Removal of Cr(VI) oxoanion from contaminated water using granular jujube stems as a porous adsorbent

The efficiency of granular Jujube stems (GJS) was investigated in removal of hazardous Cr(VI) oxoanion from contaminated solutions. The GJS was prepared under standard conditions and sized in 40-60 mesh using ASTM standard sieves. The effects of pH (3, 5, 7), adsorbent dose (4, 6 and 10 g/L), initial Cr(VI) concentration (0.5, 2 and 10 mg/L) and contact time (15, 30, 60, 120, 180, 240 min and 24 h) were investigated on the removal of Cr (VI) by batch experiments at laboratory scale. Scanning Electron Microscope (SEM)- Energy dispersive X-ray analysis (EDX) analysis showed that the GJS has a porous structure and rough surface. Also, the pores of GJS after Cr(VI) adsorption were completely covered by Cr(VI) oxoanions. The obtained results indicated that the Cr (VI) removal efficiency increased by increasing of adsorbent dose and contact time and it decreased by increasing of pH solution and initial Cr(VI) concentration. Optimal conditions for Cr(VI) adsorption were the adsorbent dose of 6 g/L, 60 min contact time, and pH = 3. The maximum removal efficiency and adsorption capacity were obtained 99.8% and 4.76 mg/g at optimum conditions. The experimental data were well fitted with the Freundlich isotherm and pseudo-first-order kinetics model. According to the results, GJS is able to adsorb the Cr(VI) oxoanion from aqueous solutions and can be used as an effective and appropriate adsorbent to remove Cr(VI) from wastewater.