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Removal of Chromium from Tannery Effluent Using Chitosan-charcoal Composite

SHAJAHAN SIRAJ
Bangladesh Council of Scientific and Industrial Research (BCSIR), Dhanmondi, Dhaka-1205, Bangladesh

MD. MONARUL ISLAM *
Bangladesh Council of Scientific and Industrial Research (BCSIR), Dhanmondi, Dhaka-1205, Bangladesh.

PROKASH CHANDRA DAS
Department of Chemistry, Jagannath University, Dhaka-1100, Bangladesh.

SHAH MD. MASUM
Department of Applied Chemistry & Chemical Engineering, University of Dhaka, Dhaka-1000, Bangladesh

ISMET ARA JAHAN
Bangladesh Council of Scientific and Industrial Research (BCSIR), Dhanmondi, Dhaka-1205, Bangladesh.

MD. AMINUL AHSAN
Bangladesh Council of Scientific and Industrial Research (BCSIR), Dhanmondi, Dhaka-1205, Bangladesh.

MD. SHAJAHAN
Department of Chemistry, Jagannath University, Dhaka-1100, Bangladesh.

Abstract/ Executive Summary:

Chitosan-charcoal composite was applied as a media to treat tannery effluent. The composite was prepared by a simple solution-evaporation method and the morphology of the prepared composite was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Adsorption of chromium (Cr) was investigated by varying the contact time between adsorbent (Cr) and composite, pH of solution and dose of composite. The concentration of Cr was determined by atomic absorption spectroscopy (AAS). Removal of Cr was found to be dependent on pH and maximum adsorption was observed at pH 4.0. The optimum dose and contact time for Cr treatment was 40 g/L and 250 minutes respectively. The results showed that prepared composite can be used efficiently for the treatment of tannery wastewater containing chromium.

Keywords: Charcoal; Composite

Location:

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity: Heavy metal

Objectives:

The aim of this study was to develop a biocomposite of chitosan coated on charcoal for the removal of Cr from industrial effluents

Methodology:

Raw Materials Shrimp shell was collected from Khulna, Bangladesh. The shell was scraped free of loose tissue, washed with cold water and dried in the sun for 2 days. Then the shell was grounded to powder. Dried ground shell was placed in opaque plastic bottles and stored at an ambient temperature for use. Activated charcoal was purchased from Merck, India and tannery wastewater was collected from Hazaribag tannery industrial area, Dhaka, Bangladesh. Preparation of chitosan and chitosan gel Chitosan (DD=72%) was obtained from shrimp shell and characterized as reported earlier10. About 50 g of chitosan was slowly added to 1000 mL of 10 wt% oxalic acid with constant stirring. The mixture was heated to 40-50ºC to facilitate mixing. At room temperature, the chitosan-oxalic acid mixture formed a whitish viscous gel14. Preparation of chitosan-charcoal composite About 250 g of the charcoal was slowly added to the chitosan gel and stirred continuously. The mixture was then dried slowly at 55-60ºC to get the product. The gel coated charcoal was then washed with deionized water and dried. The chitosan-charcoal composite was then characterized by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). X-ray diffraction (XRD) XRD patterns of composite were recorded on Philips PWO4 Xpert pro X-ray diffractometer. The X-ray source was Cu Kα with a voltage of 40 kV and a current of 30 mA. The measurement was in the scanning range of 5–70 at a scanning speed of 50 s-1. Scanning Electron Microscope (SEM) A HITACHI S-3400N, Japan (BSE) scanning electron microscope (VP-SEM) was used to examine the microstructure of chitosan and composite without any coating to the sample surface and the image was taken at an accelerated voltage of 15.0kV. Preparation of chromium (Cr) stock solution Potassium dichromate (K₂Cr₂O₇) (Merck, Germany) was used as the source of Cr (VI) in the solution. 0.707g of K₂Cr₂O₇ was dissolved in de-ionized water and was diluted to 500mL in a volumetric flask to prepare 500 ppm Cr stock solution. Then the solution was further diluted for treatment. Preparation of standard chromium (Cr) solution 0.2, 0.5, 1.0, 2.0, 3.0, and 4.0 ppm standard solutions of Cr were prepared for calibration by appropriate dilution of a 1000 ppm of chromium (stand scharlau, spain) solution. Quality control standards, duplicate samples and blanks were analyzed with samples from effluents to ensure the quality of analysis. Air acetylene flame was used during analysis of Cr by FAAS. For estimation of Cr atomic absorption spectrophotometer (AA-240FS Varian, Australia) was used. Comparison of Cr removal capacity of charcoal, chitosan and prepared composite To compare the Cr removal capacity of charcoal, chitosan and the composite, known amount (20 g/L) of chitosan, activate charcoal and composite were added to 10 ppm of Cr solution in three different polyethylene tubes. The metal solution was initially adjusted at pH 4.00 by adding 0.1M HCl or 0.1M NaOH. The tubes were shaken well and centrifuged (Digisystem Laboratory Inc.). The contact time of standard chromium solution and adsorbent was 4 hours. Treatment of tannery waste water by prepared composite Two samples were collected from Hazaribagh tannery industrial area and were analyzed in the laboratory. The samples were treated with the composite materials prepared in this research at optimized condition (pH, contact time & dose) determined by previous experiments.

Source of Information: Journal of Bangladesh Chemical Society, Vol. 25(1), 53-61, 2012

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

A chitosan-charcoal composite was prepared and characterized by SEM and XRD. The composite was used to remove Cr from aqueous solution and an optimum condition was found for maximum removal which was used later for the treatment of tannery effluents. The Cr removal efficiency of the composite was more than 90%.

Knowledge Management: Journal