Uv 2600

The effects of humic acid (HA: CAS: 68131-04-4; 0–10 mg/L) in the presence (aerobic) and relative absence (anaerobic) of oxygen, and hydrogen peroxide (H₂O₂: CAS: 7722-84-1; 0–1 mmol/L) on the mineral transformation were investigated. The oxygen content of aerobic (4 mg/L) and anaerobic (1 mg/L) HA simulated water was measured by a dissolved oxygen electrode. The concentration of total Fe and Fe²⁺ were measured by Inductively Coupled Plasma (ICP) and spectrophotometer at 510 nm (UV-2600, Shimadzu, Japan), respectively.
Batch experiments were carried out using a constant dose of 0.5 g/L (siderite/solution) by adding synthesized siderite (0.025 g) into 50 mL solution. The reaction bottles were placed on a magnetic stirrer with a temperature controller at a stirring rate of 300 rpm. After aging for a set time (1 day and 1 week), the precipitate was freeze-dried for 12 h and collected.
The influence of products generated from mineral transformation on phosphate adsorption was investigated. The desired phosphate concentration (50 mg P/L) was obtained with a pH value of 7, which was prepared by adding 0.2197 g KH₂PO₄ into 1 L deionized water (the pH value was buffered to the neutral condition with 0.1 mol/L NaOH). The phosphate concentration after adsorption in the solution was determined by the molybdenum blue method with a spectrophotometer at 700 nm (UV-2600, Shimadzu, Japan).

The total polyphenol (TP) and total flavonoid (TF) contents were determined as previously described [17 (link)].
The content of TP was measured using the Folin–Ciocalteu method [18 (link)]. The extracts were prepared using 0.1000 g of freeze-dried powder and 10 mL of 80% methanol. An aliquot (0.6 mL) of the extract, 3 mL of Folin–Ciocalteu reagent, and 2 mL of 7.5% Na₂CO₃ were mixed. The mixture was incubated for 60 min in the dark at room temperature, and the TP content was determined by the absorbance at 765 nm with a spectrophotometer (UV-2600, SHIMADZU, Tokyo, Japan). The content of total phenols is expressed as equivalent mg of gallic acid per gram of the dry sample.
The determination of TF was performed following the methodology proposed by the AlCl₃ colorimetric method [19 (link)]. Additionally, 20 mg/mL of the extract was prepared using 60% ethanol. The extract of 2 mL was used with 0.4 mL of AlCl₃ (10%, p/v) and 0.4 mL of 5% NaNO₂. Subsequently, the mixture was vortexed and incubated for 6 min before 4 mL of NaOH (4%) was added to stop the reaction. Finally, the absorbance at 510 nm was measured using a spectrophotometer (UV-2600, SHIMADZU, Tokyo, Japan) using 60% ethanol as a blank. The total flavonoid content is expressed as the equivalent mg of rutin per gram of the dry sample.

UV–VIS spectroscopy was used to monitor yellowing of the films as they were aged. The spectra of the aged and non-aged films were recorded between 800–200 nm with a resolution of 0.5 nm on a UV-2600 Shimadzu (Kyoto, Tokyo). Solid state UV–VIS of SORBACID^® 911 powder was obtained on a Shimadzu UV-2600 in a range of 200–500 nm with BaSO₄ background.