Aluminium (III) biosorption magnetotactic Alcaligenes sp. sum 123 isolated from Skudai River Johor

Abstract

The increasing application of aluminium metals in various industrial processes have raised significant concerns and health risks for humans and its environments. In its ionic form, aluminium poses higher threats to human health due to its ability to cause cellular impairment. As a remediation tool, biosorption by magnetotactic bacteria (MTB) is considered in this study for the removal of this metallic pollutant due to its ability to adsorb heavy metals. The isolation of iron oxide-producing Alcaligenes sp. strain SUM 123 for aluminium(III) biosorption was conducted from samples collected from Skudai River. Biochemical tests and 16S rRNA chararacterization was employed for the identification of the isolated magnetotactic bacterium (MTB). The characterization of this MTB was determined using a High Resolution Transmission Electron Microscope (HRTEM), X-Ray Diffraction (XRD), Scanning Transmission Electron Microscope and Energy Dispersive x-ray Spectroscopy (STEM-EDX) and the Fourier Transform Infrared Spectroscopy (FTIR). Observation by HRTEM shows the lattice spacing of iron oxide at 0.24 nm and 0.31 nm while the XRD analysis depicts the presence of crystalline planes of iron oxide at (311) and (220). The magnetosomes observed via STEM-EDX analysis confirms the presence of iron oxide and the composition of P-granules containing different heavy metals in the isolated Alcaligenes sp. strain SUM 123. The appearance of Fe-O groups of magnetosomes were observed via FTIR analysis. In addition, the decomposition of these iron oxide components was at 270-500 ºC according to thermogravimetric analysis (TGA). The MTB growth and magnetosomes formation were studied at different pH (5-8), temperature (20-40 ºC), and ferric quinate concentration (20-120 μM). It was observed that magnetosomes formation is significantly influenced by pH change and relatively unaffected by variations in temperature and ferric quinate concentrations. Aluminium(III) adsorption by the isolated Alcaligenes sp. strain SUM 123 was examined at pH 2-9, temperature 10-40 ºC, initial Al(III) concentration 80-500 mg.L-1, contact time 10-60 mins and adsorbent dosage 2-12 g.L-1. The optimal adsorption of Al(III) by SUM 123 was observed at pH 5, temperature 25 ºC, 80 mg.L-1 initial Al(III) concentration, 60 mins contact time and an adsorbent dosage of 10 g.L-1. The biosorption process of Al(III) by SUM 123 was best fitted to the Langmuir isotherm model, while the pseudo-second order was found to be the best describe the experimental data. According to FTIR analysis, it was found that the hydroxyl, amide, and amine groups of the magnetosomes were involved in the biosorption process. It is therefore established from this study that the iron oxide-producing Alcaligenes sp. strain SUM 123 is a potentially effective and economical remediation tool for aluminium(III) removal in industrial applications.