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Experimenting with the Production of Bleaching Clay in a “Poor Man’s” Way! |
To produce shiny, lemon-yellow cooking oil, few people realize that two essential substances are involved in the production process: clay and activated carbon. A Vietnamese engineer has dedicated his efforts to researching the technological process for producing these two substances using local raw materials from Vietnam…
The author of this technological process, Engineer Pham Trong Uyen – a former researcher at the Institute of Vegetable Oils, Essential Oils, and Cosmetic Fragrances in Vietnam – expressed: “For me, these are the two most satisfying and cherished research results during my scientific career.” When he first embarked on this task, he was determined: “I will pursue these two research directions to the end, no matter the cost…”.
He explained that in vegetable oil production, an important stage is the bleaching of the finished oil using clay and activated carbon. For relatively clean unrefined oils (crude), 1 ton of cooking oil requires 1.5 kg of activated carbon and 3.5 kg of bleaching clay.
However, for freshly pressed oils such as peanut oil, sesame oil, and coconut oil, the amount of bleaching clay and activated carbon required is ten times higher than the aforementioned ratios. Meanwhile, the vegetable oil industry in Vietnam has an output of hundreds of thousands of tons each year, with some forecasts suggesting that this number could reach 500,000 tons per year.
According to Uyen, to date, almost all of the bleaching clay required for production needs to be imported at prices of hundreds of USD per ton. However, he also affirmed that Vietnam has abundant raw material resources, with reserves amounting to millions of tons, which can be used to produce high-quality bleaching clay.
This resource is bentonite – a type of clay among approximately 100 types of clay found in Vietnam – located in Di Linh (Lam Dong), known for its quality, with sand, gravel, and stone content only making up 10-15%.
Uyen stated that the technological process for producing bleaching clay from Lam Dong bentonite has been successfully researched and proven feasible on a pilot scale.
He explained that when the raw bentonite is treated with acids such as hydrochloric acid (HCl) and sulfuric acid (H2SO4), the metal oxides present in the bentonite dissolve, creating extremely small voids (measured in angstroms; one angstrom equals 10^-8 cm) within the crystal structure of the bentonite.
The size of these voids is suitable for trapping pigment particles mixed in oil. When the bleaching clay is added to the oil, these pigment particles will enter and be trapped inside the voids of the bleaching clay crystals. This mechanism contributes to making the oil clean and visually appealing. Activated carbon serves a similar purpose but is more expensive than bleaching clay.
Uyen confirmed that with the research conducted, there is a solid scientific basis and capacity to produce bleaching clay from Vietnam’s abundant raw materials, making it competitive with imported bleaching clay. The same applies to activated carbon; this can also be produced from sawdust, which is readily available in Vietnam, for use in monosodium glutamate production, sugar whitening, and cooking oil.
GIANG HUONG
