ZnCl₂ activated carbon (ZnCl₂-AC, with specific surface area ~1480 m²/g) effectively adsorbs nitrate from water with uptake capacity (~5.5 mg/g) four-fold that for other commercial activated carbons (CACs). Kinetics show a small activation energy value (~7 kJ/mol) consistent with a diffusion-controlled process. This is further confirmed by intra-particle diffusion study. Negative thermodynamic parameters (ΔHº -13.859 kJ/mol, ΔSº -43.8 J/mol K, and ΔGº -0.808 kJ/mol) indicate spontaneous nitrate adsorption. The high specific surface area rationalizes the high uptake capacity for the ZnCl₂-AC. A Langmuir type adsorption, is observed. ZnCl₂-AC effectively adsorbs the nitrate from water, even at high concentrations, and brings the concentration to allowed maximum values. Despite these advantages, the ZnCl₂-AC exhibits low desorption (~20%) of pre-adsorbed nitrate ions into concentrate solutions.  Up to ~40% desorption is observed by grinding the pre-saturated ZnCl₂-AC. Developing other methods to completely recover the adsorbed nitrate and the adsorbent for multiple use is needed.

Title

Sustainable Chemistry and Pharmacy

Publisher

Elsevier

Publisher Country

Netherlands

Indexing

Scopus

Impact Factor

6.5

Publication Type

Prtinted only

Volume

18

Year

2020

Pages

100335