDMH was transformed into non-toxic small molecules.