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Bentonite is one of the clay materials that have important characteristics and is applicable to construction and for different industrial uses. Treatment of this material to enhance some of its physicochemical properties to suit the desired applicability has been a focus research area. In this work, natural bentonite from Warseisso, Afar region, Ethiopia was activated with thermal treatment. The raw and treated bentonites were then characterized using SEM, FTIR, XRD, BET, and cation exchange capacity. The effects of activation parameters (time and temperature) on its physiochemical properties and its performance for the removal of sodium ions from water were investigated. Bentonite activated for 6 h at 300 °C showed a maximum specific surface area of 81.74 m2/g while the raw one showed 57.6 m2/g. However, the cation exchange capacity value of the raw bentonite was found to be 82.1 meq/100 g while the value was reduced to 67.2 meq/100 g for treated bentonite with high specific surface area. To check the performance of the activated bentonite for desalination application, batch adsorption of sodium from synthetically produced sodium chloride solution was made. A sodium removal performance of 10% was achieved with treated bentonite at the maximum specific surface area. HIGHLIGHTS Warseisso bentonite was activated at different time periods and temperatures.; Raw and activated bentonites are characterized by SEM, BET, XRD, FTIR and CEC.; Activated bentonite was applied for sodium removal from a synthetic solution.;

Water is one of the natural resource due balance if our planet and the life on it have to sustain and economic development to be expected in the future. The increase in population of the world and level of wealth of humans is expected to withdraw more freshwater. However, since water is already one of the limited resources, global per capital water available surely drops and water shortage happens. Pollution of ground and surface water by dissolved salts are increasing and exacerbating this water shortage situation. The sources of these dissolved salts (such as primary and secondary salinity-causing agents) are known to change the chemical constituent of water. Once contributing factors for water scarcity are identified, future man should work on it to overcome the challenge. This paper therefore began with global water resource information and indicated different levels of scarcity to give overall clues on the situation. Salinity description, its global status, causative factors and challenges were revised before possible recommendations were indicated as indispensable solution.

In the present study, natural and acid activated local bentonite were investigated for removal of sodium for reduction of water salinity. Local bentonite from was collected from Warsisso area of Afar region, eastern part of Ethiopia and activated with H2SO4. The raw and activated bentonites were characterized with XRD, SEM, FTIR and BET. The raw and activated bentonites were used for adsorption of sodium from aqueous water for reduction of salinity of water. The effects of H2SO4 concentration, activation time, concertation of initial sodium concentration, adsorption time, pH of solution and adsorbent dosage on the sodium removal were studied. SEM results shows smooth aggregate with closely packed flakes for natural bentonite while the surface foe activated bentonite is foggy and ragged appearance. The specific surface area of natural bentonite is 57.6 m2/g while a maximum of 238.24 m2/g was observed for bentonite activated with 3 M H2SO4 activated for time period of 6 h. A maximum of 18% sodium adsorption was achieved at this maximum specific area condition. An optimum removal of sodium by activated bentonite was 19.4% at adsorption conditions of time 180 min, salt concentration of 3486 ppm, solution pH of 10 and adsorbent dosage of 0.5 g. The experimental data were analyzed by Freundlich, Langmuir, Dubinin-Radushkevic (D-R) and Temkin isotherms models. The results revealed that Langmuir isotherm provided a better fit to the experimental data with correlation coefficients of 0.967 and 0.979 for raw and activated bentonite, respectively. Adsorption kinetics as well was studied with pseudo first order and pseudo second order, intraparticle diffusion and Elovich models. And pseudo second order model also found best to explain adsorption kinetics with 0.994 and 0.999 correlation coefficients.