Fig. 4: SEM images of RO membrane surface after gypsum scaling experiments.

RO membrane surface after operation with 25 mM Na₂SO₄ and CaCl₂ + 0.5 mg TOC L⁻¹ of PAA antiscalant and its low and high MW fractions. a Without antiscalant, b commercial PAA, c low MW PAA, d High MW PAA; (Magnification = 500×; 20 µm).