| Abstract |
In Costa Rica, there are two high enthalpy geothermal fields: “Las Pailas†and “Alfredo Mainieri Protti (AMP)â€, both characterized by its high brine content (around 75%) and exploited to generate electricity. “Las Pailas†reinjects 410 l/s of brine, while AMP reinjects 1000 l/s brine, in a continuous basis. The main objective of this work consisted of determining the lithium extraction and exploitation potential from different geothermal brines, to use it later as raw material in manufacture of electrochemical batteries. Lithium contained in brines where quantified and extraction processes were determined in order se1ect an optimal option to implement. Initially, brine species were quantified including lithium, silica, boron, arsenic, iron, sodium, potassium, calcium, phosphorus, sulfates, sulfur, chlorine, among others through the following methods: i) inductively coupled plasma mass spectrometry (ICP-MS), ii) inductively coupled plasma optical emission spectrometry (ICP-OES), iii) ion chromatography, iv) alkaline titration to determine inorganic dissolved carbon and v) X-ray fluorescence (XRF). Measured Li concentration was obtained as 10 mg/kg for AMP’s reinjection brine and 18 mg/kg for “Las Pailas†reinjection brine. This represents a gross potential of 521.8 ton per year of lithium when adding both geothermal fields. Additionally, an extensive bibliographic review about lithium extraction processes was carried, different methods were found and grouped according to the following types: i) co-precipitation, ii) adsorption and ionic exchange, iii) solvent extraction and iv) electrochemical techniques, this last group was selected to comply with the restriction of extract the lithium without affecting the normal flow of the brines. Specifically, electrodialysis was selected as the method to test lithium extraction in a controlled environment, since electricity in Costa Rica is around 99% from renewable sources, this process would extract materials in a sustainable manner. Under laboratory conditions, a first electrodialysis cell was built, by applying the method with Las Pailas and AMP brines, lithium concentration increased 36% in the best case. |