Nessler s reagent

All chemical reagents for the experiment (such as (NH₄)₂SO₄, Na₂SO₄, NaCl, H₂SO₄, NaOH, N-(1-naphthyl)-ethylenediamine dihydrochloride, Nessler’s reagent, potassium sodium tartrate tetrahydrate etc) were purchased from Sinopharm Chemical Reagent Co., Ltd (Shanghai, China). Total and free chlorine reagent sets were bought from HACH Company (Loveland, CO, USA). Vermiculite was provided by Nan Yu Minerals Factory (Lingshou county, Hebei Province, China). Before use, vermiculite was washed by deionized water to remove possible salts and impurities during manufacture, and dried in the hot air oven at 50 °C.

Copper nitrate trihydrate (Cu(NO₃)₂·3H₂O, 99%), 1,4-benzenedicarboxylic acid (H₂BDC, 98%), sodium nitrate (NaNO₃, 99%), sodium nitrite (NaNO₂, 99%), ammonium chloride (NH₄Cl, 99%), sodium sulfate (Na₂SO₄, 99%), acetylene black, acetonitrile (CH₃CN, 99%), NaOH (96%), HCl (36-38%), N, N-dimethylformamide (DMF, 99.5%), sulfamic acid, p-aminobenzenesulfonamide, N-(1-Naphthyl) ethylenediamine dihydrochloride, phosphoric acid, trichloromethane (CHCl₃, 99%), and Nessler's reagent are from Sinopharm Chemical Reagent Co. Ltd. LiF (98.5%, 325 mesh, Alfa Aesar), Ti₃AlC₂ (98%, 400 mesh, 11 Technology Co. Ltd.), and all reagents were of analytical grade, and solutions were prepared by using ultrapure water (specific resistance of 18 MΩ cm).

Temperature, dissolved oxygen (DO), pH, and total ammonia nitrogen (TAN) of water were examined and recorded before and after the transport process directly. Water temperature, DO and pH were determined in situ by HQ40D Water Analyzer (Hach, Loveland, USA). For TAN, water samples were collected from all the bags before and after transport, and were immediately saved at −20°C until analysis. Water TAN content was assayed using the method of Nessler's reagent spectrophotometry (HJ 535-2009, National Environmental Protection Standard of the People's Republic of China). For the analysis of TAN, water sample was filtered through filter paper (Waterman) and then were added Nessler's reagent (Sinopharm Chemical Reagent Co., Ltd, Shanghai, China) to produce the light reddish brown complex compound. The absorbance of such complex compound is proportional to the ammonia nitrogen contents. TAN content was determined according to the absorbance at the wavelength of 420 nm. Moreover, these parameters were recorded for the control and the treatment groups during the period after transport from 1 day to 7 days (the recovery period). Water quality parameters during the recovery period were remained within acceptable conditions for channel catfish.