Preparation of a Thermally Modified Diatomite and a Removal Mechanism for 1-Naphthol from Solution

Xiuzhen Yang,Liping Wang,Yuezhou Zhang,Kelin Li,Lili Cao,Andrew Hursthouse

doi:10.3390/w9090651

Abstract

The adsorption of 1-naphthol (NAP) in aqueous solution was investigated using unmodified and modified diatomite at different temperature, pH, adsorbent mass and contact time. The adsorption capacity of the modified diatomite significantly improved (about 2 times at 298 K) compared to the unmodified diatomite. The adsorption showed a good fit with the Langmuir model. The further data analysis demonstrated that the adsorption of 1-NAP on both materials could be best described by the pseudo second-order kinetic model. The thermodynamic parameters, including Gibbs’ free energy (ΔG), enthalpy (ΔH) and entropy changes (ΔS) were determined. It was observed that the ΔH values (less than 40 kJ/mol) was positive, which indicated that the adsorption process is endothermic, physical adsorption. The ΔG values were negative, indicating that the adsorption of 1-NAP onto raw and modified adsorbent was spontaneous.

Highlights

Contamination of water and soil by synthetic aromatic compounds is one of the most severe environmental problems that cause serious harm to human beings and aquatic ecosystems [1].In particular 1-naphthol (1-NAP), widely used in the manufacture of industrial compounds, is one of top priority contaminants among naphthalene analogues and the main carcinogenic pollutants discharged from pharmaceutical, dyestuff, photographic, and agrochemical industries, in developing countries [2]
It was found that the adsorption of 1-NAP on raw and thermally modified diatomite could best be explained by the pseudo second-order model
For raw and thermal modified diatomite, the experimental data have been applied on Langmuir, Freundlich and D-R isotherm models

Summary

Introduction

Contamination of water and soil by synthetic aromatic compounds is one of the most severe environmental problems that cause serious harm to human beings and aquatic ecosystems [1].In particular 1-naphthol (1-NAP), widely used in the manufacture of industrial compounds, is one of top priority contaminants among naphthalene analogues and the main carcinogenic pollutants discharged from pharmaceutical, dyestuff, photographic, and agrochemical industries, in developing countries [2]. The removal of 1-NAP cannot be readily accomplished in the natural environment or in biological water treatment plants. Many methods have been used to remove naphthalene analogs, such as biological degradation [3], ozonation [4], photocatalytic degradation [5], and adsorption [6], etc. Their application is challenged by poor treatment efficiency, difficulty in generating microbial consortia, expensive analysis, and the generation of secondary pollutants [7,8]. Adsorption has been found to be potentially an effective and attractive process for the wastewater treatment because of low operational cost and high efficiency in the preconcentration process

Methods

Results

Conclusion