I. Test Purpose
The ultimate goal of the bentonite sodium modification test is to transform naturally occurring calcium-based bentonite of varying grades into high-performance sodium-based bentonite products through physical and chemical methods, meeting higher industrial requirements.
Purpose of Sodium Modification:
Performance Improvement: After sodium modification, the swelling capacity, binding property, suspension stability, dispersibility, and thermal stability of bentonite are significantly enhanced. This meets the demand for high-quality sodium-based bentonite in applications such as casting, iron ore pelletizing, drilling fluids, and waterproof blankets.
II. Material Preparation
 
1. Basic Raw Materials:

• Raw material: 10-20 kg of bentonite raw ore
• Chemical reagents: Sodium carbonate (Na₂CO₃) or sodium hexametaphosphate ((NaPO₃)₆)
• Deionized water / distilled water

2. Equipment List:

• Balance
• Stirring device
• Centrifuge
• Measuring cylinder
• Drying oven (with temperature control, 105±5°C)
• Grinding tools
• Standard sieve (200-mesh or 325-mesh)

3. Testing Instruments:

• X-ray diffractometer (XRD)
• Methylene blue absorption test device
• Colloid value measurement device
• Swelling capacity measurement device
• Cation exchange capacity (CEC) measurement equipment

III. Granulation Test Plan
1. Sodium Modification Test
The principle of sodium modification is to replace exchangeable Ca²⁺ and other cations between montmorillonite layers with Na⁺ ions:
Ca-Mont + Na₂CO₃ → 2Na-Mont + CaCO₃↓
(1) Sodium Modification Reaction:
Weigh multiple portions (e.g., 5 portions) of purified bentonite samples, 20.00 g each.
Prepare Na₂CO₃ solutions of different concentrations (e.g., 2%, 4%, 6%, 8%, 10%, based on the dry weight of bentonite), with a solid-liquid ratio maintained at 1:2 to 1:3 (a thicker slurry facilitates ion exchange).
Slowly add the bentonite powder into the sodium modifier solution while stirring vigorously to form a uniform slurry.
(2) Aging Treatment:
 
Seal the sodium-modified slurry and age it at room temperature for 24-72 hours. Stir periodically every few hours to ensure thorough and complete reaction. Aging is a critical step in sodium modification.
(3) Post-Treatment:
After aging, dilute the slurry with a large amount of deionized water and stir at high speed to remove excess Na⁺ and reaction-generated CaCO₃.
Perform centrifugal separation and discard the supernatant. Repeat this washing process 2-3 times.
Dry the obtained sodium-modified bentonite at 105°C, grind it, and sieve it through a 200-mesh sieve to obtain the final sodium-modified product. Store it in a sealed container.
(4) Evaluation of Sodium Modification Effect:
Performance Testing: Conduct colloid value and swelling capacity tests on products with different sodium modifier dosages. The Na₂CO₃ dosage corresponding to the best performance is identified as the optimal sodium modifier amount.
Structural Characterization: Perform XRD testing on the optimal sample to observe whether the d(001) interlayer spacing is reduced to the typical value of sodium-based bentonite (~1.25 nm) and compare it with the original sample.
Chemical Analysis: Analyze the changes in Na⁺ and Ca²⁺ content after exchange through CEC measurement or atomic absorption spectroscopy (AAS).