Preparation and removal effect on ammonia nitrogen and phosphates in seawater and freshwater in kaolinite-oyster shell powder modified material

YANG Yuxiang, SONG Kexin, YANG Guang, MA Xiaona, XIE Siqi, LIU Zishuo, FENG Zhihua

Journal of Dalian Fisheries University ›› 2024, Vol. 39 ›› Issue (4) : 634-647.

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Journal of Dalian Fisheries University ›› 2024, Vol. 39 ›› Issue (4) : 634-647. DOI: 10.16535/j.cnki.dlhyxb.2023-264

Preparation and removal effect on ammonia nitrogen and phosphates in seawater and freshwater in kaolinite-oyster shell powder modified material

  • YANG Yuxiang,SONG Kexin,YANG Guang,MA Xiaona,XIE Siqi,LIU Zishuo,FENG Zhihua*
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Abstract

In order to adsorption removal of phosphate and ammonia nitrogen in water, oyster shell powder and kaolin were mixed in the ratio of 3∶1, and the modified oyster shell powder with the best adsorption effect was prepared and screened out under different conditions of MgO addition of 0%, 2%, 4%, 8%, and 12%; temperatures of 0, 600, 700, 800, 900, and 1 000 ℃ by scanning electron microscopy, and Fourier infrared spectrometry. The characteristics of the modified oyster shell powder was analyzed by scanning electron microscope, Fourier infrared spectrometer, specific surface and porosity analyser and X-ray diffractometer. The adsorption process was fitted by kinetic model and isothermal adsorption model, and the effects of initial pH and adsorption column on the adsorption of phosphate and ammonia nitrogen by modified oyster shell powder were analyzed. The results showed that the best adsorption performance of modified oyster shell powder was observed at 8% MgO addition and 800 ℃ calcination temperature, with the phosphate removal rates of 91.7% (seawater) and 82.25% (freshwater), and the ammonia nitrogen removal rates of 36.67% (seawater)and 47.71%(freshwater). The adsorption of phosphate by modified oyster shell powder conformed to the quasi-secondary kinetic model and the Freundlich model, and the maximum The adsorption of phosphate by modified oyster shell powder conformed to the quasi-secondary kinetic model and Freundlich model, with the maximum adsorption of 108.37 (seawater) and 101.99 (freshwater) mg/g, and the adsorption of ammonia nitrogen conformed to the Langmuir model, with the maximum adsorption of ammonia nitrogen of 0.27 (seawater) and 0.38 (freshwater) mg/g. The adsorption of ammonia nitrogen and phosphate by the modified oyster shell powder in the adsorption columns was facilitated by the acidic conditions, and the adsorption of ammonia nitrogen was more favorable by the neutral conditions. The adsorption amounts of modified oyster shell powder on ammonia nitrogen and phosphate were found to be 0.12, 78.95 mg/g (seawater) and 0.17, 70.34 mg/g (freshwater) in the adsorption column. In the application in the sewage into the sea, the effluent reached the standards of a class of water with the removal rate of 96.83% for phosphate, and ammonia nitrogen for 9.7%. The findings indicate that the low cost modified oyster shell powder has the potential to be applied to remove phosphate and ammonia nitrogen from water efficiently.

Key words

kaolinite / oyster shell powder / ammonia nitrogen adsorption / phosphate adsorption / seawater / kinetics

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YANG Yuxiang, SONG Kexin, YANG Guang, MA Xiaona, XIE Siqi, LIU Zishuo, FENG Zhihua. Preparation and removal effect on ammonia nitrogen and phosphates in seawater and freshwater in kaolinite-oyster shell powder modified material[J]. Journal of Dalian Fisheries University, 2024, 39(4): 634-647 https://doi.org/10.16535/j.cnki.dlhyxb.2023-264
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