(117ai) Removal of Heavy Metals from Aqueous Solution through Biosorption Using Magnetotactic Bacteria

Biosorption using magnetotactic bacteria has shown to be an efficient method for the removal of heavy metals from aqueous solutions. These bacteria have unique properties that allow them to adsorb heavy metals from the environment and store them within their cells. When combined with magnetic nanoparticles, magnetotactic bacteria can be easily separated from the solution using a magnetic field, making the process of heavy metal removal faster and more efficient. A comprehensive literature covering published articles on removal of heavy metals from aqueous solution through biosorption have been reviewed. It is found that most of the studies emphasis on heavy metal interaction with the functional groups containing N, O, P and S. The parameters that significantly affect removal of heavy metals are pH, concentration of solute as wells as complexity of solution chemistry. The study here emphasise on biosorption as wells as magnetotaxis behaviour of magnetotactic bacteria (MTB). Currently, nanotechnology is considered comparatively more promising and superior than other methods in handling and removing these toxic pollutants more efficiently. The commonest means of synthesizing biogenic nanoparticles is by using microbes, fungi, yeasts and plants. This is an environment-friendly method but is now facing serious impediments due to the presence of toxic substances in the final effluent and in particular the challenge of effective biomass separation. The idea of this study is to introduce magnetotactic bacteria (MTB) for biomass separation and consider MTB as a novel biosorbent for heavy metal removal and recovery from wastewater. Experimental studies were carried out to culture indigenous MTB from fresh water sources of Guwahati, Assam. Microscopy studies revealed high motile bacteria in environmental sample. Capillary racetrack method (CRT) was used to isolate MTB from rest of non- motile culture. Surface and intracellular characterization were carried out using FETEM and FTIR for MTB. EDX was used for intracellular elemental composition of Fe₃O₄ as well mapping of Fe and O element along the chain of magnetosome was carried out. XRD method was used to determine the forms of iron sources necessary for growth of MTB in local fresh water source. Iron gluconate hydrate and iron lactate hydrate showed better motility behaviour but further investigation is necessary to determine the the necessary iron sources as Fe(III) iron salts have shown high yield in MTB growth compared to Fe(II) iron salts . In later phase, the significance of MTB in heavy metal contaminated freshwater sources of North- East India is being carried out. Soil and sediment sample from IIT Guwahati Lake (Assam, India), Deepor Beel Lake (Assam, India), Margherita coal mines and swamps (Assam, India), and Jharsuguda coal mines and swamp (Odisha, India) were analysed for heavy metals (Arsenic, Cadmium, Chromium, Lead, Nickle and Copper) using AAS. All the analyses were in ppm level. IIT Guwahati Lake (As- 0.02933, Cd- 0.043, Cr -0.151, Pb- 0, Ni- 17.944, Cu- 0.188); Deepor Beel Lake ( As- 0.01866, Cd-0.067, Cr- 0.084, Pb- 0.34, Ni- 18.168, Cu- 0.117); Margherita coal mines and swamps ( As- 0.023, Cd- 0.122, Cr- 0.460, Pb- 0.26, Ni- 11.466, Cu- 8.546). The incubated samples have confirmed presence of magnetotactic bacteria (MTB). Further extensive study confirms that this method can effectively remove a wide range of heavy metals, including lead, cadmium, and arsenic, with removal rates ranging from 80% to 99%. Overall, biosorption using magnetotactic bacteria offers a promising solution for the remediation of heavy metal-contaminated wastewater.