Laboratory scale studies on removal of chromium from industrial wastes

作     者：M.A.Baig Mohsin Mir Shazad Murtaza Zafar I. Bhatti 

作者机构：Institute of Environmental Science & Engineering National University of Science & EngineeringInstitute of Environmental Science & Engineering National University of Science & EngineeringInstitute of Environmental Science & Engineering National University of Science & EngineeringInstitute of Environmental Science & Engineering National University of Science & Engineering Rawalpindi PakistanRawalpindi PakistanRawalpindi PakistanRawalpindi Pakistan 

出 版 物：《Journal of Environmental Sciences》 (环境科学学报（英文版）)

年 卷 期：2003年第15卷第3期

页      面：417-422页

核心收录：

学科分类：083002[工学-环境工程] 0830[工学-环境科学与工程（可授工学、理学、农学学位）] 08[工学] 

主　　题：tannery waste effluents reduction precipitation efficiency chromium 

摘      要：Chromium being one of the major toxic pollutants is discharged from electroplating and chrome tanning processes and is also found in the effluents of dyes, paint pigments, manufacturing units etc. Chromium exists in aqueous systems in both trivalent (Cr 3+) and hexavalent (Cr 6+) forms. The hexavalent form is carcinogenic and toxic to aquatic life, whereas Cr 3+ is however comparatively less toxic. This study was undertaken to investigate the total chromium removal from industrial effluents by chemical means in order to achieve the Pakistan NEQS level of 1 mg/L by the methods of reduction and precipitation. The study was conducted in four phases. In phase Ⅰ, the optimum pH and cost effective reducing agent among the four popular commercial chemicals was selected. As a result, pH of 2 was found to be most suitable and sodium meta bisulfate was found to be the most cost effective reducing agent respectively. Phase Ⅱ showed that lower dose of sodium meta bisulfate was sufficient to obtain 100 % efficiency in reducing Cr 6+ to Cr 3+, and it was noted that reaction time had no significance in the whole process. A design curve for reduction process was established which can act as a tool for treatment of industrial effluents. Phase Ⅲ studies indicated the best pH was 8.5 for precipitation of Cr 3+ to chromium hydroxide by using lime. An efficiency of 100 % was achievable and a settling time of 30 minutes produced clear effluent. Finally in Phase Ⅳ actual waste samples from chrome tanning and electroplating industries, when precipitated at pH of 12 gave 100 % efficiency at a settling time of 30 minutes and confirmed that chemical means of reduction and precipitation is a feasible and viable solution for treating chromium wastes from industries.