Indeed, the spectrum of the formed ad-sorbent showed significant peaks: (i) at 2980 cm− 1 corresponding to the carbon chain ν(C\H) attached to the inorganic matrix [23,24], and (ii) around 1554 cm−1 and 1600 cm−1 corresponding to the C_C and C_N vibrations respectively [25] assigned to the immobilized Schiff base on the porous silica.