Methodology for Selective Adsorption of Lithium Ions onto Polymeric Aluminium (III) Hydroxide

The recovery of lithium as lithium aluminate from Egyptian bitterns was investigated. Studies were performed on synthetic Li + solution and on three high - salinity end brines which contain Li + of concentrations varying between 5.5- 19.5 ppm. Pretreatment with a mixture of Na 2 SO 4 - Na 2 CO 3 is achieved to precipitate BaSO 4 , SrCO 3 , CaCO 3 and possibly MgCO 3 . A co-precipitation method was employed using aluminum salt as (AlCl 3 .6H 2 O). Lithium ion is adsorbed onto aluminum hydroxide, which is freshly produced by adding AlCl 3 .6H 2 O and Na OH to the brines at Al 3+ / Li + molar ratio� 5-7. Results obtained indicate that high Li+ adsorption was performed at pH = 6-7 for Alexandria-Arish and Emissal salines, even for small concentration of aluminum salt added. Also, Lithium ions uptake decreased with increasing adsorption temperature from 10oC to 30oC but over 30oC increase in temperature does not affect lithium uptake on Al(OH) 3 , which proved that the process is physical adsorption. Equilibrium isotherms have been determined for the adsorption of Li + onto Al (OH) 3 at 30oC and pH= values (5 to 9), the maximum adsorption capacity of Al(OH) 3 at 30oC and pH = 9 is 123 mg/gm. The results indicated that applied isotherms were shown to be favorable and were fitted with Langmuir and Freundlich isotherms. Li + desorption from Al(OH) 3 was investigated using hydrofluoric acid (HF) or sulphuric acid (H 2 SO 4 ) with different concentrations, and results obtained showed that HF is more efficient than H 2 SO 4 concerning Li + desorption. From the obtained results, Li ion can be recovered successfully from bittern and saline solutions. (Journal of American Science. 2010;6(11):301-309). (ISSN: 1545-1003).