Synthesis and surface-functionalizing of ordered mesoporous carbon CMK-3 for removal of nitrate from aqueous solution as an effective adsorbent

In this study, the adsorption of nitrate onto ordered mesoporous carbon CMK-3 was investigated. First, CMK-3 was synthesized and then directly amino-functionalized by 3-aminopropyl trimethoxysilane (APTMS). The physicochemical properties of as-prepared adsorbent were characterized by XRD, EDS-SEM, FT-IR and N2 adsorption-desorption. Ultraviolet/visible spectroscopy was used to evaluate the adsorbent ability for nitrate reduction. In batch experiments, the influence of effective parameters such as contact time, adsorbent dosage, solution pH, initial concentration and temperature was investigated on the nitrate adsorption capacity. The obtained results indicated 100% removal efficiency for initial nitrate concentration of 50 mg l- 1 and 78% for the concentration of 100 mg l- 1, at low adsorbent dosage (3 g l- 1) and very fast equilibrium attainment (5 min) without pH dependency (in the range of 2.0-8.0). The maximum nitrate adsorption capacity of Amino-CMK-3 was 48.78 mg g-1 in the concentration range of 50-250 mg g-1. Kinetic studies confirmed that the process followed a pseudo-second-order and that the Langmuir isotherm best fitted the equilibrium adsorption of nitrate. Nitrate desorption occurred after a reasonable time (3 h) and confirmed the adsorbent reusability without further treatment. The higher adsorption capacity of CMK-3 stemmed from its incredible mesoporous structure, including nano-channels that were completely functionalized by amino groups. Grafting aminopropyl groups potentially turned the CMK-3 to a promising adsorbent for nitrate removal.