Comparison of sorption capacity of biochar-based sorbents for capturing heavy-metallic ions from water media

Abstract

To develop the sorption efficiency of heavy metals: Cd(II), Co(II), Zn(II) and Pb(II) ions the biochar was modified by chitosan, FeSO4 and NaBH4. The morphology, physical structure and chemical composition of the biochar based sorbents were characterized by the scanning electron miscroscopy method, N2 adsorption and desorption isotherms, X-ray diffractometry as well as the Fourier transform infrared spectroscopywith the attenuated total reflectance analyses. The research of M(II) ions sorption was carried out as a function of pH (2-6), interaction time (0-360 minutes) and temperature (293, 313, 333 K). The maximum sorption was obtained by the ChBC for Zn(II) ions -19.23 mg/g and for MBC-Pb(II) -19.11 mg/g. Different kinetic models as well as both isotherm and thermodynamic equations were used the sorption data modelling. For Cd(II), Co(II) and Zn(II) ions the nonlinear regression of the Elovich equation gave the best fit for the experimental data. On the other hand, for Pb(II) ions, the nonlinear forms of pseudo first order and pseudo second order show a better match. The value of the correlation coefficient >0.960 determined from the Freundlich isotherm model is the highest suggesting a good fit to the experimental data. The thermodynamic parameters: ∆G°, ∆H° and ∆S° were listed and indicated that the process is spontaneous and endothermic in nature. The desorption efficiency was determined with the use of nitric, hydrochloric and sulfuric acids and the largest desorption yield for Pb(II)-ChBC equal 99.5 % was gained applying HNO3.