Adsorption of nitrate from aqueous solution onto modified cassava (Manihot esculenta) straw / Adsorpcja azotanów z roztworu wodnego na zmodyfikowanej słomie manioku Manihot esculenta

The performance of a new anion exchanger prepared from raw cassava straw (RCS), for the removal of nitrate from aqueous solutions was evaluated in this study. The cassava straw was modified by epichlorohydrin in the presence of pyridine. The influencing factors, adsorption kinetics, and thermodynamics model of nitrate adsorption onto the modified cassava straw (MCS) were studied. The results showed that the zeta potentials of RCS and MCS were -20.5 mV and +37.3 mV, nitrogen contents (N %) of RCS and MCS were 0.43 and 4.96%, respectively. The best nitrate removal results was reached at 0.2 g of adsorbent dosage and pH range of 6.0÷12.0. The modified cassava straw adsorbed nitrate(V) quickly, reaching equilibrium within 30 minutes. The kinetics of nitrate adsorption at different initial concentrations (25, 50 and 75 mg/dm3) all fit a second order reaction. The adsorption rates were controlled by both membrane diffusion and intra-particle diffusion. The adsorption data fit the Freundlich adsorption isotherm and the Langmuir adsorption isotherm. The maximum adsorption capacity was 2.14, 2.00 and 1.81 mmol/dm3 at 293, 303, and 313 K, respectively.