Removal Of Low Concentration Ammonia Nitrogen From Wastewater By Modifeied Activated Carbon Fiber

This paper mainly studied the modification methods and conditions of activated carbon fibers, and the adsorption behavior of low concentration ammonia-nitrogen from aqueous solution onto modified activated carbon fibers under different conditions, then regeneration method was aslo discussed.Firstly, by comparing the ACFs’adsorption efficiency of the modification effects under different modification solution, we found that the combination of nitric acid and alkali modification was the most efficient. Then we studied the modification effect of nitric acid and sodium hydroxide under different concentration, temperature and time.Secondly, we also studied the effect of modified activated carbon fiber adsorption parameters such as time, temperature, initial concentration of ammonia nitrogen, dosing quantity, pH and coexistence cations, and determined the suitable adsorption conditions. Langmuir and Freundlich model were applied to describe the adsorption isotherms. A maximum adsorption capacity of 19.61 mg·g-1 of NH4+was achieved by Langmuir model, and Freundlich model fitting result showed that the modified activated carbon fiber can adsorb ammonia nitrogen in the water easily. The influence of flow rate was also studied though dynamic adsorption experiments. The kinetics and thermodynamics studies showed that the modified activated carbon fiber adsorption process is a spontaneous endothermic sorption processes and it followed the second-order kinetics equation. The properties of ACFs were evaluated through the SEM images, BET analysis, FTIR spectroscopy and surface acidity, which proved ion exchange mechanism of activated carbon fibers’ adsorption process.At last, the regeneration of this absorbent was also evaluated. By the comparison of regeneration efficiency under the different concentrations of hydrochloric acid, sodium hydroxide and sodium sulfate solution, we found that 0.1 mol·L-1 sodium hydroxide solution was effective to regenerate the saturated adsorption of activated carbon fiber. After immersion of 0.1 mol·L-1 sodium hydroxide solution, the 130℃ water vapor the desorption rate can reach more than 98%. And the the column test results indicated that the recovered adsorbent could be used again for NH4+ removal with nearly constant adsorption capacity after five times regeneration. Based on the results, it can be suggested that the modified ACF is a potential absorbent to remove ammonium from wastewater and has a promising perspective of industrial application.