Fixed bed study of nitrate removal from water by protonated cross-linked chitosan supported by biomass-derived carbon...

In this study, a green adsorbent was synthesized for the removal of nitrate ions from water. The adsorbent consisted of carbonaceous particles with high specific surface area (1,240 m² g^-1) and porosity derived from pyrolysis of cornelian cherry stone and modified by protonated cross-linked chitosan. The adsorbent was characterized using various techniques like SEM, FTIR, BJH and zeta potential measurements. Dynamic behavior of the adsorbent in the nitrate adsorption was studied in a packed bed system at various operating conditions and in the presence of other competing anions (PO₄^3-, HCO₃^-, SO₄^2-). Based on the error analysis, the optimum operating conditions were considered at flow rate of 3.8 mL min^-1, bed depth of 10 cm and nitrate concentration of 75 mg L^-1. The kinetics of the adsorption process was studied using Adams-Bohart and Thomas models and the q_max was calculated to be about 12.4 mg g^-1 at neutral pH and room temperature. Furthermore, the relationship between the bed height and the breakthrough time was described by bed depth service time (BDST) model. The experimental results suggested that the adsorbent possessed significant ability in nitrate removal from water due to the desired chemistry of the biopolymer and the excellent textural properties of the carbon support.