Abstract
Heavy metal pollution due to the contamination of Selenium above the tolerable limit in the natural environment is a challenging issue that environmental scientists face. This study is aimed at identifying ion exchange technology as a feasible solution to remove selenium ions using 001x7 resin. Parametric experiments were conducted to identify the optimal pH, sorbent dose and speed of agitation. Selenium removal efficiency of 85% was attained at pH 5.0 with 100 mg/L selenium concentration. The increase in resin dose was found to increase removal efficiency. However, metal uptake decreased. The experiments on the effect of concentration proved the negative effect of higher concentrations of selenium on removal efficiency. The ion exchange process was proved to be optimal at an agitation speed of 200 rpm and a temperature of 35 °C. Pseudo second order model was found to fit the kinetic data very well compared to the pseudo-first order model and the pseudo second order rate constant was estimated as 8.725x10-5 g mg-1 min-1 with a solution containing 100 mg/L selenium.
Highlights
Selenium is one of the metals which is present naturally in earth’s crust with black shale, phosphate rocks and coal as major sources[1]
Ion exchange studies were strongly influenced by pH conditions as the speciation of ions are restricted by pH variations
The fraction of free ions is dependent on the pH conditions [10]. In this set of experiments, the initial pH of the solution was varied in the range of 2.0–9.0 and the selenium removal percentages were estimated
Summary
Selenium is one of the metals which is present naturally in earth’s crust with black shale, phosphate rocks and coal as major sources[1]. Various physico-chemical methods like evaporation, chemical precipitation, coagulation and membrane processes are applied for the removal of metals [4]. The feasibility of biological methods was not investigated for high concentrations of selenium [6]. Among these various methods, Ion exchange offers a suitable choice for application. Removal of nickel and zinc using amberlite IR-120 resin has been reported and the kinetic data were presented [10]. The main objective was to investigate the feasibility of utilizing a strong acid cation exchange resin, 001x7, for the removal of selenium from aqueous solutions. The effect of process parameters, namely initial pH, selenium concentration, resin dose, shaking speed and operating temperature was studied. Kinetic modeling was performed using pseudo-first order and pseudo-second order models
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