Removal of calcium ions from aqueous solutions by sugar cane bagasse modified with carboxylic acids using microwave-assisted solvent-free synthesis

Removal of Ca(II) from aqueous solutions was potentially achieved using two new naturally benign sorbents. They were obtained via modification of sugar cane bagasse (SCB) with tartaric acid (TA) and citric acid (CA) using microwave-assisted solvent-free synthesis. The highest percentages of surface loading were realized under optimize conditions of mass ratio of SCB and TA or CA, microwave radiation power and time of radiation. Changes in spectral band positions of binding sites of SCB and its modified forms (SCB-TA and SCB-CA) were characterized using FT-IR before and after calcium ions sorption. Also, changes in surface morphology were explored in parallel, using scanning electron microscope (SEM). Moreover, for obtaining maximum Ca(II) removal, batch experiments were carried out at different parameters including hydrogen ion concentration, initial Ca(II) concentrations, mass of the sorbent and finally shaking times. Results of sorption isotherms were better fitted with the Langmuir model (r2 = 0.959 and 0.995 for SCB-TA and SCB-CA, respectively). In addition, the kinetics data were best fitted with the pseudo-second-order type. Applications of the new natural sorbents for lowering hardness and consequently conductivity and total dissolved solids (TDS) in different water samples was superior compared to the cation exchange resin Dowex 50W-X8.

Fig. 2. Scheme of synthesis route to obtain modified SCB phases.Figure optionsDownload as PowerPoint slideHighlights
► SCB-TA and SCB-CA as a natural solid phase extractors using for removal of Ca(II).
► The percentage of extraction reached their maximum values (100%) for both phases at pH = 6.0.
► The equilibrium is reached after 25 min of contact with SCB-TA and 10 min with SCB-CA.
► Sorption isotherms were better fitted with the Langmuir model (r2 > 0.95 for both phases).
► The kinetics data were best fitted with the pseudo-second-order type for both sorbents.