Abstract
Drinking water containing a high amount of ammonium-nitrogen (NH4+-N) is not effectively removed by conventional treatment processes and can cause eutrophication. In this research, a composite adsorbent based on chitosan crosslink with zeolite molecular sieve (CTS-ZMS) was prepared for NH4+-N removal through dynamic adsorption filter experiments. Effect of bed depth (30, 50 and 70 cm), flow rate (32, 49 and 65 mL/min), initial pH value (4.5, 6.5 and 8.5) and influent NH4+-N concentration (3, 5 and 7 mg/L) was examined by using a filter column packed with CTS-ZMS particles. The Thomas model was applied to study the breakthrough curves and adsorption capacity. The optimal process parameters of the aforementioned factors were obtained at bed depth of 70 cm, flow rate of 32 mL/min, pH of 6.5 and initial NH4+-N concentration of 7 mg/L. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier Transform Infrared Spectroscopy (FTIR) were investigated to analyze the structure and morphology of the CTS-ZMS adsorbents before and after 3 months running. The EDS and FTIR results showed Na+ and the active functional groups of -OH, -NH2 and -COO− on CTS-ZMS adsorbent particles reacted with ammonium nitrogen. The results of this study supported the use of CTS-ZMS to improve drinking water filtration processes by increasing ammonium nitrogen reductions.
Highlights
Drinking water sources of most cities and villages in China are affected by ammonium nitrogen pollution [1]
The ammonium nitrogen concentration in industrial-based wastewater may be in the range of 5–1000 mg/L and in the municipal wastewater is the range of 10–200 mg/L [4]
In water solution, according to the existing pH, the ammonia (NH3) is usually found in the form of NH4+-N. This fact approximates the concentration of all reduced nitrogen in the form of ammonia and combined ammonium, which is known as ammonium nitrogen [7]
Summary
Drinking water sources of most cities and villages in China are affected by ammonium nitrogen pollution [1]. Chitosan molecular structure contains amino NH2−, hydroxyl OH− and other reactive functional groups, which can be a variety of chemical modification, and can be cross-linked with the filter media to form multi-functional composite materials [17]. These materials have the effect of removing ammonia pollutants. Dynamic adsorption for ammonium nitrogen removal from water by chitosan/zeolite molecular sieve (CTS-ZMS) fixed-bed column was investigated. This study provided a potential adsorbent for the development of a cheap and efficient cycle retained in ammonium nitrogen polluted water treatment
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