Denitrification performance of kaolin and modified kaolin for the treatment of nitrate contaminated water: isotherm and kinetic studies

The present study focuses on nitrate removal from water using kaolin and modified kaolin in a batch system. The adsorption studies were executed to study the influence of initial pH (2.0–7.0), contact time (5–240 min), adsorbent dosage (1–30g/L), and initial nitrate concentration (50–250 mg/L) using kaolin and modified kaolin as adsorbents. The percentage removal of nitrate was noted to be maximum at pH 2.0. The maximum adsorption capacity of kaolin and modified kaolin was observed at 104.17 mg/g and 109.89 mg/g respectively. Denitrification process followed pseudo second-order kinetic model. The groundwater samples collected from 21 different regions of Bangalore city in India were analyzed for nitrate concentration. It was observed that the nitrate concentration of collected groundwater samples was ranging from a minimum of 3.42 mg/L to a maximum of 75.69 mg/L. Sample collected from Mandur area corresponds to the high nitrate concentration (75.69 mg/L). Higher percentage nitrate removal from the groundwater sample was achieved by modified kaolin (93.10%) compared to kaolin (66.86%). It can be concluded that modified kaolin has exhibited higher potential of nitrate removal compared to kaolin.