Removal of nitrate from aqueous solution by modified sugarcane bagasse biochar

[Display omitted] •Nitrate adsorption was studied onto modified sugarcane bagasse biochar.•The biochar prepared at temperature of 300 °C had higher stable organic matter index.•The maximum adsorption capacity of modified biochar for nitrate was 28.21mgg−1.•Solution pH was an important factor for nitrate adsorption by modified biochar. In the present study, chemically modified biochar (developed from sugarcane bagasse) was used for the nitrate removal from aqueous solution. The physico-chemical properties of modified biochar such as morphology, surface functional groups, elemental composition, cation exchange capacity, anion exchange capacity and surface area were analyzed. The effects of various operational parameters such as solution pH, adsorbent dosage, contact time, initial concentration of nitrate, co-existing anions and temperature were examined on nitrate adsorption by modified biochar. The experimental data were fitted to different adsorption kinetic models (pseudo-first-order, pseudo-second-order, intraparticle diffusion and Avrami models) and adsorption isotherms models (Langmuir, Freundlich, Sips and Dubinin–Raduskovich models). The obtained results showed that the maximum percentage of nitrate adsorption attained at equilibrium pH 4.64, after 60min of contact time and with an adsorbent dose of 2gL−1. In competing anions experiments, carbonate and chloride ions have shown maximum and minimum influence on the adsorption of nitrate by modified biochar sugarcane bagasse. Pseudo-second-order kinetic model and Langmuir isotherm model showed the best fit to the experimental adsorption data. The maximum adsorption capacity of modified biochar for nitrate removal was found to be 28.21mgg−1. The values of ΔH°, ΔG° and ΔS° indicated that the nature of adsorption was endothermic, spontaneous and feasible.