Ni2+ and Co2+ adsorption using Tectona grandis biochar: kinetics, equilibrium and desorption studies.

In this research, the potential of a relatively new adsorbent prepared from Tectona grandis leaves by pyrolysis for heavy metal removal from aqueous solution was studied. Adsorption behavior of the pyrolytic biochar was investigated with respect to Ni2+ and Co2+ removal with its affinity examined through batch studies and the mechanism elucidated using different empirical isotherm and kinetic models. A significantly higher efficiency of 92.46% and 91.21% was achieved at a weakly acidic pH of 6 and 5, dose of 3 g L-1 and 2 g L-1 for Ni2+ and Co2+ removal, respectively. Pseudo-second-order kinetics and Langmuir isotherm model best represented the adsorption process for both Ni2+ and Co2+. Thermodynamic analysis proved the endothermic and spontaneous nature of the process. Desorption studies revealed hydrochloric acid to have a high potential toward eluting the adsorbed metal ions. The well-organized microporous structure, the significant surface area value along with the presence of relative functional groups together with its high adsorption capacity for Ni2+ and Co2+, revealed the significant adsorptive potential of biochar of teak leaves powder for metal ion removal.