Bentonite Sodium Modification Test Project

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).