The origin and application of Zeolite

Zeolite is a natural mineral produced by volcanic ash falling into an alkaline water source and under pressure many years ago. This pressure combination causes Zeolite to form a 3D silica-oxygen tetrahedral structure with a honeycomb structure with pores. It is one of the rare minerals with natural negative charge. The combination of honeycomb structure and net negative charge enables Zeolite to absorb both liquid and compounds. The negative charge is balanced with cations such as calcium, magnesium, potassium, and sodium, and these cations can be exchanged.

About 250,000 years ago, in the Rotorua/Taupo area, intense volcanic activity produced huge volcanic ash. These volcanoes were washed and eroded into lakes, forming sedimentary layers up to 80 meters deep. Subsequent thermal activity in the ground forces hot water (120 degree) upwards through these stratigraphic deposits, transforming clay into soft rock with an ordered internal structure sequence, hence the name Zeolite.

Types of Zeolite

There are about 40 different Zeolite types, and their appearance depends on the conditions during the formation process. The Ngakuru Zeolites located in the Taupo volcanic zone in the central North Island of New Zealand are mainly mordenite and clinoptilolite. The location, duration and intensity of the flow of hot water in the formation determine the degree of thermal change. The deposits near thermal cracks are completely altered and usually have strong mechanical strength, while those farther away are usually poorly altered and can be broken down into constituent clays.

Working principle of Zeolite 

First, the ion adsorption capacity. In the thermal deterioration stage, the amorphous material is washed away from the clay, leaving a 3D framework of aluminum and silica. Due to the unique configuration, they have a high negative charge (cation exchange capacity, usually greater than 100meq/100g). Positively charged cations in the solution (or molecules suspended in the air) can be absorbed into the crystal lattice, and depending on the pH value, the cation concentration and charge characteristics can be released later. This combination of honeycomb structure and net negative charge allows the Zeolite to absorb both liquids and compounds. Zeolite is like a sponge and a magnet. Absorb liquids and exchange magnetic compounds, making them suitable for a variety of purposes, from eliminating odors to cleaning up toxic substances that overflow, to reducing nitrogen and phosphorus leachate on farms.

Second, the physical absorptive capacity. Zeolite has a large internal and external specific surface area (up to 145 square meters/g), which can absorb more liquid. When dry, some of these Zeolite can absorb up to 70% of their own weight in liquid form. For example, in sports lawns, Zeolite will absorb soluble nutrients from the added fertilizer, so that it can meet the needs of plants in the future to absorb water and increase water holding capacity without adversely affecting pore space and permeability.

Post time: Aug-11-2021