Mohammad Ali Karimi^{1, 2,}, Abdolhamid Hatefi-Mehrjardi^{1, 2}, Sayed Zia Mohammadi^{1, 3}, Alireza Mohadesi^{1, 3}, Javad Yarahmadi², Asghar Askarpour Kabir², Havva Mahmoodian², Shahla Nezhad Khorasani²

A new adsorbent of alumina-coated magnetite nanoparticles (ACMNPs) modified with cetyltrimethyl ammonium bromide (CTAB) was prepared for the separation/preconcentration of trace silicate from water samples and then determined by spectrophotometry method. Silicate was determined based on the molybdenum blue method, which monitored at λ_max of 830 nm. MNPs and ACMNPs characterized by SEM and VSM. Under the optimal experimental conditions, the preconcentration factor, detection limit, linear range and relative standard deviation of silicate were 70 (for 350 mL of sample solution), 0.040 µg mL⁻¹, 0.8-7.0 µg mL⁻¹ and 2.2 % (for 5.0 µg mL^-1, n=7), respectively. The method was applied to the separation/preconcentration and determination of silicate in tap water, river water and seawater samples with satisfactory results.

separation/preconcentration, silicate, modified alumina-coated magnetite nanoparticles (ACMNPs), molybdenum blue method