Mesoporous activated carbon as a green adsorbent for the removal of heavy metals and Congo red: Characterization, adsorption kinetics, and isotherm studies

In this study, an effective and green adsorbent was prepared by the self-activation of kenaf fiber and then the kenaf-based activated carbon (KAC) was applied for the removal of lead Pb(II), copper Cu(II), and Congo red (CR) dye from an aqueous solution by the process of adsorption. The surface morphology of mesoporous adsorbent was characterized. The KAC showed good capacity of adsorption of as Pb(II), Cu(II), and anionic dye CR in very short period of agitation. The adsorbent efficiency of metal ions and dye was estimated by varying the adsorbent dose, pH, contact time, initial metals and dye concentration, and temperature. Optimum adsorption of metal ions and CR dye was observed at pH 6, and at pH 4 at 120 min, respectively. The adsorption isotherm was described by the Langmuir and Freundlich isotherm equations. The green adsorbent followed the pseudo-second-order kinetic model with correlation coefficients R-2 value >0.99. The increase in adsorption temperature enhanced the adsorption efficiency for both heavy metals and dye. The KAC showed no significant loss of the adsorption capacity after 3 cycles of reuse.

Automated summary

In this study, an effective and environmentally friendly adsorbent, kenaf-based activated carbon (KAC), showed good adsorption capacity for heavy metals and dye in aqueous solution. The optimal pH for adsorption of metal ions and dye was found to be 6 and 4, respectively. The adsorption process followed pseudo-second-order kinetics and the adsorption efficiency improved with higher temperature. The KAC demonstrated stable adsorption performance even after 3 cycles of reuse.