Sodium acetate

The raw sludge was obtained from a thickening tank of a sewage treatment plant located at Wenjiang district, Chengdu city, China. The raw sludge samples were stored at 4 °C before usage, and all batch experiments were completed within one week. The main properties of raw sludge are listed in Table 1.
Ferrous sulfate heptahydrate (FeSO₄·7H₂O), sodium hydroxide (NaOH), potassium sodium tartrate tetrahydrate (C₄H₄KNaO₆·4H₂O), anhydrous sodium carbonate (Na₂CO₃), copper sulfate pentahydrate (CuSO₄·5H₂O), potassium bromide (KBr), sulfuric acid (H₂SO₄), glucose (C₆H₁₂O₆), tert-butyl alcohol (TBA), phenol, and sodium acetate (CH₃COONa) were purchased from Chengdu Kelong Chemical Reagent Co., Ltd. (Sichuan, China). Potassium periodate (KIO₄), bovine albumin (BSA), Folin–phenol reagent, ascorbic acid (AA), L-histidine, nitro blue tetrazolium chloride (NBT), phenol, and methanol (MeOH) were obtained from Shanghai Aladdin Biological Technology Co., Ltd. (Shanghai, China). All chemicals were analytically pure and used without further purification.

The experimental material was Ziyan tea fresh leaves from Mingshan District, Ya’an City, Sichuan Province, and the material tested was one bud and three leaves. Stability test materials, mainly including sodium chloride, potassium chloride, calcium chloride, magnesium chloride, aluminum chloride, zinc sulfate, copper sulfate, and sodium acetate were purchased from Chengdu Kelong Chemical Reagent Factory (Chengdu, China). Wall materials mainly included maltodextrin, gum arabic, and soybean isolate protein, and were purchased from Xilong Chemical Co., Ltd. (Chengdu, China). All other chemicals were of analytical purity and purchased from Chengdu Kelong Reagent Factory. Distilled water was used throughout the experiments.