Chemical Investigation and Separation of Chromium from Chrome Cake of BSCIC Tannery Industrial Estate at Hemayetpur, Dhaka, Bangladesh

Abstract

Leather tanning mainly depends on chrome tanning. A huge amount of basic chromium sulfate (BCS) is used in leather tanning. About 60–70% of BCS has been taken by leather and the rest of the amount is discharged as effluent and solid waste. In the Common Effluent Treatment Plant (CETP) of BSCIC Tannery Industrial Estate (Hemayetpur, Savar, Dhaka), the effluent which contained a high concentration of chromium is precipitated as solid chromium hydroxide with other elements which is called a chrome cake. Chrome cake is not exposed directly in the open space due to its toxic effect on human health as well as the environment. Human occupational experience distinctly indicates that, when inhaled, chromium compounds are respiratory tract irritants, resulting in airway irritation, airway obstruction, and lung, nasal, or sinus cancer. It is strongly suggested to extract Cr from the chrome cake before dumping it; otherwise, it will be a potential hazard to the environment. Herein, the chrome cake is characterized by inductively coupled plasma-optical emission spectroscopy (ICP-OES), X-ray fluorescence (XRF), UV-visible spectrophotometer, etc., and develops a method to separate chromium from chrome cake. ICP-OES and XRF analyses show that the total chromium contained in chrome cake is ∼17.45% and 20.7%, respectively. UV-visible spectrophotometer indicates that ∼0.04% of chromium is hexavalent. Afterward, chromium has been separated by using H2SO4 where the optimized concentration was found to be 7%. The separation efficiency of chromium from the chrome cake for optimized condition is obtained at ∼95%.