Adsorption equilibrium of lithium sorption process using synthesized inorganic sorbents

• The lithium capacity of the obtained sorbent was 32.42 mg g -1 . • The extraction of lithium from brine onto the synthesized sorbent reached 88.2 %. • Lithium sorption by the new sorbent conforms to the modified Langmuir isotherm model. • The sorption free energy of 12.195 kJ/mol indicates chemical interaction. • Lithium adsorption on the sorbent aligns with the modified Langmuir isotherm model. The adsorption equilibrium of the lithium sorption process using inorganic sorbents was investigated. A sorbent based on a manganese oxide compound was prepared for lithium extraction. The sorbent was characterized by X-ray diffraction and electron microscopy analyses, which revealed the presence of a MnO 2 ∙0·31H 2 O phase. This phase retains a cubic crystal structure (space group Fd3m) and can be formed through deintercalation from the precursor phases Li 0.78 Mn 1.88 O 4 and Li 0.49 Mn 2 O 4 . The synthesized inorganic manganese oxide sorbent, when saturated with lithium, enabled lithium extraction from oil and gas field brine with a pH of 7.25, without the need for preliminary pH adjustment. The sorbent exhibited a lithium sorption capacity of 32.42 mg g -1 . The parameters of the lithium sorption process were determined, and the distribution and separation coefficients were calculated. Optimal sorption conditions were achieved at a sorbent-to-solution volume ratio of 1:1000, a temperature of 35 °C, and a duration of 24 h. Under these conditions, lithium recovery from the solution reached 88.2 %, with a distribution coefficient of 7472 cm 3 /g. The adsorption equilibrium of lithium sorption onto the synthesized inorganic manganese dioxide sorbent was analyzed using the Langmuir, modified Langmuir, Freundlich, and Sips isotherm models. The modified Langmuir model showed the best fit to the experimental data (R 2 = 0,9851). Furthermore, the Dubinin-Radushkevich model was applied to investigate the adsorption mechanism. The calculated free energy value of 12.195 kJ/mol suggests an ion-exchange mechanism with a predominant chemical interaction component in the lithium extraction process.