Adsorption of negatively charged food tartrazine and sunset yellow dyes onto positively charged triethylenetetramine biochar: Optimization, kinetics and thermodynamic study

Biochars are economic and ecofriendly materials which are loaded with negative charges to afford strong binding with organic-inorganic cationic species. Thus, adsorptive removal of anionic species from aqueous matrices is difficult without charging the surface of biochars with positively charged derivatives via chemical modification reaction. In this study, corncob nanobiochar (NCB) has been prepared by pyrolysis in low oxygen atmosphere and found to attain high elimination efficiency of cationic dyes and low efficiency for removal the anionic dyes. Therefore, triethylenetetramine has been selected and allowed to bind with corncob biochar to produce (NCB-TA). The modified biochar has been additionally treated with sulfuric acid to form positively charged amine nanobiochar (NCB-TA-PC) for improving surface properties and forming versatile nanobiosorbents with efficiently elimination of hazardous anionic dyes such as tartrazine and sunset yellow. The characterization of modified biochar indicated amino functional group containing nanobiosorbent with average size (10–18 nm) to confirm the effective surface modification process. Various practical parameters were investigated for meliorating the elimination reaction of tartrazine and sunset yellow dyes from aqueous solutions. Four different kinetic models and four adsorption isotherms were examined and indicated physisorption dye elimination mechanism and the adsorption process was found to obey pseudo-second order kinetic model. High elimination percentage of tartrazine and sunset yellow from actual water samples were obtained as 93.73 and 95.42% from tap water, 94.29% and 94.52% from sea water and 93.31 and 92.06% from industrial wastewater. [Display omitted] •Corncob nanobiochar (NCB) was prepared by pyrolysis in low oxygen atmosphere.•Positively charged amine nanobiochar (NCB-TA-PC) was synthesized.•Particle size characterization of NCB-TA-PC with average 10–18 nm•Removal of negatively charged food tartazine and sunset yellow dyes•Evaluation of various adsorption isotherm and kinetic models