Results in Engineering (Jun 2022)
Adsorption of sodium from saline water with natural and acid activated Ethiopian bentonite
Abstract
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.
