# The Influence of Spent Portable Battery Waste on the Aquatic Environment
## 1 Introduction  
In many countries, especially underdeveloped or developing countries, discarded municipal waste may contain hazardous waste like spent portable batteries. Thus, spent portable batteries can reach landfills or various aquatic environments where, under the influence of temperature, precipitation, and the acidity or alkalinity of the storage environment, they can be corroded, releasing heavy metals and other harmful components into the environment, i.e., the aquatic system [1; 2; 3; 4; 5; 6]. One of the most important hazards associated with landfilling is the release of leachate containing heavy metals and toxic compounds, which could pose a serious environmental impact and a threat to living species [7; 8; 9; 10; 11; 12; 13; 14; 15]. The amount of disposed lithium-ion batteries is estimated to progressively increase, as demonstrated in the last decade, which saw an increase from 10,700 tons in 2012 to 250,000 tons in 2020 [16; 17; 18]. According to [PERSON] et al. (2016) [14], 4000 tons of used lithium-ion batteries could generate about 1100 tons of heavy metals and more than 200 tons of toxic electrolytes. Thus, the released toxic elements can reach the groundwater, surface water, or the air, endangering the environment and human health [14]. An alkaline portable battery consists of an anode (negative electrode), a cathode (positive electrode), and an electrolyte (a liquid solution through which ions move) [19; 20]. Usually, it uses powdered zinc (55-70%) as a negative electrode, manganese dioxide (MnO: 79-85%) with graphite as a positive electrode, and highly conductive potassium hydroxide (KOH: 35-52%) as an electrolyte [19; 20; 21]. In addition, a battery may have the structure of paper, metal (steel), plastic, etc. [19]. Based on the chemical nature of the active elements in anodes and cathodes, [PERSON] et al. (2006) [19] classified batteries into seven categories, as follows: alkaline zinc-manganese dioxide, zinc-carbon, mercury oxide, silver oxide, zinc-air, lithium, and nickel-cadmium. Batteries could be divided into two categories: primary and secondary [22; 23]. The primary ones are not rechargeable, which means that they become waste after the end of their lives, but the secondary ones are rechargeable, which allows more cycles of use. According to Eurostat (2020) [24], out of the 191,000 tons of portable batteries sold in the EU in 2018, close to 48% were collected for recycling. In some countries, used portable batteries are not collected entirely separately, and there is a risk that they will be thrown into municipal waste dumps. Emphasizing the recycling process would mean reducing waste that could endanger the environment [18]. Wasted batteries discharged into the environment are a major source of heavy metals, especially of lead, lithium, nickel, cadmium, and cobalt but also of electrolytes like lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), and lithium hexafluorophosphate (LiPF6), all of which contribute to the contamination of water and leachate [3; 4; 25; 26; 27]. Heavy metals seep into the soil or different watercourses after being released and could lead to acidification that can destroy aquatic ecosystems and damage biodiversity [28; 29; 30]. Some metals like nickel and cobalt and their compounds might be carcinogens, while others like LiCoO2 should be mutagenic [31; 32; 33]. The presence of portable lithium-ion batteries in saline aquatic environments leads to the release of heavy metals in the liquid environment as a result of the corrosion process of the metal casing and, thus, to an increase in salt content by the release of electrolyte (rich in salts and organic solvents) [1; 34; 35]. Some researchers claim that the greatest release of heavy metals from spent batteries occurs in low-pH solutions [30], and other researchers claim that this happens more in concentrated saline solutions [1]. To understand the behavior of portable alkaline batteries in aquatic systems, [PERSON] et al.