New Bioadsorbent Derived from Winemaking Waste Cluster Stalks: Application to the Removal of Toxic Cr(VI) from Liquid Effluents

Lorena Alcaraz,Francisco J Alguacil,Félix A López

doi:10.3390/app10249026

Abstract

A winemaking waste was used as a precursor of activated carbon used for the removal of hazardous Cr(VI) from solutions. The preparation process consisted of a hydrothermal process and a chemical activation of the resulting product, with KOH. The adsorption results show that the adsorption of Cr(VI) on the obtained activated carbon is strongly dependent on the stirring speed applied to the carbon/solution mixture, pH of the solution, and temperature. The equilibrium isotherm was well fitted to the Langmuir Type-II equation, whereas the kinetic can be described by the pseudo-second-order kinetic model. Thermodynamic studies revealed that Cr(VI) adsorption was an exothermic and spontaneous process. Finally, desorption experiments showed that Cr(VI) was effectively desorbed using hydrazine sulfate solutions, and, at the same time, the element was reduced to the less hazardous Cr(III) oxidation state.

Highlights

It is known that water is a critical resource with wide uses, such as for urban, agricultural, and industrial purposes [1], and is a basic requirement for humans and wildlife
The stirring speed applied to the carbon solution may have a key role in the adsorption process due to modifying the mass gradient of adsorbate from the solution to the adsorbent interface [30]
An activated carbon dosage of 0.5 g·L−1 was added into Cr(VI) solutions of 0.01 g·L−1 at 20 ◦ C

Summary

Introduction

It is known that water is a critical resource with wide uses, such as for urban, agricultural, and industrial purposes [1], and is a basic requirement for humans and wildlife. This resource is finite, with no adequate substitute. Industrial and urban activities have increased, causing subsequently water pollution, for example with heavy metals. These metals could be introduced by both natural sources (e.g., weathering of soils and rocks or from volcanic eruptions) and from anthropogenic activities (mining, processing, or use of metals). The most common heavy metal pollutants in water are Cd, Cr, Cu, Ni, Pb, and Hg

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Conclusion