Chromium(VI) sorption efficiency of acid-activated banana peel over organo-montmorillonite in aqueous solutions

Abstract

In the present study, we examined sorption of chromate (Cr(VI)) to acid-activated banana peel (AABP) and organo-montmorillonite (O-mont) as a function of pH, initial Cr(VI) concentration at a sorbent dose of 4 g L and at 20 ± 1°C in aqueous solutions. In sorption edge experiments, maximum Cr(VI) removal was obtained at pH 3 after 2 hours by AABP and O-mont (88% and 69%). Sorption isotherm data showed that the sorption capacity of AABP was higher than O-mont (15.1 vs. 6.67 mg g, respectively, at pH 4). Freundlich and Langmuir models provided the best fits to describe Cr(VI) sorption onto AABP (R = 0.97) and O-mont (R = 0.96). Fourier transform infrared spectroscopy elucidated that for AABP mainly the -OH, -COOH, -NH, and for O-mont intercalated amines and -OH surface functional groups were involved in Cr(VI) sorption. The scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM-EDX) analyses, although partly, indicate that the (wt. %) proportion of cations (e.g., Ca, Mg) in AABP decreased after Cr(VI) sorption. This may be due to ion exchange of chromite (Cr(III)) (produced from Cr(VI) reduction) with cationic elements in AABP. Also, Cr(VI) desorption (using phosphate solution) from AABP was lower (29%) than that from O-mont (51%) up to the third regeneration cycle. This bench scale comparative study highlights that the utilization of widely available and low-cost acid-activated biomaterials has a greater potential than organo-clays for Cr(VI) removal in aqueous media. However, future studies are warranted to precisely delineate different mechanisms of Cr(VI) sorption/reduction by acid-activated biomaterials and organo-clays.

Chromium Bioaccumulation and Its Impacts on Plants: An Overview

“…Chromium can easily convert from one oxidation state to another due to its high redox potential and intricate electronic and valence shell chemistry [4,5]. It exists in a wide range of oxidation states, but the most common and stable states are Cr (VI) "hexavalent" and Cr (III) "trivalent" [6]. Both forms of Cr vary significantly with respect to their bioavailability in soil, translocation and toxicity within plants [4].…”

Chromium-Induced Reactive Oxygen Species Accumulation by Altering the Enzymatic Antioxidant System and Associated Cytotoxic, Genotoxic, Ultrastructural, and Photosynthetic Changes in Plants

“…Chromium, which is the hard silver color metal with 7.19 g/cm 3 density, 51.10 g/M molecular weight, and 24 atomic number, has been ranked 21st among the most abundantly found metals on the earth's crust [2]. The trivalent [chromite; Cr(III)] and the hexavalent [chromate; Cr(VI)] are the most stable naturally found Cr species [3]. Hexavalent form of Cr is a potentially strong oxidizing agent, and higher water solubility, mobility, and bioavailability make it the most toxic form of Cr as compared to other Cr species [4].…”

Toxicity test of desorbed chromium from polluted soil around tannery industry in Yogyakarta-Indonesia by using Brassica juncea and Helianthus annuus L.

“…The release of cations will replace hydrogen ions in the soil, so hydrogen ions will be pushed into the soil solution which causes the concentration of the soil to approach the concentration of its natural conditions. Ashraf et al (2017) states that soil pH is an important factor that controls the geochemical ability of heavy metals in the solid phase and solution from the soil. Soil pH determines the adsorption and desorption processes and chemical speciation of Cr and other heavy metals in the soil.…”