Characterization of activated carbons from different sources and the simultaneous adsorption of Cu, Cr, and Zn from metallurgic effluent

Highlights

• Activated carbons produced from different raw materials were characterized.

• Principal component analysis was applied and correlations were found among the adsorbents.

• They were evaluated to remove Cu, Cr and Zn from a real effluent.

• The activated carbons showed different adsorption efficiencies.

Abstract

Activated carbon is often used in metal ion adsorption processes due to the large surface area it provides. In addition, activated carbon is an inexpensive and environmentally friendly material that provides good cost-benefit for the industries that use it. In this study, activated carbons from different sources were characterized physically and chemically. For example, surface area, thermogravimetric analysis, scanning electronic microscopy, energy dispersive X-ray fluorescence, zeta potential, surface basic and acid groups, iodine number, and ash content were determined. Principal components analysis (PCA) was also used to evaluate the relationship between these characteristics and the origin of the activated carbons examined. The capacity for these adsorbents to simultaneously remove Cu(II), Cr(VI), and Zn(II) from a metallurgic effluent were also evaluated, with some of the adsorbents being able to remove these ions very efficiently.

Introduction

Activated carbons are porous adsorbents and are used in several industrial processes. These carbons have often been used in the adsorption of pollutants present in gas or liquid phases in order to control environmental pollution, to remove organic compounds, or to remove toxic metallic species [43], [11], [3]. For industries such as leather, textile, metal plating, battery, pigments, and metallurgic, toxic metallic ions are widely used, and these can affect the environment. Moreover, toxic metallic ions can accumulate in microorganisms, flora, and aquatic fauna, thereby introducing these metals into the food chain and increasing the risk for health problems in humans [21], [30]. The removal of metallic ions can be achieved using various methodologies, including precipitation, adsorption, ion exchange, membrane processes, eletrodialysis, and reverse osmosis [29], [24], [22], [39], [16]. Among them, activated carbon adsorption is a very effective method due to the large surface area available and the characteristics of activated carbon. In addition, activated carbon can be produced from several naturally carbonaceous materials at a relative low cost [1], [32], [20], [14].

Porous materials such as activated carbons are often characterized by several chemical and physical parameters, including surface functional groups, surface area, pore volume, adsorption capacity, pH, and zeta potential. These properties are very important because they directly influence the performance of the activated carbon [31]. Principal components analysis (PCA) is a statistic tool that graphs whole data sets in order to identify correlations among the data [6], [33]. In addition, PCA can be used to examine the presence or absence of natural groupings among samples using two- and three-dimensional graphs. This type of presentation helps visualize the relationship among variables [33], [13].

The present work aims to characterize activated carbons available from different sources in order to examine correlations that may exist among these characteristics according to a PCA. The activated carbons characterized were also evaluated for their potential to provide simultaneous adsorption of metallic ions in an effluent produced in the metallurgic industry.