## What is the formula to calculate ion exchange capacity?

The IEC is defined as the milliequivalent of ion-exchange groups included in a 1-g dry membrane (meq (g dry membrane)− 1). The concentration of ion-exchange groups is obtained by dividing the IEC with the water content in a 1-g dry membrane (meq (g H2O)− 1).

### What is equivalence of ion exchange?

Equivalents refers to the equivalent weight (EW) of the substance expressed in grams (or meq in milligrams [mg], which is the molecular weight (MW) divided by the valence. Calcium (Ca), for instance has a molecular weight of 40 and is divalent (2) so the EW is 20 (40/2 = 20).

How will you measure ion exchange capacity of resin?

Total capacity is actually determined on a dry-resin basis as meq/dry gm and converted to wet values (meq/mL) based on moisture content of the resin. Tests are typically run with H+/Na+ exchange rather than Ca++/Na for cation. Ion exchange systems work by exchanging ions on a one-for-one equivalency basis.

What is total exchange capacity?

The total number of cations a soil can hold–or its total negative charge–is the soil’s cation exchange capacity. The higher the CEC, the higher the negative charge and the more cations that can be held. CEC is measured in millequivalents per 100 grams of soil (meq/100g).

## How cation exchange capacity is measured?

Cation-exchange capacity is measured by displacing all the bound cations with a concentrated solution of another cation, and then measuring either the displaced cations or the amount of added cation that is retained.

### What is MEQ 100g?

The higher the CEC, the higher the negative charge and the more cations that can be held. CEC is measured in millequivalents per 100 grams of soil (meq/100g). A meq is the number of ions which total a specific quantity of electrical charges.

How is CEC measured in the lab?

Cation exchange capacity is measured by one of several standard methods where all adsorbed cations in a soil are replaced by a common ion (such as NH4+) and then the amount of adsorbed common ion is determined.

Does CEC increase with pH?

The CEC of soil organic matter and some clay minerals varies with pH. Generally, the CEC is lowest at soil pHs of 3.5 to 4.0 and increases as the pH is increased by liming an acid soil, as shown in Figure 2. Because CEC may vary considerably with soil pH, it is a common practice to measure a soil’s CEC at a pH of 7.0.

## How are ion exchangers classified?

Ion exchange resins are classified as cation exchangers, which have positively charged mobile ions available for exchange, and anion exchangers, whose exchangeable ions are negatively charged.

### What is FMA and EMA?

The equivalent mineral acidity, EMA is equal to the sum of equivalent concentration of sulphate, chloride and nitrate. It is also called sometimes as Total Mineral Acidity. Free Mineral Acidity (FMA) Free mineral acidity is equal to (EMA – Sodium leakage).

What is free mineral acidity?

Free Mineral Acidity (FMA) is the sum of the chloride, sulfate, nitrate which are in the acid form, i.e. HCl, H2SO4, HNO3, respectively. As the sodium ion increases in the effluent of the SAC resin at exhaustion there will be a corresponding decrease in FMA.

What is the unit of CEC?

The cation exchange capacity (CEC) of a soil is measure of the negative charge of the solid phase of a soil balanced by exchangeable cations. This negative charge is usually expressed in milliequivalents per 100 grams (meq/100 g) of soil. The CEC of a silt loam soil, for example, might be 18 meq/100 g.

## Why does pH affect CEC?

The higher the pH of the surrounding solution, i.e. higher OH ion concentration more H ions are attracted from the OH bonds of the clay structure and the higher the CEC of the clay.