Removal of Cr (VI) from aqueous solution using ultrafine coal fly ash

Abstract

Coal fly ashes WSRA and BQRA were ball milled for 5 h to produce their ultrafine coal fly ashes WSUA and BQUA, respectively. Batch kinetic, isotherm and pH effect on adsorption were studied to evaluate removal of Cr (VI) from aqueous solutions by ultrafine coal fly ashes comparing with raw coal fly ashes. The kinetics of adsorption indicates the process to be intraparticle diffusion controlled and follows the Lagergren first-order kinetics for all coal fly ashes. The first-order rate constants (k ₁) of Cr (VI) adsorption onto WSRA, WSUA, BQRA and BQUA are 1.981, 1.497, 2.119 and 1.500 (×10⁻²) min⁻¹, respectively. The adsorption capacities of WSUA and BQUA are much better than those of WSRA and BQRA. Equilibrium adsorption data of all coal fly ashes well satisfy the Langmuir isotherm. The adsorbed amounts of Cr (VI) onto WSUA and BQUA decrease from pH 2 to pH 6 and then increase up to pH 12.

Keywords

ultrafine coal fly ash / Cr (VI) / adsorption / wastewater treatment

References

[1] Panday K. K., Prasad G., Singh V. N. Copper(II) Removal from Aqueous Solution by Fly Ash [J]. Water Research, 1985, 19(7): 869-873.

[2] Alinnor I. J. Adsorption of Heavy Metal ions from Aqueous Solution by Fly Ash[J]. Fuel, 2007, 86(5–6): 853-857.

[3] Bayat B. Comparative Study of Adsorption Properties of Turkish Fly Ashes II. The Case of Chromium (VI) and Cadmium (II) [J]. Journal of Hazardous Materials, 2002, 95(3): 275-290.

[4] Ramakrishna K. R., Viraraghavan T. Dye Removal Using Low Cost Adsorbents[J]. Water Science and Technology, 1997, 36(2–3): 189-196.

[5] Janoš P., Buchtová H., Rýznarová M. Sorption of Dyes from Aqueous Solutions onto Fly Ash [J]. Water Research, 2003, 37(20): 4938-4944.

[6] Wang S. B., Boyjoo Y., Choueib A., . Removal of Dyes from Aqueous Solution Using Fly Ash and Red Mud[J]. Water Research, 2005, 39(1): 129-138.

[7] Wang S. B., Soudi M., Li L., . Coal Ash Conversion into Adsorbents for Removal of Heavy Metal and dyes from Wastewater[ J]. Journal of Hazardous Materials, 2006, 133(1–3): 243-251.

[8] Hui K. S., Chao C. Y. H., Kot S. C. Removal of Mixed Heavy Metal ions in Wastewater by Zeolite 4A and Residual Products from Recycled Coal Fly Ash[J]. Journal of Hazardous Materials, 2005, 127(1–3): 89-101.

[9] Wang S. B., Li L., Zhu Z. H. Solid-state Conversion of fly ash to Effective Adsorbents for Cu Removal from Wastewater [J]. Journal of Hazardous Materials, 2007, 139(2): 254-259.

[10] Moriyama R., Takeda S., Onozaki M., . Large-scale Synthesis of Artificial Zeolite from Coal fly ash with a Small Charge of Alkaline Solution[J]. Fuel, 2005, 84(12–13): 1455-1461.

[11] Inada M., Eguchi Y., Enomoto N., . Synthesis of Zeolite from Coal Fly Ashes with Different Silica-alumina Composition [J]. Fuel, 2005, 84(2–3): 299-304.

[12] Yu Y. T. Preparation of Nanocrystalline TiO₂-coated Coal Fly Ash and Effect of Iron Oxides in Coal Fly Ash on Photocatalytic Activity[J]. Powder Technology, 2004, 146(1–2): 154-159.

[13] Charerntanyarak L. Heavy Metals Removal by Chemical Coagulation and Precipitation[J]. Water Science and Technology, 1999, 39(10–11): 135-138.

[14] Rengaraj S., Yeon K. H., Moon S. H. Removal of Chromium from Water and Wastewater by ion Exchange Resins[J]. Journal of Hazardous Materials, 2001, 87(1–3): 273-287.

[15] Dinesh M., Charles U., Pittman Jr. Activated Carbon and Low Cost Adsorbents for Remediation of Tri- and Hexavalent Chromium from Water [J]. Journal of Hazardous Materials, 2006, 137(2): 762-811.

[16] Lakatos J., Brown S. D., Snape C. E. Coals as Sorbents for the Removal and Reduction of Hexavalent Chromium from Aqueous Waste Streams [J]. Fuel, 2002, 81(5): 691-698.

[17] Babel S., Kurniawan T. A. Cr(VI) Removal from Synthetic Wastewater Using Coconut Shell Charcoal and Commercial Activated Carbon Modified with Oxidizing Agents and/or Chitosan [J]. Chemosphere, 2004, 54(7): 951-967.

[18] Garg V. K., Renuka G., Rakesh K., . Adsorption of Chromium from Aqueous Solution on Treated Sawdust [J]. Bioresource Technology, 2004, 92(1): 79-81.

[19] Pradhan J., Das S. N., Thakur R. S. Adsorption of Hexavalent Chromium from Aqueous Solution by Using Activated Red mud[J]. Journal of Colloid and Interface Science, 1999, 217(1): 137-141.

[20] Namasivayam C., Yamuna R. T. Adsorption of Direct Red 12B by Biogas Residual Slurry: Equilibrium and Rate Processes[J]. Environmental Pollution, 1995, 89(1): 1-7.

[21] Bulut Y., Aydin H. A Kinetics and Thermodynamics Study of Methylene Blue Adsorption on Wheat Shells [J]. Desalination, 2006, 194(1–3): 259-267.

[22] Gupta V. K., Ali I. Utilisation of Bagasse Fly Ash (a Sugar industry Waste) for the Removal of Copper and Zinc from Wastewater[J]. Separation and Purification Technology, 2000, 18(2): 131-140.

[23] Cho H. C., Oh D., Kim K. A Study on Removal Characteristics of Heavy Metals from Aqueous Solution by Fly Ash [J]. Journal of Hazardous Materials, 2005, 127(1–3): 187-195.