Determination of trace elements in refined brine by HK-8100 single-channel scanning spectrometer

HK-8100

Determination of trace elements in refined brine by single-pass scanning spectrometer

The ionic membrane alkali process is an advanced method of producing caustic soda. It offers low production costs, reduced energy consumption, and is environmentally friendly. This technique ensures high concentration and purity of sodium hydroxide, making it the most advanced alkali production process globally. The quality of refined brine is crucial to this technology, as it significantly affects the lifespan of the ion-exchange membrane, cell voltage, current efficiency, and overall product quality.

Impurities such as Ca²⁺, Mg²⁺, Sr²⁺, Fe²⁺, Al³⁺, Ni²⁺, and I₂, along with SO₄²⁻, are considered first-class contaminants. When these ions enter the membrane in their ionic form, they deposit on the membrane as hydroxides, sulfates, or silicates, potentially clogging its pores. Ba²⁺ can affect the activity of the anode, while Si⁴⁺, when combined with Ca²⁺, Sr²⁺, and Al³⁺, may cause plasma bonding, reducing current efficiency. These effects become more significant when multiple ions coexist.

Therefore, developing a fast, sensitive, and accurate method for determining trace elements in refined brine is essential for the ionic membrane alkali production process. Inductively coupled plasma optical emission spectrometry (ICP-AES) has become the primary tool for elemental analysis due to its low detection limit, wide linear range, and ability to simultaneously detect multiple elements. Computer-controlled single-pass scanning ICP-AES systems offer flexibility and are widely used in quantitative elemental analysis.

Experimental Setup:

(1) HK-8100 Inductively Coupled Plasma Emission Spectrometer

(2) High-salt nebulizer

(3) Swirl chamber

(4) Nitric acid (extra pure grade)

(7) Standard solutions for Ca²⁺, Mg²⁺, Sr²⁺, Fe²⁺, Al³⁺, Ni²⁺, Mn²⁺, and SiO₂

(8) Mixed standard solution

Instrument Working Conditions:

Generator power: 1150 W

Auxiliary gas flow: 1.0 L/min

Nebulizer pressure: 2.07 kPa

Experimental Method:

Under optimal working conditions, a series of 100 mL polyethylene volumetric flasks were prepared with 50 mL of sample solution. Then, 2 mL of nitric acid was added, followed by 0.2, 0.5, and 1.0 mL of SiOâ‚‚ standard solution. The volume was adjusted to 100 mL using secondary deionized water. The resulting standard solutions were then analyzed.

Results and Discussion:

In the HK-8100 spectrometer, the spectral line library was carefully selected. The line with the second highest intensity, minimal interference, low background, and high signal-to-noise ratio was chosen as the analytical line. Background correction points were also selected for each line to account for baseline irregularities. For aluminum, the most sensitive ultraviolet line at 167.1 nm was used. Argon purging was performed for 72 hours before measurement to ensure accuracy. Further experiments confirmed that the second sensitive line at 396.1 nm also provided excellent results.

Interference and Elimination:

To eliminate spectral interference from sodium ions and other elements, blank experiments, group measurements, standard addition methods, and simultaneous background subtraction techniques were employed. This approach effectively addressed the challenge of matching the high sodium chloride matrix in brine, enabling precise trace element determination that other methods struggle to achieve.

Company Introduction:

Beijing Huake Yitong Analytical Instrument Co., Ltd. is a professional manufacturer of inductively coupled plasma optical emission spectrometers. As a high-tech enterprise, the company integrates research, development, production, sales, and technical services. The HK-8100 and HK-2000 models are based on existing technologies, incorporating the latest international advancements to deliver superior performance.

Key Specifications:

1. Wavelength range: 180–800 nm (2400 lines/mm) or 180–500 nm (3600 lines/mm)

2. Resolution: ≤0.006 nm in the 180–500 nm range

3. Wavelength accuracy and repeatability: ≤0.02 nm and ≤0.003 nm, respectively

4. Scanning step: 0.0004 nm

5. Precision: RSD ≤1.5%

6. Stability: RSD ≤2.0%

7. Detection limit: PPb level

8. Element analysis range: 72 metal elements and some non-metals like B, P, Si, Se, Te

9. Linear range: Over 7 orders of magnitude

10. Analysis speed: Up to 20 elements per minute

11. Certification: National Measurement Instrument Type Approval (Class A)