Abstract
The use of microorganisms in biosorption is one of the most promising ways to remove trace amounts of heavy metal ions. Nevertheless, the enhancement of the successful removal of heavy metal ions by using different combinations of biosorbents is not generally guaranteed which leaves room to explore the application of the technique. In this study, the performance of free and immobilized forms of a yeast strain, Candida krusei (C. krusei), and calcium alginate (CaAlg) are evaluated for their ability to remove copper(II). Infrared spectroscopy, studies on the effects of pH and temperature, and kinetics and isotherm modelling are carried out to evaluate the biosorption. The infrared spectroscopy shows that the primary biosorption sites on the biosorbents are carboxylate groups. In addition, a higher pH and higher temperatures promote biosorption while a decline in biosorption ability is observed for C. krusei at 50 °C. The kinetics study shows that C. krusei, CaAlg and immobilized C. krusei (MCaAlg) conform with good correlation to pseudo-second order kinetics. MCaAlg and CaAlg fit well to the Langmuir isotherm while C. krusei fits well to the Temkin isotherm. From the experimental data, encapsulating C. krusei showed improved biosoprtion and address clogging in practical applications.
Highlights
Many industries today use heavy metal ions; for example, the electroplating, metal mining and smelting industries[1]
The carboxylate COO− of C. krusei shifted from 1402.1 cm−1 to 1384.3 cm−1; new asymmetric and symmetric COO− absorption bands of calcium alginate (CaAlg) and MCaAlg appeared at approximately 1384.3 cm−1 respectively
The effects of temperatures of 30 °C, 40 °C and 50 °C are examined, which show that CaAlg and MCaAlg have better biosorption capacity with increasing temperature while the optimum temperature for the biosorption of C. krusei is 40 °C
Summary
Many industries today use heavy metal ions; for example, the electroplating, metal mining and smelting industries[1]. The technique works well to remove large amounts of pollutants that are not limited to heavy metal ions, the costs of the operation of nanofiltration and filter regeneration are concerns. The practical application of microorganisms in waste water treatment is problematic as the small particle size and low strength of microbial cells can cause the clogging of flow lines and filter parts, which usually occur during operation[16, 17]. To address these issues, the immobilization and encapsulation of microorganisms with a polymeric matrix have been subsequently developed and studied. Batch biosorption experiments are conducted and the removal mechanism is evaluated
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