Characterization of pulverized Marula seed husk and its potential for the sequestration of methylene blue from aqueous solution

Joshua N Edokpayi,Stanley S Ndlovu,John O Odiyo

doi:10.1186/s13065-019-0530-x

Abstract

Dyes are ranked as an important class of pollutants which affect the aesthetic property of the environment when present even in very low concentrations. This study was carried out to explore the potential use of an agricultural waste (Marula seed husk) to decontaminate methylene blue (MB) from aqueous solution. The effect of change in water chemistry was also examined. The influence of basic adsorption parameters such as contact time, temperature, dosage, pH and particle size on the efficiency of adsorption were investigated. Langmuir and Freundlich isotherms were used to describe the equilibrium data while Pseudo first, second order and Elovich kinetic models were used to evaluate the kinetics of the adsorption process. Thermodynamic parameters such as change in enthalpy (ΔH°), entropy (ΔS°) and Gibbs free energy (ΔG°) were evaluated. Natural surface water showed higher MB removal efficiency than de-ionized water. The sorption process was favored more in alkaline pH range (7–10). The dye adsorption process was found to be endothermic, while ΔG° was negative implying that the reaction is spontaneous. Functional group analyses on the adsorbent showed the presence of hydroxyl, carbonyl and carboxyl groups. The Langmuir equilibrium model best described the adsorption process based on the linearized coefficient. The Pseudo second order model best described the kinetics of the reaction.

Highlights

Water is very vital to the sustenance of life on earth
Characterization of the adsorbent The results from the Fourier transform infra-red showed a broad peak at 3303 cm−1 with a high transmittance frequency (Fig. 2a), which can be attributed to the presence of hydroxyl group [27, 28]
The XRD spectra (Fig. 2b) shows a major peak at 22.3° (2θ) with other minor peaks which can be attributed to the presence of cellulosic content of the adsorbent

Summary

Introduction

Water is very vital to the sustenance of life on earth. The quality of water has a direct impact on the water use potential [1]. A lot of locally available plant materials have been reported useful for the removal of dyes from aqueous solution based on adsorption technology. Matrix effects were investigated using natural surface water collected from Mutale River (in Limpopo Province, South Africa) to examine the effects of change in water chemistry on the removal of MB by Marula seeds husk.

Results

Conclusion