Optimal oxidation with nitric acid of biochar derived from pyrolysis of weeds and its application in removal of hazardous dye methylene blue from aqueous solution

In this study, the optimal oxidized weeds-based biochar (OWC) with HNO3 was used as a sorbent to remove methylene blue (MB) dye from aqueous solution. The optimal oxidation conditions were determined according to the MB index (MI) of samples. Weeds-based biochar (WC) and its oxidized samples were characterized by their pore and chemical properties. The results showed that the oxidized WCs have a lower BET (Brunauer-Emmett-Teller) surface area, more oxygen functional groups, lower pH(pzc) and higher MI compared with the WC. Optimum conditions were determined considering the effect of process parameters such as the solution pH, initial MB concentration, agitation time and solution temperature for MB removal by the optimal OWC. The kinetic data followed the pseudo-second order kinetic model. The equilibrium data were best represented by the Langmuir isotherm model. The maximum MB sorption capacities of WC and optimal OWC were determined as 39.68 and 161.29 mg/g, respectively, under detected optimum conditions (pH 7.4, OWC dosage 0.1 g/50 mL, agitation time 480 min and temperature 50 degrees C). (C) 2017 Elsevier Ltd. All rights reserved.