China’s bentonite industry has room to grow

By Albert Li
Published: Monday, 25 January 2016

China is believed to host the world’s largest reserves of calcium bentonite, but a lack of sophisticated beneficiation technology has kept the sector’s value low. Albert Li, IM Analyst, discovers how some of the country’s top researchers are seeking to tackle this issue with new technology.

China’s bentonite industry has plenty of room for improvement. Although there is little in the way of reliable data illustrating Chinese production of the clay mineral, used principally in drilling muds, cat litter and iron ore pelletisation, the US Geological Survey’s (USGS) most recent Mineral Yearbook on clays estimates that China was one of the world’s top bentonite producers in 2013.

According to professor Dongsheng Lei of the Suzhou SINOMA Design and Research Institute of the Nonmetallic Minerals Industry Co., China has proven bentonite reserves of around 2.4bn tonnes, or 60% of the world’s total, with deposits distributed across 23 provinces (the main producing provinces include Liaoning, Inner Mongolia, Anhui, Jiangxi, Hubei, Henan, Shandong, Guangxi and Zhejiang).

The USGS estimates that global production of bentonite in 2013 was roughly around 12m tonnes in 2013, down 8% from 13m tonnes in 2012. In a sector where the US and Greece are among the dominant suppliers of high quality bentonite to the global market, China’s share of high-end output is slimmer than it could be.

In a presentation discussing the clays sector delivered at the China International High Tech Development Association Conference, held in Jian, Shandong province in December 2015, professor Zeming Zhang from the China University of Geosciences said that Chinese bentonite producers needed to do more to enhance the value of the industry.

Overall, 93% of China’s bentonite output is consumed as low value-added products, with just 7% classified as high value material. 

One of the problems is the low level of sophistication of much of China’s manufacturing technology, meaning that versatile and potentially valuable bentonite is used in low value applications, for which companies outside China are able to substitute cheaper minerals such as montmorillonite, diatomite and attapulgite. China’s domestic rubber and mineral filler industries alone each consume around 9.1m tpa bentonite, Zhang said.

Chinese bentonite research

Bentonite is a clay formed from the alteration of volcanic ash and is composed mainly of smectite minerals, usually montmorillonite. Sodium, or swelling, bentonite, can absorb several times its dry mass in water, and it is this property which underpins the mineral’s wide application field (see box). The majority of the bentonite found in China is the less commercially useful calcium, or non-swelling material, also referred to as cation-type bentonite.

The grades of calcium bentonite produced in China cannot compete on quality and performance with products from major US and Italian producers.

Zhang believes that Chinese bentonite has the potential to be used in paints, inks, rubber, plastics and waste water treatment, but there has been a lack of development to further the minerals’ application in these markets. 

Spotting an opportunity, Zhang is leading a team at the China University of Geosciences, which she claims have made some breakthroughs and filed patents for new bentonite technologies. 

In the plastics industry alone, she predicts bentonite demand to rise to around 5m tpa. Laboratory tests to see whether high purity bentonite can be used as a source of auxiliary agents for dry powder cement mortar have been successful, Zhang said, although use of the clay in oil-based and anti-salt drilling muds has so far not been achieved on a large scale.

Professor Lei calculates that current Chinese bentonite consumption exceeds the 5m tpa mark, with 2.2m tpa going into the metal pelletisation market, 1.5m tpa going into machine casting, 500,000 tpa consumed by drilling muds, 300,000 tonnes going into activated clays and the remaining 500,000 tonnes being taken up by other, smaller markets. 

For Lei, the key to upgrading the value of China’s bentonite industry lies in developing better purification technology. He and his team at SINOMA are working on two new processing methods, one dry and one wet, which they hope will result in increased output of high purity bentonite. 

The wet method is better at producing high grade montmorillonite, which is essential for products such as fine casting coatings, inorganic gels and nano clays. Whereas traditional wet methods yield a montmorillonite content of around 50-70%, Lei claims that SINOMA’s method can increase this to 95-98%.

The dry method the institute is working on is suitable for producing material with a low montmorillonite content, of around 50-60%, at a reduced production cost compared to the wet method, making it suitable for less lucrative markets such as iron ore pelletisation, drilling muds and making waterproof blankets.

For iron ore pelletisation-making technology, because bentonite is hydrous alumino-silicate mineral, its silicon dioxide (SiO2) and aluminium oxide (Al2O3) contents can reach up to 70%, while impurities like potassium oxide (K2O) and sodium oxide (Na2O) can be as high as 3%. These impurities lower the grade of the final pellet, increase energy consumption and slag discharge during smelting and make the process more polluting. 

At present, in China, bentonite accounts for 3% of the composition of iron ore pellets. If this proportion can be reduced to 1%, then the grade if the finished pellet will increase by 0.6%, Lei explained, adding that his team was developing a new binder that can reduce bentonite usage to 1-1.5% of iron ore pellets.

SINOMA is also working on other technologies for higher purity bentonite that will result in less of it being used in producing activated clays, thereby saving on production costs and cutting pollution.

Uses of bentonite

Pet waste absorbents (cat litter)

Adhesives

Animal feed

Drilling mud

Fillers and extenders

Foundry sand

Iron ore pelletising 

Waterproofing and sealing

Civil engineering

Water treatment/filtration

Cosmetics

Pharmaceuticals