Nitrate Uptake from Water by Means of Tailored Adsorbents

Two different adsorbents directed to nitrate removal from water were developed from Parkinsonia aculeata wood. An activated carbon was obtained by chemical activation with K 2 CO 3 at 800 °C, whereas another adsorbent was prepared using a dilute solution of NH 4 Cl at 450 °C. Elemental compositions, surface functional groups, and textural parameters of both adsorbents were determined and compared with those of a commercial activated carbon used as a reference. Nitrate adsorption assays were carried out to examine the effects of solution pH, adsorbent dosage, contact time, and equilibrium adsorption isotherms. The adsorbent obtained with K 2 CO 3 showed a well-developed pore structure ( S BET = 777 m 2 /g; V T = 0.35 cm 3 /g) and neutral character, while the one prepared with NH 4 Cl exhibited a low porous development ( S BET = 58 m 2 /g; V T = 0.03 cm 3 /g), acidic nature, and a noticeably high N content. The latter attained the highest nitrate removal efficiency, with a maximum adsorption capacity ( X mL = 0.40 mmol/g) higher than those estimated for the former ( X mL = 0.34 mmol/g) and the commercial sample ( X mL = 0.23 mmol/g), pointing to a predominant role of the chemical surface characteristics, mainly of N-containing groups and basic functionalities. Accordingly, the adsorbent obtained with NH 4 Cl represents a friendly novel material especially suited for nitrate removal.