Synthesis and characterization of activated carbon from Capparis decidua for removal of Pb(II) from model aqueous solution: kinetic and thermodynamics approach

Eco-friendly biomass and its activated carbon synthesized from the stem of Capparis decidua was attempted for removal of Pb(II) from model aqueous solution. Raw biomass and its activated carbon composition were analyzed by thermogravimetric analysis, scanning electron microscopy, energy-dispersive X-ray analysis and Fourier-transform infrared analysis. Various parameters such as, concentration of the metal ion, contact time, temperature, particle size of the adsorbent, pH, dosage of adsorbent and influence of shaking speed in batch experiments were investigated. Pb(II) removal from aqueous solution obeyed pseudo-second-order kinetics equation having a good correlation coefficient value of (R-2 = 0.9995 and 0.9995). Freundlich isotherm model was well fitted and adsorption capacity (q(m)) was found 327.86 mg/g for biomass and 719.42 mg/g on activated carbon. The adsorption of Pb(II) was increased with an increase of pH on both the raw biomass and activated carbon. The pH value for point of zero charge on activated carbon was found 8.8. Thermodynamics parameter, that is, Delta G degrees, Delta H degrees and Delta S degrees were also calculated which clued that process of Pb(II) adsorption on biosorbents was spontaneous and exothermic. The interaction of Pb(II) with adsorbent was physical in nature.