Investigation of adsorption and transport of nitrate in various soils

INVESTIGATION OF ADSORPTION AND TRANSPORT OF NITRATE INVARIOUS SOILSTuba ÖZDEMİRFırat UniversityGraduate School of Natural and Applied SciencesDepartment of Chemical EngineeringABSTRACTIn this study, the adsorption of nitrate on the different soils (sand, loam and clay) wascarried out in batch and packed bed systems. Batch experiments were carried out using threeparticle sizes (2.36-1.18, 1.18-0.6 ve 0.6-0.36 mm) of soil samples, different initial nitrateconcentrations changing from 25 to 500 mg/L at various temperatures (15, 25, 35 ve 45 ºC) anddifferent mixing rates in the range of 25 to 120 rpm. It was found that the values of rad, qden andads. % was increased with nitrate initial concentration. It was observed that the values ofequilibrium concentration, the initial adsorption rate and the adsorption percent decreased as thetemperature increased. It was also found that the adsorption rate increased with a decrease inparticle size for all soils. For all soils used, it was found that the adsorption of nitrate wasconsistence with Freundlich adsorption isotherm. The results indicate that the adsorptionprocess between nitrate and soils used was endothermic. The adsorption processes betweennitrate and soils used were found to obey pseudo second order kinetic model.In the second part of the study, the adsorption of nitrate on sand and loam samples wasstudied in a fixed bed using various flow rates changing from 10 to 60 mL/min, different beddepths (15, 30, 45 and 60 cm) and the nitrate initial concentrations of 50, 100 and 200 mg/L at25 ºC. It was found that the nitrate adsorption on both soil samples decreased with increasingflow rate. It was observed that the amount of nitrate adsorbed on both soil samples in the bedincreased with an increase in bed depth. The results showed that nitrate inlet concentration onadsorption both soil samples was less effective. Adams-Bohart and Yoon-Nelson models wereapplied to experimental data obtained from fixed bed to determine the characteristic bedparameters. Adams-Bohart model was found unsuitable for describing the performance of fixedbed at high flow rates. However, Yoon-Nelson model was found more suitable for describingnitrate adsorption on loam in fixed bed.Key Words: Nitrate, Soil, Adsorption, Adsorption isotherms, Packed column, Modelling