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Removal of Pb and Zn from Industrial Effluent Using Humic Acid

A. Parvin*
Soil and Environment Section, Biological Research Division, BCSIR Laboratories Dhaka, Dr. Qudrat-i-Khuda Road, Dhaka-1205, Bangladesh

S. Hoque
Department of Soil, Water and Environment, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

The present work was conducted to remove Pb and Zn from industrial effluents by coagulating the ions with humic acids. Seven types of effluents were collected from textile, tannery and pharmaceutical industries. Two commercially available humic acids one in a liquid state and another one in a semi-solid state, humic acid extracted from peat were used to remove Pb and Zn from industrial effluents as well as synthetic waste water. Optical property, carbon concentration and coagulation threshold of humic acids were studied. Same carbon concentration (1 x 10-5g L-1) of all the sources was maintained at neutral pH. The values of water soluble Pb and Zn in effluents were 0.000 0.0711 µg/mL and 0.002 - 0.024 µg/mL, respectively. Results indicated that liquid humic acid having E4: E6ratio of 1.2 removed 100% Pb and Zn only from pharmaceutical effluent whereas humic acid extracted from peat having E4: E6ratio of 3.18 completely (100%) removed these metals from pharmaceutical and tannery effluents. Semi-solid humic acid having the lowest E4: E6ratio of 1.07 did not form coagulation with the metals. The performance of humic acid extracted from peat was better than that of commercially available humic acids.

Keywords: Industrial effluents; Lead; Zinc; Humic acids

Location: Biological Research Division, BCSIR Laboratories Dhaka, Dr. Qudrat-i-Khuda Road, Dhaka-1205, Bangladesh

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity: Efluent

Objectives:

This work was carried out to evaluate the efficiency of humic acids of different properties to remove Pb and Zn from different sources of waste water.

Methodology:

Collection and analysis of humic acids Three different sources of humic acids viz commercially available liquid and semi-solid humic acid and also humic acid extracted from peat were used for removal of Pb and Zn. Carbon content of humic acids was determined by Tyurin's method (1931, 1936); coagulation threshold was observed by the method cited by Kononova (1966). The optical density at 465 nm and 665 nm was determined by a Shimadzu Spectrophotometer UV-120-02. For removal of Pb and Zn, the pH and carbon concentration of the humic acids were adjusted at 7 and 1×10-5g /L, respectively. Definite carbon concentration of humic acids was selected based on coagulation threshold of humic acid (Kononova, 1966). (b) Removal Pb and Zn from synthetic waste water using humic acids Different concentrations (20 µg/mL - 40 µg/mL) of individual Pb and Zn solution and their combination were mixed with humic acids into various tubes to remove these metals. The completion of coagulation was observed and the time required was recorded. After coagulation of pure metal solutions with humic acids, the highest (40 µg/mL) and lowest (20 µg/mL) concentrated individual and mixed metal solutions were selected. Then the selected metal solutions were filtered with Whatman No.42 and the remaining metals (Pb and Zn) were determined by Atomic Absorption Spectrophotometer. (c) Analysis of industrial effluent and removal Pb and Zn from industrial effluent using humic acids Seven effluents were collected from textile (Savar, Dhaka), tannery (Hazaribagh, Dhaka) and pharmaceutical (Tongi, Gazipur) industries. For the present study, spot sampling was done. Approximately 2 litre of different effluents was collected in plastic bottles. Total Pb and Zn were extracted by digesting the water sample with nitric acid (HNO₃). Total and water soluble Pb and Zn were measured from digested and raw water sample by Atomic Absorption Spectrophotometer (Model No. AA 240-Varian). To treat effluents, humic acids and different types of effluents were mixed in ratio of 1:1 into different tubes. Then the tubes were shaken well and the coagulation time was observed. After the complete coagulation, the solution was filtered and then the metals present in filtrate were determined by Atomic Absorption Spectrophotometer.

Source of Information: Bangladesh J. Sci. Ind. Res.51(4), 279-284, 2016

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The present study indicated that humic acid has effects on the removal of Pb and Zn. The effects were controversial depending on the types of humic acids. On the basis of the study it should be noted that liquid humic acid completely removed Pb and Zn from pharmaceutical effluent (effluent 5), semi-solid humic acid removed variable amounts of Pb and Zn only from synthetic waste water and humic acid extracted from peat was successfully removed all Pb and Zn from pharmaceutical (effluent - 5) and tennary (effluent - 6 and effluent - 7) effluents. Therefore, the performance of peat originated humic acid for removal of Pb and Zn in effluents was better than that of commercially available humic acids. Compared to effluents, humic acids effectively removed these metals from their high concentrated synthetic waste water. Thus it can be stated that effluents can be treated with humic acids even with elevated concentrations.

Knowledge Management: Journal