This study presents an interesting phenomenon of the simultaneous occurrence of adsorption and synthesis of Mg-Al layered double hydroxide (Mg-Al-LDH) by stirring a precursor in an aqueous solution with methyl orange (MO) as target adsorbate with the precursor prepared by first milling Mg(OH)(2) for 1 h followed by another 3 h milling with Al(OH)(3). The prepared precursor and LDH samples were characterized by a set of analytical methods including X-ray diffraction (XRD), thermogravimetry/differential scanning calorimetry (TG-DSC), and Fourier-transform infrared (FT-IR). The maximum adsorption capacity (Q(m)) of MO by the prepared precursor sample was 1110.2 mg/g, much higher than that from the synthesized LDH sample. Engineering application may be expected from the easy preparation of such precursor as adsorbent to purify the tremendous amounts of dye wastewater.