Removal Of Methylamine Odor By Peroxides Based-Wet Scrubbing Oxidation

Methylamine (CH3NH2) is a typical kind of organic methylamine with small molecule, which possesses a low threshold concentration (0.021 ppm), meanwhile it has a strong pungent odor of fish even at low concentrations. It has simple molecular structure, but it is difficult to be degraded. So it is one of the atmospheric pollutants in urgent need of governance.A wet scrubbing oxidation of CH3NH2(g) by peroxides, including hydrogen (H2O2), peroxymonosulfate (PMS) and persulfate (PS), was developed in this study. It meaned that CH3NH2(g) was absorbed in water and then degraded by peroxides’ oxidation under mild condition. The determination method of CH3NH2(aq) in aqueous solution should be established firstly, because peroxides with high redox potentials would result in disturbance of the determination of CH3NH2(aq) concentration. Finally, the removal of CH3NH2(g) using peroxides by wet scrubbing was realized. The experiments was conducted under different pH and different activated methods to select appropriate activation methods and to optimize the experimental conditions for the efficient removal of CH3NH2(g). Specific research contents and results were as follows:(1) The determination method of CH3NH2(aq) concentration in the solution containing strong oxidant was established. Strong oxidant can interfere with the determination of CH3nh2(aq) by spectrophotometric method. The blowing and absorption experiment which collected Ch3Nh2(aq) was conducted, in order to remove the peroxides interference.A series of experiments were conducted to find the displine that effect factors including NaOH concentration, aeration time, H2SO4 concentration affect on CH3Nh2(aq) blowing off and absorption.When inlet velocity was 0.3 L/min, NaOH concentration was 10 mol/L, the aeration time was 10 min, and H2SO4 concentration was 0.03 mol/L, the experiment of the relative standard deviation (RSD) was 3.66% and the recovery rate was 88.9%～105.9%. By this method the CH3NH2(aq) can be completely removed from the samples, and we can measure the CH3NH2(aq) concentration without of the interference of strong oxidant.(2) CH3NH2(aq) removed by oxidants in water was studied in this article. Under the condition of different pH (3～11), the effect of peroxides alone and Fe2+ activated peroxides on the removal capacity of CH3NH2(aq) was analyzed. When peroxide was used alone, only the PMS in alkaline conditions can remove CH3NH2(aq), and the influence sequence of pH was 11> 10> 9. Under acidic condition, the removal abilities of three peroxides were not ideal. After activated by Fe2+, the ability of peroxides in alkaline condition to remove CH3NH2(aq) was not changed. But the effect of oxidation by PS significantly increased under acidic condition. The removal ability of CH3NH2(aq) by three kinds of peroxides was different, which was mainly related to their molecular structure.(3)Srubbing oxidation of CH3NH2(g) removed by iron-activated PS. At pH 3 can be easily adsorbed by water under acidic condition, However, can not be removed by Fe2+ activated PS effectively. In order to improve the removal efficiency, four different ways of PS activation (the Fe2+ activation, citric acid (CA) chelating Fe2+ activation, Fe0 activation and CA unting Fe0 activation) to remove CH3NH2(g) were compared. When PS activated by iron was adopted to remove CH3NH2(g), Fe0 had better effect than Fe2+; however, after using CA, Fe2+ behaved better than Fe0. Reasons may be due to releasing rate of Fe2+, which influenced the existence time of Fe2+, then affected the PS decomposition, further impacted the removal of CH3NH2(g).(4) Wet scrubbing oxidation of CH3NH2(g) removed by alkali-activated PMS. Under alkaline conditions, PMS activated by OH- can get rid of the CH3NH2(aq). Firstly, the pH influence on the absorption of CH3NH2(g) in water was studied, preparing for wet scrubbing oxidation of CH3NH2(g). Secondly, the effect of PMS and OH- concentration on CH3NH2(g) removal was studied. Meanwhile which kind of free radicals played a leading role also was explored. When the N2 intake rate fixed, different pH value (3-11) had little influence on the absorption of CH3Nh2(g). The q) concentration in the water was only related to the ventilating amount of ). The removal efficiency of CH3NH2(g) increased with the increasing concentration of OH- and PMS. HO· had better effect than SO4-, which played a leading role in this experiment. That’s beacause the speed of HO· reacting with CH3NH2(aq) was faster. At the same time, under alkaline condition, CH3NH2(aq) was in the majority, which is beneficial for the reaction.