Lead nitrate

Copper nitrate trihydrate, Cu(NO₃)₂·3H₂O; lead nitrate, Pb(NO₃)₂; benzene-1,3,5-tricarboxylic acid, C₆H₃–1,3,5-(COOH)₃, (H₃BTC) 98%; and methanol, CH₃OH 99.5% were all purchased from Merck and Sigma-Aldrich (Darmstadt, Germany).

Anhydrous ferric chloride (FeCl₃), iron (II) sulfate hexahydrate (FeSO₄·6H₂O), cobalt (II) chloride hexahydrate (CoCl₂·6H₂O), lead nitrate (Pb(NO₃)₂), citric acid monohydrate (C₆H₈O₇·H₂O) crystal, copper (II) sulfate pentahydrate (CuSO₄·5H₂O), acetic acid (CH₃COOH) glacial 100%, hydrochloric acid (HCl) fuming 37%, sodium hydroxide (NaOH) pellets, and absolute alcohol, were purchased from Merck, a German company. Formaldehyde (CH₃CHO) solution 37% by weight was purchased from Honeywell Riedel-de Haen Research Chemicals, a German company. Vanillin (C₈H₈O₃) was purchased from BDH Chemicals Ltd., a British company. Cadmium (II) sulfate (3CdSO₄·8H₂O), was purchased from Loba Chemie Pvt. Ltd., an Indian company. Sodium tripolyphosphate (Na₅P₃O₁₀) anhydrous extra pure was purchased from Sisco Research Laboratories Pvt. Ltd., an Indian company. All chemicals used in this research work were of analytical quality and used without further purification. Double-distilled water was used in all the studies for sample synthesis and washing purposes.

Dodecyl amine (98%), tetraethyl orthosilane (TEOS, 98%) and 3-aminopropyl triethoxysilane (APTES, 99%) were purchased from Sigma Aldrich. AR grade 1,5- Diphenylcarbazide (DPC 98%) was obtained from Loba Chemie. Sulphuric acid (98%) and ethanol (99%) were obtained from Rankem. Potassium dichromate (99%), 0.1 N Hydrochloric acid, 0.1 N sodium hydroxide were purchased from Merck. Silica, Mesoporous SBA-15 (< 150 µm particle size and 450–550 m² g⁻¹ surface area, Catalogue number: 806854) was obtained from Sigma Aldrich. Lead nitrate, Copper sulphate pentahydrate, Ammonium ferrous sulphate hexahydrate, Nickel sulphate pentahydrate, Manganese sulphate monohydrate, Chromium(III) nitrate nonahydrate, Magnesium sulphate heptahydrate, Cadmium nitrate heptahydrate, Zinc nitrate hexahydrate, Barium chloride dihydrate were purchased from Merck. All experiments were conducted using ultrapure water obtained from a MilliQ system.

The chemicals used in the present work were of analytical reagent grade and used as received, unless stated otherwise. All solutions were prepared with ultra-pure water (18.3 MΩ cm, Milli-Q systems, Millipore-waters). The nitric acid 65% (suprapur) and the standard stock solutions of mercury nitrate (1,001 ± 2 mg L⁻¹), cadmium nitrate (999 ± 2 mg L⁻¹), lead nitrate (999 ± 2 mg L⁻¹), and zinc nitrate (1,000 ± 2 mg L⁻¹) were purchased from Merck. Cd(II), Pb(II), and Zn(II) solutions were prepared from dilution of the certified standard. Ludox® TM40 [40% (w/w) suspension in water] and LS30 [30% (w/w) suspension in water] colloidal silica (SiO₂) were purchased from Aldrich. Sodium nitrate electrolyte solution (10, 30, and 100 mM), MES [2-(N-morpholino)ethanesulfonic acid] buffer (200 mM), and MOPS [3-(N-morpholino)propanesulfonic acid] buffer (200 mM) were prepared from solids (Merck, suprapur and Merck >99%, respectively). The pH adjustments were performed using nitric acid (Merck, suprapur) and sodium hydroxide (100 mM standard, Merck) solutions.
Potassium thiocyanate, hydrochloric acid, and potassium chloride, all p.a. from Merck, were used to prepare the solution for the re-dissolution of the mercury film. Solutions of ammonium acetate [NH₄CH₃COO (1,000 mM)/CH₃COOH (1,000 mM)] (Merck) were prepared monthly and used without further purification.