Study on the adsorption properties of methyl orange by natural one-dimensional nano-mineral materials with different structures

Lijuan Wu,Guocheng Lv,Meng Liu,Libing Liao,Xuewen Liu,Lintao Tian,Yuxin Li,Wenxiu Rao,Runliang Zhu,Tianming Liu

doi:10.1038/s41598-021-90235-1

Abstract

Methyl orange (MO) is a common anionic azo dye that is harmful to the environment and biology, so it must be treated innocuously before it can be discharged. Adsorption is an effective method to remove anionic dyes. Nanotube mineral is a natural one-dimensional adsorption material, and its unique morphology and structure endow it with good adsorption capacity. Although there are many related studies, there is a lack of in-depth discussions on the influence of nanotube’s composition and structure on the adsorption of dyes and other pollutants. In this paper, two kinds of natural one-dimensional silicate minerals [halloysite nanotubes (HNTs) and chrysotile nanotubes (ChNTs)] with similar morphology but slightly different compositions and crystal structures were used as adsorbents, and MO solution was used as simulate pollutants. It is the first time to discuss in depth the influence of the composition and structure of nanotube minerals on their charge properties and the adsorption performance of methyl orange dyes. It is found that HNTs and ChNTs have different adsorption capacity due to the difference of electronegativity between Al3+ and Mg2+ in the crystal, so they possess negative and positive charges respectively in near-neutral solution, which leads to the adsorption capacity of MO by ChNTs with positive charges which is greater than that of HNTs.

Highlights

Methyl orange (MO) is a common anionic azo dye that is harmful to the environment and biology, so it must be treated innocuously before it can be discharged
The results show that the average maximum adsorption capacity of halloysite nanotubes (HNTs) and chrysotile nanotubes (ChNTs) to MO dyes is 13.56 mg/g and 31.46 mg/g, respectively (Fig. 7)
HNTs and ChNTs that are natural one-dimensional nano-mineral materials were used as adsorbents for the removal of MO dyes from water

Summary

Introduction

Methyl orange (MO) is a common anionic azo dye that is harmful to the environment and biology, so it must be treated innocuously before it can be discharged. Two kinds of natural one-dimensional silicate minerals [halloysite nanotubes (HNTs) and chrysotile nanotubes (ChNTs)] with similar morphology but slightly different compositions and crystal structures were used as adsorbents, and MO solution was used as simulate pollutants. Its unique morphology and structure make it to possess good environmental compatibility, large specific surface area, rich surface efficiency and high adsorption efficiency, so it is widely used in the removal of organic pollutants such as dyes[32,33,34,35,36]. Halloysite nanotubes and Chrysotile nanotubes are two kinds of one-dimensional nano tubular minerals with similar morphology but with slightly different composition and structure, and both of them belong to layered silicate minerals. This leads to the appearance of the crimped structural unit layer of HNTs with Si–O tetrahedron outside and Al-OH octahedron inside[41,42] (as shown in Fig. 2a,b), forming nanotubes with an inner diameter of about 10–20 nm

Methods

Results

Conclusion