Determination of Anions and Cations in Petroleum Wastewater Using NovaChrom Chromatographic Columns

Ion chromatography (IC) offers high sensitivity and high selectivity, enabling the accurate determination of low-concentration toxic and hazardous ions in petroleum wastewater, such as heavy metal cations and high-concentration chloride (Cl⁻). This technology provides accurate data for compliant wastewater discharge, effectively mitigates environmental risks, and ensures that enterprises meet regulatory requirements. By enabling rapid analysis of ionic composition and concentration variations in wastewater, the technique provides a scientific basis for adjusting chemical dosing in treatment processes and preventing equipment scaling and corrosion, ultimately contributing to cost reduction and operational efficiency. In pollution source tracing and emergency response, its high-efficiency detection capability enables rapid identification of contamination sources and real-time capture of concentration mutation signals, buying critical time for emergency response actions. Furthermore, this technology can provide reliable data for wastewater reuse and the recovery of valuable ions, thereby promoting resource recycling and enhancing the economic benefits of enterprises.

In this study, a NovaChrom chromatographic column and a Wayeal ion chromatograph were employed for the determination of anions and cations in petroleum wastewater. The testing process was simple, the test results were stable, and met the testing requirements. This study provides a practical reference for the determination of anions and cations in petroleum wastewater by ion chromatography.

Keywords: ion chromatography column; petroleum wastewater; anions; cations; halide ions; strontium; barium; iodine.

1. Experiment

1.1 Instrument and Reagents

Ion chromatograph: Wayeal ion chromatograph, equipped with a conductivity detector.

Anion chromatographic column: HS-5A-P3, 4.0 × 250mm;

Anion guard column: HS-5AG, 4 × 30mm;

Cation chromatographic column: MS-5C-P1, 4.6 × 250mm;

Cation guard column: MS-5CG, 4 × 30mm;

Pretreatment cartridges: RP cartridge, Na cartridge;

Chloride standard solution (1000mg/L);

Bromide standard solution (1000mg/L);

Iodide standard solution (1000mg/L);

Sodium standard solution (1000mg/L);

Potassium standard solution (1000mg/L);

Magnesium standard solution (1000mg/L);

Calcium standard solution (1000 mg/L);

Strontium standard solution (1000mg/L);

Barium standard solution (1000mg/L);

Disposable syringe (2mL);

Aqueous syringe filter (0.45μm);

1.2 Sample Pretreatment

1.2.1 Sample Pretreatment for Anion Analysis

The sample was first filtered through a 0.45μm aqueous membrane filter. The filtrate was then passed sequentially through an RP cartridge and a Na cartridge for purification, and finally diluted 1000-fold and 50-fold before analysis.

1.2.2 Sample Pretreatment for Cation Analysis

The sample was first filtered through a 0.45μm aqueous membrane filter. The filtrate was then passed through an RP cartridge for purification, and finally diluted 500-fold and 50-fold before analysis.

1.3 Instrument Operating Conditions

1.3.1 Operating Conditions for Anion Analysis

Column temperature: 30°C;

Conductivity cell temperature: 35°C;

Eluent: 21–40mM KOH gradient elution;

Flow rate: 1.0mL/min;

Injection volume: 25μL

1.3.2 Operating Conditions for Cation Analysis

Column temperature: 40°C;

Conductivity cell temperature: 45°C;

Eluent: 12mM MSA (methanesulfonic acid);

Flow rate: 1.0mL/min;

Injection volume: 25μL

2. Result and Discussion

2.1 Anion Testing

2.1.1 Standard Curve Calibration

Table 1

Fig 1. Overlaid Chromatograms of Standard Curve Calibration Solutions

Table 2. Linearity Data for Anions

2.1.2 Sample Test

Fig 2. Chromatogram of Chloride in the Sample Diluted 1000-fold

Fig 3. Chromatogram of Bromide in the Sample Diluted 50-fold

Fig 4. Chromatogram of Iodide in the Sample (without dilution)

Table 3. Analytical Results of Sample Testing

Note: Due to excessive impurities in the undiluted sample, only three injections were performed for the determination of iodide concentration. The RSDs of retention time for chloride and bromide were 0.035% and 0.033%, respectively, and the RSDs of peak area were 0.339% and 0.866%, respectively.

2.2 Cation Testing

2.2.1 Standard Curve Calibration

Table 4

Fig 5. Overlaid Chromatograms of Standard Curve Calibration Solutions for Cations

Table 5 Linearity for Cations

2.2.2 Sample Testing

Fig 6. Chromatogram of Sodium and Calcium Ions in the Sample Diluted 500-fold

Fig 7. Chromatogram of Potassium, Magnesium, Strontium, and Barium Ions in the Sample Diluted 50-fold

Table 6 Sample Test Data