Nitrate Uptake from Water Using Amine‐Functionalized Meso‐ and Macroporous Carbons

Meso‐ and macroporous carbon materials modified with protonated amino groups (−NH 3 + Cl − ) for aqueous nitrate (NO 3 − ) uptake were prepared by surface functionalization with aminopropylsilane. Although the silane coupling treatment decreased the specific surface area of the carbons, surface modification with the −NH 3 + Cl − group improved the NO 3 − uptake capacity of both meso‐ and macroporous carbons. The amount of NO 3 − adsorbed depends on the specific surface area of the adsorbent; an adsorbent with a larger specific surface area exhibits a larger uptake capacity. Enhanced NO 3 − adsorption onto the NH 3 + Cl − ‐modified surface occurred through an ion‐exchange mechanism. Changes in the pH of the sample solutions before and after NO 3 − uptake revealed the competitive exchange of NO 3 − and OH − . NO 3 − uptake is inhibited by the coexistence of anions other than NO 3 − (excess Cl − , SO 4 2− , CO 3 2− and HCO 3 − ) and/or OH − at high pH. In particular, the influence of excess Cl − reveals that NO 3 − uptake through ion exchange is not irreversible, and the adsorption capacity is determined based on the ion exchange equilibrium.