Cr(VI) adsorption on low-cost activated carbon developed from grape marc-vinasse mixture

Abstract

In the present work, an activated carbon obtained as by-product in a fertilizer preparation process was studied for Cr(VI) adsorption from aqueous solutions. Batch adsorption experiments were carried out by varying the pH, initial Cr(VI) concentration, contact time, activated carbon dosage and temperature. The adsorption of Cr(VI) was found to be highly pH-dependent and maximum adsorption was observed in the acidic pH range. Equilibrium data were applied to Langmuir, Freundlich, and D-R adsorption isotherms. Also, kinetic data were analyzed for pseudo-first, pseudo-second, and intraparticle diffusion models. Langmuir adsorption isotherm and pseudo-second kinetic model were fit best to the related data. Maximum adsorption capacity was found to be 74.63 mg/g at the conditions of the temperature of 25 °C, the pH of 3.5, the contact time of 360 min and the adsorbent dosage of 1 g/L. Activation energy, mean adsorption energy (from D–R isotherm) and thermodynamic parameters were evaluated and nature of the adsorption process was found to be as physical, endothermic, and spontaneous.

GRAPHICAL ABSTRACT

Highlights

• The potassium-removed char was washed with an acid solution and then characterized as AC.

• AC was obtained as a by-product and its Cr(VI) adsorption efficiency was determined.

• This study aimed to use AC as an adsorbent with relatively favorable surface properties for the removal of heavy metals from wastewaters.

• A slow released potassium fertilizer and an activated carbon were obtained from two waste materials in such a process.

• This novel active carbon having relatively favorable surface properties was considered to be utilized as an adsorbent in Cr(VI) removal from aqueous solutions.

KEYWORDS:

• Activated carbon
• vinasse-grape marc mixture
• Cr(VI) adsorption
• isotherm
• kinetics
• thermodynamic parameters

Disclosure statement

The authors declare that there are no conflicts of interest regarding the publication of this paper.

Additional information

Funding

This work was supported by Fırat University Scientific Research Projects Unit (FUBAP) (Project Number MF.12.38); Scientific and Technological Research Council of Turkey (TUBITAK) (Project Number 113M250).