Adsorption of Nitrate and Nitrite Anions in Aqueous Solutions Using KMnO4Modified Active Carbon

摘要

Activated carbon from Rice straw (RS) has been oxidize oxidized using KMnO4 in order tornintroduce a variety of acidic surface functional groups. Both unoxidized and oxidizedrncarbon samples are characterized using N2-adsorption, elemental analysis, Boehm’srntitration and surface fractal dimension. Results show that oxidation treatmentrnenhanced surface area and pore volume. The modified carbon was tested for thernremoval of nitrate and nitrite ions with respect to the temperature, pH, adsorbentrnconcentration and carbon dosages. The results indicate that adsorption capacity ofrnnitrate is more than 10 folds that of nitrite on the same adsorbent due to the differencernin adsorption sites. The equilibrium isotherm constants of the models: Langmuir (L),rnFreundlich (F) and Langmuir–Freundlich (LF) were evaluated at differentrntemperature.Equilibrium data fitted very well to the LF model for both anions. Thernpseudo first - and second- order kinetic models were applied assuming that thernexternal mass transfer can be neglected and the process is chemisorption controlled.rnThe thermodynamic parameters of nitrate sorption indicate that better adsorptionrnoccurred at lower temperature. In the binary system (NO3-/NO2-), the nitraternsorption was suppressed due to the competitive effect whereas; the nitrite sorptionrnwas promoted due to the cooperative adsorption.