Green synthesis of Cr2O3 nanopigments via bioremediation of chromic acid using Convolvulus arvensis L. extract en en The rapid growth of industrialization has greatly increased water pollution, and without necessary precautions, serious environmental and public health risks have emerged. In the initial stage, contaminated water samples containing chromic acid, a known carcinogen, were purified using the herbal extract of Convolvulus arvensis L. The obtained extract served as a bioremediation agent, enabling effective removal of chromic acid. After filtration, hexavalent chromium ions (Cr(VI)) were reduced to trivalent chromium ions (Cr(III)), and the resulting precipitate was transformed into chromium(III) oxide (Cr2O3) nanopigments through further processing. The removal efficiency was evaluated through detailed analyses using a Hach DR900 spectrophotometer, confirming that the target contaminant was removed to nearly 100%, indicating almost complete elimination. Further characterization of the synthesized Cr2O3 nanopigments was performed using Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible (UV-Vis) spectroscopy. These comprehensive analyses verified both the successful synthesis and the structural integrity of the nanoparticles. The results support the effective use of plant extracts for the bioremediation of toxic Cr heavy metal ions and demonstrate the practicality of this method for nanoparticle production. The Cr2O3 nanopigments with diameters ranging from approximately 10 to 30 nanometers were successfully synthesized and exhibited spherical and polygonal morphologies, with approximately 96% chromium purity. 1 11 Shanli Salahi Department of Metallurgical and Materials Engineering Gazi University, Ankara Türkiye shanli.salahi@gmail.com Mohammad Reza Mobedi Avizhe Bespar Nazhu Company, East Azarbaijan Iran Industrial heavy metal pollution Carcinogen Chromic acid Cr2O3 nanopigments Bioremediation Vol 6 No 1 Paper 1.pdf [1] B. Kakavandi, R.R. Kalantary, M. Farzadkia, A.H. Mahvi, A. Esrafili, et al., Enhanced chromium (VI) removal using activated carbon modified by zero valent iron and silver bimetallic nanoparticles, J. Environ. Heal. Sci. Eng. 12 (2014) 115. https://doi.org/10.1186/s40201-014-0115-5. ##[2] H. Norouzi, D. Jafari, M. Esfandyari, Study on a new adsorbent for biosorption of cadmium ion from aqueous solution by activated carbon prepared from Ricinus communis, Desalin. Water Treat. 191 (2020) 140–152. https:/doi.org/10.5004/dwt.2020.25702. ##[3] J.W. Ran Zhao, B. Wang, Q. Tao Cai, X. Xia Li, M. Liu, et al., Bioremediation of Hexavalent Chromium Pollution by Sporosarcina saromensis M52 Isolated from Offshore Sediments in Xiamen, China, Biomed. Environ. Sci. 29 (2016) 127–136. https://doi.org/10.3967/bes2016.014. ##[4] F.H. Khan, K. Ambreen, G. Fatima, S. Kumar, Assessment of health risks with reference to oxidative stress and DNA damage in chromium exposed population, Sci. Total Environ. 430 (2012) 68–74. https://doi.org/10.1016/j.scitotenv.2012.04.063. ##[5] F. Wu, H. Sun, T. Kluz, H.A. Clancy, K. Kiok, M. Costa, Epigallocatechin-3-gallate (EGCG) protects against chromate-induced toxicity in vitro, Toxicol. Appl. Pharmacol. 258 (2012) 166–175. https://doi.org/10.1016/j.taap.2011.10.018. ##[6] K.P. Nickens, S.R. Patierno, S. Ceryak, Chromium genotoxicity: A double-edged sword, Chem. Biol. Interact. 188 (2010) 276–288. https://doi.org/10.1016/j.cbi.2010.04.018. ##[7] C.M. Thompson, C.R. Kirman, D.M. Proctor, L.C. Haws, M. Suh, et al., A chronic oral reference dose for hexavalent chromium‐induced intestinal cancer, J. Appl. Toxicol. 34 (2014) 525–536. https://doi.org/10.1002/jat.2907. ##[8] A. Seidler, S. Jähnichen, J. Hegewald, A. Fishta, O. Krug, et al., Systematic review and quantification of respiratory cancer risk for occupational exposure to hexavalent chromium, Int. Arch. Occup. Environ. Health. 86 (2013) 943–955. https://doi.org/10.1007/s00420-012-0822-0. ##[9] Y. Mu, H. Wu, Z. Ai, Negative impact of oxygen molecular activation on Cr(VI) removal with core–shell Fe@Fe2O3 nanowires, J. Hazard. Mater. 298 (2015) 1–10. https://doi.org/10.1016/j.jhazmat.2015.05.008. ##[10] M.K. Michailides, A.G. Tekerlekopoulou, C.S. Akratos, S. Coles, S. Pavlou, D.V. Vayenas, Molasses as an efficient low-cost carbon source for biological Cr(VI) removal, J. Hazard. Mater. 281 (2015) 95–105. https://doi.org/10.1016/j.jhazmat.2014.08.004. ##[11] K. StĘpniewska, Z. Bucior, Chromiumcontamination of Soils, Waters, and Plants in the Vicinity of a Tannerywaste Lagoon, Environ. Geochem. Health. 23 (2001) 241–245. https://doi.org/10.1023/A:1012247230682. ##[12] D. Kumar, S.P. Gangwar, Role of antioxidants in detoxification of Cr (VI) toxicity in laboratory rats, J. Environ. Sci. Eng. 54 (2012) 441–446. ##[13] F.C. Manning, L.J. Blankenship, J.P. Wise, J. Xu, L.C. Bridgewater, S.R. Patierno, Induction of internucleosomal DNA fragmentation by carcinogenic chromate: relationship to DNA damage, genotoxicity, and inhibition of macromolecular synthesis, Environ. Health Perspect. 102 (1994) 159–167. https://doi.org/10.1289/ehp.94102s3159. ##[14] X.-H. Zhang, X. Zhang, X.-C. Wang, L.-F. Jin, Z.-P. Yang, et al., Chronic occupational exposure to hexavalent chromium causes DNA damage in electroplating workers, BMC Public Health. 11 (2011) 224. https://doi.org/10.1186/1471-2458-11-224. ##[15] A. Kortenkamp, M. Casadevall, S.P. Faux, A. Jenner, R.O.J. Shayer, et al., A Role for Molecular Oxygen in the Formation of DNA Damage during the Reduction of the Carcinogen Chromium(VI) by Glutathione, Arch. Biochem. Biophys. 329 (1996) 199–207. https://doi.org/10.1006/abbi.1996.0209. ##[16] L. Cheng, S. Liu, K. Dixon, Analysis of repair and mutagenesis of chromium-induced DNA damage in yeast, mammalian cells, and transgenic mice, Environ. Health Perspect. 106 (1998) 1027–1032. https://doi.org/10.1289/ehp.98106s41027. ##[17] J.F. Cerveira, M. Sánchez-Aragó, A.M. Urbano, J.M. Cuezva, Short‐term exposure of nontumorigenic human bronchial epithelial cells to carcinogenic chromium(VI) compromises their respiratory capacity and alters their bioenergetic signature, FEBS Open Bio. 4 (2014) 594–601. https://doi.org/10.1016/j.fob.2014.06.006. ##[18] T. O’Brien, Complexities of chromium carcinogenesis: role of cellular response, repair and recovery mechanisms, Mutat. Res. Mol. Mech. Mutagen. 533 (2003) 3–36. https://doi.org/10.1016/j.mrfmmm.2003.09.006. ##[19] J.P. Wise, S.S. Wise, J.E. Little, The cytotoxicity and genotoxicity of particulate and soluble hexavalent chromium in human lung cells, Mutat. Res. Toxicol. Environ. Mutagen. 517 (2002) 221–229. https://doi.org/10.1016/S1383-5718(02)00071-2. ##[20] D.M. Proctor, M. Suh, S.L. Campleman, C.M. Thompson, Assessment of the mode of action for hexavalent chromium-induced lung cancer following inhalation exposures, Toxicology. 325 (2014) 160–179. https://doi.org/10.1016/j.tox.2014.08.009. ##[21] K. Straif, L. Benbrahim-Tallaa, R. Baan, Y. Grosse, B. Secretan, et al., A review of human carcinogens—Part C: metals, arsenic, dusts, and fibres, Lancet Oncol. 10 (2009) 453–454. https://doi.org/10.1016/S1470-2045(09)70134-2. ##[22] L.M. Beaver, E.J. Stemmy, A.M. Schwartz, J.M. Damsker, S.L. Constant, et al., Lung Inflammation, Injury, and Proliferative Response after Repetitive Particulate Hexavalent Chromium Exposure, Environ. Health Perspect. 117 (2009) 1896–1902. https://doi.org/10.1289/ehp.0900715. ##[23] J.M. Cullen, J.M. Ward, C.M. Thompson, Reevaluation and Classification of Duodenal Lesions in B6C3F1 Mice and F344 Rats from 4 Studies of Hexavalent Chromium in Drinking Water, Toxicol. Pathol. 44 (2016) 279–289. https://doi.org/10.1177/0192623315611501. ##[24] Y. Wang, H. Su, Y. Gu, X. Song, J. Zhao, Carcinogenicity of chromium and chemoprevention: a brief update, Onco. Targets. Ther. 10 (2017) 4065–4079. https://doi.org/10.2147/OTT.S139262. ##[25] J. Yang, M. Yu, W. Chen, Adsorption of hexavalent chromium from aqueous solution by activated carbon prepared from longan seed: Kinetics, equilibrium and thermodynamics, J. Ind. Eng. Chem. 21 (2015) 414–422. https://doi.org/10.1016/j.jiec.2014.02.054. ##[26] S. Sugashini, K.M.M.S. Begum, Preparation of activated carbon from carbonized rice husk by ozone activation for Cr(VI) removal, New Carbon Mater. 30 (2015) 252–261. https://doi.org/10.1016/S1872-5805(15)60190-1. ##[27] S.E. Bailey, T.J. Olin, R.M. Bricka, D.D. Adrian, A review of potentially low-cost sorbents for heavy metals, Water Res. 33 (1999) 2469–2479. https://doi.org/10.1016/S0043-1354(98)00475-8. ##[28] S. Salahi, T. Ghaffari, Antibacterial efficacy of green-synthesized silver nanoparticles from rosemary, pennyroyal, and eucalyptus extracts against E. coli and S. aureus bacteria, Synth. Sinter. 4 (2024) 101–107. https://doi.org/10.53063/synsint.2024.42218. ##[29] P. Elliott, S. Ragusa, D. Catcheside, Growth of sulfate-reducing bacteria under acidic conditions in an upflow anaerobic bioreactor as a treatment system for acid mine drainage, Water Res. 32 (1998) 3724–3730. https://doi.org/10.1016/S0043-1354(98)00144-4. ##[30] G.W. Staples, Revision of Asiatic Poraneae (Convolvulaceae) – Cordisepalum, Dinetus, Duperreya, Porana, Poranopsis , and Tridynamia, Blumea - Biodiversity, Evol. Biogeogr. Plants. 51 (2006) 403–491. https://doi.org/10.3767/000651906X622067. ##[31] G.W. Staples, D.F. Austin, Revision of Neptropical Calycobolus and Porana (Convolvulaceae), Edinburgh J. Bot. 66 (2009) 133–153. https://doi.org/10.1017/S0960428609005319. ##[32] G. Chen, Y. Lu, M. Yang, J. Li, B. Fan, Medicinal uses, pharmacology, and phytochemistry of Convolvulaceae plants with central nervous system efficacies: A systematic review, Phyther. Res. 32 (2018) 823–864. https://doi.org/10.1002/ptr.6031. ##[33] S. Nacef, H. Ben Jannet, P. Abreu, Z. Mighri, Phenolic constituents of Convolvulus dorycnium L. flowers, Phytochem. Lett. 3 (2010) 66–69. https://doi.org/10.1016/j.phytol.2009.12.001. ##[34] D.F. Austin, Evolvulus alsinoides (Convolvulaceae): An American herb in the Old World, J. Ethnopharmacol. 117 (2008) 185–198. https://doi.org/10.1016/j.jep.2008.01.038. ##[35] M. Ranjbar, A. Ezazi, F. Ghahremaninejad, Taxonomic notes on Convolvulus sect. Serospinescentes (Convolvulaceae), Feddes Repert. 128 (2017) 17–35. https://doi.org/10.1002/fedr.201600020. ##[36] N.M. Al-Enazi, Phytochemical screening and biological activities of some species of alpinia and Convolvulus plants, Int. J. Pharmacol. 14 (2018) 301–309. https://doi.org/10.3923/ijp.2018.301.309. ##[37] B. Salehi, B. Krochmal‐Marczak, D. Skiba, J.K. Patra, S.K. Das, et al., Convolvulus plant—A comprehensive review from phytochemical composition to pharmacy, Phyther. Res. 34 (2020) 315–328. https://doi.org/10.1002/ptr.6540. ##[38] I. Mindru, G. Marinescu, D. Gingasu, L. Patron, C. Ghica, M. Giurginca, Blue CoAl2O4 spinel via complexation method, Mater. Chem. Phys. 122 (2010) 491–497. https://doi.org/10.1016/j.matchemphys.2010.03.032. ##[39] Li, Z.F. Yan, G.Q. Lu, Z.H. Zhu, Synthesis and Structure Characterization of Chromium Oxide Prepared by Solid Thermal Decomposition Reaction, J. Phys. Chem. B. 110 (2006) 178–183. https://doi.org/10.1021/jp053810b. ##[40] K.H. Büchel, H. Moretto, P. Woditsch, Industrial Inorganic Chemistry, Wiley. (2000). https://doi.org/10.1002/9783527613328. ##[41] M. Ocaña, Nanosized Cr2O3 hydrate spherical particles prepared by the urea method, J. Eur. Ceram. Soc. 21 (2001) 931–939. https://doi.org/10.1016/S0955-2219(00)00288-0. ##[42] A.C. Santulli, M. Feygenson, F.E. Camino, M.C. Aronson, S.S. Wong, Synthesis and Characterization of One-Dimensional Cr 2 O 3 Nanostructures, Chem. Mater. 23 (2011) 1000–1008. https://doi.org/10.1021/cm102930z. ##[43] S. Sangeetha, R. Basha, K.J. Sreeram, S.N. Sangilimuthu, B. Unni Nair, Functional pigments from chromium(III) oxide nanoparticles, Dye. Pigment. 94 (2012) 548–552. https://doi.org/10.1016/j.dyepig.2012.03.019. ##[44] K. AL-Rashedi, M. Farooqui, G. Rabbani, Characterizing Crystalline Chromium oxide Thin Film Growth by Sol-gel method on Glass Substrates, Orient. J. Chem. 34 (2018) 2203–2207. https://doi.org/10.13005/ojc/3404064. ##[45] T. Rajkumar, G. Ranga Rao, Synthesis and characterization of hybrid molecular material prepared by ionic liquid and silicotungstic acid, Mater. Chem. Phys. 112 (2008) 853–857. https://doi.org/10.1016/j.matchemphys.2008.06.046. ##[46] Rakesh, S. Ananda, N.M.M. Gowda, Synthesis of Chromium(III) Oxide Nanoparticles by Electrochemical Method and Mukia Maderaspatana Plant Extract, Characterization, KMnO Decomposition and Antibacterial Study, Mod. Res. Catal. 02 (2013) 127–135. https://doi.org/10.4236/mrc.2013.24018. ##[47] Y. Guo, N. Zhao, T. Zhang, H. Gong, H. Ma, et al., Compatibility and thermal decomposition mechanism of nitrocellulose/Cr 2 O 3 nanoparticles studied using DSC and TG-FTIR, RSC Adv. 9 (2019) 3927–3937. https://doi.org/10.1039/C8RA09632E. ##[48] M.M. Abdullah, F.M. Rajab, S.M. Al-Abbas, Structural and optical characterization of Cr2O3 nanostructures: Evaluation of its dielectric properties, AIP Adv. 4 (2014) 027121. https://doi.org/10.1063/1.4867012. ##[49] B.B. Kamble, M. Naikwade, K.M. Garadkar, R.B. Mane, K.K.K. Sharma, et al., Ionic liquid assisted synthesis of chromium oxide (Cr2O3) nanoparticles and their application in glucose sensing, J. Mater. Sci. Mater. Electron. 30 (2019) 13984–13993. https://doi.org/10.1007/s10854-019-01748-5. ##[50] T. Ivanova, K. Gesheva, A. Cziraki, A. Szekeres, E. Vlaikova, Structural transformations and their relation to the optoelectronic properties of chromium oxide thin films, J. Phys. Conf. Ser. 113 (2008) 012030. https://doi.org/10.1088/1742-6596/113/1/012030. ##[51] T.I. Alanazi, R.A. Alenazi, A.M. El Sayed, Tuning the band gap, optical, mechanical, and electrical features of a bio-blend by Cr2O3/V2O5 nanofillers for optoelectronics and energy applications, Sci. Rep. 14 (2024) 12537. https://doi.org/10.1038/s41598-024-62643-6. ##[52] M.G. Tsegay, H.G. Gebretinsae, G.G. Welegergs, S. Azizi, M.P. Seopela, et al., Optical response of green synthesized thin Cr2O3 films prepared via drop and spin coatings, Mater. Today Proc. (2023). https://doi.org/10.1016/j.matpr.2023.06.225. ##[53] J. Singh, V. Verma, R. Kumar, S. Sharma, R. Kumar, Effect of structural and thermal disorder on the optical band gap energy of Cr2O3 nanoparticles, Mater. Res. Express. 6 (2019) 085039. https://doi.org/10.1088/2053-1591/ab195c. ##[54] G. Singh, D. Jalandhara, K. Yadav, Effect of grain size on optical properties of iron oxide nanoparticles, API Conf. Proc. 1728 (2016) 020409. https://doi.org/10.1063/1.4946460.