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Removal of Chromium (iii) from Tannery Wastewater by Bioaccumulation Method Using Vallisneria Sp. River-weed

Mohammad Arifur Rahman*
Department of Chemistry, Dhaka University, Dhaka-1000, Bangladesh

Sajjad Rajeeb
Department of Chemistry, Dhaka University, Dhaka-1000, Bangladesh

A. M. Shafiqul Alam
Department of Chemistry, Dhaka University, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

The presence of chromium (III) in the wastewater is one of the major concerns for the tannery industry in Bangladesh. In this study the removal of chromium (III) from tannery effluent has been carried out by bioaccumulation method using abundantly available Vallisneria sp. river-weed in river all over Bangladesh. Various factors influencing the uptake of chromium, viz., quantity of river-weed, concentration of chromium (III), pH of the solution and duration of treatment have been optimized. Chemical modifications of the river-weed through pretreatment with H₂SO₄, CaCl₂ and MgCl₂ showed improved removal efficiency of chromium (III). Langmuir isotherm has been fitted for 0.5 g of river-weed. The dynamic method of treatment of protonated river-weed with a chromium (III) solution at a pH of 3.2 for duration of 4 days gave the maximum uptake of about 81%. A similar uptake has been established for commercial chrome tanning wastewater. In addition, the potential reuse of chromium-containing river-weed for the preparation of basic chromium sulfate (tanning agent) has been demonstrated.

Keywords: Chromium (III), Bioaccumulation, Vallisneria sp., River-weed, Tannery Wastewater.

Location: Kumar River, Muksudpur, Gopalganj

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity:

Objectives:

This work aims at the removal of chromium (III) from the tannery wastewater by abundantly available river-weed, Vallisneria s.

Methodology:

River-weed Vallisneria sp. was collected from Kumar River, Muksudpur, Gopalganj. Then the river-weed was washed with distilled water thoroughly to remove dirt and other debris materials. The washed riverweed was then shade-dried and stored in an air tight pack to prevent moisture absorption. The moisture content of the dried river-weed was estimated and was found to be 7±1%. Deionized water was used throughout the work. The industrial wastewater samples were collected from Apex Tannery Dhaka, Bangladesh. Preparation of synthetic Chrome tanning solution A stock solution containing 1000 mg/L of river-weed was prepared using commercial basic chromium sulfate, Cr₂(SO₄)3. 12H₂O. The pH was adjusted to be 3.0-3.5, and the solution was aged for 12 h and stored in a refrigerator (4 °C) temperature. For further experiments, the requisite quantity was taken from the stock solution and made up to the required volume. The pH of the synthetic chromium (III) solution was adjusted accordingly by using either 0.05M H₂SO₄ or 0.05 M NaOH solution. Pretreatment of Vallisneria sp river-weeds The river-weeds were pretreated with various chemicals before contacting them with synthetic chromium (III) solution in attempts to increase their uptake efficiency. The air dried river-weed was treated with 0.2 M H₂SO₄, a 0.25 M solution of CaCl₂, and a 0.25 M solution of MgCl₂ for a period of 10 min under stirring 26. The acid, calcium ion, and magnesium ion treated river-weed was then washed twice with deionized water. Finally, the washed materials were air dried and kept in an airtight pack for further experiments. Adsorption procedure To optimize the maximum uptake conditions for chromium, five trial experiments were carried out for each pretreated sample at varying time intervals. A 50 mL aliquot of 150 mg/L chromium (III) was taken in a 100 mL conical falsk for each trial. Pretreated river-weed was added to each flask and agited in a mechanical shaker. The amount of chromium (III) remaining in the solution was determined using an Atomic Absorption Spectroscopy (Analyst 800, Perkin Elemer, USA). Equilibrium Studies Langmuir adsorption isotherms have been tested for the validity of the chromium (III) uptake behavior of the riverweed. Adsorption isotherms were determined by the treatment of 0.25, 0.5 and 1.0 g of protonated river-weed with 50 mL of 100 mg/L chromium (III) for a contact time of 4 days in a mechanical agitator, respectively. After agitation, the contentents of the flasks were decanted. The concentration of chromium (III) remaining in the solution was determined by Atomic Absorption Spectroscopy

Source of Information: Dhaka Univ. J. Sci. 63(2): 91-96, 2015 (July)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The present study clearly indicates the possibility of using Vallisneria sp. river-weed as a suitable alternative for the removal of chromium from tannery wastewater. The strategy of using Vallisneria sp. river-weed for the removal of chromium from chrome bearing wastewater not only gives a low cost treatment option but also save the aquatic environment from this unabated plants which grow and complete their life cycle in water and cause harm to aquatic environment.

Knowledge Management: Journal