Nitrate removal from municipal effluent in the adsorption process on activated carbon of orange peel modified with chitosan and iron particles

Nitrate removal from polluted waters is one of the most important environmental issues. The aim of this study was to remove nitrate from municipal effluent by activated carbon of orange peel modified with chitosan synthesized from shrimp peel and iron (ш) chloride. Identification of activated carbon functional groups by FTIR, the morphology of carbon cavities by SEM, and porosity properties were investigated by BET analysis. The characterization results indicate a porous structure with different functional groups of modified activated carbon. Pseudo-first-order, pseudo-second-order, intra-particle, and Boyd kinetic models were used to describe the kinetic data, as well as Langmuir, Freundlich, and Dubinin-Radushkevitch isotherms to describe the adsorption equilibrium data. The effect of pH and the amount of adsorbent was investigated and the results showed that pH = 2 and the amount of adsorbent 0.2 g in 50 ml of solution are the optimal conditions to achieve maximum nitrate removal. The results showed that the adsorption followed the pseudo-second-order kinetics (R2 = 1). Also, among the studied isotherms, Langmuir model described well the adsorption of nitrate onto synthesized activated carbon (R2 = 0.999) and the maximum adsorption capacity was 263.157 mg/g activated carbon. This behavior means the adsorption of the monolayer and the predominance of the chemical adsorption mechanism. Nitrate uptake increased with decreasing temperature, indicating that the reaction was exothermic. Nitrate removal efficiency with modified activated carbon was estimated to be 99.58%. In general, it can be said that modified carbon can be a candidate for use on an industrial scale.