Investigation of the removal and recovery of nitrate by an amine-enriched composite under different fixed-bed column conditions

Continuous adsorption of nitrate in a fixed-bed column can be an effective method for its removal from water. In this study, an amine-rich polymer composite adsorbent was prepared by crosslinking chitosan (CS) and polyethyleneimine (PEI) with glutaraldehyde (GLA). The CS-PEI-GLA was packed into columns and the effect of flow rate, influent concentration, bed height, and other ionic species on the column performance was investigated. The highest adsorption capacity was achieved at the lowest flow rate and highest influent concentration and bed height. Maximum adsorption capacity of 137.62 mg NO3--N/g was determined from the Thomas model. The column had acceptable nitrate removal in the presence of 1000 ppm chloride but poor performance in the presence of 1000 ppm sulfate due to the competitive effect of sulfate for binding sites. The best recovery agent was 0.5 M NaCl as it could regenerate the column to <90 % of its capacity after 10 adsorption-desorption cycles. The adsorbent effectively removed nitrate as well as phosphate and total organic carbon from a real water sample. This study suggests that amine rich polymers can be good candidates for the removal of nitrate in contaminated water. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.