Study On Degradation Of Naproxen By Peroxymonosulfate Activated By Transition Metal Ion

Naproxen is a typical representative of nonsteroidalanti-inflammatory drug, Because of its obvious effect, mild side effect, well tolerant, naproxen is widely used around the world. Due to considerable and large-scale using, limited removal efficiency by traditional actived sludge, naproxen in low concentration exist in sewage treatment plant effluent over a long term, which result in accumulation of concentration of naproxen to 250ng/L in surface water. Studies have found that chronic intake of naproxen in trace level can cause heart disease and apoplexy and also have toxic effects on lung. Therefore, researching high-efficiency and low-cost technologies to degrade naproxen have significance.Traditional activated sludge process is ineffective and may cause more serious secondary pollution; although activated carbon adsorption and membrane filtration treatment are effective, they are hard to popularize for their significant cost. Compared with biological method, advanced oxidation no matter in treatment efficiency or on the cost has obvious advantages to promote in engineering applications. Compared with common hydroxyl radicals, sulfate radicals have better selectivity, longer half-life, stronger oxidant capacity and wider pH range. Transition metal ion reacts with persulfate at room temperature and produce SO4·- whose oxidation is stronger than persulfate. The reaction is fast, simple to operate and doesn’t consume extra energy which shows extensive application prospect.Experiments were conducted to determine the optimal conditions degrading NPX at different pH, concentration of Fe2+ and PMS. The sequential addition of Fe2+ and changing the order of Fe2+ and PMS addition resulted in an improvement in NPX removal. Results show that the highest NPX decomposition occurred at pH 3; the degradation of NPX is better at the molar ratio of PMS/Fe2+/NPX=1/0.75/1 when the concentration of Fe2+ is changed; sequential addition of Fe2+ and adding Fe2+ at first result in an efficient NPX removal. It appears that a slow and steady production of sulfate radicals is desirable of degrading organic compounds and the concentraion of Fe2+ plays an important role in formation of free radicals.Experiments were conducted to determine the optimal conditions degrading NPX at different pH, concentration of Co2+ and PMS and changing the concentration of inorganic non-metal ions Co2+and NO3 to determine their effect on NPX removal Results show that the highest NPX decomposition occurred at pH 5; the degradation of NPX is faster at the molar ratio of PMS/Co2+/NPX=1/1.25/1 when the concentration of Co2+ is changed, although there is no obvious effect on the removal rate of NPX; Cl- has a dual influences on the degradation of NPX, showing inhibitory effect at low concentration and promoting effect at high; NO3- inhibit the degradation ofNPX.