ZEOLITE- A POSSIBLE SOLUTION FOR INDUSTRIAL WASTE. Vol 133
Introduction.
Indonesia is reported to have an estimated hypothetical resource of about 500 million tonnes of zeolite in many different deposits, though only a tiny amount has been defined as drilled reserves. Domestic consumption is around 100,000m3 per year, mostly for the agriculture sector. Zeolite has the wonderful properties that allows it act as an industrial atomic sieve and to encapsulate polluting elements. There is concern that the Indonesian nickel smelting industries massive slag deposits have the potential to leach out various undesirable elements for generations to come. This article looks at the possibility for Indonesian explorers and researchers to find a zeolite solution to this Ni slag problem. The scattered coal fired plants producing undesirable fly and bottom ash may be studied with regards a similar zeolite solution to controlling their leached elements. Just as miners adopt Good Mining Practices to include waste dump encapsulation of acid drainage, then we may hope there could be Good Metallurgical Practice to allow slag and coal dust dumps to incorporate zeolite, and be redesigned as long-term safe structures.
1. Geological Setting.
Zeolite is the name given to a large group of porous, framework, aluminosilicate (their basic structure is interlocking tetrahedra of SiO4 and AlO4) minerals that contain significant water and also significant exchangeable cations, which makes them absorbent materials.
Zeolite ability to exchange one cation for another is known as their “cation- exchange capacity” or “CEC.” Cation-exchange capacity is a measure of the number of cations per unit weight available for exchange, usually expressed as milliequivalents (meq) per 100 grams of material. The zeolites are also referred to as “molecular sieves”, because the channel ways within the crystalline structure are extremely small and they can be used to separate large molecules from smaller molecules.
Zeolites are typically formed from acid to intermediate pyroclastic volcanic rocks by interaction with saline alkali fluids with specific chemistry temperature and pressure after burial. Zeolites can also be formed through hydrothermal process, burial metamorphic, weathering, open systems (tuff reacting in sea water) and closed systems (tuff reacting with connate water on burial). Approximately 48 natural zeolites are known, the most common of which are Analcime, Chabazite, Clinoptilolite, Erionite, Ferrierite, Heulandite, Laumontite, Mordenite, and Phillipsite showing a range of silica to aluminium ratios (SI:Al). Analcime and Clinoptilolite are by far the most common zeolites in sedimentary rocks. Heulandite and Laumontite occur in mafic igneous rocks.
2. Indonesian Deposits.
The reference “Potensi Zeolite di Indonesia by Kusdarto [Jurnal zeolite Indonesia Vol 7 No2 November 2008] lists 20 locations of zeolites in Indonesia, and gives a brief outline of each districts geological setting and some chemical analysis. The Mines Department (ESDM) on-line “One Map” classifies zeolite as “mineral industry” with 10 locations in Sumatra (most in Lampung), 5 locations in Java, 12 locations in Nusa Tenggara Timur, 1 location in Timur, and 2 locations in Sulawesi. Most of these locations have little to no technical data on One Map, and seem to be known occurrences. Two sites have a mining company name, that of PT. Paragon Perdana Mining and PT. Mina Tama, both in Lampung indicating these are recognized compliant mines.
The Ministry of Trade regulation 01/M-DAG/PER/1/2017 defines tariffs for the export of zeolite with recognition of various levels of quality and CEC. The Government Regulation PP 96 of 2021 about the implementation of mining business activity classifies zeolite as a “non-metallic mineral”. Earlier regulations defined zeolites as “rocks” with the “class C” classification.
3. Exploration program.
The PT. Paragon Perdana Mining project appears to be one of the most studied producing mines in Indonesia, and gives an indication of the specialized nature of zeolite exploration.
Outcrops and drilling indicate geological complexities (grain size, bedding, colour and various source rock) and the tropical weathering process. Much of the exploration was carried out in the period 1990 to 1996 with topography survey, mapping, test pitting and 113 diamond drill holes (4,445m). Minerology samples of zeolite were sent to Mintek Services in Western Ausstralia for petrology, thin section and X-Ray diffraction (XRD). Corelabs in Jakarta also ran XRD. Chemical assays were undertaken by PT. Robinson Research Utama Indonesia (later became Intertek). It was noted that higher CEC assays were associated with finer grained zeolite. The laboratory procedures; – Samples were extracted in three aliquots of 1M Ammonium Acetate and the exchangeable cations sodium (Na), potassium (K), calcium (Ca) and Magnesium (Mg) were determined on combined extracts. The sum of these cations (Total Exchangeable Cations is reported as cation exchange capacity (CEC).
Statistical comparison of assays filtered by the textural type of zeolites identified in drill core looks like there can be three plant feeds from the pit namely high-grade zeolite with no black minerals (BM); moderate grade zeolite with minor BM and low-grade zeolite with BM. The high CEC values make the products extremely marketable compared to World zeolite grades.
Oil and water adsorption analysis was undertaken at Analabs Australia, physical parameter test work was undertaken at AMMTEC [ Crushing index, abrasion index, specific gravity, bulk density, moisture uptake and loss, bond ball mill work index]. Cement parameter tests (cement pozzolan) were undertaken at Cockburn Cement WA and various sites in Indonesia.
Various block models were run to determine resource type by CEC grade, and by textural type. Textural types will have a bearing on how the zeolite is quarried and blended, influencing production runs at the plant. The overall drilled resource is around 5 million tonne.
Zeolite produced by PT. Paragon Perdana Mining (PPM) has a trade name “AsiaZeolite”, and is processed into several size ranges to suite different markets. A pilot processing plant having a production capacity is 50 tonnes/day has been commissioned, and studies to increase this plant are underway.
4. Production.
Production of zeolite in Indonesia is modest, and recorded a cubic metre (m3).
Table 1; Indonesian zeolite production (m3).
| Year | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 |
| Indonesian zeolite suppliers and manufactures | 114,000 | 130,590 | 116,600 | 102,000 | 92,250 | 61,100 | 1,059,460 | ||
| Badan Pusat statistic | 114,098 | 130,592 | 116,600 | 102,000 | 92,250 | 61,100 |
According to the Indonesian zeolite suppliers and manufactures, zeolite sales are mostly directed at the agriculture industry, with wholesale prices around $80-100/tonne, though prices increased significantly in 2019. The Badan Pusat Statistic classifies zeolite as “bahan galian” from 2011 to 2017, thereafter zeolite was included in “other”. Google search indicates zeolite products can vary in price up to $2,000 per tonne for a few high quality specialized products.
5. Uses.
Zeolite is used as a soil conditioner for plantations, aquiculture, animal feed additive, water treatment and filter media, oil spillage clean up, concrete and construction additive, animal litter (kitty litter), and is mainly sold to domestic industries. Some zeolite was sold to Japan for its clean up of their nuclear plants wherein the heavy metal adsorption properties of high-quality zeolite were applied. There are a number of scattered small distributers of zeolite throughout Indonesia.
6. Industrial Clean Up.
The discharge of toxic heavy metals in industrial waste (urban waste, refinery waste, coal ash, metalliferous mine waste dumps etc) is a cause of serious soil and water pollution. Potential toxic metals are in different geochemical forms that influence their mobility, bioavailability, and toxicity for human health. Several remediation technologies are based on heavy metal immobilization through processes of stabilization/solidification (S/S). “Stabilization” indicates that those techniques can convert contaminants into less a soluble or mobile form, thus reducing their toxicity; “solidification” refers to techniques encapsulating hazardous elements in materials or mineral structures of a high integrity. S/S techniques include chemical processes (involving complex speciation reactions) and physical processes based on the adsorption of an element on material surfaces or encapsulation in the matrix. Soil remediation by amendment with reactive minerals, such as carbonates, phosphate rocks, clay minerals, and zeolites, represents a stabilization/solidification technique reducing the bioavailability of toxic elements, in many cases without dramatically altering natural soil function.
Groundwater contaminants at industrial installations may include lead, copper, iron and chromium, zinc, nickel. In assessing treatment options, cation exchange media often prove to be the most beneficial solution. A number of adsorbents, tests have shown that natural zeolites can be cost effective agents. Every wastewater challenge is unique according to its chemistry, flow rates, and occurrence. There is no one zeolite that is practical or effectual for all situations.
6.1 Cation Exchange Capacity – Purification, Separation and Decontamination
Perhaps the most commercially valuable and dynamic property of zeolite is its cation exchange capacity (CEC). Cation exchange occurs when two or more positively charged compounds or elements exchange places on a negatively charged host, binding one cation to the zeolite and releasing another. The most common exchangeable cations found in natural zeolite molecules are sodium, calcium, potassium, and magnesium, many of which are desirable in numerous biological and industrial processes. A classic example of cation exchange is the removal of ammonia from water and air.
6.2 Encapsulation of Zeolite
Natural zeolite is often used to limit the environmental impact of radioactive waste. Historical applications include limiting the impact of the Chernobyl, Three Miles Island (fresh water) and Fukushima (sea water) nuclear accidents, removing radioactive caesium and strontium isotopes from nuclear industry effluents, and decontaminating water.
SMZ (Surface Modified Zeolites), and various other pre-treatment of zeolites (heating, iron modified etc) materials can provide specialized iron exchange adsorption features, for elements such as chromate, selenite and arsenate. SMZ materials can simultaneously adsorb the three major classes of water contaminants: inorganic cations, inorganic anions, and nonpolar organics. Modified zeolites are also used for mercury removal from flue gases at coal fired power plants.
Ni slag remediation.
The Industry Ministry estimated that 20 million tonnes of nickel slag is currently produced in Indonesia every year. More would be produced in the coming years when all nickel smelters currently under construction begin operating. Indonesia has 11 nickel smelters (2020) and is constructing another 25. The Government Regulation No. 101/2014 has regulated the exception of the nickel slag as hazardous waste and that the ministry has issued a regulation for the exception procedures for nickel slag where nickel waste must pass the LD50 (lethal dose 50) test, the Toxicity Characteristic Leaching Procedure (TCLP) and the sub-chronic toxicity test. One way is to test the Toxicity Characteristic Leaching Procedure (TCPL). Toxic characteristics test through TCLP is to determine the concentration of contaminants in nickel slag which will be compared with the specification requirements in PP 101 of 2014.
The total toxic material content is to be smaller than the TCLP-A and TCLP-B columns according to Table 1.
Table; toxic limit for Ni slag.
| NO | Parameter | Unit | Results | Requirements | Method | |
| TCLP-A | TCLP-B | |||||
| 1 | Antimony | Mg/L | <0.04 | 6 | 1 | US EPA |
| 2 | Arsenic | Mg/L | <0.07 | 3 | 0.5 | US EPA |
| 3 | Barium | Mg/L | 0.03 | 210 | 35 | US EPA |
| 4 | Beryllium | Mg/L | <0.03 | 4 | 0.5 | US EPA |
| 5 | Boron | Mg/L | 0.05 | 150 | 25 | US EPA |
| 6 | Cadmium | Mg/L | <0.01 | 0.9 | 0.15 | US EPA |
| 7 | Chromium | Mg/L | <0.01 | 15 | 2.5 | US EPA |
| 8 | Copper | Mg/L | <0.01 | 60 | 0.15 | US EPA |
| 9 | Lead | Mg/L | 0.06 | 3 | 2.5 | US EPA |
| 10 | Mercury | Mg/L | <0.018 | 0.3 | 10 | US EPA |
| 11 | Molybdenum | Mg/L | <0.01 | 21 | 0.5 | US EPA |
| 12 | Selecium | Mg/L | <0.13 | 3 | 0.05 | US EPA |
| 13 | Silver | Mg/L | <0.03 | 40 | 3.5 | US EPA |
| 14 | Selenium | Mg/L | <0.13 | 3 | 0.5 | US EPA |
| 15 | zinc | Mg/L | <0.03 | 40 | 5 | US EPA |
Indonesian Zeolite research.
A simple google search shows there are many research articles by a variety of Indonesian experts on the many aspects of Indonesian zeolites. A few examples follow;
- The Journal of Environmental Science and Sustainable Development (vol 2 issue 2 of 2019) contains the article “Indonesian natural mineral for heavy metal adsorption; a review, by Grandprix Kadja of ITB. This article provides an overview of the use of the natural materials found in Indonesia, including clay, natural zeolite, fly ash, and bottom ash, as adsorbents for several types of heavy metals in aqueous solution. It is important for providing the state of the art of reported works and highlighting the future prospect of Indonesia natural materials as their high availability and their future prospect by using several modification techniques.
- Valensi Vol 3 no 2 Nov 2013 contains the article “the characterization of Indonesia’s natural zeolite for water filtration systems by M. Razzak, T. Las and Priyambodo from the Islamic university of syarif Hidayatullah, Jakarta. The objective was to obtain a general guidance for development of natural zeolite in molecular sieves, ion exchange and catalyst applications.
- IOP conference series materials science and engineering master projects by S. Muhammad (syiah Kuala University) and M. Mariana (west university of Timisoara master project on “Characterization and activation on Indonesian natural zeolites from southwest Aceh district. This study shows the effect of activation processes of Indonesian zeolite from Southwest Aceh District.
The Lembaga Ilmu Pengetahuan Indonesian (LIPI) research institute has many articles on zeolites, with a general emphasis on the agriculture and petrochemical aspects, and does include some research on various Indonesian zeolite deposits.
The Indonesian Zeolite Association of Indonesia is located in Serpong (Jakarta). It appears to have been more active with various papers to around 2010.
Conclusion.
There are strong foundations for a growing zeolite industry in Indonesia. There are many different types of zeolites in Indonesia, there are many processes available to improve zeolites performance as sieves, cat ion capture etc. There are many capable Indonesian research engineers and laboratories.
Indonesia’s modest production of zeolite is mostly sold into the agriculture sector. However there seems to be significant potential for Indonesian zeolites to become a part of the environmental solution to reduce toxic leaching from Indonesia’s growing nickel slag dumps, numerous scattered small coal plants bottom ash disposal heaps and other industrial waste sites.