Insights into Starch Coated Nanozero Valent Iron-Graphene Composite for Cr(VI) Removal from Aqueous Medium

Prasanna Kumarathilaka,Meththika Vithanage,S R D Rosa,Vimukthi Jayaweera,I R M Kottegoda,Hasintha Wijesekara

doi:10.1155/2016/2813289

Abstract

Embedding nanoparticles into an inert material like graphene is a viable option since hybrid materials are more capable than those based on pure nanoparticulates for the removal of toxic pollutants. This study reports for the first time on Cr(VI) removal capacity of novel starch stabilized nanozero valent iron-graphene composite (NZVI-Gn) under different pHs, contact time, and initial concentrations. Starch coated NZVI-Gn composite was developed through borohydrate reduction method. The structure and surface of the composite were characterized by scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), and point of zero charge (pHpzc). The surface area and pHpzc of NZVI-Gn composite were reported as 525 m2 g−1 and 8.5, respectively. Highest Cr(VI) removal was achieved at pH 3, whereas 67.3% was removed within first few minutes and reached its equilibrium within 20 min obeying pseudo-second-order kinetic model, suggesting chemisorption as the rate limiting process. The partitioning of Cr(VI) at equilibrium is perfectly matched with Langmuir isotherm and maximum adsorption capacity of the NZVI-Gn composite is 143.28 mg g−1. Overall, these findings indicated that NZVI-Gn composite could be utilized as an efficient and magnetically separable adsorbent for removal of Cr(VI).

Highlights

Chromium generally exists as the earth’s sixth most prominent transition metal [1]
The composite was characterized by scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), BET, and pHpzc
SEM was used to study the morphology of developed nanozero valent iron-graphene composite (NZVI-Gn) composite (Figure 3(a))

Summary

Introduction

Chromite (FeCr2O4), crocoite (PbCrO4), and chrome ochre (Cr2O3) are some of the naturally occurring chromium sources on earth [2]. Both natural and anthropogenic activities may release Cr into surrounding environment. Ultramafic soils such as serpentine may release Cr into water [3, 4]. Many different types of anthropogenic uses such as leather tanning, electroplating, manufacturing of various alloys, mining, cement, metal processing, textile, wood preservation, production of paint pigments, and dye are responsible for releasing Cr into the environment [5, 6]. Chromium contamination in water results from its two stable oxidation forms, Cr(III) and Cr(VI) [7].

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Results

Conclusion