Synthesis and Characterization of Modified BiOCl and Their Application in Adsorption of Low-Concentration Dyes from Aqueous Solution

Qihang Zhao,Chunfang Du,Zhiliang Liu,Jing Ouyang,Yongxing Xing

doi:10.1186/s11671-018-2480-y

Qihang Zhao, Chunfang Du + Show 3 more

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https://doi.org/10.1186/s11671-018-2480-y

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Abstract

The synthesis and characterization of BiOCl and Fe3+-grafted BiOCl (Fe/BiOCl) is reported that are developed as efficient adsorbents for the removal of cationic dyes rhodamine B (RhB) and methylene blue (MB) as well as anionic dyes methyl orange (MO) and acid orange (AO) from aqueous solutions with low concentration of 0.01~0.04 mmol/L. Characterizations by various techniques indicate that Fe3+ grafting induced more open porous structure and higher specific surface area. Both BiOCl and Fe/BiOCl with negatively charged surfaces showed excellent adsorption efficiency toward cationic dyes, which could sharply reach 99.6 and nearly 100% within 3 min on BiOCl and 97.0 and 98.0% within 10 min on Fe/BiOCl for removing RhB and MB, respectively. However, Fe/BiOCl showed higher adsorption capacity than BiOCl toward ionic dyes. The influence of initial dye concentration, temperature, and pH value on the adsorption capacity is comprehensively studied. The adsorption process of RhB conforms to Langmuir adsorption isotherm and pseudo-second-order kinetic feature. The excellent adsorption capacities of as-prepared adsorbents toward cationic dyes are rationalized on the basis of electrostatic attraction as well as open porous structure and high specific surface area. In comparison with Fe/BiOCl, BiOCl displays higher selective efficiency toward cationic dyes in mixed dye solutions.

Highlights

Synthesis of Bismuth oxychloride (BiOCl) and Fe/BiOCl Analytical grade chemicals of Bi(NO3)3·5H2O, Fe(NO3)3·9H2O, KCl, and glycerol were purchased from Shanghai Chemical Industrial Co., all of which were used as the starting materials without further purification
No diffraction peaks corresponding to iron oxides are observed in the X-ray powder diffraction (XRD) patterns of Fe/ BiOCl (x), i.e., iron oxides did not form in our samples the samples had a thermal treatment at 400 °C for 3 h
It could be concluded that the irons are mostly present as highly dispersed Fe3+ form rather than iron oxides or doping ions on the surface or in the crystal lattice of BiOCl, which result is in accordance with that of Cu/BiOCl [39] and Fe(III)-BiOCl [34]

Summary

Introduction

A serious environmental hazard, caused by water pollution with toxic dyes, organic contaminants, and metal ions, has come to the public notice [1–4]. Various techniques, including ion exchange [5], adsorption [6, 7], chemical precipitation [8], advanced oxidation [9–11], biodegradation [12, 13], and photocatalysis [14–16] have been tried to the pollutant removal in the wastewater. Its excellent adsorption capacity toward dyes or organic pollutants in wastewater alerts little attention [26–28]. The representative morphology of BiOCl is a threedimensional (3D) hierarchical flower-like microstructure This specific porous structure and large surface area of the 3D hierarchical flower-like morphology is extensively beneficial for the adsorption process [28, 30, 31]. Surface modification is a universal technique to improve the adsorption capacity of an adsorbent. Yu et al [32] improved the adsorption capacities of BiOCl toward dyes congo red (CR)

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