Faculty Publications
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Item Kinetic and thermodynamic studies on the adsorption of heavy metals from aqueous solution by melanin nanopigment obtained from marine source: Pseudomonas stutzeri(Academic Press, 2018) Manirethan, V.; Raval, K.; Rajan, R.; Thaira, H.; Mohan Balakrishnan, R.M.The difficulty in removal of heavy metals at concentrations below 10 mg/L has led to the exploration of efficient adsorbents for removal of heavy metals. The adsorption capacity of biosynthesized melanin for Mercury (Hg(II)), Chromium (Cr(VI)), Lead (Pb(II)) and Copper (Cu(II)) was investigated at different operating conditions like pH, time, initial concentration and temperature. The heavy metals adsorption process was well illustrated by the Lagergren's pseudo-second-order kinetic model and the equilibrium data fitted excellently to Langmuir isotherm. Maximum adsorption capacity obtained from Langmuir isotherm for Hg(II) was 82.4 mg/g, Cr(VI) was 126.9 mg/g, Pb(II) was 147.5 mg/g and Cu(II) was 167.8 mg/g. The thermodynamic parameters revealed that the adsorption of heavy metals on melanin is favorable, spontaneous and endothermic in nature. Binding of heavy metals on melanin surface was proved by Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). Contemplating the results, biosynthesized melanin can be a potential adsorbent for efficient removal of Hg(II), Cr(VI), Pb(II) and Cu(II) ions from aqueous solution. © 2018 Elsevier LtdItem Melanin nano-pigments for heavy metal remediation from water(Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2019) Thaira, H.; Raval, K.; Manirethan, V.; Mohan Balakrishnan, R.M.Melanins are water insoluble polyphenol compounds. The metal ion chelating property of natural melanin is exploited for removal of heavy metals from contaminated water. We optimized biosynthesis of melanin from marine bacterium using different growth media, media components, and operating conditions. Optimized medium yielded 513 mg/L melanin at 36 h of incubation, which was 3.15 times higher than the yield before optimization. Particle size analysis of the biosynthesized melanin indicated a size of 32 ± 0.98 nm. Preliminary investigation indicated that melanin nanoparticles could adsorb different heavy metals such as chromium, selenium, and lead from very low initial concentrations. © 2018, © 2018 Taylor & Francis.Item Batch and continuous studies on the removal of heavy metals using biosynthesised melanin impregnated activated carbon(Elsevier B.V., 2020) Manirethan, V.; Mohan Balakrishnan, R.M.The adversity associated with the removal of melanin nanoparticles after adsorbing heavy metals led to the development of a system involving activated carbon on which melanin was effectively impregnated. The melanin impregnated activated carbon was handily removed from the aqueous medium by simple filtration. The batch studies performed to scrutinise the optimum conditions for maximum adsorption concluded the contact time needed to attain equilibrium to be 90 min for all metals of study. Maximum adsorption of Cr (VI) was shown at pH 3 while Hg (II), Pb (II) and Cu (II) was adsorbed efficiently at pH 5. Increase in temperature favoured the adsorption process for all metals showing maximum removal at 328 K. Melanin impregnated activated carbon could adsorb 84.59% Hg (II), 86.6% Cr (VI), 91.1% Pb (II) and 93.8% Cu (II) from 5 mg/L heavy metal solution. Dynamic studies were conducted by varying the parameters like flow rate, inlet heavy metal concentration and adsorbent loading. Optimum conditions for a maximum breakthrough was obtained with a flow rate of 0.5 mL/min, heavy metal inlet concentration of 1 mg/L and adsorbent loading of 100 mg. Experimental data modelled in equilibrium isotherms showed the best fitting with the Thomas model when compared with the Adam–Boharts model using determined coefficient and error analysis. Efficient chemical desorption of Hg (II), Pb (II) and Cu (II) was obtained using 3N HCl and Cr (VI) using 1N citric acid. © 2020 Elsevier B.V.