Adsorption performance and mechanism of binding of dye by protonated coke waste
The protonated coke waste was used as a new type of biosorbent for the removal of anionic dye Reactive Red 4(RR4) and cationic dye Methylene Blue(MB).The uptake was significantly affected by the pH of the solution.The Langmuir isotherm was found to represent the sorption data of RR4 and MB well.The maximum adsorption capacities of RR4 and MB on the biosorbent were (25.8±0.4)mg·g-1 and (161.2±10.0)mg·g-1 at pH 2 and 7 respectively.To identify the binding sites in the biosorbent, the biosorbent was potentiometrically titrated, and the data was analyzed through nonlinear regression of the proton-binding model.As a result, sulfonate, phosphonate and amine sites were present in the biosorbent, which was confirmed by FTIR.Chemical sorption dominated the binding of dye molecules.Different functional groups were ionized in different pH conditions and played a pronounced role in the sorption.