Lithium detection has become increasingly important due to the growing demand for lithium-ion batteries used in electric vehicles and other applications [2][3]. Easy and affordable detection methods are essential, especially in developing countries like Africa, where the detection cost can impede economic development and hinder sustainable resource utilization [1]. Streamlining detection processes ensures we can responsibly harness lithium's potential to support a greener future and global resource stability.
Current lithium detection methods worldwide create a divide among small-scale mining operations in Africa. Many of the most precise techniques are prohibitively costly for typical African firms and pose environmental risks. Moreover, due to the limited technical expertise within most African populations, employing these methods is challenging for ordinary prospectors. Consequently, these techniques demand specialized knowledge, becoming less accessible and significantly more expensive. Below are some of the existing methods for lithium detection:
Table 1.0: Table showing the comparaison of the different lithium detection techniques
Geodes are small devices that can detect lithium underfoot. They use a non-invasive technique called ambient noise tomography to understand the different densities in the ground below [4].
Drawback:Geodes can only detect lithium underfoot , which means they are limited in their ability to detect lithium deposits in other areas of the ground.
Remote sensing data can be used to identify Li-bearing pegmatites through alteration mapping. This method involves using innovative remote sensing methodologies capable of identifying Li-pegmatites [5].
Drawback:Remote sensing can be expensive and requires specialized equipment and expertise, making it challenging to implement in some areas.
Soil and rock samples containing high lithium content can be used as indicators of potential lithium deposits, making lithium analysis an essential step in exploring lithium deposits. Laser-induced breakdown spectroscopy (LIBS) is a rapid and non-destructive method for determining the elemental composition of soil and rock [6].
Drawback:Soil and rock analysis can be time-consuming and expensive, especially when analyzing large areas. It can also be difficult to obtain representative samples, which can affect the accuracy of the results.
A potentiometric smart sensor for lithium detection in environmental samples based on a screen-printed cell has been proposed. This sensor can detect lithium in soil and water samples [7].
Drawback:Smart sensors can be expensive and require specialized equipment and expertise. They may also have limited accuracy and sensitivity compared to other methods.
Lithium has a unique atomic emissions signature, and a flame test can detect lithium in the field. This method involves digesting the sample in a strong acid and using a flame test to detect the atomic emissions signature [8].
Drawback:The flame test is a destructive method that requires the sample to be digested in a strong acid, which can be hazardous and time-consuming. It is also limited in its ability to detect low levels of lithium.
We leveraged the lessons learned from the limitations of conventional lithium mining and used them as a foundation for developing a sustainable approach to lithium detection. Our solution primarily integrates synthetic biology into the detection process, addressing challenges such as time efficiency, cost-effectiveness, environmental sustainability, and user accessibility. The development of "The Biosensor" resulted from a series of iterations, incorporating feedback from mining companies, the general population, and laboratory experiments. This Agarose-based device capitalizes on the diffusion mechanism to detect lithium.
We chose to use sodium alginate hydrogels to encapsulate our bacteria due to their semipermeable and transparent properties [9]. Sodium alginate hydrogels are known to be a good safe keeper for bacteria, as they allow them to interact with the surroundings while preventing them from escaping easily [9]. This makes sodium alginate hydrogels a suitable material for encapsulating bacteria in various applications, such as drug delivery and tissue engineering [9].
Agarose, a transparent gel-like substance, is employed to enable interactions between the sodium alginate hydrogels containing bacteria and the surrounding saturated ground. Its semi-permeable nature selectively permits the exchange of substances, making it an essential component for facilitating these specific interactions. It is not only crucial for enhancing ion mobility but also essential for safety considerations. The agarose acts as a secondary containment system for the bacteria, serving as a barrier to prevent any potential bacterial escape into the soil in the event of hydrogel encapsulation failure.
The choice of using a partly aluminum and plastic casing was motivated by its lightweight properties and exceptional resistance to corrosion. This casing serves a dual purpose: firstly, it is utilized for casting agarose in its liquid form, allowing it to solidify. Secondly, it acts as protective housing for the agarose when it is not in active use.
These are utilized as molds when casting agarose to form perforations within the agarose. A single aluminum rod is positioned at the center to provide structural support for the agarose cylinder.
The biosensor’s small size makes it ideal for easy transportation and storage. It has an approximate height and diameter of 300 mm and 100mm respectively.
