Melamine

Melamine, phenol, formaldehyde solution (37–40 wt%), methanol, HCl, NaOH, NaCl, K₂CO₃, KNO₃, NaNO₂, Na₂SO₄, Na₂SO₃, Na₂S, Na₂S₂O₃, K₂Cr₂O₇, Sodium aceticum (NaAc), KF, KCl, KBr, KI, KMnO₄, K₃Fe(CN)₆, K₂FeO₄ and Zn(OH)₂ were provided by Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Quinine sulfate was purchased from Adamas-beta Inc. (Shanghai, China). All chemicals were of analytical grade and used directly without further purification. Ultrapure water (18.2 MΩ cm⁻¹) used in this study was obtained from a Millipore water purification system.

Silver nitrate, polyvinyl pyrrolidone, melamine, and the experimental reagents (Na₂HPO₄·12H₂O and MO) were provided by Sinopharm Chemical Reagent Co., Shanghai Branch, Shanghai, China [44 (link)]. All experimental reagents used were analytically pure and solutions were prepared with ultrapure or deionized water.

Commercially melamine, Hydrogen peroxide (H₂O₂, 30% aqueous solution), and ethanol were purchased from Sinopharm Chemical Reagent Co., Ltd. (China). Boric acid (H₃BO₃) was purchased from STREM CHEMICALS (Fluka, CAS Number: 10043-35-3).

LY-4110 polyether polyol (hydroxyl value: 430 mg KOH per g; viscosity at 25 °C: 2500 mPa s) was purchased from Jiangsu Luyuan New Material Co., Ltd., (Jiangsu, China). LCN-403 polyether polyol (hydroxyl value: 730–780 mg KOH per g; viscosity at 25 °C: 20 000–50 000 mPa s) was purchased from Shandong Lianchuang Energy Saving New Materials Co., Ltd., (Shandong, China). Silicone surfactant (AK-8805) was purchased from Jiangsu Meiside Chemical Co., Ltd., (Jiangsu, China). Polyarylpolymethyleneisocyanate (PAPI) (NCO%: 34.0–35.0; average functionality: 2.8, viscosity at 25 °C: 200 mPa s) was purchased from Wanhua Chemical Group Co., Ltd., (Hubei, China). Ethylene glycol, paraformaldehyde, melamine, urea, N,N-dimethylcyclohexylamine (PC-8), tris(2-hydroxyethyl)amine (TEOA), diethanolamine (DEA) and ammonium chloride (NH₄Cl) were purchased from Sinopharm Chemical Reagent Co., Ltd., (Shanghai, China).

Melamine (Analytical Grade) and NaOH (Analytical Grade) were purchased in Sinopharm Chemical Reagent Co. Ltd, China. Deionized water was used in this study.
g-C₃N₄ was obtained by thermopolymerization of Melamine (10 g) at 550°C for 120 min in a covered crucible under the air, and denoted as MCN. Na and cyano-group co-modified g-C₃N₄ was synthesized by following step: MCN (0.5 g) and NaOH (0.1 g) were grinding for 10 min. Resulting hybrid was heated at 450°C for 120 min under N₂ atmosphere in tube furnace. After the tube furnace cool down, the product was washed by enough deionized water and ethanol and dried. The product was denoted as Na-CMCN.

The sepiolite fiber was purchased from Neixiang Xinglei Sepiolte Co., Ltd., Nanyang, Henan Province, China. Melamine (AR, 99%), methylene blue (BS) and thiourea (AR, 99%) were purchased from Sinopharm Chemical Reagent Co., Ltd., Shanghai, China. Tert-butanol (AR, 99%) and disodium ethylene diamine tetraacetate (EDTA, AR, 99%) were purchased from Xilong Chemical Co., Ltd., Shantou, China. All the chemical reagents were used without further purification. Distilled water was used throughout the experiment.