Used dry batteries

1. Composition of batteries: Components of dry cells and rechargeable batteries include zinc casing (iron sheet), carbon rod, mercury, sulfides, and copper terminal； Batteries are primarily made of lead compounds. For example, the composition of a No. 1 used zinc-manganese battery weighs about 70 grams; of this, the carbon rod accounts for 5.2 grams, the zinc sheet 7.0 grams, the manganese powder 25 grams, the copper cap 0.5 grams, and the remaining amount is 32 grams. 　　 2. Types of batteries: Batteries mainly include disposable batteries, rechargeable batteries, and automotive batteries. Disposable batteries include button cells, ordinary zinc-manganese batteries, and alkaline batteries; many disposable batteries contain mercury. Secondary batteries mainly refer to rechargeable batteries that contain the heavy metal cadmium. Used car batteries contain acids and the heavy metal lead. 　　 3. Number of batteries: Digital products such as DC and MP3 players are developing at an extremely rapid pace, and all of them rely on batteries; the demand for batteries is increasing swiftly. If no action is taken, a situation involving mountains of batteries will eventually arise. Used batteries may seem unremarkable, but they can cause significant harm. If you are aware of the hazards of metals such as mercury, cadmium, and lead contained in batteries, then you will understand just how dangerous used batteries can be. The hazards of used batteries 　　 The main environmental impact of battery products is pollution caused by electrolyte solutions such as acids and alkalis, as well as heavy metals. Different types of battery pollutants also vary. Generally speaking, the harmful substances in batteries mainly include heavy metals such as Zn, Hg, CNi, and Pb ； H2SO4 in lead-acid batteries ； KOH in various alkaline batteries, and the LiPP6 electrolyte in lithium batteries, etc. Hg and its compounds, particularly organic mercury compounds, possess extremely high biological toxicity, a rapid rate of bioaccumulation, and a long biological half-life in brain tissues. Cd tends to accumulate in animals and plants, affecting their growth, and is highly toxic. Pb has adverse effects on human organs and systems such as the chest, kidneys, reproductive system, and cardiovascular system, manifesting as reduced intelligence, kidney damage, infertility, and high blood pressure. Zn and Ni have relatively low toxicity, but at concentrations above a certain level, they can have adverse effects and cause harm to the human body. The acid and alkaline electrolyte solutions in used batteries can affect the pH value of the soil’s water regime, causing the soil and water bodies to become more acidic or alkaline. The main components contributing to pollution in battery electrolytes are the soluble heavy metals contained within them, particularly lead sulfate in the electrolytes of lead-acid batteries, and cadmium hydroxide in nickel-cadmium batteries. Heavy metal ions in batteries dissolve in soil or water and are absorbed by plant roots; when livestock consume these plants, the heavy metals accumulate in their bodies. When humans consume grains, vegetables, and meat containing heavy metals, as well as water, these heavy metals accumulate in the human body along this food chain. Since heavy metal ions are difficult to excrete from the body, they ultimately damage the nervous system and liver function. 　Research on the Recycling of Used Batteries 2.1 Current Status of the Recycling of Used Batteries The most commonly used industrial batteries in China are lead-acid batteries, with lead accounting for over 50% of the total cost of these batteries. The main methods employed for their recycling include pyrometallurgical and hydrometallurgical processes, as well as solid-state electrolytic reduction techniques. The casing is made of plastic, which can be recycled, thus virtually eliminating secondary pollution. 　　 Commonly used small secondary batteries include nickel-cadmium, nickel-metal hydride, and lithium-ion batteries. Cadmium in nickel-cadmium batteries is one of the heavy metals that are strictly regulated due to environmental concerns. The organic electrolytes in lithium-ion batteries, the alkalis in nickel-cadmium and nickel-metal hydride batteries, as well as heavy metals such as copper used in battery manufacturing, all contribute to environmental pollution. At present, the total number of small secondary batteries in use in China is only a few hundred million, and most of them are of small size. The value of these used batteries for recycling is low, and due to their scattered use, the vast majority of them end up as household waste. There are issues related to costs and management involved in their recycling, and certain technical challenges exist as well for their reuse. 　　 Civilian dry batteries are the most widely used and most dispersed type of battery product at present, with 8 billion units consumed annually in China. There are mainly two series: zinc-manganese and alkaline zinc-manganese, along with smaller quantities of zinc-silver, lithium batteries, and other types. Zinc-manganese batteries, alkaline zinc-manganese batteries, and zinc-silver batteries generally use mercury or its compounds as corrosion inhibitors, and mercury and its compounds are highly toxic substances. When used batteries are incinerated as household waste, some of the heavy metals such as Hg, Cd, Pb, and Zn present in them are released into the exhaust gases at high temperatures, while others end up as ash, causing secondary pollution. 2.2 Technologies for the recycling of used dry batteries a. Manual sorting and recycling technology: Generally, dry batteries are first sorted, then simply mechanically separated to isolate components such as zinc shells, plastic caps, and carbon rods. The remaining mixture of MnO2, hydromanganese oxide, etc., is sent to a brick kiln for calcination to produce dehydrated MnO2. This method is simple and easy to implement, but it requires a lot of labor and does not yield significant economic benefits. b. Pyrometallurgical recycling technology: Generally, dry batteries are sorted and crushed before being fed into a rotary kiln. At high temperatures of 1100–1300 degrees Celsius, zinc and zinc chloride are oxidized to zinc oxide, which is then released along with the flue gases. A cyclone dust collector is used to recover this zinc oxide, while the remaining manganese dioxide and hydromanganese oxide end up in the residue. Further processing can then be carried out to recover materials such as manganese. This method is simple and easy to implement; smelting plants do not need to add any additional equipment to recover zinc using this approach. c. Wet recycling technology 　　 Based on the principle that zinc and manganese dioxide are soluble in acids, used dry batteries are sorted and crushed, then placed in leaching tanks where dilute sulfuric acid (100–120 g/L) is added for leaching, resulting in a zinc sulfate solution. Metal zinc can be obtained through electrolysis. After washing the residue, the copper caps and carbon rods are separated, and the remaining substances, MnO2 and hydromanganese oxide, are calcined to produce MnO2. The methods used include the roasting-leaching method and the direct leaching method. 　　 Compared with the pyrometallurgical method, the wet method has advantages such as lower investment, lower costs, faster plant construction, higher profits, and greater process flexibility; however, it cannot ensure the complete recovery of harmful components. 3 Prevention of secondary pollution in the recycling of used batteries. The three recycling methods mentioned above are simple and easy to implement, but each has its shortcomings and is prone to secondary pollution. Through numerous experiments, we have identified feasible ways to prevent such secondary pollution. 　　 First, the used dry batteries are sorted, then mechanically opened to separate the copper caps and zinc shells, which can be recycled separately. After magnetic separation to remove iron from the remaining carbonaceous material, it is soaked in water at a solid-to-liquid ratio of 1:4 for 1 hour. The upper layer of the solution is then evaporated and crystallized; the main components of the precipitate are MnO2, MnO(OH), acetylene black, carbon rods, and other substances. These materials are fed into a rotary kiln and heated to 600 degrees Celsius. The smoke generated is condensed to produce a condensed liquid, and regular cleaning of this liquid yields pure mercury. It also prevents mercury vapor from polluting the environment. During the calcination process, the large amount of acetylene black and carbon in the mixture reduce MnO2 to MnO. The reaction process is as follows: 2MnO₂ + C ---> 2MnO + CO₂. This calcined material is then added to a sulfuric acid solution with a concentration of less than 2 mol/L in a solid-to-liquid ratio of 1:4, and left to soak at 80°C for 1 hour; during this time the following reaction occurs: MnO + H₂SO₄ ---> MnSO₄ + H₂O. This yields a manganese sulfate solution, and at the same time, other soluble heavy metal sulfates are also introduced. 　　 The resulting zinc sheets and metals such as copper can be remelted for reuse; ammonium chloride can be used to make fertilizers or purified as a chemical reagent. Manganese sulfate is a component of hormones that promote the growth of plants and animals, and it can be used as a drying agent in paints and inks as well as a catalyst in various organic synthesis reactions. It is also employed in papermaking, ceramics, dyeing, and the production of electrolytic manganese. Table 1 shows the components of the recyclable materials in zinc-manganese dry cells. 　　 This recycling method requires less investment, uses simple equipment, and is easy to implement in small and medium-sized cities, thereby eliminating the problem of transporting used batteries. 　　 The solution resulting from the recycling of used batteries is concentrated and reacted with EDTA to form metal complexes, thereby completely eliminating secondary pollution. Tests have shown that the level of heavy metals in the solution obtained after recycling used batteries meets **environmental standards**. To separate these metals, they can be processed in stages by taking advantage of their different stabilities. Table 2 shows the complexation stability constants of metal ions with EDTA. 4 Problems and Suggestions in the Recycling of Used Batteries ① After being recycled, batteries cannot be properly disposed of, and they are usually piled up. During stacking, the batteries may leak or toxic substances may spread. 　 ②Due to the wide variety of battery types and the abundance of counterfeit products, battery recycling poses difficulties. Some batteries contain mercury, others contain cadmium; some use ammonium chloride as an electrolyte, while others use zinc chloride. Therefore, it is recommended that manufacturers use standardized labels to indicate the type of battery and its main components, in order to facilitate recycling. 　 ③Strengthen the development of high-performance, environmentally friendly batteries to achieve mercury-free versions of conventional consumer batteries. 　 ④Support should be provided through policy to recycle used batteries.

It’s not just used batteries; used home appliances, mobile phones, and other such high-tech waste items also have a significant impact on the environment. I’ve read a few reports in the past stating that several companies intended to handle this issue, but those efforts ended up falling through. What is actually being done now is by small-scale operations, and their methods are quite concerning. The impact of used home appliances on the environment cannot be underestimated; they can also pose a threat to human health, and even affect the growth of children and adolescents.

Problems and suggestions in the recycling of used batteries: After being recycled, batteries cannot be properly disposed of and are usually piled up. During stacking, the batteries may leak or toxic substances may spread. Due to the wide variety of battery types and the abundance of counterfeit products, battery recycling poses difficulties. Some batteries contain mercury, others contain cadmium; some use ammonium chloride as an electrolyte, while others use zinc chloride. Therefore, it is recommended that manufacturers use standardized labels to indicate the type of battery and its main components, in order to facilitate recycling. Strengthen the development of high-performance, environmentally friendly batteries to achieve mercury-free versions of conventional consumer batteries. Support should be provided through policy to recycle used batteries.