Chromium ion removal from raw water by magnetic iron composites and Shewanella oneidensis MR-1

Huiqing Wu,Qihui Gu,Jumei Zhang,Qingping Wu,Weipeng Guo,Minhong He,Linting Wei

doi:10.1038/s41598-018-37470-1

Abstract

In this study, nanoiron active carbon composites (NZVI/GAC) were used to remove chromium ions from raw water. The composites were synthesized from a novel formula of biological activated carbon and characterized by various techniques. The adsorption test data were fit by a pseudo-second-order kinetic model and Langmuir model. The qe and R2 values were 187 mg Cr/g and 0.9960, respectively, with 0.2 g/L NZVI/GAC at an initial concentration of 118 mg/L Cr according to the Langmuir isotherm model. Moreover, a Cr6+ detoxification reactor was constructed with the magnetic iron composite. The results indicated that the synthesized magnetic iron composite was a significant adsorbent for Cr6+ removal from aqueous solutions. The detoxification reactor was able to remove Cr6+ from raw water at an initial concentration of 26.5 mg/L within a short time period (3–5 min), with a removal efficiency of up to 99.90% and a treatment capacity of 45.0 mg Cr6+/g of adsorbent; the Cr6+ concentrations in the outflow met the GB5749–2006 requirements for drinking water. A synergistic effect between NZVI/GAC and a suspension of the bacterium Shewanella oneidensis MR-1 was found, showing that this bacterium can be used as a regeneration agent for iron-depleted activated carbon materials.

Highlights

Water pollution by various toxic contaminants has become one of the most serious problems worldwide[1,2,3,4,5]
To understand the mechanism underlying Cr6+ removal, the NZVI/GAC, iron-loaded active carbon composites (GAC-BCS5) and pristine NZVI were characterized by various techniques, such as transmission and scanning electron microscopy (TEM and SEM, respectively), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR), and the properties of the synthetic materials, including their Brunauer-Emmett-Teller (BET), surface area (m2/g), zeta potential and total iron content, were evaluated
The active carbon loaded with nanoiron was characterized by XRD, which revealed that the material contained both zero-valent iron and Fe3O4, a magnetic iron-loaded activated carbon composite that has demonstrated good removal capabilities for other heavy metals, such as Cd2+, Sb5+, Cu2+, Zn2+

Summary

Introduction

Water pollution by various toxic contaminants has become one of the most serious problems worldwide[1,2,3,4,5]. A wide range of nanomaterials have been tested for the removal of inorganic and/or organic pollutants Many advanced materials such as carbon nanotubes (CNTs) and carbon dots (a photocatalytic material) have been widely used in various fields since their discovery in 199116–19. Given their excellent adsorption, pure and modified CNTs have been successfully used for the purification and enrichment of food, medicines, environmental samples, etc.[20] Photocatalytic materials for the treatment of pollutants in water are a popular area of research[21]. Chemically regenerated after exhaustion[22] Such materials include a series of iron-based functional nanomaterials that can use exchange adsorption or chemical reactions to remove heavy metals and toxic organic compounds[23]. To understand the mechanism underlying Cr6+ removal, the NZVI/GAC, iron-loaded active carbon composites (GAC-BCS5) and pristine NZVI were characterized by various techniques, such as transmission and scanning electron microscopy (TEM and SEM, respectively), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR), and the properties of the synthetic materials, including their Brunauer-Emmett-Teller (BET), surface area (m2/g), zeta potential (mV) and total iron content, were evaluated

Methods

Results

Discussion

Conclusion