Adsorption of nitrate ions onto cameroonian’s volcanic soils: kinetics and equilibrium studies

The retention capacity of nitrate ions by adsorption onto two volcanic soils collected from the localities of Tiko (S-TIK) and Tombel (S-BEL) in the South-west region of Cameroon was investigated. The influence of parameters such as, contact time, pH, adsorbent dose and initial concentration of the nitrate ions were studied. The experimental results obtained show that the amount of nitrate ions adsorbed increased with contact time and reached equilibrium at 45 min and 50 min respectively for S-BEL and S-TIK. The optimal pH of adsorption of the nitrate ions is 2.0 for both adsorbent with maximum adsorption of 3.85 mg/g for S-BEL and 4.32 mg/g for S-TIK. The isotherm models used to characterize the adsorption processes were Langmuir, Freundlich, Tempkin and Dubinin-Kaganer-Raduskevich (D.K.R). The Freundlich and Tempkin models better describe the adsorption process with S-BEL while Tempkin and D.K.R models better describe the adsorption process with S-TIK.The kinetic study was carried out using pseudo first order, pseudo second order, Elovich and intraparticular diffusion. It was found that the adsorption fitted the Elovich and Intraparticular diffusion models for both adsorbents. These results showed that the retention capacity of nitrate ions is greater on S-TIK comparedto S-BEL.