Simultaneous Removal Of Nitrite And Ammonia Via Photocatalysis

A series of ZnFe₂O₄/AC,ZnFe₂O₄/NG,ZnFe₂O₄/rGO,ZnFe₂O₄/C₆₀,CuBi₂O₄/AC,CuBi₂O₄/NG,CuBi₂O₄/rGO,CuBi₂O₄/C₆₀0 photocatalysts were synthesized byhydrothermal method.The effects of different parameters on photocatalytic removal of nitrite and ammonia were investigated under white light irradiation,and the mechanism of photocatalytic reaction was explored.The details are as follows:First,ZnFe₂O₄/AC composite was synthesized by hydrothermal reaction and characterized by XRD,TEM,Raman and UV-VIS-DRS.Efects of pH,catalyst dosage,AC content,and initial concentration of ammonia on photocatalytic removal of nitrite and ammonia were investigated.The results showed that the removal ratios of photocatalytic simultaneous removal for nitrite and ammonia were 93.6%and 64.7%,respectively,under anaerobic conditions using 1.5 g/L ZnFe₂O₄/AC?7%?as the catalyst in 50 mg/L NO₂^--N and 100 mg/L NH₃-N of solution with pH 9.5 upon white light irradiation for 3 h.The removal ratios of nitrite and ammonia by ZnFe₂O₄ reached only81.2%and 54.7%under similar conditions.Then,the solution was aerated for 30 min and continued irradiation for 10 h,the results indicated that the removal rates of nitrite,ammonia,and total nitrogen reached 92.3%,90.2%,and 90.9%,respectively.Second,ZnFe₂O₄/rGO and ZnFe₂O₄/NG composites were synthesized by hydrothermal method and characterized by XRD,TEM,Raman and UV-VIS-DRS.Efects of pH,catalyst dosage,rGO content,NG content and initial concentration of ammonia on photocatalytic removal of nitrite and ammonia were investigated.The results showed that the photocatalytic simultaneous removal ratios of nitrite and ammonia were 89.6%,58.4%under anaerobic conditions using 1.5 g/L ZnFe₂O₄/rGO?3%?as the catalyst in 50 mg/L NO₂^--N and 100 mg/L NH₃-N of solution with pH 9.5upon white light irradiation for 3 h.The removal ratios of nitrite and ammonia through ZnFe₂O₄ reached 81.2%and 54.7%,respectively,and the highest removal ratios of nitrite and ammonia using 1.5 g/L ZnFe₂O₄/NG?5%?as the catalyst were 90.9%and 62.8%under similar conditions.Then,the solution was aerated for 30 min and continued irradiation for 10 h,resulting in the removal ratios of nitrite,ammonia,and total nitrogen reached 91.3%,89.2%and 89.9%,respectively,in the case of ZnFe₂O₄/rGO?3%?as the photocatalyst.Similarly,the removal ratios of nitrite,ammonia,and total nitrogen reached 92.0%,89.4%and 90.3%,respectively,in the case of ZnFe₂O₄/NG?5%?as the photocatalyst.Third,ZnFe₂O₄/C₆₀ composite was synthesized by hydrothermal reaction and characterized by XRD,TEM,Raman and UV-VIS-DRS.Efects of pH,catalyst dosage,C₆₀ content and initial concentration of ammonia on photocatalytic removal of nitrite and ammonia were investigated.The results showed that the photocatalytic simultaneous removal ratios of nitrite and ammonia using ZnFe₂O₄/C₆₀?5%?as the photocatalyst reached 90.9%and 61.9%respectively,under anaerobic conditions in 50 mg/L NO₂^--N and 100 mg/L NH₃-N of solution with pH 9.5 upon white light irradiation for 3 h.Then,the solution was aerated for 30 min and continued irradiation for 10 h,resulting in the removal ratios of nitrite,ammonia,and total nitrogen reached 91.8%,87.4%and 88.8%,respectively.Fourth,CuBi₂O₄/AC composite was synthesized by hydrothermal reaction and characterized by XRD,TEM,Raman and UV-VIS-DRS.Efects of pH,catalyst dosage,AC content,and initial concentration of ammonia on photocatalytic removal of nitrite and ammonia were investigated.The results showed that the removal ratios of photocatalytic simultaneous removal for nitrite and ammonia were 91.6%and 62.8%,respectively,under anaerobic conditions using 1.5 g/L CuBi₂O₄/AC?5%?as the catalyst in 50 mg/L NO₂^--N and 100 mg/L NH₃-N of solution with pH 9.5 upon white light irradiation for 5 h.The removal ratios of nitrite and ammonia by CuBi₂O₄ reached only75.5%and 53.8%under similar conditions.Then,the solution was aerated for 30 min and continued irradiation for 8 h,the results indicated that the removal rates of nitrite,ammonia,and total nitrogen reached 92.1%,87.8%and 89.2%,respectively.Fifth,CuBi₂O₄/rGO and CuBi₂O₄/NG composites were synthesized by hydrothermal method and characterized by XRD,TEM,Raman and UV-VIS-DRS.Efects of pH,catalyst dosage,rGO content,NG content and initial concentration of ammonia on photocatalytic removal of nitrite and ammonia were investigated.The results showed that the photocatalytic simultaneous removal ratios of nitrite and ammonia were 89.9%,60.4%under anaerobic conditions using 1.5 g/L CuBi₂O₄/rGO?3%?as the catalyst in 50 mg/L NO₂^--N and 100 mg/L NH₃-N of solution with pH 9.5upon white light irradiation for 5 h.The removal ratios of nitrite and ammonia through CuBi₂O₄ reached 75.5%and 53.8%,respectively,and the highest removal ratios of nitrite and ammonia using 1.5 g/L CuBi₂O₄/NG?5%?as the catalyst were 90.4%and 60.2%under similar conditions.Then,the solution was aerated for 30 min and continued irradiation for 8 h,resulting in the removal ratios of nitrite,ammonia,and total nitrogen reached 90.3%,84.6%and 86.5%,respectively,in the case of CuBi₂O₄/rGO?3%?as the photocatalyst.Similarly,the removal ratios of nitrite,ammonia,and total nitrogen reached 90.9%?85.8%and 87.5%,respectively,in the case of CuBi₂O₄/NG?5%?as the photocatalyst.Sixth,CuBi₂O₄/C₆₀ composite was synthesized by hydrothermal reaction and characterized by XRD,TEM,Raman and UV-VIS-DRS.Efects of pH,catalyst dosage,C₆₀ content and initial concentration of ammonia on photocatalytic removal of nitrite and ammonia were investigated.The results showed that the photocatalytic simultaneous removal ratios of nitrite and ammonia using CuBi₂O₄/C₆₀?5%?as the photocatalyst reached 89.6%and 55.4%,respectively,under anaerobic conditions in 50 mg/L NO₂^--N and 100 mg/L NH₃-N of solution with pH 9.5 upon white light irradiation for 5 h.Then,the solution was aerated for 30 min and continued irradiation for 8 h,resulting in the removal ratios of nitrite,ammonia,and total nitrogen reached 90.1%,82.3%and 84.9%,respectively.By comparison,the photocatalytic activity order for the series of ZnFe₂O₄photocatalysts are as follows:ZnFe₂O₄/AC>ZnFe₂O₄/NG>ZnFe₂O₄/rGO>ZnFe₂O₄/C₆₀for the series of CuBi₂O₄ photocatalysts,their order are as follows:CuBi₂O₄/AC>CuBi₂O₄/NG>CuBi₂O₄/rGO>CuBi₂O₄/C_60.The loading of AC resulted in the highest photocatalytic activity,which may be attributed to the porous structure in AC,improving the adsorption of nitrite and ammonia,and enhancing the photocatalytic activity of the composites.