Magnesium chloride hexahydrate

All starting chemicals were obtained commercially without further purification. Magnesium chloride hexahydrate (MgCl₂·6H₂O), sodium hydroxide (NaOH), sodium dihydrogen phosphate (NH₄H₂PO₄), triammonium phosphate ((NH₄)₃PO₄)), ammonia water (NH₃·H₂O), hydrochloric acid (HCl), and glucose are of analytical grade and purchased from Sinopharm Chemical Reagent Co., Ltd. The yeast extract and malt extract are of biotech grade and purchased from Oxoid Ltd. and BBI Life Sciences Ltd., respectively. Deionized water was used in all of the experiments.

Magnesium chloride hexahydrate (MgCl₂·6H₂O, 98%), calcium chloride (CaCl₂, 96%), manganese chloride tetrahydrate (MnCl₂·4H₂O, 99%), zinc chloride (ZnCl₂, 98%), cobalt chloride hexahydrate (CoCl₂·6H₂O, 99%), nickel chloride hexahydrate (NiCl₂·6H₂O, 98%), cadmium chloride (CdCl₂, 99%), copper chloride dihydrate (CuCl₂·2H₂O, 98%), stannic chloride pentahydrate (SnCl₄·5H₂O, 98%), 2-aminoethanol (HO(CH₂)₂NH₂, 99.9%), potassium hydroxide (KOH, 85%), and ethanol (C₂H₅OH, 99.7%) were obtained from Sinopharm Chemical Reagent Co. Ltd. Hydrogen hexachloroiridate (IV) hexahydrate (H₂IrCl₆·H₂O, 99%) was obtained from Alfa Aesar. Ferrous chloride tetrahydrate (FeCl₂·4H₂O) was obtained from Strem. Nafion solution (~5 wt.% in a mixture of lower aliphatic alcohols and water) was obtained from Sigma–Aldrich. The carbon powder (XC72R) was purchased from Vulcan. The deionized water (18 MΩ cm⁻¹) used in all experiments was prepared by passing water through an ultrapure purification system.

Reagent-grade potato starch, polyvinyl alcohol (PVA), and 4,7,10-trioxa-1,13-tridecanediamine (TTDDA) were purchased from Aldrich. Thermoplastic polyurethane (TPU) was supplied by Wanhua Chemical Group Co., Ltd. Reagent-grade N,N-dimethylformamide (DMF), dichloromethane (CH₂Cl₂), trichloromethane (CHCl₃), acetone, tetrahydrofuran (THF), methanol, concentrated nitric acid (HNO₃), and sodium carbonate (Na₂CO₃) were supplied by Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Cadmium chloride hemipentahydrate (CdCl₂·2.5H₂O), cobalt acetate tetrahydrate (Co(Ac)₂·4H₂O), copper acetate monohydrate (Cu(Ac)₂·H₂O), magnesium chloride hexahydrate (MgCl₂·6H₂O), ferric chloride anhydrous (FeCl₃), manganese chloride tetrahydrate (MnCl₂·4H₂O), nickel chloride hexahydrate (NiCl₂·6H₂O), lithium chloride monohydrate (LiCl H₂O), zinc chloride anhydrous (ZnCl₂), and ferrous chloride tetrahydrate (FeCl₂·4H₂O) were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Dialysis bags (molecular weight cut off = 14 000) were purchased from Shanghai Kayon Biological Technology Co., Ltd. Ultrapure water was used in all experiments.

The main agent of the gel was partially hydrolyzed polyacrylamide (HPAM) with a 25% hydrolysis degree and an average molecular weight of 12 × 10⁶ g/mol supplied by Hebei Liancheng Environmental Protection Technology Co., Shijiazhuang, China. The crosslinker was a water-soluble phenolic resin (WSPR) solution with an effective content of 30% provided by Dongying Tongkun Technology Co., Dongying, China. The nano-SiO₂ solution with an effective solid content of 30% and a median particle size of 15 nm for nanoparticles was purchased from Dongying Liuhe Co., Dongying, China. Analytically pure hydroquinone provided by Sinopharm Chemical Reagent Co., Shanghai, China, was also used in the experiment. In addition, analytically pure drugs, such as sodium chloride, potassium chloride, anhydrous calcium chloride, magnesium chloride hexahydrate, sodium bicarbonate, and sodium sulfate from Sinopharm Chemical Reagent Co., Shanghai, China, were used in this study to prepare synthetic saline for the preparation of gels.
To simulate the salinity conditions of formation water in the reservoir, a synthetic brine with a salinity of 12.124 g/L was synthesized using inorganic salts to formulate a gelant. The composition of the synthetic brine is shown in Table 2.

PTs were selected from a phosphorus chemical industry located in Yichang, Hubei province. Magnesium chloride hexahydrate (MgCl₂·6H₂O), aluminum chloride hexahydrate (AlCl₃·6H₂O), iron chloride hexahydrate (FeCl₃·6H₂O), sodium hydroxide (NaOH), hydrochloric acid (HCl) and 4,4′-Diamino diphenylmethane (DDM) were purchased from Sinopharm Chemical Reagent Co., Ltd. EP (production name: E-44) was purchased by Nantong Xingchen Synthetic Material Co., Ltd. (Jiangsu, China). Deionized water was used in all experimentations. The typical properties and specifications of EP and DDM were showed in Table 1.