Melanin-embedded materials effectively remove hexavalent chromium (CrVI) from aqueous solution

Abstract

BackgroundCurrently, it is recognized that water polluted with toxic heavy metal ions may cause serious effects on human health. Therefore, the development of new materials for effective removal of heavy metal ions from water is still a widely important area. Melanin is being considered as a potential material for removal of heavy metal from water.MethodsIn this study, we synthesized two melanin-embedded beads from two different melanin powder sources and named IMB (Isolated Melanin Bead originated from squid ink sac) and CMB (Commercial Melanin Bead originated from sesame seeds). These beads were of globular shape and 2–3 mm in diameter. We investigated and compared the sorption abilities of these two bead materials toward hexavalent-chromium (CrVI) in water. The isotherm sorption curves were established using Langmuir and Freundlich models in the optimized conditions of pH, sorption time, solid/liquid ratio, and initial concentration of CrVI. The FITR analysis was also carried out to show the differences in surface properties of these two beads.ResultsThe optimized conditions for isotherm sorption of CrVI on IMB/CMB were set at pH values of 2/2, sorption times of 90/300 min, and solid-liquid ratios of 10/20 mg/mL. The maximum sorption capacities calculated based on the Langmuir model were 19.60 and 6.24 for IMB and CMB, respectively. However, the adsorption kinetic of CrVI on the beads fitted the Freundlich model with R2 values of 0.992 for IMB and 0.989 for CMB. The deduced Freundlich constant, 1/n, in the range of 0.2–0.8 indicated that these beads are good adsorption materials. In addition, structure analysis data revealed great differences in physical and chemical properties between IMB and CMB. Interestingly, FTIR analysis results showed strong signals of –OH (3295.35 cm− 1) and –C=O (1608.63 cm− 1) groups harboring on the IMB but not CMB. Moreover, loading of CrVI on the IMB caused a shift of broad peaks from 3295.35 cm− 1 and 1608.63 cm− 1 to 3354.21 cm− 1 and 1597.06 cm− 1, respectively, due to –OH and –C=O stretching.ConclusionsTaken together, our study suggests that IMB has great potential as a bead material for the elimination of CrVI from aqueous solutions and may be highly useful for water treatment applications.

Health Risk Evaluation of Trace Elements in Geophagic Kaolinitic Clays within Eastern Dahomey and Niger Delta Basins, Nigeria

“…The toxicity level of hexavalent chromium (IV) (Cr 6+ ) is higher relative to trivalent chromium (Cr 3+ ). In addition, Cr 6+ is believed to become reduced into Cr 3+ in the human body [ 26 , 60 ]. Evidence for the carcinogenicity of Cr 3+ in humans is lacking, but it could cause skin rashes [ 54 ].…”

Melanin-containing feedstuffs protect Litopenaeus vannamei from white spot syndrome virus

“…Melanin was extracted from Splendid Squid (Loligo formosana) as reported in our previous study (Cuong et al 2018). Commercial feed in the bead form with a diameter of 2 mm (containing 45-50% starch) was used as the core feed to produce melanin-containing feedstuffs with different formulas.…”

“…Melanin is a natural polymer with very low toxicity (Garcia Borron et al 2014). Melanin has many important roles in the human body including UV-radiation absorbent (Brenner and Hearing 2008), antioxidant (Vate and Benjakul 2013), and heavy-metal absorbent properties (Cuong et al 2018). Melanization and melanin secretion help shrimp protect themselves by encapsulating pathogens and excreting them into the environment (Charoensapsri et al 2014;Sutthangkul et al 2015;Harikrishnan et al 2011).…”

Removal of Hexavalent Chromium from Aqueous Solutions Using Sulfonated Peat

“…[15]. 3C + 2Cr2O7 2-+ 16H + →4Cr 3+ + 3CO2 + 8H2O (9) The above three factors exerted different influences on the removal efficiency. This study also delved into the effects of adsorption under different environmental conditions through a four-level orthogonal test on the four factors.…”

“…Many authors have reported on the ability of different methods to remove Cr(VI) including adsorption, electrocoagulation, ion exchange, chemical precipitation, membrane separation, reduction, and biosorption methods [5][6][7]. Adsorption is considered as a simple, highly efficient [8], and low-cost method [9]. As such, many studies have been performed on adsorbents used in sewage treatments [10][11][12][13][14][15][16].…”