Simultaneous removal of selenite and selenate from drinking water using mesoporous activated alumina

Alok Kumar Meher,Amit Bansiwal,Asmita Jadhav,Nitin Labhsetwar

doi:10.1007/s13201-019-1090-x

Alok Kumar Meher, Amit Bansiwal + Show 2 more

Open Access

https://doi.org/10.1007/s13201-019-1090-x

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Abstract

The present study reports detailed evaluation of mesoporous activated alumina (MAA) for simultaneous removal of two hazardous inorganic species of selenium, namely selenite and selanate, from drinking water. MAA was used after washing with deionized water followed by drying at 110 °C for 8 h. The material was characterized using pXRD, FTIR, zeta potential, SEM and BET surface area measurements. Batch adsorption studies were performed, and various adsorption isotherms and kinetic parameters were computed to delineate the mechanism of adsorption. It was observed that Freundlich adsorption isotherm was the best-fit model for both the species of selenium. The adsorption capacity obtained from Freundlich isotherm for selenite and selenate was found to be 9.02 µg g−1 and 5.38 µg g−1, respectively. Kinetics studies revealed that adsorption of selenite follows pseudo-second-order model, whereas selenate adsorption follows pseudo-first-order model. The efficiency of the material was also evaluated at different pH and in the presence of different competitive co-ions, which confirms efficacy of MAA at near-neutral pH and lower concentrations of competitive co-ions. Negligible changes in the pH were observed during the course of adsorption. Further, the saturated adsorbent was subjected to regeneration and reuse studies up to ten cycles, showing insignificant reduction in adsorption efficiency of the adsorbent during few initial cycles. The study infers the effectiveness of MAA as a potential adsorbent for drinking water treatment contaminated with selenium.

Highlights

Selenium is one of the micronutrients for living organisms, but is one of the major concerns due to narrow range between deficit and toxicity levels (Goldhaber 2003)
We have considered two adsorption isotherm models, namely Langmuir and Freundlich isotherms
Tap water was spiked with 200 μg L−1 of the analytes (TW), and in another case spiking of the analytes was done in simulated water (SW), which was prepared with the composition of chloride 100 mg L −1, bicarbonate 50 mg L −1, carbonate 200 mg L−1, phosphate 1 mg L−1 and sulfate 20 mg L−1

Summary

Introduction

Selenium is one of the micronutrients for living organisms, but is one of the major concerns due to narrow range between deficit and toxicity levels (Goldhaber 2003). The presence of elevated concentration of selenium has been reported in India (2.3–11.6 mg kg−1), from the Northern parts such as Punjab (Bajaj et al 2011). Selenium has been reported for its potential toxicity with threats to both wildlife and human health (Hamilton 2004). Considering its adverse effects on human health, regulatory authorities such as the WHO (Anonymous 2015) have framed a strict permissible limit of 10 μg L−1 for selenium in drinking water, and this standard has been widely adopted by USEPA (Anonymous 2012), Australia (Anonymous 2011), Japan (Anonymous 2004), India (Anonymous 2012) and Canadian guideline value of 50 μg L−1 (Anonymous 2014)

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