Mechanisms and chemistry of dye adsorption on manganese oxides-modified diatomite |
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Authors: | Mohammad A Al-Ghouti Yehya S Al-Degs Majeda AM Khraisheh Mohammad N Ahmad Stephen J Allen |
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Institution: | aRoyal Scientific Society, Industrial Chemistry Centre, P.O. Box: 1438, Al-Jubaiha 11941, Jordan;bSchool of Chemistry, Hashemite University, Zarqa, Jordan;cDepartment of Civil and Environmental Engineering, University College London, Chadwick Building, Gower Street, London WC1E 6BT, UK;dSchool of Chemistry and Chemical Engineering, Queen's University Belfast, David Keir Building, Stranmillis Road, Belfast BT9 5AG, Northern Ireland, UK |
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Abstract: | The investigations into structural changes which occur during adsorbent modification and the adsorption mechanisms are essential for an effective design of adsorption systems. Manganese oxides were impregnated onto diatomite to form the type known as δ-birnessite. Initial investigations established the effectiveness of manganese oxides-modified diatomite (MOMD) to remove basic and reactive dyes from aqueous solution. The adsorption capacity of MOMD for methylene blue (MB), hydrolysed reactive black (RB) and hydrolysed reactive yellow (RY) was 320, 419, and 204 mg/g, respectively. Various analytical techniques were used to characterise the structure and the mechanisms of the dye adsorption process onto MOMD such as Fourier transform infrared (FTIR), X-ray diffraction (XRD) and atomic absorption spectrometry (A.A.). A small shift to higher values of the d-spacing of dye/MOMD was observed indicating that a small amount of the dye molecules were intercalated in the MOMD structure and other molecules were adsorbed on the external surface of MOMD. Two mechanisms of dye adsorption onto MOMD were proposed; intercalation of the dye in the octahedral layers and adsorption of the dye on the MOMD external surface. Moreover, the results demonstrated that the MOMD structure was changed upon insertion of MB and RY with an obvious decrease in the intensity of the second main peak of the MOMD X-ray pattern. |
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Keywords: | Diatomite Modified diatomite δ -Birnessite Reactive dyes Textile effluent Adsorption |
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