Color removal from dye-containing wastewater by magnesium chloride

• Published in: Journal of environmental management 2007, Vol.82 (2), p.167-172
• Main Authors: Gao, Bao-Yu, Yue, Qin-Yan, Wang, Yan, Zhou, Wei-Zhi
• Format: Article
• Language: English
• Subjects: adsorption; aluminum sulfate; Animal, plant and microbial ecology; Applied ecology; Applied sciences; Biological and medical sciences; calcium hydroxide; Chemical compounds; chemical precipitation; Coagulation; color; Color removal; Coloring Agents - chemistry; Conservation, protection and management of environment and wildlife; dosage; Dye-containing waste; Dyes; electrostatic interactions; Exact sciences and technology; ferrous sulfate; Fundamental and applied biological sciences. Psychology; General aspects; Hydrogen-Ion Concentration; Industrial Waste - prevention & control; Magnesium chloride; Magnesium Chloride - chemistry; mechanism of action; Pollution; polyaluminum chloride; Textile Industry; textile mill effluents; Waste Disposal, Fluid; wastewater; wastewater treatment; Wastewaters; Water Pollutants, Chemical - chemistry; Water treatment; Water treatment and pollution
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2005.12.019

Color removal by MgCl 2 when treating synthetic waste containing pure dyes was studied. The color removal efficiency of MgCl 2/Ca(OH) 2 was compared with that of Al 2(SO 4) 3, polyaluminum chloride (PAC) and FeSO 4/Ca(OH) 2. The mechanism of color removal by MgCl 2 was also investigated. The experimental results show that the color removal efficiency of MgCl 2 is related to the type of dye and depends on the pH of the waste and the dosage of the coagulants used. Treatment of waste containing reactive dye or dispersed dye with MgCl 2 yielded an optimum color removal ratio when the pH of the solution was equal to or above 12.0. For both the reactive and dispersed dye waste, MgCl 2/Ca(OH) 2 was shown to be superior to MgCl 2/NaOH, Al 2(SO 4) 3, PAC and FeSO 4/Ca(OH) 2 for color removal. A magnesium hydroxide precipitate formed at pH values greater than 12.0, which provided a large adsorptive surface area and a positive electrostatic surface charge, enabling it to remove the dyes through charge neutralization and an adsorptive coagulating mechanism. So, the MgCl 2/Ca(OH) 2 system is a viable alternative to some of the more conventional forms of chemical treatment, especially for treating actual textile waste with high natural pH.