Structural and morphological characterization of scale deposits on the reverse osmosis membranes: Case of brackish water demineralization station in Morocco

Abstract

Present study reports on the characterization of the fouling of reverse osmosis process membrane at brackish water demineralization station of Khang Lahmam in Tan Tan, Morocco, which clearly revealed difficulties related to the loss of performance of the membranes. Thus, to highlight a new anti-fouling method, a well-developed reverse osmosis module was autopsied and analyzed. The scale samples over membrane surfaces were collected from different sites and were further characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersion spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence spectrometry (XRF)and thermogravimetric and differential scanning calorimetry analysis (TG/DSC).Obtained results were thus clearly indicated that the scales were uneven over membrane sites, and the regions near feed were found to be more seriously affected. Moreover, the integrated DRX, EDS and XRF spectra suggested that the scale was mainly inorganic matter (Ca, O, and C). In addition, the FTIR spectra and TG/DSC analysis of clogged reverse osmosis membranes reveal that the constituents of scale were mainly inorganic compounds with a significant loss of mass. Moreover, the SEM images indicated that the scale deposited samples were crystalline, and then the mapping images clearly revealed the uniformity of elemental distribution over the scale. Finally, it was concluded that there is a mineral fouling (scaling) and the different tartar samples were found to have similar nature, along with indicating the calcite type calcium carbonate (CaCO3) crystal deposition over reverse osmosis membrane surface sites.