Synthesis and characterization of a novel activated carbon using nonliving lichen cetraria islandica (L.) ach. and its application in water remediation: Equilibrium, kinetic and thermodynamic studies of malachite green removal from aqueous media

Abstract

Although lichens are natural and cheap sources, there is no study in the literature about the production of activated carbon from lichen species. In this study, a novel activated carbon (ACCI) from non-living lichen Cetraria islandica (L.) Ach. (LCI) was produced, and physicochemical and morphological characterizations of the LCI and ACCI were examined with the help of Brauner-Emmett-Teller surface area (BET), X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) techniques. The BET surface area, Barrett-JoynerHelenda (BJH) adsorption total volume of pores and BJH adsorption average pore diameter of the ACCI were determined as 394.417 m(2).g(-1), 0.1216 cm(3).g(-1) and 12.768 angstrom (1.28 nm), respectively, while these values for non-living LCI were 1.103 m(2).g(-1), 0.0044 cm(3). g(-1) and 140.18 angstrom (14.02 nm), respectively. To investigate and compare the biosorption properties of the LCI and ACCI in wastewater treatment, batch mode biosorption experiments were carried out, and the effect of various parameters on malachite green (MG) dye removal from aqueous media were studied. The experimental data were fitted with 4 different kinetic models (pseudo first order (PFO), pseudo second-order (PSO), Elovich model (EM) and intra-particle diffusion (IDM)) and 3 different isotherm models (Langmuir, Freundlich and Dubinin-Radushkevich (D-R)). The biosorption of MG onto both the LCI and ACCI follows well the PSO kinetics. The rate constants k(2) for the LCI and ACCI were found as 0.0125-0.0157 g.mg(-1).min(-1) and 0.00612-0.00979 g.mg(-1).min(-1), respectively (298-318 K). The equilibrium time was 80 min for the ACCI, and the maximum biosorption capacity and the removal efficiency (%) for the ACCI were found as 666.22 mg.g(-1) and 93.46%, respectively. The biosorption mechanism of MG onto both the LCI and ACCI was physical biosorption. This result was confirmed by the activation energies (9.095 kJ.mol(-1) for LCI and 18.450 kJ.mol(-1) for ACCI), the D-R mean energies (6.8041-7.4536 kJ.mol(-1) for LCI and 7.3323-8.0582 kJ.mol(-1) for ACCI in the temperature range 298-318 K), and FTIR, XRD, TGA and SEM/EDX results. The enthalpy change (Delta H-0) values for the LCI and ACCI were found to be in the range of 8.7987-17.2582 kJ.mol(-1) and 20.4899-29.2728 kJ.mol(-1), respectively (20-70 mg.L-1 initial MG concentrations). This indicated the endothermic behaviour of the biosorption. The novelty of this study is that besides obtained and characterized the activated carbon (ACCI) from the nonliving LCI for the first time, the comparisons and discussions on the biosorption capability of the ACCI and LCI for the removal of MG dye from aqueous media are included in this paper. All results showed that the synthesized ACCI is an effective, cheap and promising biosorbent for the cleaning treatment of MG dye from wastewaters.