Author(s)

SAAD SAID AL-SHAHRANI

Abstract

This study investigates the possibility of removing strontium as a radioactive material from wastewater. Strontium ions were separated from the wastewater by adsorption using Saudi activated bentonite (SAB). Natural bentonite was activated using sulfuric acid before its application. Batch equilibrium adsorption experiments were conducted to investigate the effects of several factors on the adsorption process such as mixing time, solution pH, initial strontium concentration and the amount of SAB. Adsorption kinetics, adsorption isotherms and adsorption thermodynamics studies were conducted to investigate the process mechanism and the parameters affecting the adsorption process. It is shown that adsorption equilibrium was achieved after 50 min with solution pH being the most important factor. Increasing solution pH increases strontium adsorption percentage. At a lower pH solution (pH <4), high hydrogen ions (H+) concentration competes with strontium ions in the solution and thus decreases strontium ions adsorption efficiency. At (4 < pH < 7), adsorption percentage increases due to lesser H+ ions resulting in strontium adsorption increase. The increase in adsorption percentage with increasing solution pH above 7 may be attributed to precipitation of Sr(OH)2 rather than adsorption. On the other hand, adsorption percentage decreases as strontium concentration is increased. Whereas adsorption percentage increased with increasing the amount of SAB. Adsorption kinetic study reveals second order kinetics. The Langmuir model is better fitted for the adsorption isotherms than Freundlich model. Thermodynamics data shows the adsorption process was spontaneous and endothermic. SAB may be considered as an important adsorbent capable of removing strontium from wastewater.

Keywords

Strontium adsorption, SAB, absorption isotherm, adsorption kinetics, adsorption thermodynamics