Zinc carbonate: analysis of properties, preparation and multi-field applications

Zinc carbonate is an important carbonate compound of the zinc element with the chemical formula ZnCO₃. As a key inorganic chemical raw material, it widely exists in nature and is used in many industrial fields. It is often mentioned in conjunction with basic zinc carbonate (chemical formula 2ZnCO₃·3Zn(OH)₂·H₂O). The latter is more often referred to as "zinc carbonate" in industrial production. The two are related but different in properties and uses.
1. Core psychological properties

1. Physical properties

Zinc carbonate is a white powdery solid, odorless and tasteless. Its crystal structure belongs to the trigonal crystal system. In its natural state, it mainly exists in the form of Smithsonite. Its density is 4.3476 g/cm³. It is almost insoluble in water (solubility is only 4.692×10⁻⁵ g) and alcohols under standard conditions. It is slightly soluble in liquid ammonia and soluble in dilute acid and sodium hydroxide aqueous solution. This solubility characteristic provides an important basis for its preparation and application.

2. Chemical properties

Zinc carbonate is unstable and easily decomposes when heated. When the temperature reaches 300°C, it will decompose into zinc oxide and carbon dioxide. This reaction is one of the important ways to prepare zinc oxide in industry. The reaction equation is as follows:

$${\displaystyle {\ce {{ZnCO3}\;\xrightarrow {\triangle } \;{ZnO}+{CO2\uparrow }}}}$$

In addition, zinc carbonate can undergo metathesis reactions with acids to generate corresponding zinc salts, carbon dioxide and water, and can also react with alkali and ammonium salt solutions. This feature allows it to flexibly control the reaction process in purification and application scenarios.

2. Preparation process

The preparation of zinc carbonate is mainly divided into two categories: natural mining and artificial synthesis. Among them, industrial mass production is mainly based on chemical synthesis. The core processes include metathesis method, acid leaching method, etc., and most of them prepare basic zinc carbonate as the target product.

1. Natural mining

Natural zinc carbonate is obtained by mining smithsonite. After crushing, grinding, purification and other processes, industrial grade or reagent grade products can be obtained. However, due to limitations in the distribution of mineral resources (mainly concentrated in Inner Mongolia, Yunnan and other places) and the decline in ore grade, natural mining has gradually given way to artificial synthesis.

2. Artificial synthesis method

Metathesis method: This is the most mainstream production process. Zinc-containing raw materials (zinc oxide, zinc slag, etc.) are reacted with sulfuric acid to generate a crude zinc sulfate solution. After secondary impurity removal processes such as potassium permanganate oxidation and zinc powder replacement, impurities such as iron, manganese, copper, and nickel are removed to obtain a refined zinc sulfate solution. Subsequently, it reacts with sodium carbonate solution under conditions of controlled temperature (45-50°C) and pH value (end point is about 6.4) to generate basic zinc carbonate precipitate. After filtering, drying, fine grinding and sieving, the finished product is obtained. The reaction equation is as follows:

$${\displaystyle {\ce {3ZnSO4+3Na2CO3+3H2O\rightarrow ZnCO3·2Zn(OH)2·H2O+2CO2\uparrow +3Na2SO4}}}$$

The precipitant can be selected according to the needs during production: sodium carbonate has stable reaction and high zinc precipitation rate, and is suitable for preparing basic zinc carbonate finished products; ammonium bicarbonate has a low cost and high-grade active zinc oxide can be obtained after roasting, but the reaction system is difficult to control and the zinc precipitation rate is low.

Other methods: It can also be produced through ammonia leaching and other processes, and the process can be adjusted according to the raw material dissolution method and precipitant type to adapt to different raw material endowments and product purity requirements.

3. Main application areas

Zinc carbonate and basic zinc carbonate play an important role in rubber, medicine, feed, chemical industry and other fields by virtue of their unique properties. Each application scenario has its own focus.

1. Rubber industry

Zinc carbonate can be used as a vulcanization accelerator to accelerate the rubber vulcanization process and improve product strength and wear resistance; basic zinc carbonate is more suitable as an activator and reinforcing agent, especially in transparent rubber products, as it can take into account both vulcanization efficiency and product transparency, and is a key raw material for transparent rubber production.

2. Pharmaceutical and daily chemical fields

In medicine, zinc carbonate is the core component of calamine lotion. It has astringent and anti-itching effects and can be used to treat skin itching, eczema and other conditions. It can also be used as a skin protectant and used in daily chemical products such as talcum powder and skin cream to gently care for the skin.

3. Feed and Agriculture

As a high-quality zinc source feed additive, zinc carbonate can supplement the trace element zinc required for animal growth, promote animal growth and development, improve feed utilization and body immunity, and is widely used in livestock and poultry breeding.

4. Chemical industry and new materials field

In the fertilizer industry, it can be used as a desulfurizer to remove sulfide in gas; in oil drilling, it can react with H₂S to generate stable insoluble ZnS, effectively eliminating H₂S pollution and corrosion without affecting mud performance. In addition, the demand for high-purity zinc carbonate in high-end fields such as new energy battery materials and semiconductor packaging has grown rapidly, becoming a new growth point for the industry.

5. Other fields

In the ceramic industry, it can be used as glaze and color additives to improve the color and gloss of ceramics; in the EVA foaming industry, it can make foaming more uniform and alleviate the effect of foaming agents; it can also be used to produce rayon, catalyst carriers, etc.

4. Industry development status and trends

China is the world's largest producer and consumer of zinc carbonate, and the industry is currently in a stage of structural transformation and high-quality development. The apparent consumption of zinc carbonate in the country will reach 286,000 tons in 2024, and is expected to maintain an average annual compound growth rate of 5.8% from 2025 to 2030. The core driving force comes from the expansion of demand in high-end fields such as new energy and electronic materials.

The industry structure shows the characteristics of "head concentration and technological differentiation": the top 12 leading companies occupy 68.3% of the production capacity. The precipitation method dominates the production of high-purity zinc carbonate (purity ≥ 99.7%) to meet high-end demand; the solid-phase reaction law focuses on the mid-to-low-end market. Constrained by environmental protection policies, backward production capacity continues to be eliminated, and the average energy consumption of the industry continues to decline. At the same time, the recycling proportion of recycled zinc resources has increased to 22%, which is in line with the needs of the "double carbon" strategy.

In the future, the industry will focus on the main line of "green + digital" dual transformation, focusing on breakthroughs in high-purity purification technology and optimizing the renewable resource utilization system. There is broad room for import substitution of high-purity zinc carbonate, and companies with the ability to integrate the entire industry chain and high-end preparation technology will occupy a dominant position.

5. Safe operation and storage

Zinc carbonate itself is less dangerous, with an NFPA 704 hazard level of 0-1-0, but it still requires standardized operations: operators need to be professionally trained, work in a well-ventilated environment, and avoid inhaling dust, contact with skin and eyes; stay away from fire and heat sources, use explosion-proof ventilation equipment, and avoid contact with oxidants.

When storing, it should be sealed and placed in a dry and ventilated warehouse, away from easily oxidized and acidic substances, to prevent moisture and caking. If inhalation or accidental ingestion occurs, first aid measures must be taken promptly. Those who inhale dust should be moved to a place with fresh air. Those who ingest it by accident can dilute it with water or milk and seek medical treatment.

In summary, zinc carbonate, as an inorganic compound with both natural properties and synthetic value, is indispensable in traditional industries. At the same time, it shows strong development potential in the field of high-end new materials. Its industrial upgrading and technological innovation will continue to contribute to high-quality development in many fields.