Application of cryptocrystalline magnesite-bentonite clay hybrid for defluoridation of underground water resources: implication for point of use treatment

V. Masindi

doi:10.2166/wrd.2016.055

Abstract

A new synthesis method was established to fabricate a nanocomposite material comprising of cryptocrystalline magnesite and bentonite clay that has high adsorption capacity for ionic pollutants. To synthesize the composite at 1:1 weight (g): weight (g) ratio, a vibratory ball mill was used. Batch adsorption experiments were carried out to determine optimum conditions for fluoride adsorption. Parameters optimized included: time, dosage, concentration and pH. Optimum conditions for defluoridation were found to be 30 min of agitation, 0.5 g of dosage, 0.5:100 solid to liquid (S/L) ratios and 25 mg L−1 of initial fluoride ions. Fluoride removal was independent of pH. The adsorption kinetics and isotherms were well fitted by pseudo-second-order and Langmuir models, respectively, indicating chemical and monolayer adsorption. Findings illustrated that the newly synthesized adsorbent was a promising adsorbent for the environmental pollution clean-up of excess fluoride in underground water and it can be used as a point source treatment technology in rural areas of South Africa and other developing countries.

Highlights

Fluorosis has become a chronic peril endangering the health of the majority of the population worldwide, especially those living in rural areas (Ayoob & Gupta ; Mohapatra et al ; Bhatnagar et al ; Gitari et al ; Zulfiqar et al )
X-ray diffraction (XRD) pattern of the product synthesized shows one intense diffraction peak around about 2θ 1⁄4 27.2W which is due to quartz
The composite was determined to contain smectite, periclase, quartz, gibbsite and muscovite which are the main components of magnesite and bentonite clay

Summary

Introduction

Fluorosis has become a chronic peril endangering the health of the majority of the population worldwide, especially those living in rural areas (Ayoob & Gupta ; Mohapatra et al ; Bhatnagar et al ; Gitari et al ; Zulfiqar et al ). Zulfiqar et al ; Yu et al ), precipitation (Turner et al ; Onyango & Matsuda ; Zhang et al ), coagulation (Khatibikamal et al ; Emamjomeh et al ; Vasudevan et al ; Gong et al ; Sandoval et al ), filtration (Kettunen & Keskitalo ; Mohapatra et al ; Maliyekkal et al ; Wang et al ; Dolar et al ), reverse osmosis (Mohapatra et al ; Shen & Schäfer ; Trikha & Sharma ), ion exchange (Ruixia et al ; Luo & Inoue ; Meenakshi & Viswanathan ; Mohapatra et al ) and distillation (Hou et al ) Limitations of these methods include the daily addition of chemicals; large volumes of sludge production; and some of these methods have been reported as being ineffective with water sources having high total dissolved solids (TDS) (Ayoob & Gupta ; Onyango & Matsuda ; Mohapatra et al ; Bhatnagar et al ; Miretzky & Cirelli ; Zulfiqar et al )

Objectives

Methods

Results

Conclusion