Mechanisms and chemistry of dye adsorption on manganese oxides-modified diatomite.
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 delta-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 204mg/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.
Al-Ghouti
Mohammad A
MA
Royal Scientific Society, Industrial Chemistry Centre, P.O. Box: 1438, Al-Jubaiha 11941, Jordan. mghouti@rss.gov.jo
Al-Degs
Yehya S
YS
Khraisheh
Majeda A M
MA
Ahmad
Mohammad N
MN
Allen
Stephen J
SJ
D000327:Adsorption; D004396:Coloring Agents / Q000737:chemistry*; D007692:Diatomaceous Earth / Q000737:chemistry*; D007220:Industrial Waste; D017895:Manganese Compounds / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D013054:Spectrophotometry, Atomic; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
D004396:Coloring Agents; D007220:Industrial Waste; D017895:Manganese Compounds; D010087:Oxides; D007692:Diatomaceous Earth; C027424:manganese oxide; C033787:diatomite