Comparative study of carbon black and activated carbon adsorbents for removal of carbofuran from aqueous solution

Three commercial carbon samples of carbon black, namely Black Pearl 2000 (BP 2000), extruded activated carbon (EAC), and granular activated carbon (GAC), were evaluated as adsorbents for the removal of carbofuran from water. The specific surface area and micropore volume of the adsorbents were studied by BET measurements and t-plot, respectively. Batch experiments were conducted to examine the effects of the adsorbents as a function of the initial concentration of carbofuran, adsorption contact time, and solution pH. As per the results, the equilibrium uptake for carbofuran on all adsorbents increased with an increase in the initial carbofuran concentration in solution, and the removal potential of carbofuran followed the order BP 2000>GAC>EAC. The amount of carbofuran uptake at equilibrium was applied to investigate the suitability of the Langmuir, Freundlich, and Temkin models. The results indicated that the equilibrium data obey the Langmuir isotherm model better than Freundlich, and Temkin models. The adsorption kinetics data were used to compare the feasibility of the two models: pseudo-first-order kinetic and pseudo-second-order kinetic. The data fit the pseudo-second-order model well. The ranking order of adsorbents in terms of adsorption kinetic constants was as follows: BP 2000>EAC>GAC. Thermodynamics studies were carried out and various thermodynamics parameters such as standard free energy changes (G), standard enthalpy change (H), and standard entropy change (S) were calculated. The values of G were found as negative, which confirms the spontaneous nature of the adsorption processes. The results of the study supported the usability of BP 2000, EAC, and GAC as promising adsorbents for carbofuran adsorption.